RE: Tuned Stub Filter - alternate approach
I use a 1,2 or 3 cavity filter which has high Q and the loss is acceptable. A cavity filter in the 28/32 cm band is easy to assemble from a 2lb fruit can and if tweaked on a network analyzer can provide 30db rejection with a bandwidth of a couple of Mhz's. There are many texts describing their construction. Contact me off line if you have questions. Procedure I use is, set the filter to the desired center frequency of interest with signal gen, network analyzer, or tracking Gen / analyzer. Determine the insertion loss record at the center freq. and make the measurement. Then correct for the filter loss. Take this number and factor against the fundamental and your home. I usually re-do at the -3db points of the filter as a sanity check. If the numbers look funny they probably are and you need to check the filter center freq. Repeat for each harmonic of interest. You will probably need to adjust your signal attenuation to keep the measurement in scale. A bit cheesy but worked well for RF guy's the last 60 years. Regards, Michael Taylor Hach Group Colorado -Original Message- From: richwo...@tycoint.com [mailto:richwo...@tycoint.com] Sent: Wednesday, March 20, 2002 11:14 AM To: emc-p...@majordomo.ieee.org Subject: Tuned Stub Filter We are considering using a tuned stub filter to suppress the carrier so that we do not overload our spectrum analyzer while measuring spurious emissions. One question we have concerns the Q of the filter - i.e., will it sufficiently suppress the modulation sidebands. So, let me ask the following questions. In the frequency ranges of 860-1000 MHz and 2.45 GHz, how much suppression should I expect from a stub filter and what design steps can be taken to have the necessary bandwidth? Or, am I going down the wrong path for a filter? Richard Woods Sensormatic Electronics Tyco International 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: NEC Question
Hello Ron, Yes, as you said. Burden was a poor choice of words. In regards to your second query, as a matter of doing business, it is always in a manufacturer's best interest to know what regulations apply to the use of their products in the hands of their Customers. Having compliant product already available is advantageous to the supplier. However, if a Customer does not require NRTL listing of a product, so be it. Just because you are not listed with an NRTL doesn't mean that your product is unsafe. Also, it is not up to a manufacturer to decide what a workplace is under OSHA regulations, the Customer decides this because the applicable workplace regulations apply to them. Regards, +=+ |Ronald R. Wellman|Voice : 408-345-8229 | |Agilent Technologies |FAX : 408-553-2412 | |5301 Stevens Creek Blvd.,|E-Mail: ron_well...@agilent.com| |Mailstop 54L-BB |WWW : http://www.agilent.com | |Santa Clara, California 95052 USA| | +=+ | Common sense is the collection of prejudices acquired by age | | eighteen. - Albert Einstein | +=+ -Original Message- From: Ron Pickard [mailto:rpick...@hypercom.com] Sent: Wednesday, March 20, 2002 12:57 PM To: ron_well...@agilent.com Cc: emc-p...@ieee.org Subject: RE: NEC Question Hi Ron, You wrote: The burden of having products listed by an NRTL, like UL, falls on the purchaser of the product if the product is used in a workplace which is subject to OSHA regulations. To which OSHA regulation are you specifically referring to to make this statement? Its inconceiveable that a purchaser (customer?) be responsible for listing a supplier's product. Maybe you intended to say that, for products used in the workplace, it is the purchaser's responsibility to ensure that products installed under the purchaser's control be compliant to OSHA regulations. Anyway, please explain your statement above. Most non-IT product manufacturers do not get their products listed unless a Customer specifically requires it. In some cases, a product may get listed because it is expected that a product will be marketed in a known jurisdiction that requires listed products by an NRTL. The State of Oregon and the City of Los Angeles are a couple examples. If a product, non-IT or otherwise, is to be used in the workplace (OSHA jurisdiction), your statement appears to contradict OSHA regulation, 29CFR Part 1910.399. Please advise. I look forward to your reply for clarification. Best regards, Ron Pickard rpick...@hypercom.com --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: NEC Question
I think the simple answer is no. The NEC deals primarily with installation wiring and not with equipment plugged into that wiring. A phrase similar to where listed equipment is installed is found in many sections of the code, generally where special installation conditions are acceptable which would not be generally accepted. For instance, Article 645 deals with computer rooms. You are allowed to use the special provisions of the article if, among other things, 645-2(c) Listed information technology equipment is installed. As a general rule, the NEC does require listed equipment within the building wiring such as receptacles, panelboards, etc. But, the code does not require that all equipment have a safety agency listing. It is an article by article issue. A specific listing by UL is never required. If listed equipment is required, the listing must be from a NRTL (Nationally Recognized Testing Laboratory). A list of NRTL's may be found on the OSHA website. At least as far back as 1982 some articles in the code required listed equipment. The NEC is issued every three years. It is not a regulation. It only has the force of law when adopted by a legal jurisdiction -- town, city, county, state, etc. And, even though the NEC is updated every three years, local legislation may not be. There are some cities whose electrical code ordnance is the NEC from as far back as 2988 or earlier. John P. Wagner Regulatory Compliance Mandatory Standards AVAYA Strategic Standards. 1300 W. 120th Ave, Room B3-D16 Phone/Fax: (303) 538-4241 johnwag...@avaya.com -- From: sbr...@prodigy.net[SMTP:sbr...@prodigy.net] Reply To: sbr...@prodigy.net Sent: Wednesday, March 20, 2002 8:57 AM To: emc-p...@ieee.org Subject: NEC Question Colleagues: The question was asked if all products sold in the US, specifically industrial products, that plugged into the mains had to be UL Listed. The answer was that not necessarily UL Listed, but according to the NEC they did have to be listed, labeled, certified, classified, etc., by a 3rd party. The answer went on to say that this was only applicable if the locality in which the product were to be used, and their AHJ, adhered to the NEC and that not all areas of the country adopted and adhered to the NEC. 1. Do you agree with the above responses? 2. How long has the NEC required products to be listed, labeled, certified, classified, etc.? Your comments and feedback would be appreciated. Thanks in advance, Steve Brody sbr...@prodigy.net --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: NEC Question
Manufacturers of capital equipment for the semiconductor industry have been wrestling with these complicated listing problems for a while. We sponsored an all-day meeting on the topic last summer, and the 207 pages of handouts from that meeting can be found at http://www.semi.org/web/winitiatives.nsf/url/ehsW01NRTLpresent which is on the web site of SEMI, our trade organization. Mike Sherman FSI International --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Relative merits of various logic families in not generating RFI
