Re: EMC-related safety issues
Dear John Sorry to be so late replying. I am pleased that you now understand the situation that I attempted to describe earlier, where an HCMOS inverter with an unterminated input was the cause of surprisingly powerful radiated emissions at 200MHz, due to an unfortunate, unlikely, but not impossible combination of events. All the very best! Keith In a message dated 14/01/02 18:54:00 GMT Standard Time, j...@jmwa.demon.co.uk writes: Subj:Re: EMC-related safety issues Date:14/01/02 18:54:00 GMT Standard Time From:j...@jmwa.demon.co.uk (John Woodgate) Sender:owner-emc-p...@majordomo.ieee.org Reply-to: A HREF=mailto:j...@jmwa.demon.co.uk;j...@jmwa.demon.co.uk/A (John Woodgate) To:emc-p...@majordomo.ieee.org I read in !emc-pstc that cherryclo...@aol.com wrote (in 14b.7351131.297 42...@aol.com) about 'EMC-related safety issues', on Mon, 14 Jan 2002: I'm sure I said in my original posting on this example, that the HCMOS was 'hard switching' and not producing a sine wave. A hot device was, of course, the first thing I looked for, and didn't find any. See the additional information above. Yes, you did, BUT I wrote: The absence of harmonics even suggests that this gate was producing a sine-wave, which makes the figures even higher and less credible. The presence of the high-Q resonant structure that you describe is clearly the real reason why no harmonics were observed. It is not only a good antenna *but it very probably cannot radiate odd harmonics*, which should be the only ones present if the drive waveform was square. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero.
Re: EMC-related safety issues
Dear Bob Sorry to be so late replying. Thank you for this reference, I was unaware of it. I shall add it to my list of EMC-related safety references. If anyone wants a copy of my list, I'll be pleased to email it to them in Word format. If anyone knows of any books, articles, or papers on the issue, I'll be pleased to hear from them about them. Regards, Keith In a message dated 15/01/02 04:08:48 GMT Standard Time, john...@itesafety.com writes: Subj:RE: EMC-related safety issues Date:15/01/02 04:08:48 GMT Standard Time From:john...@itesafety.com (Robert Johnson) Sender:owner-emc-p...@majordomo.ieee.org Reply-to: A HREF=mailto:john...@itesafety.com;john...@itesafety.com/A (Robert Johnson) To:emc-p...@ieee.org The latest IEC Just Published points to an article on this subject http://www.iec.ch/etech/etech-live/frames-prod-e.htm It discusses the application of IEC 61000-1-2. Also of related significance when talking about safety of complex systems and the impact of outside influences like EMC is IEC 61000-1-2 FAQs http://www.iec.ch/61508/Index.htm Bob Johnson
Re: EMC-related safety issues
I read in !emc-pstc that Cortland Richmond cortland.richm...@alcatel.co m wrote (in 3c438c09.7e606...@alcatel.com) about 'EMC-related safety issues', on Mon, 14 Jan 2002: A loop can indeed radiate harmonics, if it is a reasonable fraction of a wavelength long. A very small loop, tuned to resonance by some capacitance, is less likely to do so. The structure described by Keith is not a conventional loop and is small compared with a wavelength of 200 MHz: QUOTE The large PCB on which the HCMOS hex inverter was located had a 0.5 inch wide ground and power trace running all around its perimeter, one on each side of the two-layer PCB. Thin traces ran from these 'power buses' to all the ICs on the PCB. The dimensions of the perimeter traces were perfectly right for resonance at 200MHz (and there were no decouplers between the traces) and they made a wonderful rectangular frame antenna at that frequency too. The HCMOS device that suffered the unterminated gate was in the centre of the PCB and got its +5V from the trace at the top of the PCB, its 0V from the trace at the bottom, thereby making an excellent driver for the resonant circuit. The end result was a high-Q resonant 'tank' circuit being driven by the hard-switching device, and setting the basic oscillation frequency. Because the device was hard switching, it didn't heat up. Because the tank circuit had such high-Q and was also a great antenna it radiated the 200MHz component but not the other harmonics of the hard switching device. UNQUOTE I don't necessarily agree with everything in the above, but the ground and power traces are inductors (you could say, 'two inductors in parallel' in view of the geometrically symmetrical drive configuration) and the capacitance between them has the board as dielectric. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that cherryclo...@aol.com wrote (in 14b.7351131.297 42...@aol.com) about 'EMC-related safety issues', on Mon, 14 Jan 2002: I'm sure I said in my original posting on this example, that the HCMOS was 'hard switching' and not producing a sine wave. A hot device was, of course, the first thing I looked for, and didn't find any. See the additional information above. Yes, you did, BUT I wrote: The absence of harmonics even suggests that this gate was producing a sine-wave, which makes the figures even higher and less credible. The presence of the high-Q resonant structure that you describe is clearly the real reason why no harmonics were observed. It is not only a good antenna *but it very probably cannot radiate odd harmonics*, which should be the only ones present if the drive waveform was square. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
Dear Ken Sorry to be so late replying, but I have been unable to read any of the correspondence in this thread for a week. In an attempt to spare the emc-pstc more of our arguing I will not reply in detail to three of your emails, one from the 6th Jan, and two from the 7th Jan, because they all deal with what I think is the core issue: Can the emissions from an 'intentional radiator' such as a laptop that is compliant with CISPR22 and/or FCC limits interfere with an electronic product that is not an intentional radio receiver and possibly cause a safety problem? Have I summarised the issue correctly? I am of the opinion, and I think the other correspondents are too, that the answer is: Yes they can in some circumstances but it should be unlikely these days. I think the reasons for this conclusion include... a) Products with compliant fields at 10 metres distance might have considerably stronger fields closer to, especially in their near field. b) The mandatory standards don't measure all the frequencies that could be emitted from the compliant laptop and possibly cause interference (e.g. audio frequency magnetic fields from fluctuating dc power supply currents can interfere directly with nearby audio or low-frequency transducer circuits). c) Some circuits are very sensitive (especially some transducer amplifiers), or not well-designed for RF immunity, or both at the same time. What do you think, Ken? What do the other emc-pstc members think? Can we please finish this debate now? Regards, Keith Armstrong PS: I will not be able to reply to postings in this thread for about another week.
Re: EMC-related safety issues
Dear Ken Sorry to have taken so long to reply to this. I haven't been able to read any of the contributions for a week. I have to say that I don't recognise myself, or the IEE's guide on EMC and Functional Safety or the 30+ respected and senior engineers who contributed to it, or the IEE itself, in any way whatsoever in your descriptions below. Have you read the IEEE's Ethical Policy? (That's the IEEE not the IEE). What do you think of it? Regards, Keith Armstrong PS: I will not be able to reply to postings in this thread for about another week. In a message dated 07/01/02 02:37:17 GMT Standard Time, ken.ja...@emccompliance.com writes: Subj:Re: EMC-related safety issues Date:07/01/02 02:37:17 GMT Standard Time From:ken.ja...@emccompliance.com (Ken Javor) To:cherryclo...@aol.com, j...@jmwa.demon.co.uk CC:emc-p...@majordomo.ieee.org The question of ethics or morality is at the heart of this discussion which makes it much more important than technical discussions about electromagnetism, which is the ONLY reason I have pursued this so far. I was critical of the IEE safety guide on MORAL grounds. It is part of the morality which says that businessmen or producers are considered guilty until proven innocent because of what they are - profit-making producers. That it is immoral to make a profit and anyone doing so is taking advantage of someone else. This is not the morality which built the USA into the world's wealthiest nation, but it is the morality which will reduce us to the most impecunious. The strict Muslim countries that have been in the news of late forbid loaning of money at interest, because the Koran forbids usury. It is no accident that these countries all belong to the third world. Progress depends on the ability to raise capital. The most efficient way to do that is for people who have profited from past ventures to invest those profits in new ventures. That is what banks facilitate. If there are no profits, then there is no money to borrow and to start a venture and progress stops or becomes agonizingly slow. A policy which says that producers are liable for unlimited damages without needing to show defect or negligence is on a moral level with the prohibition of lending money at interest. We have to decide if we wish to live in a civilized world or not. That is a question of moral significance. The idea that businessmen are immoral greedy people who give no thought to the quality of their products is an ugly lie spread by enemies of capitalism. A little thought will show that businessmen who operate like this do not stay in business long because their products get a bad reputation. Certainly you can find examples of bad or ignorant behavior. Does this justify policies which assume all businessmen are evil and that they must be reined in by pure-hearted regulators? What makes the regulators pure-hearted? That they don't make profit, but siphon profits away? What is the cost of the regulation relative to the benefit? What marvelous inventions didn't occur because the seed money necessary to initiate a development wasn't there? When engineers make false claims that unintentional RE from ITE can cause safety-critical circuits to fail catastrophically, we engage in another moral transgression. We attempt to get a short term gain at the cost of long term loss. The short term gain is to make ourselves and our profession look more important. But the long term loss is that of the little boy who cried wolf. After a long enough period of false alarms, we will lose the respect and ear of management and if we must raise a REAL issue, it will fall on deaf ears. I have no way of knowing, but I wonder how many unfulfilled warnings the managers who OK'd the launch of 51L (Challenger) had listened to prior to making their fateful decision.
Re: EMC-related safety issues
Dear Ken Sorry to have taken so long to reply to this. Pressure of work has kept me away from the thread for a week. I don't know where you get your maths from. The usual formula (commonly available in a number of variants) for the radiated emissions E in V/m at 10 metres due to a common-mode current is: E = 1.26 10^-4 (f.L.ICM) f = frequency in MHz L = length of the radiating cable in metres ICM = common-mode current in the cable in milliamps Using L = 1.5 metres (not a long cable) and f = 100MHz, I find that 92dBuV/m (= 40mV/m) can be created at 10 metres distance by a CM current of just 2mA. 2mA is a far cry from your significant fraction of an Ampere of common mode rf current. Hence my serious concerns about your math. I also don't agree with a number of other things in your analysis below, especially as you finish by saying: If you consider that any signal with information content carried by 2 mV is shielded, the issue becomes, once again, a non-problem. I don't think you can make the assumption that cables carrying low level signals are shielded. Remember that this thread began with a discussion of EMC-related safety issues, and where safety is involved one shouldn't make assumptions that everyone else designs equipment as well as you would like them to. If we consider a country such as the US with no mandatory EMC immunity regulations, and a measuring device that uses analogue technology and does not have to meet emissions standards, it is obvious that the lowest cost way to design and market it is to leave out all the shielding and filtering, and I would expect a proportion of manufacturers to do just that. I will spare the emc-pstc a longer email by not responding to the other issues I don't agree with at this time. Maybe other contributors would like to support your analysis below? or not. Regards, Keith Armstrong. PS: It will be another week before I can reply again to postings in this thread. In a message dated 07/01/02 02:46:46 GMT Standard Time, ken.ja...@emccompliance.com writes: Subj:Re: EMC-related safety issues Date:07/01/02 02:46:46 GMT Standard Time From:ken.ja...@emccompliance.com (Ken Javor) Sender:owner-emc-p...@majordomo.ieee.org Reply-to: A HREF=mailto:ken.ja...@emccompliance.com;ken.ja...@emccompliance.com/A (Ken Javor) To:cherryclo...@aol.com CC:emc-p...@majordomo.ieee.org QUOTE: And I don't think that 92dBuV/m is a high field strength to be emitted by a PC placed nearby, or for a non-compliant laptop at 10 metres. You may not think so, but I am sorry, the numbers just don't add up. 92 dBuV/m at 10 meters implies an effective radiated power of 5.3 mW. Consider that the source is not an intentional antenna. It will have no more directivity than a dipole and its efficiency will be much less since it isn't matched to the source. If we simply assume no gain (meaning matching losses just offset directivity) , that means 5.3 mW of rf power are emitted from the EUT or its attached cables. If one makes the reasonable assumption that it is common mode rf current which is radiating, then the potential associated with rf power will be a small number of millivolts (in the frequency domain). This in turn implies a significant fraction of an Ampere of common mode rf current. A highly unlikely situation! Once again, with an impossible conclusion, either the assumption or the logic must be wrong. You can choose to disbelieve, but please point out where the logic has gone awry. You have several times cited Mr. Woodgate for non-constructive criticism. Now I am asking you, don't give more hearsay: explain where my physics is incorrect. We are engineers here, not pollsters. And if you are saying that specification level compliance at 10 meters can scale up to 92 dBuV/m nearby, that is either false or misleading depending on the frequency range. At the low end, say 30 MHz, the area subtended by position near the offending PC isn't large enough to efficiently radiate or couple the field (the wavelength is 10 meters, and the other gentleman's antenna factor calculation assumed a tuned dipole antenna in order to get a small antenna factor). So the field will not scale up as per your prediction, and the pickup mechanism will be nowhere near the antenna factor that gentleman calculated. In fact at 30 MHz your antenna factor will be on the order of 20 dB or worse (assuming the mutual coupling length to be 1 m). At the high end (near 1 GHz) you could be in the far field in close and the field could scale up to a value of 92 dBuV/m, but the antenna factor of a matched tuned dipole at 1 GHz is 26 dB so the potential from that perfect antenna is 92 dBuV/m - 26 dB/m = 66 dBuV or 2 mV. If you consider that any signal with information content carried by 2 mV is shielded, the issue becomes, once again, a non-problem. on 1/6/02 10:43 AM,
Re: EMC-related safety issues
Dear John Sorry to have taken so long to reply. We were talking about safety-related systems. The general approach is to add additional back-ups to the safety related system to provide it with necessary reliability as far as safety is concerned, as I had hoped the examples in the full version of my original reply would help to make clear. Such reliability improvement exercises might have nothing to do with improving the EMC of a product or of making its functionality more reliable. Safety engineers are not usually concerned about whether a product is reliable, merely that if it fails to function correctly (e.g. due to interference) then it should not become unsafe. Another example that does not involve a dual (or triple) electronic system with voting is a gas boiler control. These days, large commercial and industrial gas boilers are controlled by microprocessors taking inputs from a lot of sensors. We don't want to add to the cost by duplicating the electronic control systems and transducers using diverse technologies - as you so rightly pointed should be done to avoid what are known as 'common-cause failures'. So what we can do is use some good old fashioned engineering to ensure that if the controller goes haywire, the boiler shuts down safely. For instance, we can use a simple and well-understood type of gas valve that cuts the gas supply off if the flame goes out. No electronics, nothing to interfere with, but it stops the microprocessor from erroneously pumping out gas when the flame isn't lit because (for instance) someone is standing too near by talking on their cellphone. If the microprocessor turns the flame up too high for too long and the boiler could overheat, our old friends the pressure relief valve and thermal trip come to the rescue. By using these additional components (and considering a few more failure scenarios) we can use an unreliable and cheap microprocessor with terrible EMC immunity performance and yet have great safety performance. The reliability of the system might be poor, and customers might be always complaining about their boilers cutting out, but as I said safety engineers (and safety test labs) don't care if you have a poor product that nobody will be pleased with, as long as it is safe. The mistake that many people make is to confuse functional reliability (sometimes called availability or uptime, the reciprocal of downtime) with functional safety. A very unreliable and low-cost system can be a perfectly safe one, with appropriate design techniques. Regards, Keith Armstrong PS: It will be another week before I can reply again to postings in this thread. In a message dated 06/01/02 19:34:49 GMT Standard Time, j...@jmwa.demon.co.uk writes: Subj:Re: EMC-related safety issues Date:06/01/02 19:34:49 GMT Standard Time From:j...@jmwa.demon.co.uk (John Woodgate) Sender:owner-emc-p...@majordomo.ieee.org Reply-to: A HREF=mailto:j...@jmwa.demon.co.uk;j...@jmwa.demon.co.uk/A (John Woodgate) To:emc-p...@majordomo.ieee.org I read in !emc-pstc that cherryclo...@aol.com wrote (in 162.6b92ca5.296 9c...@aol.com) about 'EMC-related safety issues', on Sun, 6 Jan 2002: Yes, John, you are quite right in both your comments as far as you go: 1) You are not the only person who can dramatise an issue so as to encourage people to debate it; I don't know what you are referring to. I have 146 articles already read in the thread: I don't see that the debate needs any encouragement. 2) If you sold a single electronic safety-related circuit with a failure probability of 10^ -9 to 100,000 customers the cumulative failure probability is indeed 10^ -4. As you correctly said, Olber's Paradox does not apply in this area. But nevertheless this does not mean we need to make electronic circuits with failure rates equal to or better than 10^ -9. As you have said (and I agree) this would be a very difficult task indeed and likely to be very expensive, especially for any product using software. So how do we square this particular circle? Those members who are familiar with safety engineering techniques will be familiar with the idea of building very reliable systems up using a number of independent systems or devices each with lower reliability. These have various names, such as 'redundant channels' or 'duplicate channels' or 'safety back-ups' or 'fail-safe circuits' and many others. I don't see how this applies to the reduction of emissions or, practicably, to the improvement of immunity. Do you envisage three separate systems in every product, with majority voting? I suspect that in terms of improving immunity, it would be ineffective, because a disturbance that compromised one system would be very likely to compromise at least one other. Consider you incubator, for example. -- Regards, John
Re: EMC-related safety issues
Dear John Sorry to have taken so long to reply. We will have to disagree over the educational value of the EMC + Compliance Journal's Banana Skins column. If you haven't seen anything that was CE marked but which was obviously not compliant, then I think you must be lucky. As I mentioned earlier, whenever EMC enforcers in the EU carry out random checks on products in the marketplace, they seem to find that around 30% are clearly not compliant (a broad-brush average, since it seems to depend on the type of product), and there have been some papers presented by such enforcers in recent years for which I will be pleased to provide such references as I have. Your 'unfoggy' replacement statement was good, but only relevant to carefully limited circumstances. I notice you included the lines: ...are extremely unlikely to cause malfunction of other equipment having the degree of immunity afforded by normal design practices. – but could you please define exactly what you mean by extremely unlikely, malfunction and normal design practices. It seems to me that in the end, your improved alternative statement still needs to use foggy' language after all. I am pleased that you agree with me that the debate in question – (which I seem to remember concerned whether unintentional emitters that are compliant with emissions standards when measured at 10 metres can interfere with electronic circuits which are not intentional radio receivers) – cannot be answered with a definitive yes or no. Everyone other than a single correspondent to this thread seem to have difficulty in accepting this basic and scientifically correct statement. As for the assertion that : Doctors and surgeons kill people one at a time, but engineers do it by the thousand. - consider that in the EU in the mid-90's there were around 30,000 fires caused by failures in washing machines every year, a proportion of which resulted in property damage and a few end in deaths. An engineer who designs a faulty consumer product or vehicle can put thousands of lives at risk. Ask Ford and Firestone about the deaths (and the cost to their companies) of their recent engineering error in fitting the Ford Explorer with Firestone Wilderness tyres (maybe that should be tires). Maybe a more accurate statement (if a little foggier) would be Doctors and surgeons kill people one at a time, but some engineers could do it by the thousand. Regards, Keith Armstrong PS: It will be another week before I can reply again to postings in this thread. In a message dated 06/01/02 19:34:57 GMT Standard Time, j...@jmwa.demon.co.uk writes: Subj:Re: EMC-related safety issues Date:06/01/02 19:34:57 GMT Standard Time From:j...@jmwa.demon.co.uk (John Woodgate) Sender:owner-emc-p...@majordomo.ieee.org Reply-to: A HREF=mailto:j...@jmwa.demon.co.uk;j...@jmwa.demon.co.uk/A (John Woodgate) To:emc-p...@majordomo.ieee.org I read in !emc-pstc that cherryclo...@aol.com wrote (in 14b.6d4a617.296 9c...@aol.com) about 'EMC-related safety issues', on Sun, 6 Jan 2002: Dear John The incubator I described was already on the EU market in the latter half of the 1990s, when I helped to test and fix it. And I'm sorry to disappoint Inappropriate word; I'm not interested in scoring debating points but exploring the approaches to 'EMC and Safety', which I think need to be explored. but I have already experienced several similar examples I could quote, such as the electric blanket that would change its heat settings randomly when a bedside light was switched on or off, or from other low-level mains transients. This is a potentially fatal issue for certain kinds of invalid, or people who are blind drunk (surely no person reading this would ever be in such a state) and by the way, this is not me being emotive again, I agree; what you have written here is not emotive. it was the expressed concern of the manufacturer and one of the reasons why they called me in. They sacked their Technical Director over this incident. They also didn't do a product recall despite having an estimated 100,000 products with the problem already out in the field. Of course, as a responsible engineer (and to cover my ass) I wrote them a letter recommending that they did a product recall (while thinking of the designers of the Challenger Space Shuttle's infamous O-ring seals). I find that many independent EMC people have dozens of similar examples, which they can't talk about very much because of commercial confidentiality. This is one reason why the EMC + Compliance Journal (www.compliance-club.com) started its 'Banana Skins' column - to help educate practising engineers about real EMC engineering problems they almost certainly weren't taught about at college and may not (yet) have experienced
Re: EMC-related safety issues
I read in !emc-pstc that Wan Juang Foo f...@np.edu.sg wrote (in of20fd77f8.c4438312-on48256b3b.002ee...@np.edu.sg) about 'EMC-related safety issues', on Tue, 8 Jan 2002: EMI from the ASMD (anti ship missile defence) radar had cause the communication equipment to be inoperable. During this brief period, an Exocet missile was not seen homing in on HMS Sheffield According to a TV documentary the other day, the two systems were on nearly the same frequency, so this was really a case of a clash between military and civilian spectrum usage rather than normal EMC. Note 'usage'; at that time the military had almost carte blanche on spectrum usage, especially in a combat situation. Presumably the Commander (E) should have ditched the satellite link, but the TV documentary said that the surveillance radar lost the echoes from the Super-Etandards flying at zero altitude and the potential threat was not passed on to Commander (E). The moral here is that you ALWAYS give Jack-the-Operator the benefit of the doubt if he says he saw or heard something, whether it's radar or ASDIC. These days, it is at least alleged that there is much better co- ordination between the UK military and the civil authority on spectrum usage. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that Crabb, John jo...@exchange.scotland.ncr.com wrote (in B6CD5947CF30D411A1350050DA4B75FF03C2338C@sgbdun200.scotland.n cr.com) about 'EMC-related safety issues', on Mon, 7 Jan 2002: Any suggestions how to overcome this ? My previous antique datalogger didn't have this problem, but it eventually had to be scrapped due to lack of spare parts - and the expectation that a more modern unit would be better !. AS Gert Gremmen says, this problem is pretty fundamental. Maybe the only solution is to use resistive temperature sensors instead, such as precision thermistors. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
Regarding the snip below. The fact that it is a radio that is the victim is still the salient factor here. The emissions in close to the lamp are higher than at three meters, but only enough higher to affect a radio, nothing else. Regarding the thermocouple based incubator issue (sensitivity on the order of uV). If the sensitivity is truly at the level of uV, then yes this device could respond to lower level emissions, IF the pickup mechanism were of the same efficiency as a radio antenna. If it is not, and they actually took some pains to shield the wiring, then it should have a little more immunity. But I said before, and I don't believe was rebutted on this, that if the device was susceptible at or near CISPR22/FCC limits, then it should never have worked from the get-go, as anyone who has ever made measurements on an OATS would understand. 1/7/02 6:49 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote: Secondly maybe when you wrote the above you weren't thinking of the previous correspondence in this thread about the proximity of the low-energy lamp to a bedside radio. Yes, I know, this concerned a radio receiver, what I mean to draw your attention to is the discussion about the intention and validity of the EMC standards they simply do not cover situations where devices are placed close to each other so they cannot be relied upon to provide compatibility in such situations. Military EMC standards are more thorough in this respect.