You might find the following website from Intel useful for this question. It'll give edge rates, input and output construction, ... From there, you can make some conclusions. http://focus.ti.com/docs/logic/catalog/resources/selectionmatrix.jhtml?fileN ame=seltree_by_volt Regards, 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: Tuned Stub Filter
-Original Message- From: richwo...@tycoint.com [mailto:richwo...@tycoint.com] Sent: Wednesday, March 20, 2002 11:14 AM To: emc-p...@majordomo.ieee.org Subject: Tuned Stub Filter We are considering using a tuned stub filter to suppress the carrier so that we do not overload our spectrum analyzer while measuring spurious emissions. One question we have concerns the Q of the filter - i.e., will it sufficiently suppress the modulation sidebands. So, let me ask the following questions. In the frequency ranges of 860-1000 MHz and 2.45 GHz, how much suppression should I expect from a stub filter and what design steps can be taken to have the necessary bandwidth? Or, am I going down the wrong path for a filter? Richard Woods Sensormatic Electronics Tyco International Rich: I have tried using double-stub tuners to do this job, and it's usually not very good. I seem to recall getting about 35 dB of rejection from a double-stub, and the Q is not great. I now use a combination of KL tunable band-rejection filters (which have a 5% wide 55 dB rejection band) and high-pass / low-pass filters. One problem with resonant band rejection filters is that if you tune them to notch out the fundamental, you also get rejection at harmonic frequencies too. So this makes measuring harmonic content a problem. I typically use the band rejection filter to notch out the fundamental while looking near the fundamental for spurious emissions. Looking below the fundamental for spurious, I use a low-pass filter. Above the fundamental, I measure harmonics with a high-pass filter that has a cutoff just below the second harmonic. Once above the second harmonic, you can usually use the high-pass filter for measuring spurious emissions too. Needless to say, after a while, you build up a decent collection of filters. (I especially like some high-pass filters I have made from waveguide; they give 80 dB well below cutoff, the cutoff is sharp, and the passband is just about zero dB loss. Actually, waveguides are band-pass filters, and you need to switch to a waveguide of smaller size as you progress up in frequency.) And remember, you have to characterize all of your filters. 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Tuned Stub Filter
When using a stub, its reflected signal combines with the incident signal at the junction. If this reflected signal were equal in amplitude to the incident signal, it would offer (theoretically) infinite rejection. Because a stub has a non-zero loss, there is never complete cancellation. If the reflection is just 1 dB down, (about 89 percent amplitude) it will only give about 20 dB of attenuation. It is pretty easy to do better than this. But I'll stick with it for this example. If the signal is also not shifted exactly 180 degrees, as when slightly off frequency, full cancellation is not possible. If it is 10 degrees off, (900 Mhz instead of, say 810) then it is reduced to about 82 percent due to phase shift. If you had a 89 percent cancellation before, now you effectively have only about about 73 percent, and can expect a null of about 11 dB. This assumes nearly lossless coax. If you include the RC or RL phase shift due to loss, you get the total effect of imperfect Q. These numbers are close if I did the arithmetic right (grin). All this disregards the other effects on DESIRED signals. Placing a stub in parallel with the feedline parallels a reactive impedance which is numerically equal to the product of the tangent of its length in degrees and its characteristic impedance. A quarter wave 810 mhz open stub would at 405 Mhz be 45 degrees long and shunt 50 ohms of capacitive reactance with your coax. I have had some luck, in non-critical applications, with placing two tee-fittings or two splitters in a line, then adding a length of coax in parallel with the main feedline but a half wavelength (in coax) longer than the distance between the fittings. The signal is delayed 180 degrees and then summed with the original signal. If the two junctions are colocated (no distance at all, just four receptacles at one spot) this reduces to a parallel quarter-wave open stub. The farther apart the junctions are, the less upset (except for SWR in the paralleled section) you get. There are multiple notches due to this setup. When using tee's there are SWR reflections from the tee's, which might be reduced by using 93 ohm coax (100 ohms is perfect if it's available) for the notching section parts. If you use hybrids instead of tee's you avoid the matching problems. Let me know what you end up with. It's a fun experiment. Cortland --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: Pro-audio and ground lifting
Well, What's legal? What's smart? What gets by unnoticed? What is practical? What's legal: If a product is Class 1 (needs Earth Ground) then legally it needs to have its ground conductor plugged in. That's regardless of if it's the US, UK, U(anywhere).I say legally in the sense that you are violating UL, OSHA, (the authority having jurisdiction) the manufacturer's instructions... The penalty depends upon who inspects your facility. It also depends on who you are. For instance, we unground oscilloscopes on a regular basis when conducting noise measurements on sensitive circuitry. But, we're engineers, we know the risks. We do it of our own free will. We are professionals trained to deal with risks that the general public shouldn't be exposed to. What's smart: It's always smart to ground Class 1 equipment.I have a feeling that hum could be solved by power filtering without disconnecting grounds; the ground removal is probably just an easy way out. What gets by unnoticed: You may have heard about buildings with no ground because there are a ton of them here in the states. Many of them go unnoticed because the Authority having Jurisdiction hasn't had an excuse to inspect them. For instance, my own house is almost entirely ungrounded; I don't get any greif because it hasn't changed ownership (no mortgage loan inspection) and it hasn't been remodeled (no building permits applied for)...so it hasn't been inspected. Theoretically, I could put a professional audio system in my house without grounding it and nobody would know. OSHA wouldn't inspect it because I'm not an employer. --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Pro-audio and ground lifting