RE: EMC-related safety issues
In addition, the junction of any thermocouple is an inherent AC rectifier that is out of control by the designer. Any impedance unbalance between the two thermocouple wires (including the PCB and OPAMP) will cause current to flow in the thermocouple junction and give rise to (large errors) I personally found error from 120 degrees Kelvin at room temperature using thermocouple meters for the process industry. This inherent sensitivity of thermocouples disqualifies most designs for reliability purposes. Gert Gremmen ce-test, qualified testing http://www.cetest.nl -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of cherryclo...@aol.com Sent: maandag 7 januari 2002 12:49 To: ken.ja...@emccompliance.com Cc: emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues Sorry everyone! When I replied yesterday to Ken's posting I didn't spot an error he had made. He had assumed an incubator compliant to 1V/m close to a laptop, whereas the question I originally posed concerned an incubator such as the one I had tested that had full-scale temperature errors at 1V/m from 30 to 1000MHz. So I hope you'll all forgive me if I redo part of my reply. Here goes... Ken said (06/01/02 06:56:46 GMT Standard Time)... Would I feel comfortable placing a CISPR compliant PC next to a medical device qualified to 1 V/m? There is an inherent (not planned) margin of safety here that is many orders of magnitude. The answer is absolutely yes. If there were a problem, I would expect it more to occur below 30 MHz, at the power supply switching frequency, IF the medical device processed extremely low levels of electrical signals and was poorly shielded. But I believe there are separate immunity requirements which cover this eventuality as well. Firstly – my original question concerned how close one would be prepared to place a fully-compliant laptop to the unmodified incubator, which as you will recall I found to give full-scale temperature errors at 1V/m field strengths from 30 to 1000MHz. An incubator that was qualified to 1V/m (as per Ken's reply above) would be at least 28dB less sensitive to RF fields (assuming a square-law relationship for error voltage versus field strength) and would be much more robust. In the EU such medical devices are expected to work properly in fields of at least 3V/m (you can't rely on the CE mark as any guarantee), but I posed the question about the unmodified incubator because I understand that outside of the EU few countries have mandatory immunity regulations. Note that thermocouples have an output of between 3 and 50 uV/degreeC, so if you want to achieve ±0.1C accuracy you are looking to keep error voltages below 0.3 to 5uV. It doesn't take much RF ingress to cause that level of error. Note also that traditional thermocouple amplifier design (such as commonly seen in the 1960s and 1970s, and still lingering on in some products) brings the thermocouple wires straight into an opamp. No shielding, no filtering, and no CMR in the opamp at RF. Worst-case RF demodulation performance is almost a certainty with such a design. Many other 'traditional' transducers using microvolt signal levels used to use amplifiers designed just as badly for EMC, and I sincerely hope there are none of them left any more. Aside: A typical comment from a UK EMC test lab manager (this one from a personal communication in 1998): I was testing a temperature control system for immunity yesterday. As usual, I found that I could get any temperature I wanted simply by varying the RF frequency. Just so you don't think my incubator example was a one-off. Secondly – maybe when you wrote the above you weren't thinking of the previous correspondence in this thread about the proximity of the low-energy lamp to a bedside radio. Yes, I know, this concerned a radio receiver, what I mean to draw your attention to is the discussion about the intention and validity of the EMC standards – they simply do not cover situations where devices are placed close to each other – so they cannot be relied upon to provide compatibility in such situations. Military EMC standards are more thorough in this respect. And as I have already said, commercial EMC standards were not written with safety issues in mind, and most safety standards have not been written with EMC-related issues in mind (see my IEEE 2001 EMC Symposium paper and my longer article in ITEM UPDATE 2001 for details). Regards again, Keith Armstrong In a message dated 06/01/02 15:51:27 GMT Standard Time, cherryclo...@aol.com writes: Subj:Re: EMC-related safety issues Date:06/01/02 15:51:27 GMT Standard Time From:cherryclo...@aol.com Sender:owner-emc-p...@majordomo.ieee.org Reply-to: cherryclo...@aol.com To:ken.ja...@emccompliance.com CC
RE: EMC-related safety issues
Yes, Gert, there is a fine line. The alarm systems standards are written around performance. It would be highly unlikely that the failure of a CCTV camera to comply with the increased immunity standards would create a physical hazard from the camera itself. Rather, failure of the camera to perform as intented might result in an hazard caused by external conditions that occur undetected (e.g., fire, robbery, intrusion, etc). Richard Woods Sensormatic Electronics Tyco International -Original Message- From: CE-TEST [mailto:cet...@cetest.nl] Sent: Monday, January 07, 2002 9:13 AM To: richwo...@tycoint.com; emc-p...@majordomo.ieee.org Subject: RE: EMC-related safety issues Hi Richard, Group I agree that those requirements look safety related, but they are strictly functional. The difference is subtle: As this standard is concerned with equipment used for safety purposes, the requirements are thus safety related in THAT sense, but not in the sense of equipment's safety or safety risks CAUSED by using the equipment. These are not considered, althouigh testin according to EN 50130 may contribute to increased product safety. Most safety topics can be found in LVD related standards, such as EN 60730 (not for EN 50130 equipment). Many LVD standards are not very elaborate about EM Safety, and directly point to a deviation of the Generic standards. I might say that EM and safety of equipment is an area that is completely unexplored. (i do not use the abbreviation EMC as this topic is not about compatibility. I should use EMS (afety) but this abbreviation has already been taken...) Gert Gremmen -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of richwo...@tycoint.com Sent: maandag 7 januari 2002 14:13 To: emc-p...@majordomo.ieee.org Subject: RE: EMC-related safety issues John, I have to disagree with your statement, As far as CENELEC is concerned, it was a conscious decision not to incorporate 'EMC and Safety' issues into EMC standards, but to treat it as a separate subject. If this is true, how do you explain the fact that the Alarm Systems immunity standard EN 50130-4 requires a higher immunity levels and that, per clause 6, the acceptance criteria is per the requirements of a CENELEC performance standard if it is published - e.g. EN 50132-2-1 (CCTV cameras), EN50132-4-1 (Access Control). This certainly appears to be safety related. Richard Woods Sensormatic Electronics Tyco International -Original Message- From: John Woodgate [mailto:j...@jmwa.demon.co.uk] Sent: Friday, January 04, 2002 11:49 AM To: emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues I read in !emc-pstc that cherryclo...@aol.com wrote (in 167.698dddc.296 70...@aol.com) about 'EMC-related safety issues', on Fri, 4 Jan 2002: As my paper at the IEEE's EMC Symposium in Montreal and my recent article in ITEM UPDATE 2001 show - at present EMC standards don't address safety issues, and most safety standards don't address EMC-related functional safety issues. As far as CENELEC is concerned, it was a conscious decision not to incorporate 'EMC and Safety' issues into EMC standards, but to treat it as a separate subject. Some people may find a clarification helpful. We have EMC matters, concerned with compatibility between items of equipment, ensuring that they continue to work (Criterion A in the Generic Standards) or fail gracefully (Criteria B and C). These criteria do not address safety issues, as indicated in paragraph 1 above. However, the Generic Standards do have a limited 'blanket' requirement, that equipment must not become unsafe *during testing*. We also have safety matters per se, which don't involve EMC. We ALSO have the separate subject, called 'EMC and Safety' or reasonable variants thereof. This addresses the matter of equipment becoming unsafe *in service* due to excessive emission levels in the environment, or lack of sufficient immunity to acceptable emission levels. So far, this seems perfectly reasonable. BUT it stops seeming reasonable when the question 'What could go wrong?' is asked and statistical data is used to attempt to answer it. To take a very simple example (maybe over-simplified), we might say that the probability of an unsafe occurrence should be less than 10^-9. That immediately means that the designer of the equipment has to look at ALL risk scenarios down to the billion-to-one against level of probability. To say that that is difficult is surely a great understatement. But some experts in the field seem to ignore that great difficulty, and simply (or maybe not so simply) state that if the designer fails to take into account ANY scenario that subsequently results in an unsafe condition, the designer has failed in his professional responsibility, and may be held criminally responsible for negligence. Well, let us be very circumspect designers and look at what immunity levels
RE: EMC-related safety issues
Hi Richard, Group I agree that those requirements look safety related, but they are strictly functional. The difference is subtle: As this standard is concerned with equipment used for safety purposes, the requirements are thus safety related in THAT sense, but not in the sense of equipment's safety or safety risks CAUSED by using the equipment. These are not considered, althouigh testin according to EN 50130 may contribute to increased product safety. Most safety topics can be found in LVD related standards, such as EN 60730 (not for EN 50130 equipment). Many LVD standards are not very elaborate about EM Safety, and directly point to a deviation of the Generic standards. I might say that EM and safety of equipment is an area that is completely unexplored. (i do not use the abbreviation EMC as this topic is not about compatibility. I should use EMS (afety) but this abbreviation has already been taken...) Gert Gremmen -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of richwo...@tycoint.com Sent: maandag 7 januari 2002 14:13 To: emc-p...@majordomo.ieee.org Subject: RE: EMC-related safety issues John, I have to disagree with your statement, As far as CENELEC is concerned, it was a conscious decision not to incorporate 'EMC and Safety' issues into EMC standards, but to treat it as a separate subject. If this is true, how do you explain the fact that the Alarm Systems immunity standard EN 50130-4 requires a higher immunity levels and that, per clause 6, the acceptance criteria is per the requirements of a CENELEC performance standard if it is published - e.g. EN 50132-2-1 (CCTV cameras), EN50132-4-1 (Access Control). This certainly appears to be safety related. Richard Woods Sensormatic Electronics Tyco International -Original Message- From: John Woodgate [mailto:j...@jmwa.demon.co.uk] Sent: Friday, January 04, 2002 11:49 AM To: emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues I read in !emc-pstc that cherryclo...@aol.com wrote (in 167.698dddc.296 70...@aol.com) about 'EMC-related safety issues', on Fri, 4 Jan 2002: As my paper at the IEEE's EMC Symposium in Montreal and my recent article in ITEM UPDATE 2001 show - at present EMC standards don't address safety issues, and most safety standards don't address EMC-related functional safety issues. As far as CENELEC is concerned, it was a conscious decision not to incorporate 'EMC and Safety' issues into EMC standards, but to treat it as a separate subject. Some people may find a clarification helpful. We have EMC matters, concerned with compatibility between items of equipment, ensuring that they continue to work (Criterion A in the Generic Standards) or fail gracefully (Criteria B and C). These criteria do not address safety issues, as indicated in paragraph 1 above. However, the Generic Standards do have a limited 'blanket' requirement, that equipment must not become unsafe *during testing*. We also have safety matters per se, which don't involve EMC. We ALSO have the separate subject, called 'EMC and Safety' or reasonable variants thereof. This addresses the matter of equipment becoming unsafe *in service* due to excessive emission levels in the environment, or lack of sufficient immunity to acceptable emission levels. So far, this seems perfectly reasonable. BUT it stops seeming reasonable when the question 'What could go wrong?' is asked and statistical data is used to attempt to answer it. To take a very simple example (maybe over-simplified), we might say that the probability of an unsafe occurrence should be less than 10^-9. That immediately means that the designer of the equipment has to look at ALL risk scenarios down to the billion-to-one against level of probability. To say that that is difficult is surely a great understatement. But some experts in the field seem to ignore that great difficulty, and simply (or maybe not so simply) state that if the designer fails to take into account ANY scenario that subsequently results in an unsafe condition, the designer has failed in his professional responsibility, and may be held criminally responsible for negligence. Well, let us be very circumspect designers and look at what immunity levels we might need to get down to that 10^-9 probability. For radiated emissions, the necessary test levels seem to be of the order of 100 V/m. Test levels for other disturbances seem to be equally distantly related to the levels normally experienced and to the test levels in pure EMC standards. We might conclude that assessment of EMC immunity per se is completely unnecessary, because testing for 'EMC and Safety' requires test levels of the order of 30 dB higher! One could go, with the sort of reasoning advocated by some experts, further into the realms of fantasy. Suppose, for a particular piece of equipment, the designer, with great diligence, identifies a million threat scenarios
Re: EMC-related safety issues
I read in !emc-pstc that richwo...@tycoint.com wrote (in 846BF526A205F8 4BA2B6045BBF7E9A6ABC4FEA@flbocexu05) about 'EMC-related safety issues', on Mon, 7 Jan 2002: John, I have to disagree with your statement, As far as CENELEC is concerned, it was a conscious decision not to incorporate 'EMC and Safety' issues into EMC standards, but to treat it as a separate subject. If this is true, how do you explain the fact that the Alarm Systems immunity standard EN 50130-4 requires a higher immunity levels and that, per clause 6, the acceptance criteria is per the requirements of a CENELEC performance standard if it is published - e.g. EN 50132-2-1 (CCTV cameras), EN50132-4-1 (Access Control). This certainly appears to be safety related. I was referring to the Generic and Basic Standards. But the cases you cite are related to *false alarms* or the opposite, i.e. purely system malfunction. Insofar as the standards apply to fire alarms and/or social alarms, safety-of-life is a consequent issue. AFAIK, none of those more stringent limits was determined according to the principles specified in IEC61508. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that Ken Javor ken.ja...@emccompliance.com wrote (in b85e7016.c59%ken.ja...@emccompliance.com) about 'EMC-related safety issues', on Sun, 6 Jan 2002: Quote : Who would have expected an unterminated HCMOS gate to be able to emit 2W at 200MHz? Not me - 2 Watts of effective radiated power implies over 2.5 V/m at 3 m! I guess I have a hard time believing that was transmitted from an HCMOS gate. I think a little common sense will go a long way towards retiring some of these EMC-urban legends. on 1/6/02 10:40 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote: A.2) A portable computing device used in an automatic change machine on board transport was tested to be fully compliant with EN 55022 (approx = CISPR 22). I helped the manufacturer investigate complaints of interference and discovered that sub-fitted variant, which had not been tested for EMC compliance, left an HCMOS inverter IC with an unterminated inverter - which promptly decided to self-oscillate at 200MHz. (Many manufacturers of products with a number of build variants only test the fully-loaded one for EMCD compliance and assume the others are at least as good.) The very interesting thing about this example is that the power-ground structure of the PCB made a beautifully tuned antenna and resonant circuit at 200MHz, so although the inverter was hard-switching and did not run hot, the only emissions were at the 200MHz fundamental - no harmonics were emitted at all. Another very interesting thing is that some of the complainants had measured the equivalent radiated RF power from these devices as 2W. Who would have expected an unterminated HCMOS gate to be able to emit 2W at 200MHz? Indeed, and assuming a 5 V supply, the current would be around 400 mA. At 200 MHz, the dissipation would be several hundred milliwatts. The absence of harmonics even suggests that this gate was producing a sine-wave, which makes the figures even higher and less credible. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
Quote : Who would have expected an unterminated HCMOS gate to be able to emit 2W at 200MHz? Not me - 2 Watts of effective radiated power implies over 2.5 V/m at 3 m! I guess I have a hard time believing that was transmitted from an HCMOS gate. I think a little common sense will go a long way towards retiring some of these EMC-urban legends. on 1/6/02 10:40 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote: A.2) A portable computing device used in an automatic change machine on board transport was tested to be fully compliant with EN 55022 (approx = CISPR 22). I helped the manufacturer investigate complaints of interference and discovered that sub-fitted variant, which had not been tested for EMC compliance, left an HCMOS inverter IC with an unterminated inverter - which promptly decided to self-oscillate at 200MHz. (Many manufacturers of products with a number of build variants only test the fully-loaded one for EMCD compliance and assume the others are at least as good.) The very interesting thing about this example is that the power-ground structure of the PCB made a beautifully tuned antenna and resonant circuit at 200MHz, so although the inverter was hard-switching and did not run hot, the only emissions were at the 200MHz fundamental - no harmonics were emitted at all. Another very interesting thing is that some of the complainants had measured the equivalent radiated RF power from these devices as 2W. Who would have expected an unterminated HCMOS gate to be able to emit 2W at 200MHz?
Re: EMC-related safety issues
QUOTE: And I don't think that 92dBuV/m is a high field strength to be emitted by a PC placed nearby, or for a non-compliant laptop at 10 metres. You may not think so, but I am sorry, the numbers just don't add up. 92 dBuV/m at 10 meters implies an effective radiated power of 5.3 mW. Consider that the source is not an intentional antenna. It will have no more directivity than a dipole and its efficiency will be much less since it isn't matched to the source. If we simply assume no gain (meaning matching losses just offset directivity) , that means 5.3 mW of rf power are emitted from the EUT or its attached cables. If one makes the reasonable assumption that it is common mode rf current which is radiating, then the potential associated with rf power will be a small number of millivolts (in the frequency domain). This in turn implies a significant fraction of an Ampere of common mode rf current. A highly unlikely situation! Once again, with an impossible conclusion, either the assumption or the logic must be wrong. You can choose to disbelieve, but please point out where the logic has gone awry. You have several times cited Mr. Woodgate for non-constructive criticism. Now I am asking you, don't give more hearsay: explain where my physics is incorrect. We are engineers here, not pollsters. And if you are saying that specification level compliance at 10 meters can scale up to 92 dBuV/m nearby, that is either false or misleading depending on the frequency range. At the low end, say 30 MHz, the area subtended by position near the offending PC isn't large enough to efficiently radiate or couple the field (the wavelength is 10 meters, and the other gentleman's antenna factor calculation assumed a tuned dipole antenna in order to get a small antenna factor). So the field will not scale up as per your prediction, and the pickup mechanism will be nowhere near the antenna factor that gentleman calculated. In fact at 30 MHz your antenna factor will be on the order of 20 dB or worse (assuming the mutual coupling length to be 1 m). At the high end (near 1 GHz) you could be in the far field in close and the field could scale up to a value of 92 dBuV/m, but the antenna factor of a matched tuned dipole at 1 GHz is 26 dB so the potential from that perfect antenna is 92 dBuV/m - 26 dB/m = 66 dBuV or 2 mV. If you consider that any signal with information content carried by 2 mV is shielded, the issue becomes, once again, a non-problem. on 1/6/02 10:43 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote: Snip: And I don't think that 92dBuV/m is a high field strength to be emitted by a PC placed nearby, or for a non-compliant laptop at 10 metres.
Re: EMC-related safety issues
The question of ethics or morality is at the heart of this discussion which makes it much more important than technical discussions about electromagnetism, which is the ONLY reason I have pursued this so far. I was critical of the IEE safety guide on MORAL grounds. It is part of the morality which says that businessmen or producers are considered guilty until proven innocent because of what they are - profit-making producers. That it is immoral to make a profit and anyone doing so is taking advantage of someone else. This is not the morality which built the USA into the world's wealthiest nation, but it is the morality which will reduce us to the most impecunious. The strict Muslim countries that have been in the news of late forbid loaning of money at interest, because the Koran forbids usury. It is no accident that these countries all belong to the third world. Progress depends on the ability to raise capital. The most efficient way to do that is for people who have profited from past ventures to invest those profits in new ventures. That is what banks facilitate. If there are no profits, then there is no money to borrow and to start a venture and progress stops or becomes agonizingly slow. A policy which says that producers are liable for unlimited damages without needing to show defect or negligence is on a moral level with the prohibition of lending money at interest. We have to decide if we wish to live in a civilized world or not. That is a question of moral significance. The idea that businessmen are immoral greedy people who give no thought to the quality of their products is an ugly lie spread by enemies of capitalism. A little thought will show that businessmen who operate like this do not stay in business long because their products get a bad reputation. Certainly you can find examples of bad or ignorant behavior. Does this justify policies which assume all businessmen are evil and that they must be reined in by pure-hearted regulators? What makes the regulators pure-hearted? That they don't make profit, but siphon profits away? What is the cost of the regulation relative to the benefit? What marvelous inventions didn't occur because the seed money necessary to initiate a development wasn't there? When engineers make false claims that unintentional RE from ITE can cause safety-critical circuits to fail catastrophically, we engage in another moral transgression. We attempt to get a short term gain at the cost of long term loss. The short term gain is to make ourselves and our profession look more important. But the long term loss is that of the little boy who cried wolf. After a long enough period of false alarms, we will lose the respect and ear of management and if we must raise a REAL issue, it will fall on deaf ears. I have no way of knowing, but I wonder how many unfulfilled warnings the managers who OK'd the launch of 51L (Challenger) had listened to prior to making their fateful decision. on 1/6/02 10:24 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote: Dear John The incubator I described was already on the EU market in the latter half of the 1990s, when I helped to test and fix it. And I'm sorry to disappoint but I have already experienced several similar examples I could quote, such as the electric blanket that would change its heat settings randomly when a bedside light was switched on or off, or from other low-level mains transients. This is a potentially fatal issue for certain kinds of invalid, or people who are blind drunk (surely no person reading this would ever be in such a state) and by the way, this is not me being emotive again, it was the expressed concern of the manufacturer and one of the reasons why they called me in. They sacked their Technical Director over this incident. They also didn't do a product recall despite having an estimated 100,000 products with the problem already out in the field. Of course, as a responsible engineer (and to cover my ass) I wrote them a letter recommending that they did a product recall (while thinking of the designers of the Challenger Space Shuttle's infamous O-ring seals). I find that many independent EMC people have dozens of similar examples, which they can't talk about very much because of commercial confidentiality.. This is one reason why the EMC + Compliance Journal (www.compliance-club.com) started its 'Banana Skins' column - to help educate practising engineers about real EMC engineering problems they almost certainly weren't taught about at college and may not (yet) have experienced for themselves. I also have personal experience of a UK company that in the late 90's was selling a range of over 110 CE-marked products (such as incubators) intended for medical and chemical laboratories although less than 10% of their products met both the EMCD and the LVD. The company in question had just been purchased by another, which is why I was involved. Interestingly, the new owners continued to
Re: EMC-related safety issues
I abstracted the physical process and did not attach numbers. 80 dBuV/m is orders of magnitude above RE limits. That is 10 mV/m.If you use the worst case assumptions of IEC 1000-4-6 and associate an open circuit drive potential numerically equivalent to the field intensity, but with a 150 Ohm source impedance, then you would have 10 mV driving current from a 150 Ohm source. If you assume the impedance (not transfer impedance) of the shield to be a dead short, then 10 mV will cause 67 uA to flow on the shield. If shield transfer impedance were 100 milliohms (pretty high, especially at frequencies where an op-amp might respond) you would get 6.7 uV induced common mode on the circuit. Assuming no CMR, this is the potential that is added to the intentional signal. That can affect a radio front-end, but not an op-amp. Once again, unintentional RE from ITE, even at unsuppressed levels, do not cause interference to other non-antenna connected electronics. on 1/6/02 10:28 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote: Ken, can we take it that in the posting below you are agreeing that interference with non radio-receiving circuits from what you meant by unintentional emitters is a possibility, albeit a worst-case one? If my reading above is correct, how can you then go on to say that ...unintentional emissions from ITE can only upset a radio receiver tuned to the emission frequency. It seems to me that the words can only in the your quote above should be replaced by are most likely to, which I would agree with. Regards, Keith Armstrong In a message dated 06/01/02 06:56:07 GMT Standard Time, ken.ja...@emccompliance.com writes: Subj:Re: EMC-related safety issues List-Post: emc-pstc@listserv.ieee.org Date:06/01/02 06:56:07 GMT Standard Time From:ken.ja...@emccompliance.com (Ken Javor) To:t...@tncokenias.org (Tom Cokenias), cherryclo...@aol.com, emc-p...@majordomo.ieee.org The analytical portion of this post is, as the author stated, worst case. A cable attached to a susceptible circuit picks up a common-mode potential, which most likely drives a current on a shield if the the circuit is sensitive. Then only the current multiplied by shield transfer impedance actually gets into the victim, assuming no CMR. Which just makes my original point - unintentional emissions from ITE can only upset a radio receiver tuned to the emission frequency. That is why, as another contributor posted, we use EMI receivers and spectrum analyzers with preamps to make OATS measurements. on 1/4/02 12:51 PM, Tom Cokenias at t...@tncokenias.org wrote: At 8:34 AM -0500 1/4/2002, Keith Armstrong wrote: Does anyone else think that ordinary semiconductors doesn't respond to RF? I agree that commonly used semiconductors have responses well into the 100's of MHz. How much of a problem this is will depend on the nature and function of the circuitry using these components. The EUT wires, cables, pcb traces etc. act like antennae, on which the incident field voltages and currents. An antenna factor can be thought of as ratio of the field strength to the voltage induced on the terminated cable connected to the antenna. In an impedance matched system, AF=9.734/lamda*(G)^0.5, lamda being wavelength in meters, G being antenna gain over isotropic, or in dB AF dB = - G dBi -29.7 dB + 20logFMHz Assuming G is 1 (isotropic antenna), AF is 1 (= 0 dB) at about 30.8 MHz, and AF get larger as frequency increases, to a factor of 32.7 (= 30.3 dB) at 1 GHz . Since AF is field strength divided by induced voltage, the voltage induced on the trace goes down as frequency goes up for the same incident field strength. An effective receive antenna needs to be on the order of 1/2 wavelength or so; for 30 MHz this is 15m, for 1000 MHz this is 15 cm. So if a victim EUT circuit has a pretty effective receive antenna, and does not have any filtering and is equally sensitive across the frequency range under consideration (all taken together, a worst case scenario for susceptibility), (1) A 10 V/m field will theoretically induce a voltage 0.33V to 10V, depending on frequency (2) A 5000 uV/m field (10x the FCC class B limit above 960 MHz) will theoretically induce a voltage from 152 uV to 5 mV, depending on frequency. (3) A 500 uV/m field will theoretically induce a voltage from 15 uV to 500 uV depending on frequency. These are first order approximations, but they are useful in determining the level of the potential EMI threat. For instance a 4-30 mA sensor circuit using high gain operational amps will most likely be interfered with in scenario (1), there may be some susceptibility detected in scenario (2), and most likely no problem encountered with scenario (3). A sensitive all - band AM communications receiver will have problems with all three, a broadcast TV operating in a strong signal area will probably be OK with scenario 3
Re: EMC-related safety issues
I read in !emc-pstc that cherryclo...@aol.com wrote (in 14b.6d4a617.296 9c...@aol.com) about 'EMC-related safety issues', on Sun, 6 Jan 2002: Dear John The incubator I described was already on the EU market in the latter half of the 1990s, when I helped to test and fix it. And I'm sorry to disappoint Inappropriate word; I'm not interested in scoring debating points but exploring the approaches to 'EMC and Safety', which I think need to be explored. but I have already experienced several similar examples I could quote, such as the electric blanket that would change its heat settings randomly when a bedside light was switched on or off, or from other low-level mains transients. This is a potentially fatal issue for certain kinds of invalid, or people who are blind drunk (surely no person reading this would ever be in such a state) and by the way, this is not me being emotive again, I agree; what you have written here is not emotive. it was the expressed concern of the manufacturer and one of the reasons why they called me in. They sacked their Technical Director over this incident. They also didn't do a product recall despite having an estimated 100,000 products with the problem already out in the field. Of course, as a responsible engineer (and to cover my ass) I wrote them a letter recommending that they did a product recall (while thinking of the designers of the Challenger Space Shuttle's infamous O-ring seals). I find that many independent EMC people have dozens of similar examples, which they can't talk about very much because of commercial confidentiality. This is one reason why the EMC + Compliance Journal (www.compliance-club.com) started its 'Banana Skins' column - to help educate practising engineers about real EMC engineering problems they almost certainly weren't taught about at college and may not (yet) have experienced for themselves. But, by its nature, it tends to report very low-probability occurrences and/or anecdotes, which are probably not very effective as training examples. I also have personal experience of a UK company that in the late 90's was selling a range of over 110 CE-marked products (such as incubators) intended for medical and chemical laboratories although less than 10% of their products met both the EMCD and the LVD. The company in question had just been purchased by another, which is why I was involved. Interestingly, the new owners continued to sell the non-compliant products while they re-engineered them one at a time to be compliant (which took several years). My simple investigations over a number of years into a number of companies' CE marked products have led me to be very cynical. As a rule of thumb I guess that around 30% of CE marked products are non-compliant with EMC or LVD, with another 30% being borderline cases. This seems to be borne out by recent enforcement surveys in Finland and in the UK and published articles from some test labs. You experiences are certainly a great deal worse than mine. I do find quite a few 'compliance failures' i.e. things like incorrect labelling or items omitted from instruction books, but few real hazards. I have found many products that were submitted for pre-compliance EMC assessment that would never pass unless completely redesigned, but I haven't (yet) seen anything CE marked that obviously fails. Changing to another of your criticisms below... If you think my proposed statement is fog-filled, what do you propose instead? Lets have constructive criticism instead of merely criticism. There are many possible statements that could be made on the subject, but here is one: 'Conducted and radiated emissions from equipment which does not include any one of: - switching of voltages above 10 V and currents above 100 mA; - generation of radio-frequency (150 kHz to 400 GHz) voltages above 100 mV; - power consumption greater than 75 W are extremely unlikely to cause malfunction of other equipment having the degree of immunity afforded by normal design practices.' This is the sort of statement/guideline that can be used by a designer or compliance engineer to determine what testing, if any, is necessary. In fact, in most scientific or engineering activities, one can only make public statements using foggy words like 'generally'. See above. Remember the UK government's teams of scientific advisors and their pronouncements on BSE and the foot and mouth epidemic? Would you have expected them to produce precise and accurate predictions? I am of the opinion that the outbreak of foot and mouth disease in the UK was better understood, had fewer variables, and could be better controlled than many real-life EMC-related safety engineering problems. I
Re: EMC-related safety issues
Ken, I believe other postings on this topic this weekend clearly show that electronic circuits which were not designed as radio receivers can possibly be interfered with by the emissions from products which meet FCC/CISPR 22 limits, for a number of possible reasons, especially when the product is closer than 10 metres to the source of the emissions. Certain kinds of transducers and their amplifiers appear to be particularly at risk because of the low levels of their transducer signals. Regards, Keith Armstrong In a message dated 06/01/02 06:56:28 GMT Standard Time, ken.ja...@emccompliance.com writes: Subj:Re: EMC-related safety issues Date:06/01/02 06:56:28 GMT Standard Time From:ken.ja...@emccompliance.com (Ken Javor) To:cherryclo...@aol.com CC:emc-p...@majordomo.ieee.org My point was that only radios are sensitive to rf fields at the levels controlled by FCC/CISPR22 and indeed, as Ing. Gremen pointed out, levels well above the limits. Which means that the only rationale behind FCC/CISPR22 is protection of radio broadcast reception. Period. on 1/5/02 12:10 PM, cherryclo...@aol.com at cherryclo...@aol.com wrote: Dear Ken I am truly sorry if I irritated you by misunderstanding your words, but I took your posting to imply that electronic circuits which are not designed as RF receivers would not respond very well to radio frequencies. My example was not intended to be a full answer to your example (there are other postings which are dealing with that) just to indicate that the frequency response of slow and commonplace ICs can be very high indeed. I am sensitive to this issue because I keep on running across electronics designers who say things like: I don't need to worry about the RF immunity of my audio amplifier/motor controller/temperature/pressure/flow/weight/velocity measurement and control system (please delete where applicable) because the opamps I use have a GBW of under 1MHz so they won't see the RF shy; which is of course complete bollocks (a UK phrase that I hope translates well enough for all emc-pstc subscribers). And no, I still don't agree with you that only radio receivers are sensitive enough to RF to have a problem with what you are still calling 'unintentional emissions' (even though this term means very little in an international forum unless you define the relevant standards or laws). I think the problem you are concerned with is application dependant and we cannot make such broad assumptions. As I said earlier, most interference problems are caused by radio transmitters or radio receivers, but not all. Regards, Keith Armstrong In a message dated 05/01/02 01:20:27 GMT Standard Time, ken.ja...@emccompliance.com writes: Subj:Re: EMC-related safety issues Date:05/01/02 01:20:27 GMT Standard Time From:ken.ja...@emccompliance.com (Ken Javor) To:cherryclo...@aol.com, emc-p...@majordomo.ieee.org One sure way to REALLY irritate me is to twist my words and try to make me look stupid (I do a fine job by myself on occasion and don't appreciate any outside help). I did not say that pn junctions don't detect and rectify rf, I said that the field intensities associated with unintentional emissions from ITE are too low to cause susceptibility in circuits other than radios. Your example here is 10 V/m, and you are talking about an op-amp (gain unspecified) and that it was susceptible at that level should be no surprise to anyone. on 1/4/02 7:34 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote: Does anyone else think that ordinary semiconductors doesn't respond to RF? I have tested a product which was little more than an LM324 quad op-amp for RF immunity using IEC 61000-4-3. This op-amp has a slew rate of 1V/micro-second on a good day with the wind in its favour. It was housed in an unshielded plastic enclosure. Demodulated noise that exceeded the (not very tough) product specification were seen all the way up to 500MHz at a number of spot frequencies that appeared to be due to the natural resonances of the input and output cables. Above 500MHz this resonant behaviour vanished to be replaced by a steadily rising level of demodulated 1kHz tone as the frequency increased. I stopped testing at 1GHz, where the output error from the product was about 10% and still rising with increased frequency. OK, the field strength for the test was 10V/m (unmodulated) but the real surprise was how well this very cheap and very slow opamp demodulated the RF, and that it demodulated better at 1GHz than at 500MHz. I have done many many immunity tests using IEC 61000-4-3 on audio equipment and found much the same effects with every product I've ever tested. With most larger products there is usually a roll-off in the demodulation above 500MHz - not because the semiconductors in the ICs can't respond (they can) but
Re: EMC-related safety issues
Taking Toms' calculations a little further Typical thermocouple sensors have output voltages in the range 3 - 50 microvolts per degree C. So to create a 60C error in a thermocouple-based temperature control system (see my recent posting about the RF immunity of a blood sample incubator) all we need is an error voltage in the range 180 microvolts to 3 millivolts. According to Toms' calculations below: (3) A 500 uV/m field will theoretically induce a voltage from 15 uV to 500 uV depending on frequency. Now, 500 microvolts per meter = 54dBmicrovolts/meter which is only 7dB above the CISPR 22 10 metre Class A limit and 17dB above the Class B limit, between 230 and 1000MHz. This implies a fully CISPR 22 compliant laptop PC is capable of generating significant errors (10s of degrees C) in certain kinds of thermocouple measuring and control systems even when the laptop is 10 metres away. If the laptop was closer to the thermocouple system than 10 metres the field strength of its RF emissions will obviously increase. But when it is in the laptop's near field we would expect the 10 metre measurements to be meaningless because there are components of near field emissions which fall off with the cube of the distance and are not detected by 10 metre tests. For example, many products seem to have very quite strong frequency magnetic fields nearby, at audio frequencies and lower, caused by variations in the loading on their DC power supplies. For this and several other reasons I can't agree with the idea that emissions from what are known under some US laws as unintentional radiators cannot possibly cause interference in circuits which are not intentional radio receivers. It seems to me that many types of transducer systems (maybe even the fluxgate magnetometers used in some types of compasses) can be vulnerable. Regards, Keith Armstrong In a message dated 04/01/02 19:03:15 GMT Standard Time, t...@tncokenias.org writes: Subj:Re: EMC-related safety issues Date:04/01/02 19:03:15 GMT Standard Time From:t...@tncokenias.org (Tom Cokenias) Sender:owner-emc-p...@majordomo.ieee.org Reply-to: A HREF=mailto:t...@tncokenias.org;t...@tncokenias.org/A (Tom Cokenias) To:cherryclo...@aol.com, emc-p...@majordomo.ieee.org At 8:34 AM -0500 1/4/2002, Keith Armstrong wrote: Does anyone else think that ordinary semiconductors doesn't respond to RF? I agree that commonly used semiconductors have responses well into the 100's of MHz. How much of a problem this is will depend on the nature and function of the circuitry using these components. The EUT wires, cables, pcb traces etc. act like antennae, on which the incident field voltages and currents. An antenna factor can be thought of as ratio of the field strength to the voltage induced on the terminated cable connected to the antenna. In an impedance matched system, AF=9.734/lamda*(G)^0.5, lamda being wavelength in meters, G being antenna gain over isotropic, or in dB AF dB = - G dBi -29.7 dB + 20logFMHz Assuming G is 1 (isotropic antenna), AF is 1 (= 0 dB) at about 30.8 MHz, and AF get larger as frequency increases, to a factor of 32.7 (= 30.3 dB) at 1 GHz . Since AF is field strength divided by induced voltage, the voltage induced on the trace goes down as frequency goes up for the same incident field strength. An effective receive antenna needs to be on the order of 1/2 wavelength or so; for 30 MHz this is 15m, for 1000 MHz this is 15 cm. So if a victim EUT circuit has a pretty effective receive antenna, and does not have any filtering and is equally sensitive across the frequency range under consideration (all taken together, a worst case scenario for susceptibility), (1) A 10 V/m field will theoretically induce a voltage 0.33V to 10V, depending on frequency (2) A 5000 uV/m field (10x the FCC class B limit above 960 MHz) will theoretically induce a voltage from 152 uV to 5 mV, depending on frequency. (3) A 500 uV/m field will theoretically induce a voltage from 15 uV to 500 uV depending on frequency. These are first order approximations, but they are useful in determining the level of the potential EMI threat. For instance a 4-30 mA sensor circuit using high gain operational amps will most likely be interfered with in scenario (1), there may be some susceptibility detected in scenario (2), and most likely no problem encountered with scenario (3). A sensitive all - band AM communications receiver will have problems with all three, a broadcast TV operating in a strong signal area will probably be OK with scenario 3 but not with 1 or 2. I guess what I'm really trying to say with all this is that EMC is a systems thing, taking into account the nature of the culprit EMI generator, the nature of the victim EMI receiver, and the path between them. Then we have the economics of operating
Re: EMC-related safety issues
Yes, John, you are quite right in both your comments as far as you go: 1) You are not the only person who can dramatise an issue so as to encourage people to debate it; 2) If you sold a single electronic safety-related circuit with a failure probability of 10^ -9 to 100,000 customers the cumulative failure probability is indeed 10^ -4. As you correctly said, Olber's Paradox does not apply in this area. But nevertheless this does not mean we need to make electronic circuits with failure rates equal to or better than 10^ -9. As you have said (and I agree) this would be a very difficult task indeed and likely to be very expensive, especially for any product using software. So how do we square this particular circle? Those members who are familiar with safety engineering techniques will be familiar with the idea of building very reliable systems up using a number of independent systems or devices each with lower reliability. These have various names, such as 'redundant channels' or 'duplicate channels' or 'safety back-ups' or 'fail-safe circuits' and many others. Some examples... I understand that car braking systems have (by law in Europe and North America at least) an independent hydraulic back-up system in case the primary system fails - because it is practically impossible to make the primary system reliable enough at a cost anyone would want to pay. The electronic flight-control systems in modern aircraft have two or three independent hardware 'channels'. Where software is involved they sometimes use three sets of independently-coded software each using architecturally-different operating systems and each running on an architecturally different hardware processor voting 2 out of 3 on every decision/output). I understand that the Space Shuttle launch control system uses 5 independent computers voting on each decision/output. The pressure relief valve on most pressure systems does not have a very high reliability, but when combined with the statistical probability of the system pressure going out of control the whole system is considered to be reliable enough. (Of course, pressure system designers must remember to site the pressure relief valve so that if it operates it doesn't cause a hazard of its own.) Three cheap and cheerful independent circuits, each achieving merely 10^ -3 reliability, can easily be combined together to create a system with 10^ -9 reliability – achieving very high levels of safety at low cost without any heartache in design or heart attacks from management. This is the way that high reliability is normally achieved at reasonable cost in practice (and has been achieved for many many years). IEC 61508 describes (or refers to) the necessary techniques. (PS: My statistical maths is rusty, so don't rely on the above simple calculation for any designs. Refer to IEC 61508 for more detail). Regards, Keith Armstrong In a message dated 05/01/02 21:01:18 GMT Standard Time, j...@jmwa.demon.co.uk writes: Subj:Re: EMC-related safety issues Date:05/01/02 21:01:18 GMT Standard Time From:j...@jmwa.demon.co.uk (John Woodgate) Sender:owner-emc-p...@majordomo.ieee.org Reply-to: A HREF=mailto:j...@jmwa.demon.co.uk;j...@jmwa.demon.co.uk/A (John Woodgate) To:emc-p...@majordomo.ieee.org I read in !emc-pstc that cherryclo...@aol.com wrote (in 43.47bb025.29689...@aol.com) about 'EMC-related safety issues', on Sat, 5 Jan 2002: The one in a billion John refers to sounds very dramatic and difficult. More dramatic than you 'infant daughter' and '40 mph past a school'? I explained in VERY GREAT DETAIL the effect of cumulative probability in requiring very low probability events to be taken into account. In principle, as the probability goes down, the number of risk scenarios increases *combinatorially*. There is no Olber's Paradox in this area, the 'night sky is infinitely brighter than the Sun'! So it may be helpful to refer to IEC 61508 which is a recently-published 'basic safety publication' covering The functional safety of electrical / electronic / programmable safety-related systems IEC 61508 uses the concept of the Safety Integrity Level (or SIL) to help design safety-related systems which have quantified failure probabilities. The SILs for average probability of failure to perform design function on demand are: SIL level 1: up to 10^ -2 SIL level 2: 10^ -2 to 10^ -3 SIL level 3: 10^ -3 to 10^ -4 SIL level 4: 10^ -4 to 10^ -5 or even lower levels The SILs for average probability of dangerous failure per hour of operation are: SIL level 1: up to 10^ -6 SIL level 2: 10^ -6 to 10^ -7 SIL level 3: 10^ -7 to 10^ -8 SIL level 4: 10^ -8 to 10^ -9 or even lower levels The standard describes how to select the SIL level for a particular safety-related application, and we find that SIL4
Re: EMC-related safety issues
A) I don't agree with Ken that: Emissions from a laptop are naturally (without suppression) on the order of 10 uV/m to 100s of uV/m. Maybe IBM PC clone laptops use similar enough architecture and chipsets and design techniques to be this consistent (I don't know) but I have seen the following emissions in portable computing products that would come under the same FCC/EMCD emissions standards as a laptop... A.1) A portable computing device with a large additional RAM array for use by people who had lost the power of speech. They would type the word they wanted to say and it would speak it for them using loudspeakers. This was a product that was sold in the UK without a CE mark at around the time the EMC directive came into force (1996). I only measured its with a 1cm diameter unshielded shorted-turn probe. I am used to seeing levels of around 60 to 100 dBmicrovolts from this probe when it is closer than one inch to typical laptop PCBs, with less than 20 dBmicrovolts at a distance of more than one foot. But with this product I saw over 50 dBmicrovolts at frequencies from 30 to 300MHz when my 1cm loop probe was 4 feet away! Maybe some less mathematically-challenged member of the group would like to work out what the electric field strength could have been measured at 10 metres. I've never seen anything quite as bad as that before or since, but it shows what poor EMC design can achieve in the hands of some designers of computing-related products. (Incidentally, they sold it with a clamp for fixing to wheelchairs - some models of which have already been mentioned in this thread as being known to run amok under certain conditions of RF field.) A.2) A portable computing device used in an automatic change machine on board transport was tested to be fully compliant with EN 55022 (approx = CISPR 22). I helped the manufacturer investigate complaints of interference and discovered that sub-fitted variant, which had not been tested for EMC compliance, left an HCMOS inverter IC with an unterminated inverter - which promptly decided to self-oscillate at 200MHz. (Many manufacturers of products with a number of build variants only test the fully-loaded one for EMCD compliance and assume the others are at least as good.) The very interesting thing about this example is that the power-ground structure of the PCB made a beautifully tuned antenna and resonant circuit at 200MHz, so although the inverter was hard-switching and did not run hot, the only emissions were at the 200MHz fundamental - no harmonics were emitted at all. Another very interesting thing is that some of the complainants had measured the equivalent radiated RF power from these devices as 2W. Who would have expected an unterminated HCMOS gate to be able to emit 2W at 200MHz? Well, now you know that it is possible (if not probable) it becomes something you should think about when designing safety-related systems. A.3) Laptops which are fully compliant with CISPR 22 or the equivalent US regs will have higher field strengths when they are less than 10 metres away. How many of us can guarantee that there is always at least 10 metres between each item of electronic equipment? Another thread to this discussion has discussed the problems of low-energy lamps interfering with bedside radios, and this shows up the difficulties of confusing compliance with standards intended for legal market entry and protection of the radio spectrum with the actual EMC engineering to prevent interference in real applications. Another problem is that when we are in the near field of a product its 10 metre emissions measurements are meaningless. There are components of near field emissions which fall off with the cube of the distance and are not usually detected at all by 10 metre tests. For example I understand that many products have very quite strong frequency magnetic fields nearby, at audio frequencies and lower, caused by variations in the loading on their DC power supplies. A.4) The standard commercial and industrial tests for emissions do not test the full range of possible emissions, since they were only ever intended to protect the radio communication and broadcasting spectrum. Actual electronic devices, especially certain kinds of transducers and their amplifiers, can be very sensitive to frequencies outside said spectrum. Military EMC standards recognise this real-life problem and typically test for emissions down to 100 or even 20Hz. B) I don't agree with Ken that 1000 uV/m would represent at least a 20 dB outage at frequencies that could possibly interfere with sensor electronics. See my other posting today adding to Tom Cokenias's calculations to show that RF field strengths of 500uV/m can easily cause severe errors (tens of degrees C) in some thermocouple temperature measuring systems. Also refer to my recent posting about the significant RF immunity problems experienced with a blood sample
Re: EMC-related safety issues
Ken, can we take it that in the posting below you are agreeing that interference with non radio-receiving circuits from what you meant by unintentional emitters is a possibility, albeit a worst-case one? If my reading above is correct, how can you then go on to say that ...unintentional emissions from ITE can only upset a radio receiver tuned to the emission frequency. It seems to me that the words can only in the your quote above should be replaced by are most likely to, which I would agree with. Regards, Keith Armstrong In a message dated 06/01/02 06:56:07 GMT Standard Time, ken.ja...@emccompliance.com writes: Subj:Re: EMC-related safety issues Date:06/01/02 06:56:07 GMT Standard Time From:ken.ja...@emccompliance.com (Ken Javor) To:t...@tncokenias.org (Tom Cokenias), cherryclo...@aol.com, emc-p...@majordomo.ieee.org The analytical portion of this post is, as the author stated, worst case. A cable attached to a susceptible circuit picks up a common-mode potential, which most likely drives a current on a shield if the the circuit is sensitive. Then only the current multiplied by shield transfer impedance actually gets into the victim, assuming no CMR. Which just makes my original point - unintentional emissions from ITE can only upset a radio receiver tuned to the emission frequency. That is why, as another contributor posted, we use EMI receivers and spectrum analyzers with preamps to make OATS measurements. on 1/4/02 12:51 PM, Tom Cokenias at t...@tncokenias.org wrote: At 8:34 AM -0500 1/4/2002, Keith Armstrong wrote: Does anyone else think that ordinary semiconductors doesn't respond to RF? I agree that commonly used semiconductors have responses well into the 100's of MHz. How much of a problem this is will depend on the nature and function of the circuitry using these components. The EUT wires, cables, pcb traces etc. act like antennae, on which the incident field voltages and currents. An antenna factor can be thought of as ratio of the field strength to the voltage induced on the terminated cable connected to the antenna. In an impedance matched system, AF=9.734/lamda*(G)^0.5, lamda being wavelength in meters, G being antenna gain over isotropic, or in dB AF dB = - G dBi -29.7 dB + 20logFMHz Assuming G is 1 (isotropic antenna), AF is 1 (= 0 dB) at about 30.8 MHz, and AF get larger as frequency increases, to a factor of 32.7 (= 30.3 dB) at 1 GHz . Since AF is field strength divided by induced voltage, the voltage induced on the trace goes down as frequency goes up for the same incident field strength. An effective receive antenna needs to be on the order of 1/2 wavelength or so; for 30 MHz this is 15m, for 1000 MHz this is 15 cm. So if a victim EUT circuit has a pretty effective receive antenna, and does not have any filtering and is equally sensitive across the frequency range under consideration (all taken together, a worst case scenario for susceptibility), (1) A 10 V/m field will theoretically induce a voltage 0.33V to 10V, depending on frequency (2) A 5000 uV/m field (10x the FCC class B limit above 960 MHz) will theoretically induce a voltage from 152 uV to 5 mV, depending on frequency. (3) A 500 uV/m field will theoretically induce a voltage from 15 uV to 500 uV depending on frequency. These are first order approximations, but they are useful in determining the level of the potential EMI threat. For instance a 4-30 mA sensor circuit using high gain operational amps will most likely be interfered with in scenario (1), there may be some susceptibility detected in scenario (2), and most likely no problem encountered with scenario (3). A sensitive all - band AM communications receiver will have problems with all three, a broadcast TV operating in a strong signal area will probably be OK with scenario 3 but not with 1 or 2. I guess what I'm really trying to say with all this is that EMC is a systems thing, taking into account the nature of the culprit EMI generator, the nature of the victim EMI receiver, and the path between them. Then we have the economics of operating different devices in the same vicinity, the politics of who gets how much of what kind of protection, etc., etc. All things considered, we should have jobs for life! best regards and a Happy New Year to all. Tom Cokenias T.N. Cokenias Consulting P.O. Box 1086 El Granada CA 94018 tel 650 726 1263 cell 650 302 0887 fax 650 726 1252
Re: EMC-related safety issues
Dear John In previous postings from Ken Javor and myself, I believe that Ken (who I was replying to in the fragment below) has made it clear that what he is really concerned with is the kinds of emissions controlled by CISPR 22 and Title 47, part 15B of the US Code of Federal Regulations (I hope I have got this right, Ken!). In earlier postings I believe that Ken complained that I was widening the definition to include such things as the unintentional emissions from welding apparatus (I didn't think of your electric fence example). I think John's comments emphasise a point I made earlier in this correspondence, which is that we need to be very careful in an international forum when using terms like unintentional emitter. Such terms can have specific definitions in some EMC standards or Regulations in some countries, but they can also have a wider EMC engineering usage, such as that mentioned by John below. Confusion is possible unless we are more precise. Regards, Keith Armstrong In a message dated 05/01/02 21:01:28 GMT Standard Time, j...@jmwa.demon.co.uk writes: And no, I still don't agree with you that only radio receivers are sensitive enough to RF to have a problem with what you are still calling 'unintentional emissions' (even though this term means very little in an international forum unless you define the relevant standards or laws). I think this term is quite legitimate and well-understood. If the equipment requires to emit in order to perform its intended function, it is an 'intentional emitter'. If it does not need to do so, but emits anyway, it is an 'unintentional emitter'. It is difficult to see how there could be any confusion or ambiguity about this.