Dear Ted OK, OK, after two postings making much the same point maybe I should have been more careful to make it clear that I was only worried about the kind of ground lift switches which disconnect the protective ground from the chassis of the equipment. I have seen them used in pro-audio equipment in the past. It is also a traditional bad habit in the pro-audio business to remove the protective conductor connection from the mains plug or the chassis if it helps cure a hum. I am trying to see if there is anyone out there who will make a case for such unsafe practices, or point me to US regulations or standards of codes of practice that permit it. All the very best! Keith Armstrong www.cherryclough.com In a message dated 20/03/02 20:01:41 GMT Standard Time, t...@crestaudio.com writes: Subj:Re: Pro-audio and ground lifting Date:20/03/02 20:01:41 GMT Standard Time From:t...@crestaudio.com (Ted Rook) Sender:owner-emc-p...@majordomo.ieee.org Reply-to: A HREF=mailto:t...@crestaudio.com;t...@crestaudio.com/A (Ted Rook) X-INFO: INVALID TO LINE This reply is a personal opinion and does not represent the views of my employer. Ground lift switches do not affect the protective ground electrical connection between the AC third wire and the equipment chassis. Ground lift switches separate the audio input and/or output shield connection from the protective ground. I hope that this distinction makes it clear that a ground lift link or switch is not an electrical hazard. Ground lift switches and links are common on pro-audio equipment to facilitate the task of the quality conscious installer who has to deliver a system free of hum and RF pick-up to his customer. Remember the Spinal Tap gig at the Airbase? Voice communications between tower and pilot coming through loud and clear on the stage amplifiers? Ground everything once and you're OK. Ground stuff a second time via the audio cable shields and you have a problem. The cc recipient of the original message has the company name of a major UK based professional audio sound console company 'CADAC' with installations the world over. I expect they are already aware of the difference between audio ground lifting and protective ground lifting. It is necessary to distinguish lest confusion spreads. cherryclo...@aol.com 20-Mar-02 11:59:19 AM Dear Group Does anyone know if it is legally permissible in the USA to remove the safety grounds from Class I equipment used in pro-audio systems and installations? It has been a common practice over many many years in professional audio systems and installations to 'lift the grounds' on equipment to cure hum problems. I'm comfortable with the knowledge that in Europe it is a breach of the Low Voltage Directive to supply equipment that is constructed using Class I methods if its protective ground conductor is not connected, or if it could be 'lifted' by operation of a user-accessible switch or jumper. I am also comfortable with the idea that in Europe if the user does not connect a protective ground conductor to Class I equipment, the health and safety at work directives mean that he/she is probably committing a criminal act. A Health and Safety Inspector could close down his/her facility if he/she discovered such an error. My question concerns the comparable situation in the USA. I am under the impression that my summary above for European protective grounding requirements for Class I equipment also applies to the US, both for the supply of the equipment and the installation of systems using it. But I am reliably told that there are a great many pro-audio products, systems, and installations in the USA where protective grounding is treated as just a hum control measure and safety issues take second place. I am also reliably told that in the US one can even find whole buildings wired using two-core mains cables, without any safety ground wires to any of the pro-audio equipment. So what are your views on removing the safety grounds from Class I equipment used in pro-audio systems and installations? Can anyone defend this practice or show that it is legal in the USA? All the very best Keith Armstrong Note: Class I equipment uses basic insulation plus protective ground bonding to protect against electrical hazards, and must use three-pin mains connectors and three-core mains leads (for single-phase supplies). The only alternative permitted (in Europe, anyway) for mains-powered equipment is Class II - 'double insulation' . This must have no protective ground conductor and must use two-pin mains connectors and two-core mains leads (again, for single phase supplies). Best Regards Ted Rook, Console Engineering, ext 4659 Please note our new location and phone numbers: Crest Audio Inc, 16-00 Pollitt Drive Fair Lawn, NJ 07410 USA 201 475 4600
re: NEC Question
Thanks to all who responded. Great information, as always. --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: NEC Question
Found a link to a version of the article that was run in 1999. http://www.conformity.com/9903whentolist.pdf Regards, Kaz Gawrzyjal Dell Computer Corporation -Original Message- From: richwo...@tycoint.com [mailto:richwo...@tycoint.com] Sent: Wednesday, March 20, 2002 12:32 PM To: emc-p...@ieee.org Subject: RE: NEC Question An excellent paper, Know when you need to list your product...and when you don't, can be found in Conformity 2002, the annual guide published by Conformity magazine. The paper covers commercial or business statutes, building or fire codes including the NEC, and labor codes. The states of Oregon, Washington, North Carolina and California are discussed as examples. I did not find the article posted on their web site, unfortunately. It might be worth contacting them for a reprint, if it is available. www.conformity.com Richard Woods Sensormatic Electronics Tyco International -Original Message- From: sbr...@prodigy.net [mailto:sbr...@prodigy.net] Sent: Wednesday, March 20, 2002 10:57 AM To: emc-p...@ieee.org Subject: NEC Question Colleagues: The question was asked if all products sold in the US, specifically industrial products, that plugged into the mains had to be UL Listed. The answer was that not necessarily UL Listed, but according to the NEC they did have to be listed, labeled, certified, classified, etc., by a 3rd party. The answer went on to say that this was only applicable if the locality in which the product were to be used, and their AHJ, adhered to the NEC and that not all areas of the country adopted and adhered to the NEC. 1. Do you agree with the above responses? 2. How long has the NEC required products to be listed, labeled, certified, classified, etc.? Your comments and feedback would be appreciated. Thanks in advance, Steve Brody sbr...@prodigy.net --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Pro-audio and ground lifting
Dear John I was aware of the ability to mix Class I and II construction in a single product, but as I understand it such a product must be treated as if were simply Class I, in that it must have a protective ground connection via its power cord. I was sure that the AES would not condone removing the safety ground connection where it is needed for safety, and am pleased that you have confirmed that this is the case. All the very best! Keith Armstrong www.cherryclough.com In a message dated 20/03/02 19:19:04 GMT Standard Time, j...@jmwa.demon.co.uk writes: Subj:Re: Pro-audio and ground lifting Date:20/03/02 19:19:04 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 17d.557eff5.29c a1...@aol.com) about 'Pro-audio and ground lifting', on Wed, 20 Mar 2002: Class I equipment uses basic insulation plus protective ground bonding to protect against electrical hazards, and must use three-pin mains connectors and three-core mains leads (for single-phase supplies). The only alternative permitted (in Europe, anyway) for mains-powered equipment is Class II - 'double insulation' . This must have no protective ground conductor and must use two-pin mains connectors and two-core mains leads (again, for single phase supplies). This is true for consumer products but for professional audio equipment under IEC/EN60065, an arrangement whereby *parts* of the product meet Class II requirements while other parts meet Class I requirements has been accepted by Notified Bodies for some years. These can be shown to be just as safe as conventional products. With regard to your main enquiry, professional audio engineers in the Audio Engineering Society are severely critical of 'ground lift' solutions. The correct, and safe, solutions, lie in the signal circuits that sustain the ground loops. The subject is extensively treated in the June 1995 issue of the Journal of the Audio Engineering Society. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL!