Re: EMC-related safety issues
Dear John The incubator I described was already on the EU market in the latter half of the 1990s, when I helped to test and fix it. And I'm sorry to disappoint but I have already experienced several similar examples I could quote, such as the electric blanket that would change its heat settings randomly when a bedside light was switched on or off, or from other low-level mains transients. This is a potentially fatal issue for certain kinds of invalid, or people who are blind drunk (surely no person reading this would ever be in such a state) – and by the way, this is not me being emotive again, it was the expressed concern of the manufacturer and one of the reasons why they called me in. They sacked their Technical Director over this incident. They also didn't do a product recall despite having an estimated 100,000 products with the problem already out in the field. Of course, as a responsible engineer (and to cover my ass) I wrote them a letter recommending that they did a product recall (while thinking of the designers of the Challenger Space Shuttle's infamous O-ring seals). I find that many independent EMC people have dozens of similar examples, which they can't talk about very much because of commercial confidentiality. This is one reason why the EMC + Compliance Journal (www.compliance-club.com) started its 'Banana Skins' column - to help educate practising engineers about real EMC engineering problems they almost certainly weren't taught about at college and may not (yet) have experienced for themselves. I also have personal experience of a UK company that in the late 90's was selling a range of over 110 CE-marked products (such as incubators) intended for medical and chemical laboratories although less than 10% of their products met both the EMCD and the LVD. The company in question had just been purchased by another, which is why I was involved. Interestingly, the new owners continued to sell the non-compliant products while they re-engineered them one at a time to be compliant (which took several years). My simple investigations over a number of years into a number of companies' CE marked products have led me to be very cynical. As a rule of thumb I guess that around 30% of CE marked products are non-compliant with EMC or LVD, with another 30% being borderline cases. This seems to be borne out by recent enforcement surveys in Finland and in the UK and published articles from some test labs. Changing to another of your criticisms below... If you think my proposed statement is fog-filled, what do you propose instead? Lets have constructive criticism instead of merely criticism. In fact, in most scientific or engineering activities, one can only make public statements using foggy words like 'generally'. Remember the UK government's teams of scientific advisors and their pronouncements on BSE and the foot and mouth epidemic? Would you have expected them to produce precise and accurate predictions? I am of the opinion that the outbreak of foot and mouth disease in the UK was better understood, had fewer variables, and could be better controlled than many real-life EMC-related safety engineering problems. I believe the debate in question (whether unintentional emitters can interfere with electronic circuits which are not intentional radio receivers) cannot be answered with a definitive yes or no. I believe that each safety-related application needs to be investigated and firm engineering conclusions drawn. Even then, when one actually does such exercises in real life (and I have) one still finds statements concerning personal estimates of probability are necessary. You can deride these as being 'foggy' if you like but I don't think even you could be more precise in such circumstances. Absolute certainty just does not exist in the real engineering world of interactions between complex systems and I am sure you understand this well. As for the rest of your comments, I plead guilty to raising the emotional stakes. I deliberately used emotive arguments because I find that most designers (and test lab engineers) prefer to keep their heads down doing the engineering work they believe they are paid to do. Where people could be injured or killed by their products I generally find that designers are uncomfortable even thinking about this. Maybe this is because it would mean them fighting with their management to get more resources allocated. I also find that most designers (and their managers) - if they think about their potential 'victims' at all - also tend to think of them as 'other people'. They don't seem to think of their customers ands third parties as if they were members of their own family (as if other people's families were less important). So this is an emotive litmus test I often use to test designers' and managers ethics. Yes, ETHICS. Now that the word has been mentioned no doubt there will be a new thread begun,
Re: EMC-related safety issues
My point was that only radios are sensitive to rf fields at the levels controlled by FCC/CISPR22 and indeed, as Ing. Gremen pointed out, levels well above the limits. Which means that the only rationale behind FCC/CISPR22 is protection of radio broadcast reception. Period. on 1/5/02 12:10 PM, cherryclo...@aol.com at cherryclo...@aol.com wrote: Dear Ken I am truly sorry if I irritated you by misunderstanding your words, but I took your posting to imply that electronic circuits which are not designed as RF receivers would not respond very well to radio frequencies. My example was not intended to be a full answer to your example (there are other postings which are dealing with that) just to indicate that the frequency response of slow and commonplace ICs can be very high indeed. I am sensitive to this issue because I keep on running across electronics designers who say things like: I don't need to worry about the RF immunity of my audio amplifier/motor controller/temperature/pressure/flow/weight/velocity measurement and control system (please delete where applicable) because the opamps I use have a GBW of under 1MHz so they won't see the RF which is of course complete bollocks (a UK phrase that I hope translates well enough for all emc-pstc subscribers). And no, I still don't agree with you that only radio receivers are sensitive enough to RF to have a problem with what you are still calling 'unintentional emissions' (even though this term means very little in an international forum unless you define the relevant standards or laws). I think the problem you are concerned with is application dependant and we cannot make such broad assumptions. As I said earlier, most interference problems are caused by radio transmitters or radio receivers, but not all. Regards, Keith Armstrong In a message dated 05/01/02 01:20:27 GMT Standard Time, ken.ja...@emccompliance.com writes: Subj:Re: EMC-related safety issues List-Post: emc-pstc@listserv.ieee.org Date:05/01/02 01:20:27 GMT Standard Time From:ken.ja...@emccompliance.com (Ken Javor) To:cherryclo...@aol.com, emc-p...@majordomo.ieee.org One sure way to REALLY irritate me is to twist my words and try to make me look stupid (I do a fine job by myself on occasion and don't appreciate any outside help). I did not say that pn junctions don't detect and rectify rf, I said that the field intensities associated with unintentional emissions from ITE are too low to cause susceptibility in circuits other than radios. Your example here is 10 V/m, and you are talking about an op-amp (gain unspecified) and that it was susceptible at that level should be no surprise to anyone. on 1/4/02 7:34 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote: Does anyone else think that ordinary semiconductors doesn't respond to RF? I have tested a product which was little more than an LM324 quad op-amp for RF immunity using IEC 61000-4-3. This op-amp has a slew rate of 1V/micro-second on a good day with the wind in its favour. It was housed in an unshielded plastic enclosure. Demodulated noise that exceeded the (not very tough) product specification were seen all the way up to 500MHz at a number of spot frequencies that appeared to be due to the natural resonances of the input and output cables. Above 500MHz this resonant behaviour vanished to be replaced by a steadily rising level of demodulated 1kHz tone as the frequency increased. I stopped testing at 1GHz, where the output error from the product was about 10% and still rising with increased frequency. OK, the field strength for the test was 10V/m (unmodulated) but the real surprise was how well this very cheap and very slow opamp demodulated the RF, and that it demodulated better at 1GHz than at 500MHz. I have done many many immunity tests using IEC 61000-4-3 on audio equipment and found much the same effects with every product I've ever tested. With most larger products there is usually a roll-off in the demodulation above 500MHz - not because the semiconductors in the ICs can't respond (they can) but apparently because larger products have higher losses above 500MHz or so between the cable ports and the semiconductors, plus a denser structure that might provide more self-screening. The transistors and diodes in all modern ICs (analog or digital) are so tiny that they make excellent detectors at UHF and beyond. As they get smaller (and they are) their frequency response increases (and their vulnerability to upset and damage decreases). Regards, Keith Armstrong
Re: EMC-related safety issues
What an EMC engineer who understands the physics of field-to-wire coupling would say is that the operation of non-antenna connected electronics associated with one subsystem will not be degraded by close proximity with the non-antenna connected electronics of another subsystem. Forget 10 meters. Are the PCs in your office separated by 10 m? Would you expect two PCs stacked side-by-side or one on top of the other to interact in any manner? These are rhetorical questions. About the blood pressure monitor example. Not enough info here to back out what is wrong, but basic logic theory says when the conclusion is impossible, you must re-examine your assumptions. If 92 dBuV/m were enough to make the device malfunction, it would malfunction a lot and there would have been enough trouble reports to get it fixed or withdrawn. And 92 dBuV/m at 10 meters is SCREAMING!!! I am on location and don't have FCC regs easily available, but the limits stair-step around 40 dBuV/m at 3 m, per my recollection. Would I feel comfortable placing a CISPR compliant PC next to a medical device qualified to 1 V/m? There is an inherent (not planned) margin of safety here that is many orders of magnitude. The answer is absolutely yes. If there were a problem, I would expect it more to occur below 30 MHz, at the power supply switching frequency, IF the medical device processed extremely low levels of electrical signals and was poorly shielded. But I believe there are separate immunity requirements which cover this eventuality as well. on 1/5/02 12:23 PM, cherryclo...@aol.com at cherryclo...@aol.com wrote: Dear Cortland People can't simply say: ordinary semiconductors won't demodulate RF levels produced by an unintentional radiator even the smallest amount of RF can be demodulated there are no hysteresis or threshold effects in a PN semiconductor junction or FET that is biased into its conduction region (at least not until you get below signal levels equivalent to less than a single electron). What I am sure most engineers would really mean to say is: ordinary semiconductors exposed to RF levels from an information technology product which is fully compliant with all relevant EMC emissions standards and is at 10 metres distance will generally not demodulate a sufficient level of interference to make an appreciable difference to most electronic systems. Now we have a statement which has some scientific rigor and some engineering validity to it. (Although I do worry that in Europe our harmonised EMC standards only test emissions up to 1GHz, so what does that say about the possible emitted fields strengths from a PC with a 1.2GHz clock frequency?) Let's see if we can put some meat into this discussion with a real-life example... I once tested a blood sample incubator for RF field immunity. The incubator was used during screening programs (for cancer and other diseases) and kept about 100 test tubes at 37.1C (normal blood temperature), while the reagents in the test tubes changed colour. After 24 hours of incubation medical staff would inspect the test tubes and write letters to people telling them they were sick, or that they were clear of the disease. I don't know what temperature tolerance the reagents had to give an accurate medical diagnosis, so assume ±0.1C. On the front panel of the incubator was a display of its temperature, which was of course 37.1C. We found that field strengths as low as 1V/m would cause the incubation temperature to range over full scale, from heaters fully off (in which case the temperature would decline to ambient) to maximum (in which case the water used to incubate the test tubes would boil). We could use the RF test frequency to control the temperature between plus and minus full scale over the frequency range 80 to 1000MHz at 1V/m (and did not test beyond 1GHz). Most worryingly, the front panel display would only show temporary variations from its 37.1C when the RF field was turned off or on, and would continue to show 37.1C even when the water in the incubator was stone cold or actually boiling. Most demodulation effects in bipolar and FET devices approximate to a square law - for example a 1dB fall in the field strength (keeping everything else constant) would typically result in a 2dB fall in the demodulated 'interference' error signal, as John Woodgate has recently pointed out. If we assume that the 1V/m field strength was causing a 60C temperature error, how low would we need to make the RF field to get down to the 0.1C accuracy of the front panel display? Assuming square-law characteristics for the device doing the demodulation I calculate a field strength of around 40mV/m or 92dBmicrovolts/metre. You will notice that I have been generous to the incubator and assumed that the 1V/m field just about caused its temperature error to increase by 60C to boil the water, whereas it could have been overdriving the internal circuits by a considerable margin and still
Re: EMC-related safety issues
Thanks for the correction. Medicine is not something I know much about.
The point remains that a huge benefit was derived from these vaccines which
were discontinued due to a very small fraction of bad reactions. Forum
members: when it turned out that a small number of people were killed or
hurt by airbags, there was no general hue and cry to remove them or sue the
automobile manufacturers. Why?
Diphtheria and whooping cough are not mere viruses. They are life
threatening illnesses that in former centuries contributed greatly to infant
morality. And tetanus is potentially deadly at any age.
on 1/4/02 11:31 PM, Jim Freeman at free...@chelsio.com wrote:
Hi Ken,
The reason that those companies stopped was because it was found that
there was mercury in the formulation of the vaccine. The mercury had no
other use other than stabilization. The mercury is known to cause brain
damage. Prior to around 1980, DPT was not given to infants. The rise in
autism has correlated with the increased use of the infant vaccines.Those
companies were also found to have poor process control that allowed too much
of a live virus in their vaccines causing a so-called 'hot batch'. The
company that is left doesn't have mercury in their formulation and has
superior process control. I would much rather see my child suffer through a
virus than be permanently brain damaged(usually undetectably)
BTW, whooping cough and pertusis are the same thing. the D stands for
Diptheria.
Jim Freeman
Ken Javor wrote:
My take on it is that rather than appease ridiculous demands, a company
ought to look at the profit vs. risk vs. cost to consumer and decide, heck,
it ain't worth it. Case in point on the news today I heard that DPT shots
are in short supply, because two companies quit making it. They quit making
it because there were a very small number of bad reactions to it and there
were lawsuits or gov't action. Well, my kids are beyond that stage but I
sure feel sorry for the people out there whose infants are at risk for
whooping cough, diphtheria and pertussis. The only thing worse than
watching your child become seriously ill is knowing it was easily
preventable.
S on 1/4/02 7:37 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:
Hey, Ken, let's try to be realistic here!
Sure - we should try to get laws we don't like changed, but that isn't going
to happen overnight and in the meantime we have to operate within the law as
it stands.
Or are you suggesting immediate insurrection by product manufacturers?
(Outlaw manufacturers roaming the wild wild west - an interesting concept!)
The IEE's guide on EMC and Functional Safety is concerned with such legal
aspects, but is also concerned with saving lives in a world where electronic
control of safety-related functions is proliferating madly.
As my paper at the IEEE's EMC Symposium in Montreal and my recent article in
ITEM UPDATE 2001 show - at present EMC standards don't address safety
issues, and most safety standards don't address EMC-related functional
safety issues.
Regards, Keith Armstrong
In a message dated 03/01/02 17:24:42 GMT Standard Time,
ken.ja...@emccompliance.com writes:
Subj:Re: EMC-related safety issues
List-Post: emc-pstc@listserv.ieee.org
Date:03/01/02 17:24:42 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
Sender:owner-emc-p...@majordomo.ieee.org
Reply-to: ken.ja...@emccompliance.com (Ken Javor)
To:c...@dolby.co.uk (James, Chris), acar...@uk.xyratex.com
('acar...@uk.xyratex.com'), emc-p...@majordomo.ieee.org
There is an inherent contradiction in this anti-profit, anti-technology
point-of-view that I cannot and will not defend. All I am saying is that
people who feel this is wrong should stand up and say so, not write guides
for how to go along with it.
Re: EMC-related safety issues
The analytical portion of this post is, as the author stated, worst case. A cable attached to a susceptible circuit picks up a common-mode potential, which most likely drives a current on a shield if the the circuit is sensitive. Then only the current multiplied by shield transfer impedance actually gets into the victim, assuming no CMR. Which just makes my original point - unintentional emissions from ITE can only upset a radio receiver tuned to the emission frequency. That is why, as another contributor posted, we use EMI receivers and spectrum analyzers with preamps to make OATS measurements. on 1/4/02 12:51 PM, Tom Cokenias at t...@tncokenias.org wrote: At 8:34 AM -0500 1/4/2002, Keith Armstrong wrote: Does anyone else think that ordinary semiconductors doesn't respond to RF? I agree that commonly used semiconductors have responses well into the 100's of MHz. How much of a problem this is will depend on the nature and function of the circuitry using these components. The EUT wires, cables, pcb traces etc. act like antennae, on which the incident field voltages and currents. An antenna factor can be thought of as ratio of the field strength to the voltage induced on the terminated cable connected to the antenna. In an impedance matched system, AF=9.734/lamda*(G)^0.5, lamda being wavelength in meters, G being antenna gain over isotropic, or in dB AF dB = - G dBi -29.7 dB + 20logFMHz Assuming G is 1 (isotropic antenna), AF is 1 (= 0 dB) at about 30.8 MHz, and AF get larger as frequency increases, to a factor of 32.7 (= 30.3 dB) at 1 GHz . Since AF is field strength divided by induced voltage, the voltage induced on the trace goes down as frequency goes up for the same incident field strength. An effective receive antenna needs to be on the order of 1/2 wavelength or so; for 30 MHz this is 15m, for 1000 MHz this is 15 cm. So if a victim EUT circuit has a pretty effective receive antenna, and does not have any filtering and is equally sensitive across the frequency range under consideration (all taken together, a worst case scenario for susceptibility), (1) A 10 V/m field will theoretically induce a voltage 0.33V to 10V, depending on frequency (2) A 5000 uV/m field (10x the FCC class B limit above 960 MHz) will theoretically induce a voltage from 152 uV to 5 mV, depending on frequency. (3) A 500 uV/m field will theoretically induce a voltage from 15 uV to 500 uV depending on frequency. These are first order approximations, but they are useful in determining the level of the potential EMI threat. For instance a 4-30 mA sensor circuit using high gain operational amps will most likely be interfered with in scenario (1), there may be some susceptibility detected in scenario (2), and most likely no problem encountered with scenario (3). A sensitive all - band AM communications receiver will have problems with all three, a broadcast TV operating in a strong signal area will probably be OK with scenario 3 but not with 1 or 2. I guess what I'm really trying to say with all this is that EMC is a systems thing, taking into account the nature of the culprit EMI generator, the nature of the victim EMI receiver, and the path between them. Then we have the economics of operating different devices in the same vicinity, the politics of who gets how much of what kind of protection, etc., etc. All things considered, we should have jobs for life! best regards and a Happy New Year to all. Tom Cokenias T.N. Cokenias Consulting P.O. Box 1086 El Granada CA 94018 tel 650 726 1263 cell 650 302 0887 fax 650 726 1252 --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that cherryclo...@aol.com wrote (in 43.47bb025.29689...@aol.com) about 'EMC-related safety issues', on Sat, 5 Jan 2002: The one in a billion John refers to sounds very dramatic and difficult. More dramatic than you 'infant daughter' and '40 mph past a school'? I explained in VERY GREAT DETAIL the effect of cumulative probability in requiring very low probability events to be taken into account. In principle, as the probability goes down, the number of risk scenarios increases *combinatorially*. There is no Olber's Paradox in this area, the 'night sky is infinitely brighter than the Sun'! So it may be helpful to refer to IEC 61508 which is a recently-published 'basic safety publication' covering The functional safety of electrical / electronic / programmable safety-related systems IEC 61508 uses the concept of the Safety Integrity Level (or SIL) to help design safety-related systems which have quantified failure probabilities. The SILs for average probability of failure to perform design function on demand are: SIL level 1: up to 10^ -2 SIL level 2: 10^ -2 to 10^ -3 SIL level 3: 10^ -3 to 10^ -4 SIL level 4: 10^ -4 to 10^ -5 or even lower levels The SILs for average probability of dangerous failure per hour of operation are: SIL level 1: up to 10^ -6 SIL level 2: 10^ -6 to 10^ -7 SIL level 3: 10^ -7 to 10^ -8 SIL level 4: 10^ -8 to 10^ -9 or even lower levels The standard describes how to select the SIL level for a particular safety-related application, and we find that SIL4 is required where a failure of the safety system could result in the deaths or serious injuries of large numbers of people. Yes, my 10^-9 figure was in the context of your 'relatives sobbing all over the courtroom'. Most safety-related applications that most practising engineers will be involved in will be SIL1 or 2, maybe even SIL3, and hence require very much lower reliability than one in a billion. You are neglecting cumulative probability, in spite of quoting my whole text on it! SIL2, if it is applied to individual risk scenarios, is a recipe for disaster if you are putting many thousands of units, such as PCs or TVs, into the field. If is it applied, as it should be, to the cumulative probability of ALL risk scenarios, then *each one* needs to be constrained to that 10^-9 probability, preferably well below it. 100 scenarios at 10^-9 each gives a cumulative of 10^-7, after all. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that cherryclo...@aol.com wrote (in 132.6f59d2b.296 89...@aol.com) about 'EMC-related safety issues', on Sat, 5 Jan 2002: Dear Cortland People can't simply say: ordinary semiconductors won't demodulate RF levels produced by an unintentional radiator even the smallest amount of RF can be demodulated there are no hysteresis or threshold effects in a PN semiconductor junction or FET that is biased into its conduction region (at least not until you get below signal levels equivalent to less than a single electron). The question is not whether demodulation occurs, but whether the recovered modulation is at a level to cause a problem. 1 mV of r.f. can't produce even 1 mV of recovered modulation. What I am sure most engineers would really mean to say is: ordinary semiconductors exposed to RF levels from an information technology product which is fully compliant with all relevant EMC emissions standards and is at 10 metres distance will generally not demodulate a sufficient level of interference to make an appreciable difference to most electronic systems. I don't think most engineers would go along with a statement with such a high fog-factor. That is one of the points of contention; this subject seems to attract fog-factor like a superconducting magnet. Now we have a statement which has some scientific rigor and some engineering validity to it. Are you seriously putting that forward? It's so vague, IMO, as to be not useful; it does not help in any way to realise solutions. (Although I do worry that in Europe our harmonised EMC standards only test emissions up to 1GHz, so what does that say about the possible emitted fields strengths from a PC with a 1.2GHz clock frequency?) Extension up to 3 GHz (much higher in some cases) is being studied intensively. One major problem is that repeatable measurements above 1 GHz are very difficult to achieve. Let's see if we can put some meat into this discussion with a real-life example... Well, it's a very extreme case of real life! I doubt that you'll come across another one before you retire! I once tested a blood sample incubator for RF field immunity. When was this? Before or after 1976, when EMC of medical equipment first (AFAIK) surfaced as a matter to be studied intensively. [Big snip] How many people reading this would be now be quite happy to place even a fully-compliant PC (compliant at 10 metres distance, that is) right next to the unmodified incubator? If it helps, imagine that it is your young daughter whose blood sample is in the incubator to discover which drugs she needs to survive. Shall we have a vote on how close we would be prepared to place the PC? Might be interesting. This appeal to emotion is out of place. Let's not even think about the problems of proximity to cellphones and other intentional radiators. I didn't mention that the incubator was a small model used for mobile screening, for installation in a truck adapted for medical screening purposes which travels to various communities and parks there for a few days while it tests the local people for disease - hardly a very well controlled electromagnetic environment. What does the above imply for similar incubators in countries that do not have mandatory EMC immunity standards? Or for older incubators in the EU that have never had to meet the EMC directive? (Please don't reply with the old chestnut that we haven't heard of any problems so far, so everything must be OK - people who should have known better were using that phrase before September 11th. It is just not an acceptable argument where safety issues are involved, as any expert in safety law will tell you. Try: I've been driving past that school at 40mph for ten years and haven't hit a kid yet, so it must be safe mustn't it? as a test of the concept.) More emotion. This is another point of contention: as soon as any critique is offered to some pronouncement, these emotional arguments are trotted out. I had a similar experience with a militant carer of disabled people. Anything that suggested that her views were perhaps just a *little* extreme (like scrapping all London's black cabs overnight because they won't accommodate a wheelchair with the user in it) was greeted with 'Oh, so you are prejudiced against disabled people, are you?' IMO, your reasoning is utterly unreasonable. Designers are not omniscient, or had better assume they are not. So they must assume that they have not thought of every possible scenario down to that 10^-9 probability. How, then, can the designer be reasonably assured that his design is satisfactory, if he cannot rely on the absence of reports of problems? Is he to continue to refine it for years and years, before releasing
Re: EMC-related safety issues
I read in !emc-pstc that cherryclo...@aol.com wrote (in 92.1f676722.296 88...@aol.com) about 'EMC-related safety issues', on Sat, 5 Jan 2002: I am truly sorry if I irritated you by misunderstanding your words, but I took your posting to imply that electronic circuits which are not designed as RF receivers would not respond very well to radio frequencies. They DON'T respond very well, if compared with a receiver. My example was not intended to be a full answer to your example (there are other postings which are dealing with that) just to indicate that the frequency response of slow and commonplace ICs can be very high indeed. Well, that is not really correct. The r.f is demodulated at the first junction (usually) and beyond that point the device is only handling the modulation, at much lower frequencies. I am sensitive to this issue because I keep on running across electronics designers who say things like: I don't need to worry about the RF immunity of my audio amplifier/motor controller/temperature/pressure/flow/weight/velocity measurement and control system (please delete where applicable) because the opamps I use have a GBW of under 1MHz so they won't see the RF which is of course complete bollocks (a UK phrase that I hope translates well enough for all emc-pstc subscribers). There are always some! And no, I still don't agree with you that only radio receivers are sensitive enough to RF to have a problem with what you are still calling 'unintentional emissions' (even though this term means very little in an international forum unless you define the relevant standards or laws). I think this term is quite legitimate and well-understood. If the equipment requires to emit in order to perform its intended function, it is an 'intentional emitter'. If it does not need to do so, but emits anyway, it is an 'unintentional emitter'. It is difficult to see how there could be any confusion or ambiguity about this. I think the problem you are concerned with is application dependant and we cannot make such broad assumptions. As I said earlier, most interference problems are caused by radio transmitters or radio receivers, but not all. Well, electric fences -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
The one in a billion John refers to sounds very dramatic and difficult. So it may be helpful to refer to IEC 61508 which is a recently-published 'basic safety publication' covering The functional safety of electrical / electronic / programmable safety-related systems IEC 61508 uses the concept of the Safety Integrity Level (or SIL) to help design safety-related systems which have quantified failure probabilities. The SILs for “average probability of failure to perform design function on demand” are: SIL level 1: up to 10^ -2 SIL level 2: 10^ -2 to 10^ -3 SIL level 3: 10^ -3 to 10^ -4 SIL level 4: 10^ -4 to 10^ -5 or even lower levels The SILs for ““average probability of dangerous failure per hour of operation” are: SIL level 1: up to 10^ -6 SIL level 2: 10^ -6 to 10^ -7 SIL level 3: 10^ -7 to 10^ -8 SIL level 4: 10^ -8 to 10^ -9 or even lower levels The standard describes how to select the SIL level for a particular safety-related application, and we find that SIL4 is required where a failure of the safety system could result in the deaths or serious injuries of large numbers of people. Most safety-related applications that most practising engineers will be involved in will be SIL1 or 2, maybe even SIL3, and hence require very much lower reliability than one in a billion. 'm sure that when we are driving our cars, or living near a nuclear plant, we would like to think that the designers of the braking system or control rod control systems (respectively) had looked at 'ALL risk scenarios down to the billion-to-one against level of probability' - to use John's words. Regards, Keith Armstrong In a message dated 04/01/02 19:31:57 GMT Standard Time, j...@jmwa.demon.co.uk writes: Subj:Re: EMC-related safety issues Date:04/01/02 19:31:57 GMT Standard Time From:j...@jmwa.demon.co.uk (John Woodgate) I read in !emc-pstc that cherryclo...@aol.com wrote (in 167.698dddc.296 70...@aol.com) about 'EMC-related safety issues', on Fri, 4 Jan 2002: As my paper at the IEEE's EMC Symposium in Montreal and my recent article in ITEM UPDATE 2001 show - at present EMC standards don't address safety issues, and most safety standards don't address EMC-related functional safety issues. As far as CENELEC is concerned, it was a conscious decision not to incorporate 'EMC and Safety' issues into EMC standards, but to treat it as a separate subject. Some people may find a clarification helpful. We have EMC matters, concerned with compatibility between items of equipment, ensuring that they continue to work (Criterion A in the Generic Standards) or fail gracefully (Criteria B and C). These criteria do not address safety issues, as indicated in paragraph 1 above. However, the Generic Standards do have a limited 'blanket' requirement, that equipment must not become unsafe *during testing*. We also have safety matters per se, which don't involve EMC. We ALSO have the separate subject, called 'EMC and Safety' or reasonable variants thereof. This addresses the matter of equipment becoming unsafe *in service* due to excessive emission levels in the environment, or lack of sufficient immunity to acceptable emission levels. So far, this seems perfectly reasonable. BUT it stops seeming reasonable when the question 'What could go wrong?' is asked and statistical data is used to attempt to answer it. To take a very simple example (maybe over-simplified), we might say that the probability of an unsafe occurrence should be less than 10^-9. That immediately means that the designer of the equipment has to look at ALL risk scenarios down to the billion-to-one against level of probability. To say that that is difficult is surely a great understatement. But some experts in the field seem to ignore that great difficulty, and simply (or maybe not so simply) state that if the designer fails to take into account ANY scenario that subsequently results in an unsafe condition, the designer has failed in his professional responsibility, and may be held criminally responsible for negligence. Well, let us be very circumspect designers and look at what immunity levels we might need to get down to that 10^-9 probability. For radiated emissions, the necessary test levels seem to be of the order of 100 V/m. Test levels for other disturbances seem to be equally distantly related to the levels normally experienced and to the test levels in pure EMC standards. We might conclude that assessment of EMC immunity per se is completely unnecessary, because testing for 'EMC and Safety' requires test levels of the order of 30 dB higher! One could go, with the sort of reasoning advocated by some experts, further into the realms of fantasy. Suppose, for a particular piece of equipment, the designer, with great diligence, identifies a million threat scenarios, each of which has a probability of 10^-9. The cumulative probability of ANY ONE of them occurring
Re: EMC-related safety issues
In a message dated 04/01/02 19:31:51 GMT Standard Time, j...@jmwa.demon.co.uk writes: The trick, I believe, is not to be in that position in the first place. Design your products using the latest safety knowledge and test them well to discover if they have any weaknesses you did not address. How do you decide what tests to do **for weaknesses you don't suspect**? Isn't that fundamentally impossible? I actually said for weaknesses you did not address not for weaknesses you did not suspect - quite a different matter. Mind you, if a designer is not very competent in safety matters there might be quite a number of things that he/she did not suspect, much less address, that he/she should have done. But I was thinking of tests such as bump and vibration, thermal extremes, etc, that reputable companies do to test the reliability of their products. Also safety tests such as simulating faults in components (such as shorting or opening power transistors and capacitors, disconnecting connections to resistors and ICs, etc.). These tests tend to reveal many safety issues that were overlooked in the heat of the design process, or through lack of knowledge of the design staff, and sometimes even reveal things that safety experts familiar with the product type would not have expected. Because such tests can be done and are available from many suppliers (if you don't do them yourself) I understand from UK safety enforcers (Trading Standards) that a manufacturer would have a hard time proving compliance with the LVD or PLD directives if using them would have revealed a safety problem that contributed to an actual safety incident. Regards, Keith Armstrong
Re: EMC-related safety issues
Dear Cortland People can't simply say: ordinary semiconductors won't demodulate RF levels produced by an unintentional radiator – even the smallest amount of RF can be demodulated – there are no hysteresis or threshold effects in a PN semiconductor junction or FET that is biased into its conduction region (at least not until you get below signal levels equivalent to less than a single electron). What I am sure most engineers would really mean to say is: ordinary semiconductors exposed to RF levels from an information technology product which is fully compliant with all relevant EMC emissions standards and is at 10 metres distance will generally not demodulate a sufficient level of interference to make an appreciable difference to most electronic systems. Now we have a statement which has some scientific rigor and some engineering validity to it. (Although I do worry that in Europe our harmonised EMC standards only test emissions up to 1GHz, so what does that say about the possible emitted fields strengths from a PC with a 1.2GHz clock frequency?) Let's see if we can put some meat into this discussion with a real-life example... I once tested a blood sample incubator for RF field immunity. The incubator was used during screening programs (for cancer and other diseases) and kept about 100 test tubes at 37.1C (normal blood temperature), while the reagents in the test tubes changed colour. After 24 hours of incubation medical staff would inspect the test tubes and write letters to people telling them they were sick, or that they were clear of the disease. I don't know what temperature tolerance the reagents had to give an accurate medical diagnosis, so assume ±0.1C. On the front panel of the incubator was a display of its temperature, which was of course 37.1C. We found that field strengths as low as 1V/m would cause the incubation temperature to range over full scale, from heaters fully off (in which case the temperature would decline to ambient) to maximum (in which case the water used to incubate the test tubes would boil). We could use the RF test frequency to control the temperature between plus and minus full scale over the frequency range 80 to 1000MHz at 1V/m (and did not test beyond 1GHz). Most worryingly, the front panel display would only show temporary variations from its 37.1C when the RF field was turned off or on, and would continue to show 37.1C even when the water in the incubator was stone cold or actually boiling. Most demodulation effects in bipolar and FET devices approximate to a square law - for example a 1dB fall in the field strength (keeping everything else constant) would typically result in a 2dB fall in the demodulated 'interference' error signal, as John Woodgate has recently pointed out. If we assume that the 1V/m field strength was causing a 60C temperature error, how low would we need to make the RF field to get down to the 0.1C accuracy of the front panel display? Assuming square-law characteristics for the device doing the demodulation I calculate a field strength of around 40mV/m or 92dBmicrovolts/metre. You will notice that I have been generous to the incubator and assumed that the 1V/m field just about caused its temperature error to increase by 60C to boil the water, whereas it could have been overdriving the internal circuits by a considerable margin and still suffered a 60C error at 0.1V/m. We didn't test this possibility as our focus was (as in most of these cases) on quickly modifying the product so it passed the immunity test - which we did. 92dBmicrovolts/metre is not a very high RF field level for a PC without any EMC precautions at a distance of 10 metres. How many people reading this would be now be quite happy to place even a fully-compliant PC (compliant at 10 metres distance, that is) right next to the unmodified incubator? If it helps, imagine that it is your young daughter whose blood sample is in the incubator to discover which drugs she needs to survive. Shall we have a vote on how close we would be prepared to place the PC? Might be interesting. Let's not even think about the problems of proximity to cellphones and other intentional radiators. I didn't mention that the incubator was a small model used for mobile screening, for installation in a truck adapted for medical screening purposes which travels to various communities and parks there for a few days while it tests the local people for disease - hardly a very well controlled electromagnetic environment. What does the above imply for similar incubators in countries that do not have mandatory EMC immunity standards? Or for older incubators in the EU that have never had to meet the EMC directive? (Please don't reply with the old chestnut that we haven't heard of any problems so far, so everything must be OK - people who should have known better were using that phrase before September 11th. It is just not an acceptable
Re: EMC-related safety issues
Dear Ken That is exactly what I am saying: under the EU's Product Liability Directive a company can be held liable for unlimited damages with no proof of negligence on the manufacturer's part. It is of course a valid management decision to ignore a market that is almost as large as USA/Canada because of financial risk issues – but you'll notice that a lot of manufacturers are still making lots of money selling goods in the EU. Regards, Keith Armstrong In a message dated 05/01/02 01:31:03 GMT Standard Time, ken.ja...@emccompliance.com writes: Subj:Re: EMC-related safety issues Date:05/01/02 01:31:03 GMT Standard Time From:ken.ja...@emccompliance.com (Ken Javor) To:cherryclo...@aol.com, emc-p...@majordomo.ieee.org Interesting to note that this country (USA) got started in part because of a tax on tea. I think you are saying here that a company can be held liable for unlimited damages with no proof of negligence on the manufacturer's part. If I were a manufacturer I would simply not market to the EU.
Re: EMC-related safety issues
Dear Ken
That is precisely the point I was trying to make: all companies (and people)
always weigh up all the costs and risks that they know about and act
accordingly.
The problem arises when certain risks are unknown or ignored, for whatever
reasons.
I see it as part of every engineer's job to inform the people who make the
cost/risk decisions about all the costs and risks associated with a certain
course of action.
What I find in practice is that most engineers are aware of the costs but as
it is so hard to quantify the risks they often don't bother. Also, many
engineers are uncomfortable with quoting numbers that they can't accurately
calculate to five decimal places.
Hands up all those whose formal (or in-company) engineering education
included risk analysis and estimation and how to present the data to
management
So in many cases management don't have the full information on which to base
their cost/risk decisions.
Regards, Keith Armstrong
In a message dated 05/01/02 01:27:34 GMT Standard Time,
ken.ja...@emccompliance.com writes:
Subj:Re: EMC-related safety issues
Date:05/01/02 01:27:34 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
To:cherryclo...@aol.com, emc-p...@majordomo.ieee.org
My take on it is that rather than appease ridiculous demands, a company
ought to look at the profit vs. risk vs. cost to consumer and decide, heck,
it ain't worth it. Case in point on the news today I heard that DPT shots
are in short supply, because two companies quit making it. They quit
making it because there were a very small number of bad reactions to it and
there were lawsuits or gov't action. Well, my kids are beyond that stage
but I sure feel sorry for the people out there whose infants are at risk
for whooping cough, diphtheria and pertussis. The only thing worse than
watching your child become seriously ill is knowing it was easily
preventable.
S on 1/4/02 7:37 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:
Hey, Ken, let's try to be realistic here!
Sure - we should try to get laws we don't like changed, but that isn't
going to happen overnight and in the meantime we have to operate within
the law as it stands.
Or are you suggesting immediate insurrection by product manufacturers?
(Outlaw manufacturers roaming the wild wild west - an interesting
concept!)
The IEE's guide on EMC and Functional Safety is concerned with such legal
aspects, but is also concerned with saving lives in a world where
electronic control of safety-related functions is proliferating madly.
As my paper at the IEEE's EMC Symposium in Montreal and my recent article
in ITEM UPDATE 2001 show - at present EMC standards don't address safety
issues, and most safety standards don't address EMC-related functional
safety issues.
Regards, Keith Armstrong
In a message dated 03/01/02 17:24:42 GMT Standard Time,
ken.ja...@emccompliance.com writes:
Subj:Re: EMC-related safety issues
Date:03/01/02 17:24:42 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
Sender:owner-emc-p...@majordomo.ieee.org
Reply-to: ken.ja...@emccompliance.com (Ken Javor)
To:c...@dolby.co.uk (James, Chris), acar...@uk.xyratex.com
('acar...@uk.xyratex.com'), emc-p...@majordomo.ieee.org
There is an inherent contradiction in this anti-profit, anti-technology
point-of-view that I cannot and will not defend. All I am saying is that
people who feel this is wrong should stand up and say so, not write
guides for how to go along with it.
Re: EMC-related safety issues
Dear Ken I am truly sorry if I irritated you by misunderstanding your words, but I took your posting to imply that electronic circuits which are not designed as RF receivers would not respond very well to radio frequencies. My example was not intended to be a full answer to your example (there are other postings which are dealing with that) just to indicate that the frequency response of slow and commonplace ICs can be very high indeed. I am sensitive to this issue because I keep on running across electronics designers who say things like: I don't need to worry about the RF immunity of my audio amplifier/motor controller/temperature/pressure/flow/weight/velocity measurement and control system (please delete where applicable) because the opamps I use have a GBW of under 1MHz so they won't see the RF – which is of course complete bollocks (a UK phrase that I hope translates well enough for all emc-pstc subscribers). And no, I still don't agree with you that only radio receivers are sensitive enough to RF to have a problem with what you are still calling 'unintentional emissions' (even though this term means very little in an international forum unless you define the relevant standards or laws). I think the problem you are concerned with is application dependant and we cannot make such broad assumptions. As I said earlier, most interference problems are caused by radio transmitters or radio receivers, but not all. Regards, Keith Armstrong In a message dated 05/01/02 01:20:27 GMT Standard Time, ken.ja...@emccompliance.com writes: Subj:Re: EMC-related safety issues Date:05/01/02 01:20:27 GMT Standard Time From:ken.ja...@emccompliance.com (Ken Javor) To:cherryclo...@aol.com, emc-p...@majordomo.ieee.org One sure way to REALLY irritate me is to twist my words and try to make me look stupid (I do a fine job by myself on occasion and don't appreciate any outside help). I did not say that pn junctions don't detect and rectify rf, I said that the field intensities associated with unintentional emissions from ITE are too low to cause susceptibility in circuits other than radios. Your example here is 10 V/m, and you are talking about an op-amp (gain unspecified) and that it was susceptible at that level should be no surprise to anyone. on 1/4/02 7:34 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote: Does anyone else think that ordinary semiconductors doesn't respond to RF? I have tested a product which was little more than an LM324 quad op-amp for RF immunity using IEC 61000-4-3. This op-amp has a slew rate of 1V/micro-second on a good day with the wind in its favour. It was housed in an unshielded plastic enclosure. Demodulated noise that exceeded the (not very tough) product specification were seen all the way up to 500MHz at a number of spot frequencies that appeared to be due to the natural resonances of the input and output cables. Above 500MHz this resonant behaviour vanished to be replaced by a steadily rising level of demodulated 1kHz tone as the frequency increased. I stopped testing at 1GHz, where the output error from the product was about 10% and still rising with increased frequency. OK, the field strength for the test was 10V/m (unmodulated) but the real surprise was how well this very cheap and very slow opamp demodulated the RF, and that it demodulated better at 1GHz than at 500MHz. I have done many many immunity tests using IEC 61000-4-3 on audio equipment and found much the same effects with every product I've ever tested. With most larger products there is usually a roll-off in the demodulation above 500MHz - not because the semiconductors in the ICs can't respond (they can) but apparently because larger products have higher losses above 500MHz or so between the cable ports and the semiconductors, plus a denser structure that might provide more self-screening. The transistors and diodes in all modern ICs (analog or digital) are so tiny that they make excellent detectors at UHF and beyond. As they get smaller (and they are) their frequency response increases (and their vulnerability to upset and damage decreases). Regards, Keith Armstrong
Re: EMC-related safety issues
I read in !emc-pstc that John Shinn john.sh...@sanmina-sci.com wrote (in 002401c19584$35f73660$0b3d1...@hadco.comsanmina.com) about 'EMC- related safety issues', on Fri, 4 Jan 2002: So where do I drill the hole in my fuel injection system? You don't. You put a pint of water in the tank and a spoonful of liquid detergent to make it mix with the fuel. Don't forget to replace the whole engine after you've passed the emission test. (;-) -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that Ken Javor ken.ja...@emccompliance.com wrote (in b85bb29d.c04%ken.ja...@emccompliance.com) about 'EMC-related safety issues', on Fri, 4 Jan 2002: My take on it is that rather than appease ridiculous demands, a company ought to look at the profit vs. risk vs. cost to consumer and decide, heck, it ain't worth it. Case in point on the news today I heard that DPT shots are in short supply, because two companies quit making it. They quit making it because there were a very small number of bad reactions to it and there were lawsuits or gov't action. Well, my kids are beyond that stage but I sure feel sorry for the people out there whose infants are at risk for whooping cough, diphtheria and pertussis. Ahem, whooping cough IS pertussis. 'DPT' = Diphtheria, pertussis and tetanus. The only thing worse than watching your child become seriously ill is knowing it was easily preventable. This is wildly OT, but there is a big issue in Britain in this area, because what we call the 'triple vaccine' or 'MMR' (measles, mumps and rubella) is alleged to be implicated in autism and serious bowel disorders. The connection is, AIUI, considered by a *small* number of qualified medical people, to be proved, or very probable. This is another case of (alleged) dire results of a very low probability, but much higher that my suggested 'generic' 10^-9 level. The government has, if anything, made matters worse, by denying parents the right to choose, on the National Health (free) Service, three separate vaccinations instead of the triple, so it's the triple or none and it seems about 20% of parents are choosing 'none', in addition to the 10% or so who reject or do not bother about vaccination per se. With only 70% of infants vaccinated, there is a real risk of an epidemic. Matters were made even worse by the indignant reaction of the Prime Minister, who refused to answer in Parliament when asked if his infant son has had the triple vaccine! The implication is that the PM has paid for three separate vaccinations instead. I believe also that the DPT vaccine is not licensed in Europe because of the (alleged) incidence of serious side-effects. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
Hi Ken,
The reason that those companies stopped was because it was found
that there was mercury in the formulation of the vaccine. The mercury
had no other use other than stabilization. The mercury is known to
cause brain damage. Prior to around 1980, DPT was not given to infants.
The rise in autism has correlated with the increased use of the infant
vaccines.Those companies were also found to have poor process control
that allowed too much of a live virus in their vaccines causing a
so-called 'hot batch'. The company that is left doesn't have mercury in
their formulation and has superior process control. I would much rather
see my child suffer through a virus than be permanently brain
damaged(usually undetectably)
BTW, whooping cough and pertusis are the same thing. the D stands
for Diptheria.
Jim Freeman
Ken Javor wrote:
My take on it is that rather than appease ridiculous demands, a
company ought to look at the profit vs. risk vs. cost to consumer and
decide, heck, it ain't worth it. Case in point on the news today I
heard that DPT shots are in short supply, because two companies quit
making it. They quit making it because there were a very small number
of bad reactions to it and there were lawsuits or gov't action. Well,
my kids are beyond that stage but I sure feel sorry for the people out
there whose infants are at risk for whooping cough, diphtheria and
pertussis. The only thing worse than watching your child become
seriously ill is knowing it was easily preventable.
S on 1/4/02 7:37 AM, cherryclo...@aol.com at cherryclo...@aol.com
wrote:
Hey, Ken, let's try to be realistic here!
Sure - we should try to get laws we don't like changed, but
that isn't going to happen overnight and in the meantime we
have to operate within the law as it stands.
Or are you suggesting immediate insurrection by product
manufacturers?
(Outlaw manufacturers roaming the wild wild west - an
interesting concept!)
The IEE's guide on EMC and Functional Safety is concerned
with such legal aspects, but is also concerned with saving
lives in a world where electronic control of safety-related
functions is proliferating madly.
As my paper at the IEEE's EMC Symposium in Montreal and my
recent article in ITEM UPDATE 2001 show - at present EMC
standards don't address safety issues, and most safety
standards don't address EMC-related functional safety
issues.
Regards, Keith Armstrong
In a message dated 03/01/02 17:24:42 GMT Standard Time,
ken.ja...@emccompliance.com writes:
Subj:Re: EMC-related safety issues
Date:03/01/02 17:24:42 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
Sender:owner-emc-p...@majordomo.ieee.org
Reply-to: ken.ja...@emccompliance.com (Ken Javor)
To:c...@dolby.co.uk (James, Chris),
acar...@uk.xyratex.com ('acar...@uk.xyratex.com'),
emc-p...@majordomo.ieee.org
There is an inherent contradiction in this
anti-profit, anti-technology point-of-view that I
cannot and will not defend. All I am saying is
that people who feel this is wrong should stand up
and say so, not write guides for how to go along
with it.
Re: EMC-related safety issues
Interesting to note that this country (USA) got started in part because of a tax on tea. I think you are saying here that a company can be held liable for unlimited damages with no proof of negligence on the manufacturer's part. If I were a manufacturer I would simply not market to the EU. on 1/4/02 7:39 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote: As I understand the way the civil law section of the EU's Product Liability Directive operates (I am not a lawyer) it does in fact place the burden of proof on the manufacturer, who is effectively considered 'guilty until proved innocent'. I also understand that any number of manufacturers can be sued in the civil courts under one safety incident, and the liabilities of each awarded 'on the balance of probabilities' that their product caused the damage, injury or death being complained about. Also...nobody has to prove negligence on the part of the manufacturer, this is sometimes called 'no-fault liability' - you can be held to be liable under the law even though nobody has proved that your product was actually the cause of the safety incident. Another interesting fact about EU Product Liability is that in the civil courts in most EU member states there is no financial upper limit to the damages that can be awarded against a manufacturer. We may not like it, but that's how the world appears to be at the moment. Regards, Keith Armstrong In a message dated 03/01/02 19:52:20 GMT Standard Time, j...@jmwa.demon.co.uk writes: Subj:Re: EMC-related safety issues List-Post: emc-pstc@listserv.ieee.org Date:03/01/02 19:52:20 GMT Standard Time From:j...@jmwa.demon.co.uk (John Woodgate) Sender:owner-emc-p...@majordomo.ieee.org Reply-to: j...@jmwa.demon.co.uk (John Woodgate) To:emc-p...@majordomo.ieee.org I read in !emc-pstc that Gary McInturff Gary.McInturff@worldwidepackets .com wrote (in 917063bab0ddb043af5faa73c7a835d40ac...@windlord.wwp.com ) about 'EMC-related safety issues', on Thu, 3 Jan 2002: While I take your point - I'll challenge with the equally valid argument that says show me the data that they do cause SIDS! Out of order! That's the whole point! Manufacturers are being required to prepare to prove a negative, which is inherently impossible in most cases. No-one is required to prove a positive, which is easy if it is true.
Re: EMC-related safety issues
My take on it is that rather than appease ridiculous demands, a company
ought to look at the profit vs. risk vs. cost to consumer and decide, heck,
it ain't worth it. Case in point on the news today I heard that DPT shots
are in short supply, because two companies quit making it. They quit making
it because there were a very small number of bad reactions to it and there
were lawsuits or gov't action. Well, my kids are beyond that stage but I
sure feel sorry for the people out there whose infants are at risk for
whooping cough, diphtheria and pertussis. The only thing worse than
watching your child become seriously ill is knowing it was easily
preventable.
S on 1/4/02 7:37 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:
Hey, Ken, let's try to be realistic here!
Sure - we should try to get laws we don't like changed, but that isn't going
to happen overnight and in the meantime we have to operate within the law as
it stands.
Or are you suggesting immediate insurrection by product manufacturers?
(Outlaw manufacturers roaming the wild wild west - an interesting concept!)
The IEE's guide on EMC and Functional Safety is concerned with such legal
aspects, but is also concerned with saving lives in a world where electronic
control of safety-related functions is proliferating madly.
As my paper at the IEEE's EMC Symposium in Montreal and my recent article in
ITEM UPDATE 2001 show - at present EMC standards don't address safety
issues, and most safety standards don't address EMC-related functional
safety issues.
Regards, Keith Armstrong
In a message dated 03/01/02 17:24:42 GMT Standard Time,
ken.ja...@emccompliance.com writes:
Subj:Re: EMC-related safety issues
List-Post: emc-pstc@listserv.ieee.org
Date:03/01/02 17:24:42 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
Sender:owner-emc-p...@majordomo.ieee.org
Reply-to: ken.ja...@emccompliance.com (Ken Javor)
To:c...@dolby.co.uk (James, Chris), acar...@uk.xyratex.com
('acar...@uk.xyratex.com'), emc-p...@majordomo.ieee.org
There is an inherent contradiction in this anti-profit, anti-technology
point-of-view that I cannot and will not defend. All I am saying is that
people who feel this is wrong should stand up and say so, not write guides
for how to go along with it.
Re: EMC-related safety issues
One sure way to REALLY irritate me is to twist my words and try to make me
look stupid (I do a fine job by myself on occasion and don't appreciate any
outside help). I did not say that pn junctions don't detect and rectify rf,
I said that the field intensities associated with unintentional emissions
from ITE are too low to cause susceptibility in circuits other than radios.
Your example here is 10 V/m, and you are talking about an op-amp (gain
unspecified) and that it was susceptible at that level should be no surprise
to anyone.
on 1/4/02 7:34 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:
Does anyone else think that ordinary semiconductors doesn't respond to RF?
I have tested a product which was little more than an LM324 quad op-amp for
RF immunity using IEC 61000-4-3. This op-amp has a slew rate of
1V/micro-second on a good day with the wind in its favour. It was housed in
an unshielded plastic enclosure.
Demodulated noise that exceeded the (not very tough) product specification
were seen all the way up to 500MHz at a number of spot frequencies that
appeared to be due to the natural resonances of the input and output cables.
Above 500MHz this resonant behaviour vanished to be replaced by a steadily
rising level of demodulated 1kHz tone as the frequency increased. I stopped
testing at 1GHz, where the output error from the product was about 10% and
still rising with increased frequency.
OK, the field strength for the test was 10V/m (unmodulated) but the real
surprise was how well this very cheap and very slow opamp demodulated the
RF, and that it demodulated better at 1GHz than at 500MHz.
I have done many many immunity tests using IEC 61000-4-3 on audio equipment
and found much the same effects with every product I've ever tested.
With most larger products there is usually a roll-off in the demodulation
above 500MHz - not because the semiconductors in the ICs can't respond (they
can) but apparently because larger products have higher losses above 500MHz
or so between the cable ports and the semiconductors, plus a denser
structure that might provide more self-screening.
The transistors and diodes in all modern ICs (analog or digital) are so tiny
that they make excellent detectors at UHF and beyond. As they get smaller
(and they are) their frequency response increases (and their vulnerability
to upset and damage decreases).
Regards, Keith Armstrong
In a message dated 03/01/02 23:27:19 GMT Standard Time,
ken.ja...@emccompliance.com writes:
Subj:Re: EMC-related safety issues
List-Post: emc-pstc@listserv.ieee.org
Date:03/01/02 23:27:19 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
Sender:owner-emc-p...@majordomo.ieee.org
Reply-to: ken.ja...@emccompliance.com (Ken Javor)
To:m...@california.com (Robert Macy), ghery.pet...@intel.com (Pettit,
Ghery), james.col...@usa.alcatel.com ('James Collum'),
emc-p...@majordomo.ieee.org
Emissions from a laptop are naturally (without suppression) on the order of
10 uV/m to 100s of uV/m. 1000 uV/m would represent at least a 20 dB outage
at frequencies that could possibly interfere with sensor electronics. The
coupling is lossy: 1 mV/m will generate far less than 1 mV signal in the
electronics, and this at rf. Does anyone really see this as a remotely
possible mechanism? I don't.
--
From: Robert Macy m...@california.com
To: Pettit, Ghery ghery.pet...@intel.com, 'James Collum'
james.col...@usa.alcatel.com, emc-p...@majordomo.ieee.org
Subject: Re: EMC-related safety issues
Date: Thu, Jan 3, 2002, 3:25 PM
Perhaps, it merely interfered with the sensor electronics, not the true
magnetic field that was being sensed.
- Robert -
Robert A. Macy, PEm...@california.com
408 286 3985 fx 408 297 9121
AJM International Electronics Consultants
619 North First St, San Jose, CA 95112
-Original Message-
From: Pettit, Ghery ghery.pet...@intel.com
To: 'James Collum' james.col...@usa.alcatel.com;
emc-p...@majordomo.ieee.org emc-p...@majordomo.ieee.org
Date: Thursday, January 03, 2002 11:46 AM
Subject: RE: EMC-related safety issues
I still have a hard time believing it was a compass that was affected by
a laptop computer. ADF indication, could be. VOR, maybe. Magnetic
compass? I wouldn't want a magnetic source that strong in my lap! My belt
buckle would be stuck to it. There is quite a distance between a magnetic
compass in the cockpit of an airliner and anything a passenger is carrying.
Not so in a Cessna 172, but in a DC-10?