radiated HIRF testing levels modulations
Please note that the following are personal comments and not those of my employer. I am looking for information both on the environments (assume aircraft) that justify the following levels and the methods for testing. I have been asked to find EMI labs that can test to the following: 900MHz - 1GHz 1100 V/m peak 1kHz pulse modulation, 90% depth with a 1% duty cycle; in addition signal will be switched on/off at a 1Hz rate (on 200ms; off 800ms) Thanks in advance, Susan H. Beard EMC Consultant --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
IP Rating and EN60950
I would like someone to explain to me why EN60950 does not normative reference EN60529. While the latter is referenced in the OJ, the scope of the standard seems to indicate that it is a basic standard to be referenced in product standards. The scope says, It will remain the reponsibility of the individual Technical Committes to decide on the extent and manner in which the classification is used in their standards and to define 'enclosure' as it applies to their equipment. Richard Woods Sensormatic Electronics Tyco International --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: RES: Pro-audio and ground lifting
Dear Sergio Many thanks for replying. I have no problems with switches such as you describe, and have used them myself. It is switches that disconnect the protective earth, which I have also seen (plus just plain disconnecting the green/yellow wire) that I am concerned about. All the very best! Keith In a message dated 20/03/02 17:45:50 GMT Standard Time, sergioro...@siemens.com.br writes: Subj:RES: Pro-audio and ground lifting Date:20/03/02 17:45:50 GMT Standard Time From:sergioro...@siemens.com.br (SERGIO LUIZ DA ROCHA LOURES) To:cherryclo...@aol.com, emc-p...@ieee.org CC:t...@cadac-sound.com keith, In pro-audio systems, normally you found a ground lift switch. This switch disconnects the signal shield from the equipment ground. It doesn’t disconnect the protection earth from the main supply. Regards Sérgio L. Rocha Loures Siemens Ltda. - Brazil Supply Chain - Quality and Engineering IC SC QE L Tel: +55 41 341-5898 Fax: +55 41 341-5058 E-mail: sergioro...@siemens.com.br Minha opinião e não necessariamente a do meu empregador. -Mensagem original- De: cherryclo...@aol.com [mailto:cherryclo...@aol.com] Enviada em: quarta-feira, 20 de março de 2002 13:59 Para: emc-p...@ieee.org Cc: t...@cadac-sound.com Assunto: Pro-audio and ground lifting Dear Group Does anyone know if it is legally permissible in the USA to remove the safety grounds from Class I equipment used in pro-audio systems and installations? It has been a common practice over many many years in professional audio systems and installations to 'lift the grounds' on equipment to cure hum problems. I'm comfortable with the knowledge that in Europe it is a breach of the Low Voltage Directive to supply equipment that is constructed using Class I methods if its protective ground conductor is not connected, or if it could be 'lifted' by operation of a user-accessible switch or jumper. I am also comfortable with the idea that in Europe if the user does not connect a protective ground conductor to Class I equipment, the health and safety at work directives mean that he/she is probably committing a criminal act. A Health and Safety Inspector could close down his/her facility if he/she discovered such an error. My question concerns the comparable situation in the USA. I am under the impression that my summary above for European protective grounding requirements for Class I equipment also applies to the US, both for the supply of the equipment and the installation of systems using it. But I am reliably told that there are a great many pro-audio products, systems, and installations in the USA where protective grounding is treated as just a hum control measure and safety issues take second place. I am also reliably told that in the US one can even find whole buildings wired using two-core mains cables, without any safety ground wires to any of the pro-audio equipment. So what are your views on removing the safety grounds from Class I equipment used in pro-audio systems and installations? Can anyone defend this practice or show that it is legal in the USA? All the very best Keith Armstrong Note: Class I equipment uses basic insulation plus protective ground bonding to protect against electrical hazards, and must use three-pin mains connectors and three-core mains leads (for single-phase supplies). The only alternative permitted (in Europe, anyway) for mains-powered equipment is Class II - 'double insulation' . This must have no protective ground conductor and must use two-pin mains connectors and two-core mains leads (again, for single phase supplies).
Re: Pro-audio and ground lifting
This reply is a personal opinion and does not represent the views of my employer. Ground lift switches do not affect the protective ground electrical connection between the AC third wire and the equipment chassis. Ground lift switches separate the audio input and/or output shield connection from the protective ground. I hope that this distinction makes it clear that a ground lift link or switch is not an electrical hazard. Ground lift switches and links are common on pro-audio equipment to facilitate the task of the quality conscious installer who has to deliver a system free of hum and RF pick-up to his customer. Remember the Spinal Tap gig at the Airbase? Voice communications between tower and pilot coming through loud and clear on the stage amplifiers? Ground everything once and you're OK. Ground stuff a second time via the audio cable shields and you have a problem. The cc recipient of the original message has the company name of a major UK based professional audio sound console company 'CADAC' with installations the world over. I expect they are already aware of the difference between audio ground lifting and protective ground lifting. It is necessary to distinguish lest confusion spreads. cherryclo...@aol.com 20-Mar-02 11:59:19 AM Dear Group Does anyone know if it is legally permissible in the USA to remove the safety grounds from Class I equipment used in pro-audio systems and installations? It has been a common practice over many many years in professional audio systems and installations to 'lift the grounds' on equipment to cure hum problems. I'm comfortable with the knowledge that in Europe it is a breach of the Low Voltage Directive to supply equipment that is constructed using Class I methods if its protective ground conductor is not connected, or if it could be 'lifted' by operation of a user-accessible switch or jumper. I am also comfortable with the idea that in Europe if the user does not connect a protective ground conductor to Class I equipment, the health and safety at work directives mean that he/she is probably committing a criminal act. A Health and Safety Inspector could close down his/her facility if he/she discovered such an error. My question concerns the comparable situation in the USA. I am under the impression that my summary above for European protective grounding requirements for Class I equipment also applies to the US, both for the supply of the equipment and the installation of systems using it. But I am reliably told that there are a great many pro-audio products, systems, and installations in the USA where protective grounding is treated as just a hum control measure and safety issues take second place. I am also reliably told that in the US one can even find whole buildings wired using two-core mains cables, without any safety ground wires to any of the pro-audio equipment. So what are your views on removing the safety grounds from Class I equipment used in pro-audio systems and installations? Can anyone defend this practice or show that it is legal in the USA? All the very best Keith Armstrong Note: Class I equipment uses basic insulation plus protective ground bonding to protect against electrical hazards, and must use three-pin mains connectors and three-core mains leads (for single-phase supplies). The only alternative permitted (in Europe, anyway) for mains-powered equipment is Class II - 'double insulation' . This must have no protective ground conductor and must use two-pin mains connectors and two-core mains leads (again, for single phase supplies). Best Regards Ted Rook, Console Engineering, ext 4659 Please note our new location and phone numbers: Crest Audio Inc, 16-00 Pollitt Drive Fair Lawn, NJ 07410 USA 201 475 4600 telephone receptionist, 8.30 - 5 pm EST. 201 475 4659 direct line w/voice mail, 24 hrs. 201 475 4677 fax, 24 hrs. --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Tuned Stub Filter
We are considering using a tuned stub filter to suppress the carrier so that we do not overload our spectrum analyzer while measuring spurious emissions. One question we have concerns the Q of the filter - i.e., will it sufficiently suppress the modulation sidebands. So, let me ask the following questions. In the frequency ranges of 860-1000 MHz and 2.45 GHz, how much suppression should I expect from a stub filter and what design steps can be taken to have the necessary bandwidth? Or, am I going down the wrong path for a filter? Richard Woods Sensormatic Electronics Tyco International --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: NEC Question
Hello Steve, The NEC doesn't list products. Nationally Recognized Testing Laboratories (NRTLs) do, under OSHA regulations. However, it is not a requirement for a manufacturer to get products listed. The burden of having products listed by an NRTL, like UL, falls on the purchaser of the product if the product is used in a workplace which is subject to OSHA regulations. Most non-IT product manufacturers do not get their products listed unless a Customer specifically requires it. In some cases, a product may get listed because it is expected that a product will be marketed in a known jurisdiction that requires listed products by an NRTL. The State of Oregon and the City of Los Angeles are a couple examples. Regards, +=+ |Ronald R. Wellman|Voice : 408-345-8229 | |Agilent Technologies |FAX : 408-553-2412 | |5301 Stevens Creek Blvd.,|E-Mail: ron_well...@agilent.com| |Mailstop 54L-BB |WWW : http://www.agilent.com | |Santa Clara, California 95052 USA| | +=+ | Common sense is the collection of prejudices acquired by age | | eighteen. - Albert Einstein | +=+ -Original Message- From: sbr...@prodigy.net [mailto:sbr...@prodigy.net] Sent: Wednesday, March 20, 2002 7:57 AM To: emc-p...@ieee.org Subject: NEC Question Colleagues: The question was asked if all products sold in the US, specifically industrial products, that plugged into the mains had to be UL Listed. The answer was that not necessarily UL Listed, but according to the NEC they did have to be listed, labeled, certified, classified, etc., by a 3rd party. The answer went on to say that this was only applicable if the locality in which the product were to be used, and their AHJ, adhered to the NEC and that not all areas of the country adopted and adhered to the NEC. 1. Do you agree with the above responses? 2. How long has the NEC required products to be listed, labeled, certified, classified, etc.? Your comments and feedback would be appreciated. Thanks in advance, Steve Brody sbr...@prodigy.net --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Pro-audio and ground lifting
Building wiring is such that separate mains and grounds are provided for audio power and lighting power. Mics are provided with above ground circuits so that mic output is immune from ground noise. All pro-audio gear is provided a case ground green wire and that is not defeated. The above related to me by an EMC engineer who used to work as a roadie. -- From: cherryclo...@aol.com To: emc-p...@ieee.org Cc: t...@cadac-sound.com Subject: Pro-audio and ground lifting List-Post: emc-pstc@listserv.ieee.org Date: Wed, Mar 20, 2002, 10:59 AM Dear Group Does anyone know if it is legally permissible in the USA to remove the safety grounds from Class I equipment used in pro-audio systems and installations? It has been a common practice over many many years in professional audio systems and installations to 'lift the grounds' on equipment to cure hum problems. I'm comfortable with the knowledge that in Europe it is a breach of the Low Voltage Directive to supply equipment that is constructed using Class I methods if its protective ground conductor is not connected, or if it could be 'lifted' by operation of a user-accessible switch or jumper. I am also comfortable with the idea that in Europe if the user does not connect a protective ground conductor to Class I equipment, the health and safety at work directives mean that he/she is probably committing a criminal act. A Health and Safety Inspector could close down his/her facility if he/she discovered such an error. My question concerns the comparable situation in the USA. I am under the impression that my summary above for European protective grounding requirements for Class I equipment also applies to the US, both for the supply of the equipment and the installation of systems using it. But I am reliably told that there are a great many pro-audio products, systems, and installations in the USA where protective grounding is treated as just a hum control measure and safety issues take second place. I am also reliably told that in the US one can even find whole buildings wired using two-core mains cables, without any safety ground wires to any of the pro-audio equipment. So what are your views on removing the safety grounds from Class I equipment used in pro-audio systems and installations? Can anyone defend this practice or show that it is legal in the USA? All the very best Keith Armstrong Note: Class I equipment uses basic insulation plus protective ground bonding to protect against electrical hazards, and must use three-pin mains connectors and three-core mains leads (for single-phase supplies). The only alternative permitted (in Europe, anyway) for mains-powered equipment is Class II - 'double insulation' . This must have no protective ground conductor and must use two-pin mains connectors and two-core mains leads (again, for single phase supplies).