Ghery Pettit
-Original Message-
From: James Collum [mailto:james.col...@usa.alcatel.com]
Sent: Thursday, January 03, 2002 10:47 AM
To: emc-p...@majordomo.ieee.org
Subject: Re: EMC-related safety issues
*
A routine flight over Dallas-Fort Worth was disrupted when one of
the compasses suddenly shifted
Re: EMC-related safety issues
We need to separate specific regulation from general. The FCC does not care if a radio front end is wide open, though it now requires scanning receivers to have 38 dB image rejection. This does not mean they have narrow front ends, however. A SW receiver with a 75 MHz If may well have nothing but a low-pass filter in front of it. Cortland (What I write here is mine alone. My employer does not Concur, agree or else endorse These words, their tone, or thought.) John Shinn wrote: Actually, if you consider that there are two issues here. First, the TV and Radio manufacturers are required to no longer have a wide-open front end ... --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: EMC-related safety issues
So where do I drill the hole in my fuel injection system? John -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Doug McKean Sent: Friday, January 04, 2002 2:37 PM To: EMC-PSTC Discussion Group Subject: Re: EMC-related safety issues RE: EMC-related safety issuesKyle Ehler wrote: Another point of trivia is that a fresh oil change and new air filter prior to having your vehicle smog tested will improve the emissions results. At one time there was available OTC a fuel additive that one could deploy to further skew the results in your favor. I knew a guy who drilled a small hole in the side of his carborator, attatched a hose setup that you would use for an acquirium the other end of which was put into a water bottle. While the car was in idle, he'd adjust a valve on the hose to a slow drip of water into the carborator. This setup was on an old truck of his and he always got terrifically low emissions readings. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: EMC-related safety issues
As I recall, a tank of gasohol and a long trip down the freeway beforehand was another method. Of course it didn't work as well if you then got in a long waiting line for the test. -George S. -Original Message- From: Doug McKean [mailto:dmck...@auspex.com] Sent: Friday, January 04, 2002 2:37 PM To: EMC-PSTC Discussion Group Subject:Re: EMC-related safety issues RE: EMC-related safety issuesKyle Ehler wrote: Another point of trivia is that a fresh oil change and new air filter prior to having your vehicle smog tested will improve the emissions results. At one time there was available OTC a fuel additive that one could deploy to further skew the results in your favor. I knew a guy who drilled a small hole in the side of his carborator, attatched a hose setup that you would use for an acquirium the other end of which was put into a water bottle. While the car was in idle, he'd adjust a valve on the hose to a slow drip of water into the carborator. This setup was on an old truck of his and he always got terrifically low emissions readings. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
Cortland Richmond wrote: AIrbag testing? Well, since it costs about $US 1500 to replace them (here), I suppose there WOULD be a price hike! A couple of kids were caught by the police in a parking lot. Seems the fun thing to do to people's cars was to walk around the parking lot with baseball bats and bang on the front bumper causing the air bags to activate. Can't imagine what that all cost. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
RE: EMC-related safety issuesKyle Ehler wrote: Another point of trivia is that a fresh oil change and new air filter prior to having your vehicle smog tested will improve the emissions results. At one time there was available OTC a fuel additive that one could deploy to further skew the results in your favor. I knew a guy who drilled a small hole in the side of his carborator, attatched a hose setup that you would use for an acquirium the other end of which was put into a water bottle. While the car was in idle, he'd adjust a valve on the hose to a slow drip of water into the carborator. This setup was on an old truck of his and he always got terrifically low emissions readings. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: EMC-related safety issues
Sorry Rich, I support John's statement about the 3 meters separation distance. After all, you're in control in your own sleeping room. BTW listening radio in the dark is an enlightening experience. If it were your neighbour sleeping that close to your lamp this would have given rise to discussion between you or worse . (if he understood the cause of the interference) Govenrment regulations were not there to prevent interference under all circumstances, just to regulate the number of complaints that might give rise to legal issues. Or would you sue yourself for operating your bedlamp so close to your AM radio ;))) I suggest you reinsert your old filament bulb or buy a receiver with external antenna (but keep it away from your neighnours bedlamp ;)) Regards, Gert Gremmen, (Ing) ce-test, qualified testing === Web presence http://www.cetest.nl CE-shop http://www.cetest.nl/ce_shop.htm /-/ Compliance testing is our core business /-/ === -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Rich Nute Sent: Thursday, January 03, 2002 10:09 PM To: j...@jmwa.demon.co.uk Cc: emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues Hi John: I've replaced the incandescent lamp on my bedside table with a new energy-saving compact flourescent lamp. With the lamp on, I cannot listen to even the strongest AM radio station on my clock radio (on the same bedside table) due to the lamp interference. This must not be the usage contemplated by EMC requirements. Limits in the household environment are based on a 3 m separation between source and receiver. Wonderful! Either the lamp or the radio must be on the opposite side of the room from my bedside table. When I am in bed, one or the other is not controllable, and is therefore useless to me. Whine mode on: I want both on my bedside table, and I want both to do all of their functions. This IS not the usage contemplated by 3 m separation EMC requirements. :-) Best wishes for the New Year, Rich --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. attachment: Gert Gremmen.vcf
RE: EMC-related safety issues
I agree - ALL semiconductor demodulate. If they did not then there would be NO distortion in amplifiers and most of the HiFi industry would be out of business. Demodulation is only part of the problem however. Consider a semiconductor switching a relay. The semiconductor may switch the relay due to external EMC - but it is more likely that the semiconductor or the relay will fail and produce an 'unsafe' output. I spent 6 months designing a fail-safe synchronous gating circuit and 3 months writing the patent so Please don't tell me that it is impossible to design a safe circuit. In my experience (20 years of RD) spurious EMC/safety issues are mostly due to poor design, in the first place, and then inadequate testing. EXAMPLE from the last 10 years - when the 5Volt PSU for a safety circuit was disconnected, the system was ARMED. This was discover just before the product went into production and after through(sic) testing. Best regards Gregg PLEASE NOTE NEW NUMBERS P.O. Box 310, Reedville, Virginia 22539 USA Phone: (804) 453-3141 Fax: (804) 453-9039 Web: www.test4safety.com -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Cortland Richmond Sent: Friday, January 04, 2002 12:54 PM To: cherryclo...@aol.com Cc: emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues I don't believe this is what people are saying here. What they are saying is, ordinary semiconductors won't demodulate RF levels produced by an unintentional radiator. Cortland (What I write here is mine alone. My employer does not Concur, agree or else endorse These words, their tone, or thought.) cherryclo...@aol.com wrote: Does anyone else think that ordinary semiconductors doesn't respond to RF? I have tested a product which was little more than an LM324 quad op-amp for RF immunity using IEC 61000-4-3. This op-amp has a slew rate of 1V/micro-second on a good day with the wind in its favour. It was housed in an unshielded plastic enclosure. Demodulated noise that exceeded the (not very tough) product specification were seen all the way up to 500MHz at a number of spot frequencies that appeared to be due to the natural resonances of the input and output cables. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that Cortland Richmond cortland.richm...@alcatel.co m wrote (in 3c35ec35.5d1a...@alcatel.com) about 'EMC-related safety issues', on Fri, 4 Jan 2002: I don't believe this is what people are saying here. What they are saying is, ordinary semiconductors won't demodulate RF levels produced by an unintentional radiator. Oh, is THAT what the message meant? There's not much comparison between 10 V/m or even 3 V/m and the permitted emission levels of around 1 mV/m! -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in 200201041623.iaa13...@epgc264.sdd.hp.com) about 'EMC-related safety issues', on Fri, 4 Jan 2002: So, I am acting unreasonably by using a CFL and a radio on my bedside table. If we're being very meticulous, it is not unreasonable to use a CFL next to a radio, but it IS unreasonable to complain about what happens! Is there another solution? Further reducing the emissions is simply too costly, and is bad economics anyway, since all the mitigation components, probably still in good working order, are thrown away when the lamp fails (usually the filter capacitor in the d.c. supply dries out). -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: EMC-related safety issues
Ghery: Every couple of years, I rise to the level of personal expert, as I endure the local bi-annual vehicle smog inspection. Two days ago, I had my 1974 Chevy Nova tested. (It passed, as usual, with measured emissions at 3% to 10% of allowable limits, but I had to buy a new gas tank cap.) They check the hydrocarbon, carbon monoxide and nitrogen oxide emission levels. They look to be sure you still have all your Federally required emission systems. They check the function of engine systems like the PC valve, the exhaust gas valve and the ignition timing. Testing is performed on a dynamometer, at low high speed. They even take off your gas tank cap and make sure it holds a vacuum. The rules are a labyrinth. California does smog checks on 1974 and newer models only. Unless your car is new, or up to a few (?) years old, and then you are also exempt. Not every county in California requires the smog checks. And in counties which do require the testing, some parts of counties are exempt. I live in El Cajon in San Diego county, but if I had a legal address in Julian (same county, just about 40 miles away) I would be exempt. (It's interesting that Julian has a huge population that uses PO boxes and never seems to be in town.) When your car is from the 70's, you periodically are notified that you are a gross polluter and have to get your smog check done at a special test only station. (This type of test station is supposed to be more honest, since they are prohibited from providing any repairs, or even advice on your car's condition, other than handing you the computer print-out.) The whole test takes about 30 minutes, with almost everything under computer control. Newer cars, with on-board computers, are being tested by connecting the station computer to the vehicle's data port. Makes you wonder how much information about your driving habits and maintenance is being stored in your car's computer. Maybe the DMV will soon be able to download speed and acceleration data. Maybe you can get a moving violation from pulling too many g's (higher gas consumption, higher emissions) or exceeding 65 MPH (maybe billed like power, in increments of MPH-minutes). Maybe ignoring your check engine idiot light will become a DMV felony. The ultimate step will be to equip your on-board computer with a short-range data link. Then, periodic roadway sensors can determine if you are allowed to drive under current conditions. You might be given an option to slow to 42 MPH maximum, or pay a speed surcharge, or halt until 10 PM when smog control limits relax. I'm thinking about moving to Julian. Ed Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military Avionics EMC Services Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis -Original Message- From: Pettit, Ghery [mailto:ghery.pet...@intel.com] Sent: Friday, January 04, 2002 8:28 AM To: 'James, Chris'; 'Ken Javor'; Doug McKean; EMC-PSTC Discussion Group Subject: RE: EMC-related safety issues Chris, Annual inspections of motor vehicles are done on a state by state basis, rather than as a national requirement in the U.S. Automobiles are registered at the state level, so the federal government doesn't get involved. Some states have annual inspections, others don't. Likewise, smog inspections are at a state or lower level. California cars get smogged. Here in Washington it depends on what county you live in. If air quality in your county is good enough, you don't have to have your car smogged. If not, you get to pay more for the privilege of having a car. I live in a county where I don't have to deal with the fight. BTW, a trick I learned when I lived in California is that you stand a much better chance of passing the smog test if the engine is well warmed up when you arrive at the inspection station. Take it for what it's worth. Be thankful that we don't have to have annual inspections on our cars to the extent that one does on an airplane... $$$ Ghery Pettit Intel -Original Message- From: James, Chris [mailto:c...@dolby.co.uk] Sent: Friday, January 04, 2002 1:02 AM To: 'Ken Javor'; Doug McKean; EMC-PSTC Discussion Group Subject: RE: EMC-related safety issues Sorry disagree about turn and brake lights not being in the same class. Their very failure is often the reason for very serious accidents. I have long wished that all car manufacturers had to by law fit bulb failure warning devices to cars (but what happens when that fails). In the UK it is an offence to drive a vehicle with defective lights, (although many do). It is the driver's (not owner's) obligation to be satisfied the vehicle they are driving is fit to be on the road irespective of whether it passed it's MOT the previous day. The UK mandatory annual vehicle inspection (MOT) for vehicles over 3 years old, covers seat belts, brake efficiency
RE: EMC-related safety issues
In Kansas there are no emissions laws or annual inspections. The entire state gets a full air change every 10 minutes -so why bother? We also benefit from no mandated vehicle inspections -ever. The only thing that does get a check is the odometer and VIN, but only when a title transfer occurs. The state is more interested in indentity than safety of the machines the public chooses to play caroms with. IIRC, California and many states have an amendment to their respective emissions law that states that once a car is more than XX years old, they are considered 'antique' and exempt from the law. The threshold ranges from 20 to 30 years, depending on state/county. Another point of trivia is that a fresh oil change and new air filter prior to having your vehicle smog tested will improve the emissions results. At one time there was available OTC a fuel additive that one could deploy to further skew the results in your favor. Kyle Ehler '73 and '76 914 2.0 'Euro' antiques -Original Message- From: Pettit, Ghery [mailto:ghery.pet...@intel.com] Sent: Friday, January 04, 2002 10:28 AM To: 'James, Chris'; 'Ken Javor'; Doug McKean; EMC-PSTC Discussion Group Subject: RE: EMC-related safety issues Chris, Annual inspections of motor vehicles are done on a state by state basis, rather than as a national requirement in the U.S. Automobiles are registered at the state level, so the federal government doesn't get involved. Some states have annual inspections, others don't. Likewise, smog inspections are at a state or lower level. California cars get smogged. Here in Washington it depends on what county you live in. If air quality in your county is good enough, you don't have to have your car smogged. If not, you get to pay more for the privilege of having a car. I live in a county where I don't have to deal with the fight. BTW, a trick I learned when I lived in California is that you stand a much better chance of passing the smog test if the engine is well warmed up when you arrive at the inspection station. Take it for what it's worth. Be thankful that we don't have to have annual inspections on our cars to the extent that one does on an airplane... $$$ Ghery Pettit Intel -Original Message- From: James, Chris [mailto:c...@dolby.co.uk] Sent: Friday, January 04, 2002 1:02 AM To: 'Ken Javor'; Doug McKean; EMC-PSTC Discussion Group Subject: RE: EMC-related safety issues Sorry disagree about turn and brake lights not being in the same class. Their very failure is often the reason for very serious accidents. I have long wished that all car manufacturers had to by law fit bulb failure warning devices to cars (but what happens when that fails). In the UK it is an offence to drive a vehicle with defective lights, (although many do). It is the driver's (not owner's) obligation to be satisfied the vehicle they are driving is fit to be on the road irespective of whether it passed it's MOT the previous day. The UK mandatory annual vehicle inspection (MOT) for vehicles over 3 years old, covers seat belts, brake efficiency on a rolling road, mirrors, windshield cracks (a 20mm, 3/4inch crack in the wrong place will fail a vehicle), tyres, wheel bearings, gaiters, steering components, structural body condition, lights, smog emissions, etcI don't believe airbags are tested but guess it will come, along with the inevitable hike in price. I'm surprised the US does not have a similar Federal requirement - with all the vehicles this is a cash cow waiting to be milked. Chris -Original Message- From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: 04 January 2002 02:40 To: Doug McKean; EMC-PSTC Discussion Group Subject: Re: EMC-related safety issues A signal light is easily replaceable in terms of time and money. Most people don't use them (well, in good old Huntsville, AL, anyway, where a favorite bumper sticker reads, Turn signals, not just for smart people anymore). Failure of a light is not in the same class as an airbag deploying at the wrong time or not deploying, or ditto for brakes. -- From: Doug McKean dmck...@auspex.com To: EMC-PSTC Discussion Group emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues Date: Thu, Jan 3, 2002, 7:00 PM Point taken Ken, but consider signal lights. They're essentially safety devices and they're supposed to be maintained on cars which have been transferred amongst several owners and are decades old. Same idea with windshields, I guess also. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad
Re: EMC-related safety issues
At 8:34 AM -0500 1/4/2002, Keith Armstrong wrote: Does anyone else think that ordinary semiconductors doesn't respond to RF? I agree that commonly used semiconductors have responses well into the 100's of MHz. How much of a problem this is will depend on the nature and function of the circuitry using these components. The EUT wires, cables, pcb traces etc. act like antennae, on which the incident field voltages and currents. An antenna factor can be thought of as ratio of the field strength to the voltage induced on the terminated cable connected to the antenna. In an impedance matched system, AF=9.734/lamda*(G)^0.5, lamda being wavelength in meters, G being antenna gain over isotropic, or in dB AF dB = - G dBi -29.7 dB + 20logFMHz Assuming G is 1 (isotropic antenna), AF is 1 (= 0 dB) at about 30.8 MHz, and AF get larger as frequency increases, to a factor of 32.7 (= 30.3 dB) at 1 GHz . Since AF is field strength divided by induced voltage, the voltage induced on the trace goes down as frequency goes up for the same incident field strength. An effective receive antenna needs to be on the order of 1/2 wavelength or so; for 30 MHz this is 15m, for 1000 MHz this is 15 cm. So if a victim EUT circuit has a pretty effective receive antenna, and does not have any filtering and is equally sensitive across the frequency range under consideration (all taken together, a worst case scenario for susceptibility), (1) A 10 V/m field will theoretically induce a voltage 0.33V to 10V, depending on frequency (2) A 5000 uV/m field (10x the FCC class B limit above 960 MHz) will theoretically induce a voltage from 152 uV to 5 mV, depending on frequency. (3) A 500 uV/m field will theoretically induce a voltage from 15 uV to 500 uV depending on frequency. These are first order approximations, but they are useful in determining the level of the potential EMI threat. For instance a 4-30 mA sensor circuit using high gain operational amps will most likely be interfered with in scenario (1), there may be some susceptibility detected in scenario (2), and most likely no problem encountered with scenario (3). A sensitive all - band AM communications receiver will have problems with all three, a broadcast TV operating in a strong signal area will probably be OK with scenario 3 but not with 1 or 2. I guess what I'm really trying to say with all this is that EMC is a systems thing, taking into account the nature of the culprit EMI generator, the nature of the victim EMI receiver, and the path between them. Then we have the economics of operating different devices in the same vicinity, the politics of who gets how much of what kind of protection, etc., etc. All things considered, we should have jobs for life! best regards and a Happy New Year to all. Tom Cokenias T.N. Cokenias Consulting P.O. Box 1086 El Granada CA 94018 tel 650 726 1263 cell 650 302 0887 fax 650 726 1252
Re: EMC-related safety issues
There is a difference between extending a warranty and being liable for failure. If your seat belts fail some time after the warranty is up, the manufacturer won't pay for fixing them on your car. But the manufacturer may well be held liable for the failure. Cortland Andrews, Kurt wrote: From what I have found out it is not a requirement for safety related items to be warranted for the life of the car. I have recently been shopping for a --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
AIrbag testing? Well, since it costs about $US 1500 to replace them (here), I suppose there WOULD be a price hike! One of the tests run on a modern, computerized auto when the ignition is turned on is for airbag activation circuitry. Cortland James, Chris wrote: I don't believe airbags are tested but guess it will come, along with the inevitable hike in price. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that cherryclo...@aol.com wrote (in 131.6a66623.296 70...@aol.com) about 'EMC-related safety issues', on Fri, 4 Jan 2002: As I recall, the EU's Product Liability Directive (85/374/EEC amended by 99/34/EC) requires manufacturers to produce products that are: as safe as people generally have the right to expect. I believe it does. Note that it does not require things to be 100% safe - that is impossible. Indeed. The real problem is that whether a product really is as safe as people generally have the right to expect is usually tested in a court of law where there are lots of photographs of a dead or maimed person or a burnt-down building, or whatever. It is difficult to argue that your product is safe enough when there are relatives sobbing all over the courtroom. Indeed. The trick, I believe, is not to be in that position in the first place. Design your products using the latest safety knowledge and test them well to discover if they have any weaknesses you did not address. How do you decide what tests to do **for weaknesses you don't suspect**? Isn't that fundamentally impossible? And yes, you must consider foreseeable misuse and stupid users too. (The trouble with trying to make something foolproof is that fools are so ingenious!) Exactly! Is replacing the mains fuse in a product with a bit of fencing wire 'foreseeable misuse'? I have put this question to an IEC safety committee; it's not just a debating point! Then hopefully you won't ever find yourself trying to defend your design decisions in a court of law. Hopefully! Will your CEO accept that 'hopefully' your design won't put him in jail for corporate manslaughter? But can you ever give a better assurance than 'hopefully', at the necessary 1 in a billion probability level? I think not. Also, your company's exposure to significant financial and commercial risks will be reduced - this is the key to justifying the expense of good safety design to your employers. But it seems that the expense of 'good safety design', as determined by some safety experts, is going through the roof. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that cherryclo...@aol.com wrote (in 17d.1b28bc2.296 70...@aol.com) about 'EMC-related safety issues', on Fri, 4 Jan 2002: Does anyone else think that ordinary semiconductors doesn't respond to RF? Your experience has been shared by thousands. The demodulation normally occurs at the first semiconductor junction that the r.f signal 'sees', although at 10 V/m there may be propagation effects. The faulty reasoning that makes this effect surprising is 'silicon diodes and transistors need 0.6 V forward bias in order to conduct'. It isn't TRUE! If you add 'more than a few microamps' it's less untrue. But conduction occurs right down to minute signal voltages, resulting, certainly, in even more minute currents, but current enough to cause trouble. 'Underbiased' junctions act as excellent square-law detectors; for every 1 dB increase in input signal level you get 2 dB increase in level of recovered modulation. You may well find that JFET-input op-amps are far less sensitive to r.f. A test that I carried out a while back, on a very simple board with no EMC counter-measures at all, indicated a 26 dB difference between an LM324 and a TL072, the difference being substantially independent of frequency from 150 kHz to 1 GHz. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
Warranted parts for a car is a whole other discussion. Warranties are simply for as long as the mfr/dealer want to do the contract. I'm not sure if there's a law concerning minimum time of warranty or if it's simply driven by the free market. Supplying a parts inventory by the car mfr is I think is required for a maximum of up to 10 years. The contract for making that part is then picked up by some other shop who thinks they can turn a profit. I can't imagine Moter Vehicles passing a car for inspection with a big gaping hole in the dash or steering column where the air bag used to be. But I'll be the first to admit that I don't know any of the laws requiring parts such as selt belts and air bags being replaced years down the road. I did have an experience back in the early 80's in trying to replace a faulty seatbelt with a used one and I was prohibited from doing that. I had to buy a new one. That was back in CT so that may have been a state thing. I can only think of at least one or two modes of transportation that are covered by federal law for replacement parts being available for the entire life of the thing for as long as that may be - jet airliners and trains. Elevators and escalators also come to mind as well. Anyone here work at Otis? - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that cherryclo...@aol.com wrote (in 167.698dddc.296 70...@aol.com) about 'EMC-related safety issues', on Fri, 4 Jan 2002: As my paper at the IEEE's EMC Symposium in Montreal and my recent article in ITEM UPDATE 2001 show - at present EMC standards don't address safety issues, and most safety standards don't address EMC-related functional safety issues. As far as CENELEC is concerned, it was a conscious decision not to incorporate 'EMC and Safety' issues into EMC standards, but to treat it as a separate subject. Some people may find a clarification helpful. We have EMC matters, concerned with compatibility between items of equipment, ensuring that they continue to work (Criterion A in the Generic Standards) or fail gracefully (Criteria B and C). These criteria do not address safety issues, as indicated in paragraph 1 above. However, the Generic Standards do have a limited 'blanket' requirement, that equipment must not become unsafe *during testing*. We also have safety matters per se, which don't involve EMC. We ALSO have the separate subject, called 'EMC and Safety' or reasonable variants thereof. This addresses the matter of equipment becoming unsafe *in service* due to excessive emission levels in the environment, or lack of sufficient immunity to acceptable emission levels. So far, this seems perfectly reasonable. BUT it stops seeming reasonable when the question 'What could go wrong?' is asked and statistical data is used to attempt to answer it. To take a very simple example (maybe over-simplified), we might say that the probability of an unsafe occurrence should be less than 10^-9. That immediately means that the designer of the equipment has to look at ALL risk scenarios down to the billion-to-one against level of probability. To say that that is difficult is surely a great understatement. But some experts in the field seem to ignore that great difficulty, and simply (or maybe not so simply) state that if the designer fails to take into account ANY scenario that subsequently results in an unsafe condition, the designer has failed in his professional responsibility, and may be held criminally responsible for negligence. Well, let us be very circumspect designers and look at what immunity levels we might need to get down to that 10^-9 probability. For radiated emissions, the necessary test levels seem to be of the order of 100 V/m. Test levels for other disturbances seem to be equally distantly related to the levels normally experienced and to the test levels in pure EMC standards. We might conclude that assessment of EMC immunity per se is completely unnecessary, because testing for 'EMC and Safety' requires test levels of the order of 30 dB higher! One could go, with the sort of reasoning advocated by some experts, further into the realms of fantasy. Suppose, for a particular piece of equipment, the designer, with great diligence, identifies a million threat scenarios, each of which has a probability of 10^-9. The cumulative probability of ANY ONE of them occurring is only 10^-3. Bit risky, that! If the above reasoning seems flawed, consider a specific case, a lottery with 2000 tickets, numbered to 1999. One person can buy up to 5 tickets, and all tickets are sold. Consider the probability of a 'remarkable occurrence'. This might be the drawing of the number '' or '' or '1234' or even '1010', depending on what you think is 'remarkable'. OK, we already have a cumulative probability down from 1 in 2000 to 1 in 667 or 1 in 500. Now add in the probability that a participant in the lottery is chosen at random to draw the winning number, and draws (one of) his or her own numbers .. You shouldn't be able to get very long odds on a 'remarkable occurrence'! -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: EMC-related safety issues
Chris, Annual inspections of motor vehicles are done on a state by state basis, rather than as a national requirement in the U.S. Automobiles are registered at the state level, so the federal government doesn't get involved. Some states have annual inspections, others don't. Likewise, smog inspections are at a state or lower level. California cars get smogged. Here in Washington it depends on what county you live in. If air quality in your county is good enough, you don't have to have your car smogged. If not, you get to pay more for the privilege of having a car. I live in a county where I don't have to deal with the fight. BTW, a trick I learned when I lived in California is that you stand a much better chance of passing the smog test if the engine is well warmed up when you arrive at the inspection station. Take it for what it's worth. Be thankful that we don't have to have annual inspections on our cars to the extent that one does on an airplane... $$$ Ghery Pettit Intel -Original Message- From: James, Chris [mailto:c...@dolby.co.uk] Sent: Friday, January 04, 2002 1:02 AM To: 'Ken Javor'; Doug McKean; EMC-PSTC Discussion Group Subject: RE: EMC-related safety issues Sorry disagree about turn and brake lights not being in the same class. Their very failure is often the reason for very serious accidents. I have long wished that all car manufacturers had to by law fit bulb failure warning devices to cars (but what happens when that fails). In the UK it is an offence to drive a vehicle with defective lights, (although many do). It is the driver's (not owner's) obligation to be satisfied the vehicle they are driving is fit to be on the road irespective of whether it passed it's MOT the previous day. The UK mandatory annual vehicle inspection (MOT) for vehicles over 3 years old, covers seat belts, brake efficiency on a rolling road, mirrors, windshield cracks (a 20mm, 3/4inch crack in the wrong place will fail a vehicle), tyres, wheel bearings, gaiters, steering components, structural body condition, lights, smog emissions, etcI don't believe airbags are tested but guess it will come, along with the inevitable hike in price. I'm surprised the US does not have a similar Federal requirement - with all the vehicles this is a cash cow waiting to be milked. Chris -Original Message- From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: 04 January 2002 02:40 To: Doug McKean; EMC-PSTC Discussion Group Subject: Re: EMC-related safety issues A signal light is easily replaceable in terms of time and money. Most people don't use them (well, in good old Huntsville, AL, anyway, where a favorite bumper sticker reads, Turn signals, not just for smart people anymore). Failure of a light is not in the same class as an airbag deploying at the wrong time or not deploying, or ditto for brakes. -- From: Doug McKean dmck...@auspex.com To: EMC-PSTC Discussion Group emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues Date: Thu, Jan 3, 2002, 7:00 PM Point taken Ken, but consider signal lights. They're essentially safety devices and they're supposed to be maintained on cars which have been transferred amongst several owners and are decades old. Same idea with windshields, I guess also. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server
Re: EMC-related safety issues
No, it's simply that it isn't considered reasonable to have a radio and a CFL in close proximity. If you want a lamp and a radio close together, use an incandescent lamp. That's the bottom line, isn't it? Somebody has decided for me (in terms of what is reasonable) that if I use a CFL, then I must separate it from a radio by 3 m or more. So, I am acting unreasonably by using a CFL and a radio on my bedside table. :-( Rich --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: EMC-related safety issues
From what I have found out it is not a requirement for safety related items to be warranted for the life of the car. I have recently been shopping for a new car and one of the ones I looked at is the Toyota Celica. It states the following in the brochure: The seat belts and air bags are covered under the powertrain warranty which is for 5 years or 60,000 miles. The emission control components are also not covered for the life of the car. The brochure states that components covered under the Federal emission defect warranty are covered for 3 years or 36,000 miles and specified major emission control components are covered for 8 years or 80,000 miles. My current car, a 1990 Acura Integra, has the following coverage. The anti-lock brakes are covered under the normal 3 year/36,000 mile coverage. According to the owners manual the seat belts are covered for the life of the car because Acura considers them vital to safety. The car does not have airbags, it has those stupid mouse (automatic) seatbelts. So it appears that the only reason that the seat belts are covered longer than the standard warranty is because Acura chose to do so, not because they have to (and I applaud them for that). I do not recall what the warranty is on the emission control components. I would suspect it is the same as the Toyota if the federal rules were the same in 1990 as they are now. Kurt Andrews Compliance Engineer Tracewell Systems, Inc. 567 Enterprise Drive Westerville, Ohio 43081 voice: 614.846.6175 toll free: 800.848.4525 fax: 614.846.7791 http://www.tracewellsystems.com/ -Original Message- From: Doug McKean [mailto:dmck...@auspex.com] Sent: Thursday, January 03, 2002 5:43 PM To: EMC-PSTC Discussion Group Subject:Re: EMC-related safety issues Ken Javor wrote: Curiosity. How long must airbags work? As long as you have the car, supposedly. Same with seat belts. They're all safety features. Interestingly, if you have a cracked or broken windshield, a cop *can* write you up for the car being unsafe. I've never heard of it, but a classmate of mine who became a statie told me when he saw a huge crack in my windshield. I'm also under the impression that manufacturers are responsible for maintaining a repair/replacement parts inventory to dealers for only 10 years. Not sure about that one. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
As I understand the way the civil law section of the EU's Product Liability Directive operates (I am not a lawyer) it does in fact place the burden of proof on the manufacturer, who is effectively considered 'guilty until proved innocent'. I also understand that any number of manufacturers can be sued in the civil courts under one safety incident, and the liabilities of each awarded 'on the balance of probabilities' that their product caused the damage, injury or death being complained about. Also...nobody has to prove negligence on the part of the manufacturer, this is sometimes called 'no-fault liability' - you can be held to be liable under the law even though nobody has proved that your product was actually the cause of the safety incident. Another interesting fact about EU Product Liability is that in the civil courts in most EU member states there is no financial upper limit to the damages that can be awarded against a manufacturer. We may not like it, but that's how the world appears to be at the moment. Regards, Keith Armstrong In a message dated 03/01/02 19:52:20 GMT Standard Time, j...@jmwa.demon.co.uk writes: Subj:Re: EMC-related safety issues Date:03/01/02 19:52:20 GMT Standard Time From:j...@jmwa.demon.co.uk (John Woodgate) Sender:owner-emc-p...@majordomo.ieee.org Reply-to: A HREF=mailto:j...@jmwa.demon.co.uk;j...@jmwa.demon.co.uk/A (John Woodgate) To:emc-p...@majordomo.ieee.org I read in !emc-pstc that Gary McInturff Gary.McInturff@worldwidepackets .com wrote (in 917063bab0ddb043af5faa73c7a835d40ac...@windlord.wwp.com ) about 'EMC-related safety issues', on Thu, 3 Jan 2002: While I take your point - I'll challenge with the equally valid argument that says show me the data that they do cause SIDS! Out of order! That's the whole point! Manufacturers are being required to prepare to prove a negative, which is inherently impossible in most cases. No-one is required to prove a positive, which is easy if it is true. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Re: EMC-related safety issues
Hey, Ken, let's try to be realistic here!