Re: Pro-audio and ground lifting
I read in !emc-pstc that cherryclo...@aol.com wrote (in 17d.557eff5.29c a1...@aol.com) about 'Pro-audio and ground lifting', on Wed, 20 Mar 2002: Class I equipment uses basic insulation plus protective ground bonding to protect against electrical hazards, and must use three-pin mains connectors and three-core mains leads (for single-phase supplies). The only alternative permitted (in Europe, anyway) for mains-powered equipment is Class II - 'double insulation' . This must have no protective ground conductor and must use two-pin mains connectors and two-core mains leads (again, for single phase supplies). This is true for consumer products but for professional audio equipment under IEC/EN60065, an arrangement whereby *parts* of the product meet Class II requirements while other parts meet Class I requirements has been accepted by Notified Bodies for some years. These can be shown to be just as safe as conventional products. With regard to your main enquiry, professional audio engineers in the Audio Engineering Society are severely critical of 'ground lift' solutions. The correct, and safe, solutions, lie in the signal circuits that sustain the ground loops. The subject is extensively treated in the June 1995 issue of the Journal of the Audio Engineering Society. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: NEC Question
A couple of exceptions to what has been posted before by George and John. Referring to OSHA section 1910.399: With respect to an installation or equipment of a kind which no nationally recognized testing laboratory accepts, certifies, lists, labels, or determines to be safe, if it is inspected or tested by another federal agency, or by a state, municipal, or other local authority responsible for enforcing occupational safety provisions of the National Electrical Code as applied in this Subpart, or: With respect to custom-made equipment or related installations which are designed, fabricated for, and intended for use by a particular customer, if it is determined to be safe for its intended use by its manufacturer on the basis of test data which the employer keeps and makes available for the inspection to the Assistant Secretary or his authorized representatives. The first part will probably boil down to the same thing, get an NRTL to accept the product. The second part is much more flexible, but limits it to a particular customer. An excercise in Risk Management if you pursue that approach. Regards, Eric Petitpierre Pulsecom Herndon, VA ** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This footnote also confirms that this email message has been swept for the presence of computer viruses. www.hubbell.com - Hubbell Incorporated ** --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: NEC Question
An excellent paper, Know when you need to list your product...and when you don't, can be found in Conformity 2002, the annual guide published by Conformity magazine. The paper covers commercial or business statutes, building or fire codes including the NEC, and labor codes. The states of Oregon, Washington, North Carolina and California are discussed as examples. I did not find the article posted on their web site, unfortunately. It might be worth contacting them for a reprint, if it is available. www.conformity.com Richard Woods Sensormatic Electronics Tyco International -Original Message- From: sbr...@prodigy.net [mailto:sbr...@prodigy.net] Sent: Wednesday, March 20, 2002 10:57 AM To: emc-p...@ieee.org Subject: NEC Question Colleagues: The question was asked if all products sold in the US, specifically industrial products, that plugged into the mains had to be UL Listed. The answer was that not necessarily UL Listed, but according to the NEC they did have to be listed, labeled, certified, classified, etc., by a 3rd party. The answer went on to say that this was only applicable if the locality in which the product were to be used, and their AHJ, adhered to the NEC and that not all areas of the country adopted and adhered to the NEC. 1. Do you agree with the above responses? 2. How long has the NEC required products to be listed, labeled, certified, classified, etc.? Your comments and feedback would be appreciated. Thanks in advance, Steve Brody sbr...@prodigy.net --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: Earthing of conductive floor tiles
Funny you should mention that. We had the same problem only it turned out to be an access plate in our turntable. Even though the plate is screwed into the turntable, over time the screws loosen enough through vibrations and the plate starts arcing. Like all great inventions, we accidentally found this out during our troubleshooting by making a scan with the access plate removed. The plate is now a permanent part of our turntable preventive maintenance schedule. Bob Heller 3M Product Safety, 76-1-01 St. Paul, MN 55107-1208 Tel: 651- 778-6336 Fax: 651-778-6252 = - Forwarded by Robert E. Heller/US-Corporate/3M/US on 03/20/2002 12:14 PM - Hans Mellberg emcconsultant@ To: David Spencer dspen...@oresis.com yahoo.com 'Arno van Kesteren ' avkes...@eso.org 'emc-p...@majordomo.ieee.org ' emc-p...@majordomo.ieee.org 03/20/2002 cc: (bcc: Robert E. Heller/US-Corporate/3M/US) 10:31 AM Subject: RE: Earthing of conductive floor tiles Please respond to Hans Mellberg Several years ago I was called in to debug a chamber that had spurious emissions whilst turning the table. Naturally, everyone accused the tt manufacturer but after several hours of frustrating dead ends, it turned out that the small amount of vibration caused by the tt was causing the floor tiles to move and shift ever so slightly. This was enough for small amounts of static charge to develop and discharge causing the emissions in the chamber. Once this was ascertained, grounding the floor tiles eliminated the problem. We used copper tape under every tile folded over till the tile manufacturer came in with a permanent solution which included spring fingers. These metal lined tiles were for a false raised floor for cabling and a/c and not the ferrite types. --- David Spencer dspen...@oresis.com wrote: Hi Arno, John gave you the short answer...the MFG should have installation instructions. In all of the installation I have been party, there is a grid of copper tape laid down in the conductive adhesive. This keeps the adhesive from getting excessively resistive over large areas. Surface resistance tests run anywhere from 100k-400k ohms when it's all done. Note that if you are installing relay racks or metal benches that you can run into ground loops. Have a Great Day, Dave Spencer Oresis Communications -Original Message- From: Arno van Kesteren To: Arno van Kesteren; emc-p...@majordomo.ieee.org Sent: 3/18/02 1:48 PM Subject: Earthing of conductive floor tiles Dear Group, Do conductive tiles in floors for ESD prevention have to be connected together (e.g. through a low impedance earth bond) ? Arno van Kesteren ESO Munich, Germany e-mail: avkes...@eso.org --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- 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: Ron Pickard:
RES: Pro-audio and ground lifting
keith, In pro-audio systems, normally you found a ground lift switch. This switch disconnects the signal shield from the equipment ground. It doesn't disconnect the protection earth from the main supply. Regards Sérgio L. Rocha Loures Siemens Ltda. - Brazil Supply Chain - Quality and Engineering IC SC QE L Tel: +55 41 341-5898 Fax: +55 41 341-5058 E-mail: sergioro...@siemens.com.br Minha opinião e não necessariamente a do meu empregador. -Mensagem original- De: cherryclo...@aol.com [mailto:cherryclo...@aol.com] Enviada em: quarta-feira, 20 de março de 2002 13:59 Para: emc-p...@ieee.org Cc: t...@cadac-sound.com Assunto: Pro-audio and ground lifting Dear Group Does anyone know if it is legally permissible in the USA to remove the safety grounds from Class I equipment used in pro-audio systems and installations? It has been a common practice over many many years in professional audio systems and installations to 'lift the grounds' on equipment to cure hum problems. I'm comfortable with the knowledge that in Europe it is a breach of the Low Voltage Directive to supply equipment that is constructed using Class I methods if its protective ground conductor is not connected, or if it could be 'lifted' by operation of a user-accessible switch or jumper. I am also comfortable with the idea that in Europe if the user does not connect a protective ground conductor to Class I equipment, the health and safety at work directives mean that he/she is probably committing a criminal act. A Health and Safety Inspector could close down his/her facility if he/she discovered such an error. My question concerns the comparable situation in the USA. I am under the impression that my summary above for European protective grounding requirements for Class I equipment also applies to the US, both for the supply of the equipment and the installation of systems using it. But I am reliably told that there are a great many pro-audio products, systems, and installations in the USA where protective grounding is treated as just a hum control measure and safety issues take second place. I am also reliably told that in the US one can even find whole buildings wired using two-core mains cables, without any safety ground wires to any of the pro-audio equipment. So what are your views on removing the safety grounds from Class I equipment used in pro-audio systems and installations? Can anyone defend this practice or show that it is legal in the USA? All the very best Keith Armstrong Note: Class I equipment uses basic insulation plus protective ground bonding to protect against electrical hazards, and must use three-pin mains connectors and three-core mains leads (for single-phase supplies). The only alternative permitted (in Europe, anyway) for mains-powered equipment is Class II - 'double insulation' . This must have no protective ground conductor and must use two-pin mains connectors and two-core mains leads (again, for single phase supplies).
Re: DSL on residential buildings.
We agree. The gray area arises from the fact that residential is not strictly defined. When the distinction was first made in subpart B, it hinged on whether equipment was sold for use in the home, not whether it was installed close to a home or farther away. I take the position that the need may be defined by whether the field strength from a class A device would be above the Class B limit at or inside a residential property. Whether Class B is enough is debatable. It is certainly not enough to protect non-broadcast communications, where received signals may be less than 20 dBuV/m. Cheers, Cortland On Wednesday, 20 Mar 2002, Hans Mellberg hans.mellb...@ieee.org wrote I may have gotten in on the tail end of the dicussion, but here is my take on residential DSL. The FCC rules are quite clear on equipment marketed to residential environments, Class B. The DSL equipment being sold to residences must comply with class B limits notwithstanding office use. small, non-rack mounted routers and switches are probably still being argued as class A devices although most major mfg make them already as class B. Eventually, when a lot of homes incorporate hubs and routers then those will also have to be class B. --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
DSL on residential buildings.
Your comments remind me of how FCC limits began a few decades ago. As many may recall, in the days before real PCs, Playstations and the like, Coleman and others began marketing ping pong games one could play on their TV set. Since TVs had no direct inputs at the time, the small game box fed VHF signals to the TV antenna inputs, which were demodulated within the TV. The user was directed to remove the TV antenna leads to do this. However, it was not uncommon for a consumer to leave both the antenna and game leads attached to the TV. When the game was tured on and played, faint images of ping pong balls and paddles were transmitted via the outside antenna to neighbors' TV sets, prompting compliants. Due to this and related phenomena the FCC created EMI limits for digitally clocked systems employing a 10kHz clock or higher. You know the rest of the story. Oddly, our many electrical appliances not involving digital controls are not regulated, and create most of the EMI in a typical household. George --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: NEC Question
Steve, To further George's remarks, if you have a product that may be 'custom' or the construction is inconsistent enough to make a general 'listing' by an NRTL unfeasible (more common with industrial products/installations), you may want to consider a 'Field Evaluation' by an NRTL for the product. John Juhasz GE Interlogix Fiber Options Div. Bohemia, NY -Original Message- From: geor...@lexmark.com [mailto:geor...@lexmark.com] Sent: Wednesday, March 20, 2002 11:16 AM To: sbr...@prodigy.net Cc: emc-p...@ieee.org Subject: Re: NEC Question Steve, If the products in question are going into U.S. workplaces, they are bound under the OSHA requirements in the U.S. Code of Federal Regulations to be listed by an NRTL, regardless of the locale. Approved NRTLs can be found at: http://www.osha-slc.gov/dts/otpca/nrtl/index.html#nrtls Note that not all NRTLs are approved to test to all the standards. You can use any approved to test to the standard covering your products. George sbrody%prodigy@interlock.lexmark.com on 03/20/2002 10:57:28 AM Please respond to sbrody%prodigy@interlock.lexmark.com To: emc-pstc%ieee@interlock.lexmark.com cc:(bcc: George Alspaugh/Lex/Lexmark) Subject: NEC Question Colleagues: The question was asked if all products sold in the US, specifically industrial products, that plugged into the mains had to be UL Listed. The answer was that not necessarily UL Listed, but according to the NEC they did have to be listed, labeled, certified, classified, etc., by a 3rd party. The answer went on to say that this was only applicable if the locality in which the product were to be used, and their AHJ, adhered to the NEC and that not all areas of the country adopted and adhered to the NEC. 1. Do you agree with the above responses? 2. How long has the NEC required products to be listed, labeled, certified, classified, etc.? Your comments and feedback would be appreciated. Thanks in advance, Steve Brody sbr...@prodigy.net --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Pro-audio and ground lifting
Dear Group Does anyone know if it is legally permissible in the USA to remove the safety grounds from Class I equipment used in pro-audio systems and installations? It has been a common practice over many many years in professional audio systems and installations to 'lift the grounds' on equipment to cure hum problems. I'm comfortable with the knowledge that in Europe it is a breach of the Low Voltage Directive to supply equipment that is constructed using Class I methods if its protective ground conductor is not connected, or if it could be 'lifted' by operation of a user-accessible switch or jumper. I am also comfortable with the idea that in Europe if the user does not connect a protective ground conductor to Class I equipment, the health and safety at work directives mean that he/she is probably committing a criminal act. A Health and Safety Inspector could close down his/her facility if he/she discovered such an error. My question concerns the comparable situation in the USA. I am under the impression that my summary above for European protective grounding requirements for Class I equipment also applies to the US, both for the supply of the equipment and the installation of systems using it. But I am reliably told that there are a great many pro-audio products, systems, and installations in the USA where protective grounding is treated as just a hum control measure and safety issues take second place. I am also reliably told that in the US one can even find whole buildings wired using two-core mains cables, without any safety ground wires to any of the pro-audio equipment. So what are your views on removing the safety grounds from Class I equipment used in pro-audio systems and installations? Can anyone defend this practice or show that it is legal in the USA? All the very best Keith Armstrong Note: Class I equipment uses basic insulation plus protective ground bonding to protect against electrical hazards, and must use three-pin mains connectors and three-core mains leads (for single-phase supplies). The only alternative permitted (in Europe, anyway) for mains-powered equipment is Class II - 'double insulation' . This must have no protective ground conductor and must use two-pin mains connectors and two-core mains leads (again, for single phase supplies).