Sure - we should try to get laws we don't like changed, but that isn't going
to happen overnight and in the meantime we have to operate within the law as
it stands.
Or are you suggesting immediate insurrection by product manufacturers?
(Outlaw manufacturers roaming the wild wild west - an interesting concept!)
The IEE's guide on EMC and Functional Safety is concerned with such legal
aspects, but is also concerned with saving lives in a world where electronic
control of safety-related functions is proliferating madly.
As my paper at the IEEE's EMC Symposium in Montreal and my recent article in
ITEM UPDATE 2001 show - at present EMC standards don't address safety issues,
and most safety standards don't address EMC-related functional safety issues.
Regards, Keith Armstrong
In a message dated 03/01/02 17:24:42 GMT Standard Time,
ken.ja...@emccompliance.com writes:
Subj:Re: EMC-related safety issues
Date:03/01/02 17:24:42 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
Sender:owner-emc-p...@majordomo.ieee.org
Reply-to: A
HREF=mailto:ken.ja...@emccompliance.com;ken.ja...@emccompliance.com/A
(Ken Javor)
To:c...@dolby.co.uk (James, Chris), acar...@uk.xyratex.com
('acar...@uk.xyratex.com'), emc-p...@majordomo.ieee.org
There is an inherent contradiction in this anti-profit, anti-technology
point-of-view that I cannot and will not defend. All I am saying is that
people who feel this is wrong should stand up and say so, not write guides
for how to go along with it.
Re: EMC-related safety issues
Does anyone else think that ordinary semiconductors doesn't respond to RF?
I have tested a product which was little more than an LM324 quad op-amp for
RF immunity using IEC 61000-4-3. This op-amp has a slew rate of
1V/micro-second on a good day with the wind in its favour. It was housed in
an unshielded plastic enclosure.
Demodulated noise that exceeded the (not very tough) product specification
were seen all the way up to 500MHz at a number of spot frequencies that
appeared to be due to the natural resonances of the input and output cables.
Above 500MHz this resonant behaviour vanished to be replaced by a steadily
rising level of demodulated 1kHz tone as the frequency increased. I stopped
testing at 1GHz, where the output error from the product was about 10% and
still rising with increased frequency.
OK, the field strength for the test was 10V/m (unmodulated) but the real
surprise was how well this very cheap and very slow opamp demodulated the RF,
and that it demodulated better at 1GHz than at 500MHz.
I have done many many immunity tests using IEC 61000-4-3 on audio equipment
and found much the same effects with every product I've ever tested.
With most larger products there is usually a roll-off in the demodulation
above 500MHz - not because the semiconductors in the ICs can't respond (they
can) but apparently because larger products have higher losses above 500MHz
or so between the cable ports and the semiconductors, plus a denser structure
that might provide more self-screening.
The transistors and diodes in all modern ICs (analog or digital) are so tiny
that they make excellent detectors at UHF and beyond. As they get smaller
(and they are) their frequency response increases (and their vulnerability to
upset and damage decreases).
Regards, Keith Armstrong
In a message dated 03/01/02 23:27:19 GMT Standard Time,
ken.ja...@emccompliance.com writes:
Subj:Re: EMC-related safety issues
Date:03/01/02 23:27:19 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
Sender:owner-emc-p...@majordomo.ieee.org
Reply-to: A
HREF=mailto:ken.ja...@emccompliance.com;ken.ja...@emccompliance.com/A
(Ken Javor)
To:m...@california.com (Robert Macy), ghery.pet...@intel.com (Pettit,
Ghery), james.col...@usa.alcatel.com ('James Collum'),
emc-p...@majordomo.ieee.org
Emissions from a laptop are naturally (without suppression) on the order of
10 uV/m to 100s of uV/m. 1000 uV/m would represent at least a 20 dB outage
at frequencies that could possibly interfere with sensor electronics. The
coupling is lossy: 1 mV/m will generate far less than 1 mV signal in the
electronics, and this at rf. Does anyone really see this as a remotely
possible mechanism? I don't.
--
From: Robert Macy m...@california.com
To: Pettit, Ghery ghery.pet...@intel.com, 'James Collum'
james.col...@usa.alcatel.com, emc-p...@majordomo.ieee.org
Subject: Re: EMC-related safety issues
Date: Thu, Jan 3, 2002, 3:25 PM
Perhaps, it merely interfered with the sensor electronics, not the true
magnetic field that was being sensed.
- Robert -
Robert A. Macy, PEm...@california.com
408 286 3985 fx 408 297 9121
AJM International Electronics Consultants
619 North First St, San Jose, CA 95112
-Original Message-
From: Pettit, Ghery ghery.pet...@intel.com
To: 'James Collum' james.col...@usa.alcatel.com;
emc-p...@majordomo.ieee.org emc-p...@majordomo.ieee.org
Date: Thursday, January 03, 2002 11:46 AM
Subject: RE: EMC-related safety issues
I still have a hard time believing it was a compass that was affected
by
a laptop computer. ADF indication, could be. VOR, maybe. Magnetic
compass? I wouldn't want a magnetic source that strong in my lap! My
belt
buckle would be stuck to it. There is quite a distance between a magnetic
compass in the cockpit of an airliner and anything a passenger is
carrying.
Not so in a Cessna 172, but in a DC-10?
Ghery Pettit
-Original Message-
From: James Collum [mailto:james.col...@usa.alcatel.com]
Sent: Thursday, January 03, 2002 10:47 AM
To: emc-p...@majordomo.ieee.org
Subject: Re: EMC-related safety issues
*
A routine flight over Dallas-Fort Worth was disrupted when one of
the compasses suddenly shifted 10 degrees to the right. The pilot asked
if
any passenger was operating an electronic device, and finding that a
laptop
computer had just been turned on requested that it be turned off,
whereupon
the compass returned to normal. Following RTCA guidelines the pilot
requested that the laptop be turned on again 10 minutes later, when the
compass error returned.
Ref: Compliance Engineering (European edition) Nov/Dec 1996 p12
*
I am fascinated by this amazing story
Re: EMC-related safety issues
The IEE's guide on EMC and Functional Safety is concerned with helping engineers and managers avoid legal problems - but I don't call this appeasement, just good practice. But the guide is also concerned with saving lives in a world where electronic control of safety-related functions is proliferating madly. As my paper at the IEEE's EMC Symposium in Montreal and my recent article in ITEM UPDATE 2001 show - at present EMC standards don't address safety issues, and most safety standards don't address EMC-related functional safety issues. Regards, Keith Armstrong In a message dated 03/01/02 20:04:46 GMT Standard Time, ken.ja...@emccompliance.com writes: Subj:Re: EMC-related safety issues Date:03/01/02 20:04:46 GMT Standard Time From:ken.ja...@emccompliance.com (Ken Javor) Sender:owner-emc-p...@majordomo.ieee.org Reply-to: A HREF=mailto:ken.ja...@emccompliance.com;ken.ja...@emccompliance.com/A (Ken Javor) To:cortland.richm...@alcatel.com (Cortland Richmond), acar...@uk.xyratex.com (Andrew Carson) CC:emc-p...@majordomo.ieee.org Curiosity. How long must airbags work? A car can be driven for two decades or more, by an uncontrolled number of owners, and with no mandatory inspection or service. How long is a manufacturer liable for the proper operation of those airbags? Same question for anti-lock brakes. If the warning light comes on and is ignored, who is at fault? If the warning light is disabled by an owner, and the next owner suffers injury due to improper operation of either of these systems, who is at fault? Don't give me the logical answer. I can figure that out. Knowing that the culpable seller is not a tempting target but the manufacturer is, in the present climate some bright lawyer will come up with a rationale for suing the manufacturer. It is the climate that must be changed and the IEE guide that started this thread, in my opinion, appeases this trend rather than opposes it. -- From: Cortland Richmond cortland.richm...@alcatel.com To: Andrew Carson acar...@uk.xyratex.com Cc: emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues Date: Thu, Jan 3, 2002, 12:22 PM As engineers, we should consider the safety implications of what we design, test or otherwise work on. EMI is part of that. What is considered a safety risk depends a great deal on corporate policy, the legal, political and popular climate in one's state of residence, and the kind of equipment under consideration. As it happens, the issue of pacemaker vulnerability is addressed in more regulations than USC 47. That is why, in the United States, we have not only a limit on microwave oven leakage, but also pacemaker warning signs on microwave ovens used by the public. The robotic arm is a great example. Others are automotive airbags, or electronically controlled brakes. These sort of things are the reason why industry associations develop limits of their own. Those limits accommodate both a performance requirement and practical aspects; they can't make the product too expensive to build or no one will be able to sell them at a profit. They can't be unreliable in the field or people won't buy them at all. And they can't cause too many problems, or the company will be sued. One factor weighs against another. We are at the balance point. Regards, Cortland Richmond (What I write here is mine alone. My employer does not Concur, agree or else endorse These words, their tone, or thought.) Andrew Carson wrote: I get the idea that we a missing the whole point of this discussion. Should we as Professional Safety Engineers and Product designers consider the safety implications of EMC emissions ? The answer is a definite Yes. We have a clear duty of care and responsibility to consider all implications of our products being used in there intended application. Even if the consideration on EMC emissions and safety is Do not be silly. We still have to at least consider it. ...
RE: EMC-related safety issues
Sorry disagree about turn and brake lights not being in the same class. Their very failure is often the reason for very serious accidents. I have long wished that all car manufacturers had to by law fit bulb failure warning devices to cars (but what happens when that fails). In the UK it is an offence to drive a vehicle with defective lights, (although many do). It is the driver's (not owner's) obligation to be satisfied the vehicle they are driving is fit to be on the road irespective of whether it passed it's MOT the previous day. The UK mandatory annual vehicle inspection (MOT) for vehicles over 3 years old, covers seat belts, brake efficiency on a rolling road, mirrors, windshield cracks (a 20mm, 3/4inch crack in the wrong place will fail a vehicle), tyres, wheel bearings, gaiters, steering components, structural body condition, lights, smog emissions, etcI don't believe airbags are tested but guess it will come, along with the inevitable hike in price. I'm surprised the US does not have a similar Federal requirement - with all the vehicles this is a cash cow waiting to be milked. Chris -Original Message- From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: 04 January 2002 02:40 To: Doug McKean; EMC-PSTC Discussion Group Subject: Re: EMC-related safety issues A signal light is easily replaceable in terms of time and money. Most people don't use them (well, in good old Huntsville, AL, anyway, where a favorite bumper sticker reads, Turn signals, not just for smart people anymore). Failure of a light is not in the same class as an airbag deploying at the wrong time or not deploying, or ditto for brakes. -- From: Doug McKean dmck...@auspex.com To: EMC-PSTC Discussion Group emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues Date: Thu, Jan 3, 2002, 7:00 PM Point taken Ken, but consider signal lights. They're essentially safety devices and they're supposed to be maintained on cars which have been transferred amongst several owners and are decades old. Same idea with windshields, I guess also. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues - lighting noise
George is correct so far as normal fluorescent, and of course, incandescent, lighting. These are not regulated for emissions in the US. But the new energy-saving RF lighting devices (bulbs) are regulated under FCC Part 18. The limits appear to be quite generous. The regulations are found in 18.305 for radiated (above 30 MHz) and in 18.307 for conducted (including the AM/MW Broadcast band). I recall that the ARRL fought the relaxation of the emission limits because some lamps operate (if I tremember correctly) in the amateur 20 meter band or nearby (maybe 13.56 MHz ??). Jack Jacob Z. Schanker, P.E. 65 Crandon Way Rochester, NY 14618 Phone: 585 442 3909 Fax: 585 442 2182 j.schan...@ieee.org - Original Message - From: geor...@lexmark.com To: Rich Nute ri...@sdd.hp.com Cc: j...@jmwa.demon.co.uk; emc-p...@majordomo.ieee.org Sent: Thursday, January 03, 2002 4:32 PM Subject: Re: EMC-related safety issues | | | | I think the issue is that the lamp is not an EMC regulated | device. In fact, in Europe, ITE conducted emissions must | be regulated so as not to cause desk/room lights to flicker, | as in when a fuser lamp in a printer kicks on. | | Apparantly the proper functioning of lighting takes precedence | over the propoer functioning of radios and the like affected by | the lights? | | George | | | | | Rich Nute richn%sdd.hp@interlock.lexmark.com on 01/03/2002 04:08:51 PM | | Please respond to Rich Nute richn%sdd.hp@interlock.lexmark.com | | To: jmw%jmwa.demon.co...@interlock.lexmark.com | cc: emc-pstc%majordomo.ieee@interlock.lexmark.com (bcc: George | Alspaugh/Lex/Lexmark) | Subject: Re: EMC-related safety issues | | | | | | | | Hi John: | | |I've replaced the incandescent lamp on my bedside |table with a new energy-saving compact flourescent |lamp. With the lamp on, I cannot listen to even |the strongest AM radio station on my clock radio |(on the same bedside table) due to the lamp |interference. This must not be the usage |contemplated by EMC requirements. | |Limits in the household environment are based on a 3 m separation |between source and receiver. | | Wonderful! | | Either the lamp or the radio must be on the opposite | side of the room from my bedside table. When I am in | bed, one or the other is not controllable, and is | therefore useless to me. | | Whine mode on: I want both on my bedside table, and | I want both to do all of their functions. This IS | not the usage contemplated by 3 m separation EMC | requirements. | | :-) | | | Best wishes for the New Year, | Rich | | | | | --- | This message is from the IEEE EMC Society Product Safety | Technical Committee emc-pstc discussion list. | | Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ | | To cancel your subscription, send mail to: | majord...@ieee.org | with the single line: | unsubscribe emc-pstc | | For help, send mail to the list administrators: | Michael Garretson:pstc_ad...@garretson.org | Dave Healddavehe...@mediaone.net | | For policy questions, send mail to: | Richard Nute: ri...@ieee.org | Jim Bacher: j.bac...@ieee.org | | All emc-pstc postings are archived and searchable on the web at: | No longer online until our new server is brought online and the old messages are imported into the new server. | --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in 200201032108.naa11...@epgc264.sdd.hp.com) about 'EMC-related safety issues', on Thu, 3 Jan 2002: Whine mode on: I want both on my bedside table, and I want both to do all of their functions. This IS not the usage contemplated by 3 m separation EMC requirements. :-) Use an incandescent lamp. For a bedside table, quite a low power lamp is OK, especially if you use a low-voltage lamp. But keep a switch-mode 'electronic transformer' at least 3 m from the radio, of course! Or stick to an ordinary transformer. Old technology is NOT always BAD! Grandpa is your FRIEND. Since it isn't practicable to reduce the emissions of CFLs well below the limits of CISPR15/EN55015 without heroic measures, the 3 m separation has to be observed, or CFLs have to be banned or made much more costly. The latter possibilities are clearly not environmentally acceptable. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that david_ster...@ademco.com wrote (in 2DF7C54A75B dd311b61700508b64231002c5a...@nyhqex1.ademcohq.com) about 'EMC-related safety issues', on Thu, 3 Jan 2002: My copy of BS EN 50140-4:1996 50140-4? ENV50140 was an early version of EN61000-4-3 and is withdrawn. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that Kevin Harris harr...@dscltd.com wrote (in D886DC8708ACD3118A0500606DD5DA6328C655@DSC_MAIL) about 'EMC-related safety issues', on Thu, 3 Jan 2002: If the BSI site says that, then it is yet another proof of you can't always believe what you read. :) My Aug 2001 version of the BSI electronic catalog shows a publication date of 1996 for the BS EN ( but the document was actually released in late 1995) with an addendum A1 published in 1998. The hard copy sitting in front of me (from BSI) agrees with the electronic catalog :) There was a very generous transition period which ended in January of 2001. I'll check again. Maybe there was some sort of glitch. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: EMC-related safety issues
Actually, if you consider that there are two issues here. First, the TV and Radio manufacturers are required to no longer have a wide-open front end as was prevalent quite a few years ago. This single action by the FCC improved the immunity (decreased the susceptability) to incidental RF. Secondly, by requiring the label to say must accept, eliminates a lot of complaints about LEGAL incidental as well as intentional radiators (you might also read that as easer to dismiss complaints). It was a start. John Shinn -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Doug McKean Sent: Thursday, January 03, 2002 2:36 PM To: EMC-PSTC Discussion Group Subject: Re: EMC-related safety issues Rich Nute wrote: EMC? Ha! You raise a good point since the FCC legally can but hasn't implemented an American version of immunity standards. The words must accept on the FCC labels of your effected devices are evident of it. Maybe some day we will have do immunity testing. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
Point taken Ken, but consider signal lights. They're essentially safety devices and they're supposed to be maintained on cars which have been transferred amongst several owners and are decades old. Same idea with windshields, I guess also. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I have it from a message on the r...@contesting.com list that Phillips bulbs produce less RF noise than others. I can't vouch for that, however. Cortland (What I write here is mine alone. My employer does not Concur, agree or else endorse These words, their tone, or thought.) Rich Nute wrote: I've replaced the incandescent lamp on my bedside table with a new energy-saving compact flourescent lamp. With the lamp on, I cannot listen to even the strongest AM radio station on my clock radio (on the same bedside table) due to the lamp interference. This must not be the usage contemplated by EMC requirements. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
The answer is in the original posting, the new lamp saves energy. Which translates into saving the planet. That trumps all, these days. -- From: geor...@lexmark.com To: Rich Nute ri...@sdd.hp.com Cc: j...@jmwa.demon.co.uk, emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues Date: Thu, Jan 3, 2002, 3:32 PM I think the issue is that the lamp is not an EMC regulated device. In fact, in Europe, ITE conducted emissions must be regulated so as not to cause desk/room lights to flicker, as in when a fuser lamp in a printer kicks on. Apparantly the proper functioning of lighting takes precedence over the propoer functioning of radios and the like affected by the lights? George Rich Nute richn%sdd.hp@interlock.lexmark.com on 01/03/2002 04:08:51 PM Please respond to Rich Nute richn%sdd.hp@interlock.lexmark.com To: jmw%jmwa.demon.co...@interlock.lexmark.com cc: emc-pstc%majordomo.ieee@interlock.lexmark.com (bcc: George Alspaugh/Lex/Lexmark) Subject: Re: EMC-related safety issues Hi John: I've replaced the incandescent lamp on my bedside table with a new energy-saving compact flourescent lamp. With the lamp on, I cannot listen to even the strongest AM radio station on my clock radio (on the same bedside table) due to the lamp interference. This must not be the usage contemplated by EMC requirements. Limits in the household environment are based on a 3 m separation between source and receiver. Wonderful! Either the lamp or the radio must be on the opposite side of the room from my bedside table. When I am in bed, one or the other is not controllable, and is therefore useless to me. Whine mode on: I want both on my bedside table, and I want both to do all of their functions. This IS not the usage contemplated by 3 m separation EMC requirements. :-) Best wishes for the New Year, Rich --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
Emissions from a laptop are naturally (without suppression) on the order of 10 uV/m to 100s of uV/m. 1000 uV/m would represent at least a 20 dB outage at frequencies that could possibly interfere with sensor electronics. The coupling is lossy: 1 mV/m will generate far less than 1 mV signal in the electronics, and this at rf. Does anyone really see this as a remotely possible mechanism? I don't. -- From: Robert Macy m...@california.com To: Pettit, Ghery ghery.pet...@intel.com, 'James Collum' james.col...@usa.alcatel.com, emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues Date: Thu, Jan 3, 2002, 3:25 PM Perhaps, it merely interfered with the sensor electronics, not the true magnetic field that was being sensed. - Robert - Robert A. Macy, PEm...@california.com 408 286 3985 fx 408 297 9121 AJM International Electronics Consultants 619 North First St, San Jose, CA 95112 -Original Message- From: Pettit, Ghery ghery.pet...@intel.com To: 'James Collum' james.col...@usa.alcatel.com; emc-p...@majordomo.ieee.org emc-p...@majordomo.ieee.org Date: Thursday, January 03, 2002 11:46 AM Subject: RE: EMC-related safety issues I still have a hard time believing it was a compass that was affected by a laptop computer. ADF indication, could be. VOR, maybe. Magnetic compass? I wouldn't want a magnetic source that strong in my lap! My belt buckle would be stuck to it. There is quite a distance between a magnetic compass in the cockpit of an airliner and anything a passenger is carrying. Not so in a Cessna 172, but in a DC-10? Ghery Pettit -Original Message- From: James Collum [mailto:james.col...@usa.alcatel.com] Sent: Thursday, January 03, 2002 10:47 AM To: emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues * A routine flight over Dallas-Fort Worth was disrupted when one of the compasses suddenly shifted 10 degrees to the right. The pilot asked if any passenger was operating an electronic device, and finding that a laptop computer had just been turned on requested that it be turned off, whereupon the compass returned to normal. Following RTCA guidelines the pilot requested that the laptop be turned on again 10 minutes later, when the compass error returned. Ref: Compliance Engineering (European edition) Nov/Dec 1996 p12 * I am fascinated by this amazing story (which must surely be an urban myth) and went in search of more info on the internet. I had never heard of the RTCA ( a private corporation) before, but noticed via their web site that you have to be a member company (i.e. pay) to receive the wisdom that it contains. Aviation is merely a hobby of mine but I'm interested in reading a copy of the RTCA's DO-233/214 and 196 documents without shelling out hundreds for the privilege, can anyone advise? Also does anyone know what recommendations have they made to modifying FAR 91.21 (as per their web site). In reading this again, I'm curious as to how the pilot would have known about a private companies convoluted guideline for fault finding on errant radio direction equipment involving locating industrious passengers and commandeering their computers at 10 minute intervals. Surely he would have done what any professional engineer would do, beat or kick the 10 degree error out of the RDF equipment? Or maybe just wonder to him/herself about how strange things happen in the Dallas Fort Worth area? Tounge in cheek, my comments and not those of my employer etc. Jim --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave
Re: EMC-related safety issues
Ken Javor wrote: Curiosity. How long must airbags work? As long as you have the car, supposedly. Same with seat belts. They're all safety features. Interestingly, if you have a cracked or broken windshield, a cop *can* write you up for the car being unsafe. I've never heard of it, but a classmate of mine who became a statie told me when he saw a huge crack in my windshield. I'm also under the impression that manufacturers are responsible for maintaining a repair/replacement parts inventory to dealers for only 10 years. Not sure about that one. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: EMC-related safety issues
Rich, I think you're right. Both lawyer and plaintiff are responsible. The jury that goes along with the whole thing just because an insurance company is going to pay the whole thing is no help either. The lady years ago (Oakland Calif if memory serves) that sued the store that sold, and the manufacturer who design, a skateboard. Seems her son fell off and broke and arm. She sued as an attractive nusiance I have fantasies of just once someone in the Jury standing up and screaning. What the heck did you expect when you bought your son a board that was mounted to little wheels lady, and then giving the plantiffs lawyer a swift kick for wasting everyones time. I have a wonderful lawyer joke, but I'll spare the group - but I'm chuckling pretty hard Gary -Original Message- From: Rich Nute [mailto:ri...@sdd.hp.com] Sent: Thursday, January 03, 2002 12:21 PM To: ken.ja...@emccompliance.com Cc: cherryclo...@aol.com; m...@california.com; emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues Hi Ken: Trial lawyers and their clients have an obvious interest in portraying consumers as helpless and child-like, and rich corporations as robber-barons preying on the poor and weak. But why does the rest of society jump on that bandwagon? Because profit and wealth, once badges of achievement, are now considered prima facie evidence of malfeasance. The trail lawyers, in an attempt to enrich themselves, have launched a full-scale attack on the system of capitalism itself. But unlike a real capitalist, who enriches himself by serving others, the trial lawyer is a parasite - he achieves his success at the expense of others, and the degree of his success is the degree of destruction visited on society. It is not the lawyers, but the client/plaintiff who sees an opportunity for a free ride for the rest of his life. Society wants to see the little guy get the free ride and the deep-pocket corporation pay through the nose for his misdeeds. I don't really believe that the client/plaintiff motive is punishment of the deep-pocket corporation, although that theory may be the one used in court. Ambulance-chasing lawyers do influence the client/ plaintiff in their path to the free ride, as the lawyers, too, want a free ride. (It seems to me that there is a prepronderance of very nice cars that bear the wheelchair symbol.) Best wishes for the New Year, Rich --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
Rich Nute wrote: EMC? Ha! You raise a good point since the FCC legally can but hasn't implemented an American version of immunity standards. The words must accept on the FCC labels of your effected devices are evident of it. Maybe some day we will have do immunity testing. - Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: EMC-related safety issues
Re: EMC-related safety issues I do not disagree but what about the use of mobile phones in emergencies - should the FCC require all advertisements to carry a warning that mobile phones cannot be relied upon for emergencies? I think that would be a great idea as it might even focus the minds of the service provides to provide service! : ^ ] Best regards Gregg (Kervill) -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of richwo...@tycoint.com Sent: Thursday, January 03, 2002 8:26 AM To: emc-p...@majordomo.ieee.org Subject: RE: EMC-related safety issues Ken, let me address the specific case you mentioned - the RF camera used for baby surveillance. In that particular application, surveillance for the protection of persons, more severe immunity requirements apply. Those requirements are either specified in EN 50130-4 or the particular ETSI product EMC standard. A manucturer should understand that the product may be used for protection of persons and apply the appropriate immunity requirements. Failure to do so, could create a liability issue. Richard Woods Sensormatic Electronics Tyco International -Original Message- From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Wednesday, January 02, 2002 2:22 PM To: cherryclo...@aol.com; emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues I have read a part of the IEE guide mentioned below. What I have read on a paragraph by paragraph basis is fine, but I find the overall philosophy deeply troubling. The tone of the document is that the manufacturer is responsible for all uses or misuse of the equipment he sells in concert with every other type of equipment made or that might be made at some time in the future. This document is a trial lawyer's dream. It takes us from a society in which a sale was deemed a transaction of mutual benefit between equals to a society in which an Omniscient Producer must cater to the needs of an ignorant, childlike Consumer, and in direct corollary, any misuse of any product by any consumer is deemed proof that the Omniscient Producer was profiting by taking advantage of a helpless victim. I realize this document merely reflects this prevalent view, but the idea that an Industry group would provide such a smoking gun for some trial lawyer to use in defense of some poor misled swindled consumer is, to say the least, troubling. To say that Industry standards don't go far enough, that it is the responsibility of the Producer to be able to determine all possible environments and failure modes that might ever occur is placing an impossible burden and any rationale entity, upon reading this document will immediately cease production of anything that could conceivably ever malfunction in anyway whatsoever. Case in point: A friend of mine bought one of these 2.4 GHz remote miniature video cameras with integral IREDs and is able to monitor his infant twins from his own bedroom, even in the middle of the night with no lights on in the twins' bedroom. Suppose that 2.4 GHz link is disturbed in some way and he misses something important happening in that bedroom. Is the manufacturer of that video system responsible for any ill that then befalls my friend's twins? I think not. But this safety guide says yes, and places the manufacturer at risk. -- From: cherryclo...@aol.com To: emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues Date: Wed, Jan 2, 2002, 9:49 AM Once again, John, you seem to be trying to give a negative impression about the IEE's guide on EMC and Functional Safety (which you now admit you haven't read) instead of simply saying what it is that you think is wrong with it. Of course I am passionate about the IEE guide - my colleagues and I spent a long time working on it! When I discovered you were criticising it to the emc-pstc of course I had to respond - but I was not (and am not) trying to defend the guide, merely trying to find out just exactly what it is that you (and your silent 'equally senior experts') don't like about it so I can get it improved. I am sorry if my wordy emails give the wrong impression - the simple fact is that I always write too much (as any editor who has had an article from me will confirm!). Once again I ask you - and everyone else in the entire EMC or Safety community world-wide - to read the IEE's guide and let me have constructive comments about how to improve it. You can easily download it for free from www.iee.org.uk/Policy/Areas/Electro (- you only need to download the 'core' document for this exercise and can leave the nine 'industry annexes' for later criticism). I'll make it easy for anyone to comment even if they haven't read the Core of the IEE's guide ...the guide is based on the following engineering approach, explicitly stated
Re: EMC-related safety issues
LOL. Not entirely beside the point. That rubbish attracts listeners. The more listeners, the more advertising time is worth. The less interference, the more potential listeners. Advertising revenue then depends on clear reception and no rfi. Now you have the fundamental reason for FCC/CISPR EMI control. No rubbish! -- From: John Woodgate j...@jmwa.demon.co.uk To: emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues Date: Thu, Jan 3, 2002, 2:20 PM I do not find that. In most US hotels I've stayed in, the bedroom radios are cheapo-squared but still receive 99 stations - all putting out rubbish, so any interference is beside the point. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: EMC-related safety issues
Re: EMC-related safety issuesIn Ken's second scenario, Chrysler Corp. had to fix the Dodge/Plymoth min-van's rear door latch. I'm sure of the other two. However, note that it is not the US government that would be after the knife (actually a box cutter) manufacturer, but what we call on this side of the pond, ambulace chasers, also known as lawers. Now for my Lawyer Joke - There are two kinds of lawyers. Good ones and Bad ones. And, we do not need any more of either kind. John -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of James, Chris Sent: Thursday, January 03, 2002 9:06 AM To: 'Ken Javor'; 'acar...@uk.xyratex.com'; emc-p...@majordomo.ieee.org Subject: RE: EMC-related safety issues So why ain't the US government chasing the knife manufacturer of the knives used by the terrorists rather than Bin Laden I'm sorry but stories like the below make me despair at the way society is headed. If people want technology they will have to accept some of the pitfalls that come with it, within reason, else where will it end? -Original Message- From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: 03 January 2002 17:00 To: James, Chris; 'acar...@uk.xyratex.com'; emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues I agree with what you say, but at least in this country the anti-business pendulum has swung farther than you imagine. A couple examples. Thurman Munson, a Yankee catcher in the '70s, was killed in his twin engine Cessna jet. He crashed short of a runway. His estate sued Cessna, not on the grounds that the jet was defective, but that Cessna had sold Munson more aircraft than he was capable of handling. Cessna demonstrated that it had sold Munson the model he wanted, but the plaintiff claimed that it was Cessna' duty to assess Munson's skills as a pilot and tell him, the customer, what aircraft they would sell him. I don't recall how the verdict was rendered, but I know Cessna paid something. Another case involved the death of a child in an automobile accident involving a minivan. The child was thrown from the vehicle, in part because the rear door sprang open on impact. Plaintiff claimed the door was poorly designed and that the child would have remained in the vehicle and maybe not been killed had the doors remained closed. Defendant pointed out that child was not restrained in vehicle, he was up and and about at the moment of impact. Documentation supplied with vehicle clearly states all passengers should wear restraining belts. Plaintiff countered that defendant should have known that if they built a vehicle as large as a minivan that kids would be up and about and vehicle should have been designed with that in mind. Again do not recall verdict but I am sure plaintiff did not walk away empty-handed. Agreed that a manufacturer is responsible for the safety of a product put into normal use. That was established by case law as far back as the Babylonian Code of Hammurabi, wherein an architect who builds a house that collapses and kills the owner is liable to the same fate. But the manufacturer today labors under a presumption of evil: if he makes a profit from selling a product, he must have skimped somewhere, because profits are intrinsically evil. -- From: James, Chris c...@dolby.co.uk To: 'acar...@uk.xyratex.com' acar...@uk.xyratex.com, emc-p...@majordomo.ieee.org Subject: RE: EMC-related safety issues Date: Thu, Jan 3, 2002, 8:25 AM Ken, I don't think anyone could disagree with your sentiments. The problem is attributing the level of liability between user and manufacturer. Car manufacturers sleep at night yet their products kill thousands each year, they design them to high standards yet by their use they still kill and maim. Do we hold them liable, no, in 99.9% of cases we don't. You slip down the stairs and break your leg, do you sue: a.. the caveman who invented the staircase? b.. your shoe manufacturer for using a shoe sole incompatible with the stair carpet? c.. the stair carpet manufacturer for using material incompatible with the shoe sole material? d.. the distiller for not putting a warning on the bottle of whisky you just drank It's reasonable responsibility/diligence that needs defining, not spurious emissions!! In addition the legal fraternity should have some standards imposed upon them to put an end to pure gold digging through litigation that seems to just escalate and to which we thus have to pander. If every foreseeable mis-use of every commodity sold was accounted for then no-one would sell anything. Chris __ Chris James Engineering Services Manager Dolby Laboratories, Inc. (UK) -Original Message- From: acar
RE: EMC-related safety issues
-Original Message- From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Thursday, January 03, 2002 11:55 AM To: Cortland Richmond; Andrew Carson Cc: emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues Curiosity. How long must airbags work? A car can be driven for two decades or more, by an uncontrolled number of owners, and with no mandatory inspection or service. How long is a manufacturer liable for the proper operation of those airbags? Same question for anti-lock brakes. If the warning light comes on and is ignored, who is at fault? If the warning light is disabled by an owner, and the next owner suffers injury due to improper operation of either of these systems, who is at fault? Don't give me the logical answer. I can figure that out. Knowing that the culpable seller is not a tempting target but the manufacturer is, in the present climate some bright lawyer will come up with a rationale for suing the manufacturer. It is the climate that must be changed and the IEE guide that started this thread, in my opinion, appeases this trend rather than opposes it. My non-expert opinion is that warranties on systems like air-bags, anti-lock brakes and seatbelts may have the same legal obligations as the Federal requirements for (fuel) Emission controls (IIRC, 6 years or 100k miles?). Ed Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military Avionics EMC Services Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: EMC-related safety issues
My copy of BS EN 50140-4:1996 was 'published under the authority of the Standards Board and comes into effect on 15 August 1996.' BS DOW was 2001-01-01 for the 1998 version. Amendment 10102 dated September 1998 affects page 3, adding 'alarm transmission systems' to the scope. Comments: 1) Supersedes generic immunity requirements if product is positioned within scope EN50130-4. 2) Test conditions and acceptance criteria differ from generic immunity David -Original Message- From: John Woodgate [mailto:j...@jmwa.demon.co.uk] Sent: Thursday, January 03, 2002 1:59 PM To: emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues I read in !emc-pstc that richwo...@tycoint.com wrote (in 846BF526A205F8 4BA2B6045BBF7E9A6ABC4FD5@flbocexu05) about 'EMC-related safety issues', on Thu, 3 Jan 2002: more severe immunity requirements apply. Those requirements are either specified in EN 50130-4 According to the BSI web site, BS EN 50130-4 is not yet published. Comments? -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I think the issue is that the lamp is not an EMC regulated device. In fact, in Europe, ITE conducted emissions must be regulated so as not to cause desk/room lights to flicker, as in when a fuser lamp in a printer kicks on. Apparantly the proper functioning of lighting takes precedence over the propoer functioning of radios and the like affected by the lights? George Rich Nute richn%sdd.hp@interlock.lexmark.com on 01/03/2002 04:08:51 PM Please respond to Rich Nute richn%sdd.hp@interlock.lexmark.com To: jmw%jmwa.demon.co...@interlock.lexmark.com cc: emc-pstc%majordomo.ieee@interlock.lexmark.com (bcc: George Alspaugh/Lex/Lexmark) Subject: Re: EMC-related safety issues Hi John: I've replaced the incandescent lamp on my bedside table with a new energy-saving compact flourescent lamp. With the lamp on, I cannot listen to even the strongest AM radio station on my clock radio (on the same bedside table) due to the lamp interference. This must not be the usage contemplated by EMC requirements. Limits in the household environment are based on a 3 m separation between source and receiver. Wonderful! Either the lamp or the radio must be on the opposite side of the room from my bedside table. When I am in bed, one or the other is not controllable, and is therefore useless to me. Whine mode on: I want both on my bedside table, and I want both to do all of their functions. This IS not the usage contemplated by 3 m separation EMC requirements. :-) Best wishes for the New Year, Rich --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
Perhaps, it merely interfered with the sensor electronics, not the true magnetic field that was being sensed. - Robert - Robert A. Macy, PEm...@california.com 408 286 3985 fx 408 297 9121 AJM International Electronics Consultants 619 North First St, San Jose, CA 95112 -Original Message- From: Pettit, Ghery ghery.pet...@intel.com To: 'James Collum' james.col...@usa.alcatel.com; emc-p...@majordomo.ieee.org emc-p...@majordomo.ieee.org Date: Thursday, January 03, 2002 11:46 AM Subject: RE: EMC-related safety issues I still have a hard time believing it was a compass that was affected by a laptop computer. ADF indication, could be. VOR, maybe. Magnetic compass? I wouldn't want a magnetic source that strong in my lap! My belt buckle would be stuck to it. There is quite a distance between a magnetic compass in the cockpit of an airliner and anything a passenger is carrying. Not so in a Cessna 172, but in a DC-10? Ghery Pettit -Original Message- From: James Collum [mailto:james.col...@usa.alcatel.com] Sent: Thursday, January 03, 2002 10:47 AM To: emc-p...@majordomo.ieee.org Subject: Re: EMC-related safety issues * A routine flight over Dallas-Fort Worth was disrupted when one of the compasses suddenly shifted 10 degrees to the right. The pilot asked if any passenger was operating an electronic device, and finding that a laptop computer had just been turned on requested that it be turned off, whereupon the compass returned to normal. Following RTCA guidelines the pilot requested that the laptop be turned on again 10 minutes later, when the compass error returned. Ref: Compliance Engineering (European edition) Nov/Dec 1996 p12 * I am fascinated by this amazing story (which must surely be an urban myth) and went in search of more info on the internet. I had never heard of the RTCA ( a private corporation) before, but noticed via their web site that you have to be a member company (i.e. pay) to receive the wisdom that it contains. Aviation is merely a hobby of mine but I'm interested in reading a copy of the RTCA's DO-233/214 and 196 documents without shelling out hundreds for the privilege, can anyone advise? Also does anyone know what recommendations have they made to modifying FAR 91.21 (as per their web site). In reading this again, I'm curious as to how the pilot would have known about a private companies convoluted guideline for fault finding on errant radio direction equipment involving locating industrious passengers and commandeering their computers at 10 minute intervals. Surely he would have done what any professional engineer would do, beat or kick the 10 degree error out of the RDF equipment? Or maybe just wonder to him/herself about how strange things happen in the Dallas Fort Worth area? Tounge in cheek, my comments and not those of my employer etc. Jim --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
Hi John: I've replaced the incandescent lamp on my bedside table with a new energy-saving compact flourescent lamp. With the lamp on, I cannot listen to even the strongest AM radio station on my clock radio (on the same bedside table) due to the lamp interference. This must not be the usage contemplated by EMC requirements. Limits in the household environment are based on a 3 m separation between source and receiver. Wonderful! Either the lamp or the radio must be on the opposite side of the room from my bedside table. When I am in bed, one or the other is not controllable, and is therefore useless to me. Whine mode on: I want both on my bedside table, and I want both to do all of their functions. This IS not the usage contemplated by 3 m separation EMC requirements. :-) Best wishes for the New Year, Rich --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: EMC-related safety issues
Hello John, If the BSI site says that, then it is yet another proof of you can't always believe what you read. :) My Aug 2001 version of the BSI electronic catalog shows a publication date of 1996 for the BS EN ( but the document was actually released in late 1995) with an addendum A1 published in 1998. The hard copy sitting in front of me (from BSI) agrees with the electronic catalog :) There was a very generous transition period which ended in January of 2001. Best Regards, Kevin Harris Manager, Approval Services Digital Security Controls 3301 Langstaff Road Concord, Ontario CANADA L4K 4L2 Tel: +1 905 760 3000 Ext. 2378 Fax +1 905 760 3020 Email: harr...@dscltd.com -Original Message- From: John Woodgate [mailto:j...@jmwa.demon.co.uk] Sent: Thursday, January 03, 2002 1:59 PM To: emc-p...@majordomo.ieee.org Subject:Re: EMC-related safety issues I read in !emc-pstc that richwo...@tycoint.com wrote (in 846BF526A205F8 4BA2B6045BBF7E9A6ABC4FD5@flbocexu05) about 'EMC-related safety issues', on Thu, 3 Jan 2002: more severe immunity requirements apply. Those requirements are either specified in EN 50130-4 According to the BSI web site, BS EN 50130-4 is not yet published. Comments? -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
Hi Ken: Trial lawyers and their clients have an obvious interest in portraying consumers as helpless and child-like, and rich corporations as robber-barons preying on the poor and weak. But why does the rest of society jump on that bandwagon? Because profit and wealth, once badges of achievement, are now considered prima facie evidence of malfeasance. The trail lawyers, in an attempt to enrich themselves, have launched a full-scale attack on the system of capitalism itself. But unlike a real capitalist, who enriches himself by serving others, the trial lawyer is a parasite - he achieves his success at the expense of others, and the degree of his success is the degree of destruction visited on society. It is not the lawyers, but the client/plaintiff who sees an opportunity for a free ride for the rest of his life. Society wants to see the little guy get the free ride and the deep-pocket corporation pay through the nose for his misdeeds. I don't really believe that the client/plaintiff motive is punishment of the deep-pocket corporation, although that theory may be the one used in court. Ambulance-chasing lawyers do influence the client/ plaintiff in their path to the free ride, as the lawyers, too, want a free ride. (It seems to me that there is a prepronderance of very nice cars that bear the wheelchair symbol.) Best wishes for the New Year, Rich --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in 200201031919.laa11...@epgc264.sdd.hp.com) about 'EMC-related safety issues', on Thu, 3 Jan 2002: I've replaced the incandescent lamp on my bedside table with a new energy-saving compact flourescent lamp. With the lamp on, I cannot listen to even the strongest AM radio station on my clock radio (on the same bedside table) due to the lamp interference. This must not be the usage contemplated by EMC requirements. Limits in the household environment are based on a 3 m separation between source and receiver. My TV and stereo are more-or-less integrated (they are in close proximity). On New Year's Day, I wanted to listen to the radio version of the football game description while watching the TV. With the TV on, I cannot listen to even the strongest AM radio station due to the TV interference. This must not be the usage contemplated by EMC requirements. See above. I take my Grundig portable radio with me when I travel. Most hotels have sufficient interference sources that I cannot listen to AM radio, and sometimes not even FM radio (with lights and TV off!). This must not be the usage contemplated by EMC requirements. I do not find that. In most US hotels I've stayed in, the bedroom radios are cheapo-squared but still receive 99 stations - all putting out rubbish, so any interference is beside the point. But at least the bedroom radios have an antenna system. It is not surprising that you cannot get good reception on built-in antennas in steel-framed buildings. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I read in !emc-pstc that John Shinn john.sh...@sanmina-sci.com wrote (in 00c001c1948d$a53fb580$0b3d1...@hadco.comsanmina.com) about 'EMC- related safety issues', on Thu, 3 Jan 2002: NO NO NO. Don't think about the plane. There will be more red tape than you want to think about, especially if it is bolted down (permanently installed). If not approved by the appropriate government agency (the FAA's FSDO - Flight Safety District Office), it could cause loss of airworthyness of the aircraft. Even more problems if you have to punch a hole in the skin. But, just from the paperwork issue, don't go there. I don't actually have a plane, but the camera manufacturer doesn't know that, so in the present circumstances he must assume that I do! I'll mount it on my hydrogen balloon instead.(;-) -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
I don't understand the part I snipped. Isn't that what immunity/susceptibility testing is all about? We already do that. The part I had a problem with was the statement that industry standards are not enough, we must try to anticipate all problems that might ever arise, in effect forcing the manufacturer to have god-like omniscience, and when he predictably fails, punishing him for not living up to our preconceived notions of how smart he should have been. -- From: Rich Nute ri...@sdd.hp.com To: ken.ja...@emccompliance.com Cc: geor...@lexmark.com, emc-p...@ieee.org Subject: Re: EMC-related safety issues Date: Thu, Jan 3, 2002, 1:55 PM Today, we simply don't have processes by which we can test equipment for RF-induced bad experiences. So, we argue both sides without a conclusion. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: EMC-related safety issues
Hi Ken: The Forrestal incident occurred during the Vietnam conflict, July 1967. It was pretty much as you describe except I would not say EMI was not controlled. All DOD services had EMI requirements at his time. In fact, 1967 was the year that MIL-STD-461 was adopted as a Tri-Service requirement superseding Service-unique standards. The actual mechanism was that a shield termination on a pyro actuation circuit on one fighter was degraded or broken and radar illumination of it fired a weapon inadvertently, into another fully loaded, and fully fueled fighter. That was the cause of the disaster. In September 1967, MIL-E-6051C, Aircraft EMC was updated to the D revision. In D, for the first time you have 20 dB safety margin demonstration on pyro electrical actuation. Coincidence? A colleague once said: Safety standards are the inversion of bad experiences. Your story confirms this approach to safety. For commercial aircraft, especially since September 11, we can also say: Security standards are the inversion of bad experiences. The trick, of course, is to anticipate the bad experience so as to prevent it in the first place. FMEA (Failure Mode and Effects Analysis) and FTA (Fault Tree Analysis) are two process by which some specific bad experiences can be anticipated. We don't have a process by which all possible bad experiences can be anticipated. Speculation as to either the bad experience itself or the probability of the bad experience is often pooh-poohed by those who would either implement the fix or authorize implementation of the fix. In the absence of data, prevention of a speculated bad experience is unlikely, no matter the ultimate validity of the speculation. As I recall, the issue of this thread is that of anticipation of an RF signal causing a bad experience by mal-operation (not a mal-function) of an equipment. Today, we simply don't have processes by which we can test equipment for RF-induced bad experiences. So, we argue both sides without a conclusion. Hopefully, through such arguments, some of us may get an idea of how such anticipation can be implemented. Best regards, Rich --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