RE: Relative merits of various logic families in not generating RFI
I generally agree, although your comment that double sided PCBs are about to disappear is rather premature. Way over half of the PCBs manufactured in the world today are SINGLE sided (look in any piece of high volume electronics). Double sided PCBs still will be used in volume for many years to come. Many 4 layer PCBs are simply the result of lack of designer layout skill, or (in particular) a result of the use of autoplace and autoroute programs that would otherwise ventilate a 2-sided board with an absurd number of vias and serpentine tracks snaking willy-nilly all over the place. The solution to the need for actual skill in board layout is often to let the machine do it, and suffer the cost of more layers. Time to market is, it seems, more important than cost or quality. At least here in North America. Bob Wilson TIR Systems Ltd. Vancouver. -Original Message- From: Cortland Richmond [mailto:72146@compuserve.com] Sent: March 19, 2002 4:02 PM To: Robert Macy; ieee pstc list Subject: Re: Relative merits of various logic families in not generating RFI Probably, you won't get much choice. I've often found older, slower, quieter logic impractical or even uneconomical to use. It may be made only by one (thus off limits single-source) manufacturer, or it may be built using older, more expensive technologies and cost an arm and a leg. And it may happen one day that a manufacturer lets you know production is simply ending, and with no chance of an equivalent substitute. I am rather afraid that the best solution in these cases is to go with later, even if noisier devices -- and then design for them. Then too, if you use current devices, you may escape being blind-sided when they go to a smaller fabrication technology without letting you know. Even spting advertised an spe'd as an older device may in fact be a newer one. Who, after all, specifies devices by the fastest they go? It's always a minimum guaranteed speed. Yes, that means even MHz and KHz clock-rates with nanosecond transitions. You have to deal with it. Slew rate limiting is available, sometimes, built-in. If not, you have to add it externally. I've seen a 30 dB difference at 147 Mhz from a single 33 ohm resistor on a 1 Mhz clock. You have to be more careful with layout. You have to avoid inadvertent peaking networks - DON'T let anyone just throw HF bypasses willy-nilly on logic signals; you'd be AMAZED where the high frequencies can end up. And it means the end, really of 2-layer boards, at least as the old engineers know them. They have to be redesigned for RF, even if we weren't dealing with RF. But in the end, we get reliable boards, cheaper, that won't have to be replaced when the foundry discovers shorter-wavelength lithography. And your totem-pole short circuit? Yes, they know about that. Don't DO it. (grin) If you MUST have that kind of output, put a charge reservoir right at the device power pins, faster than a speeding junction, able to leap tall short circuits at a single bound, with enough charge to keep the transient local. But you already KNEW that! Cheers, Cortland --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: DSL on residential buildings.
I may have gotten in on the tail end of the dicussion, but here is my take on residential DSL. The FCC rules are quite clear on equipment marketed to residential environments, Class B. The DSL equipment being sold to residences must comply with class B limits notwithstanding office use. small, non-rack mounted routers and switches are probably still being argued as class A devices although most major mfg make them already as class B. Eventually, when a lot of homes incorporate hubs and routers then those will also have to be class B. --- Cortland Richmond 72146@compuserve.com wrote: The reason for the Part 15 residential (Class B) limit is to protect reception, and the levels prescribed are (arguably) low enough to do so. If we allow higher levels, we are asking for service calls and perhaps official attention. But (unless I am mistaken) it is now the USER who responsible for interference generated by his Class A devices, and it's perfectly legal for us to sell them to him. I recently spent some years working for a company that makes telecomm equipment. I there encountered for the first time the telco point of view (which is probably not uncommon). In the telephone world, the service provider is responsible for everything up to the network interface. Everything beyond that is the responsibility of the customer. Therefore, some people assume that equipment installed prior to the NIC can be, and should be Class A for Part 15. I have argued, with success, that this is an error with potentially expensive consequences. Part 15 contains an exemption for equipment located within a facility - even just a locked room, cabinet or vault - controlled by the telco. There is an argument, which I make, that when we do this in a residential building, if we are NOT Class B compliant, we may wish we had been. (Even Class B is often not enough, and I have seen equipment meant for customer use whose specification was well below the FCC limit.) And though our employers' products may comply with Part 15 we are still liable for harmful interference. However, emissions may be suppressed by other means than installing only Class B equipment and this is often the way to go. The utility exemption does make this easier. I personally believe that one may make a case for the mechanical room being Class A. It often contains furnaces, motors, and many other unregulated devices which generate high levels of radio and television interference, and to impose a stricter standard on telecom equipment in the same place seems a bit of a reach. But look at the environment! Will emissions reaching a customer location be above the Class B limit? If so, then I would say due diligence requires suppressing them further. A vault in a steel reinforced building's basement is a different matter than a rooftop utility hut with TV antennas just 3 meters away. If deployment entails a wide range of installations, then it is probably best to suppress all of it to Class B, rather than install Class B retrofit kits on a case-by-case basis. This is a decision I believe has to be made when the product is proposed. Regards, Cortland Richmond (unemployed, and looking) --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list = Best Regards Hans Mellberg Regulatory Compliance EMC Design Services Consultant By the Pacific Coast next to Silicon Valley, Santa Cruz, CA, USA 408-507-9694 __ Do You Yahoo!? Yahoo! Sports - live college hoops coverage http://sports.yahoo.com/ --- 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: Ron Pickard: emc-p...@hypercom.com 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
RE: Earthing of conductive floor tiles
Several years ago I was called in to debug a chamber that had spurious emissions whilst turning the table. Naturally, everyone accused the tt manufacturer but after several hours of frustrating dead ends, it turned out that the small amount of vibration caused by the tt was causing the floor tiles to move and shift ever so slightly. This was enough for small amounts of static charge to develop and discharge causing the emissions in the chamber. Once this was ascertained, grounding the floor tiles eliminated the problem. We used copper tape under every tile folded over till the tile manufacturer came in with a permanent solution which included spring fingers. These metal lined tiles were for a false raised floor for cabling and a/c and not the ferrite types. --- David Spencer dspen...@oresis.com wrote: Hi Arno, John gave you the short answer...the MFG should have installation instructions. In all of the installation I have been party, there is a grid of copper tape laid down in the conductive adhesive. This keeps the adhesive from getting excessively resistive over large areas. Surface resistance tests run anywhere from 100k-400k ohms when it's all done. Note that if you are installing relay racks or metal benches that you can run into ground loops. Have a Great Day, Dave Spencer Oresis Communications -Original Message- From: Arno van Kesteren To: Arno van Kesteren; emc-p...@majordomo.ieee.org Sent: 3/18/02 1:48 PM Subject: Earthing of conductive floor tiles Dear Group, Do conductive tiles in floors for ESD prevention have to be connected together (e.g. through a low impedance earth bond) ? Arno van Kesteren ESO Munich, Germany e-mail: avkes...@eso.org --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list = Best Regards Hans Mellberg Regulatory Compliance EMC Design Services Consultant By the Pacific Coast next to Silicon Valley, Santa Cruz, CA, USA 408-507-9694 __ Do You Yahoo!? Yahoo! Sports - live college hoops coverage http://sports.yahoo.com/ --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: NEC Question
Steve, If the products in question are going into U.S. workplaces, they are bound under the OSHA requirements in the U.S. Code of Federal Regulations to be listed by an NRTL, regardless of the locale. Approved NRTLs can be found at: http://www.osha-slc.gov/dts/otpca/nrtl/index.html#nrtls Note that not all NRTLs are approved to test to all the standards. You can use any approved to test to the standard covering your products. George sbrody%prodigy@interlock.lexmark.com on 03/20/2002 10:57:28 AM Please respond to sbrody%prodigy@interlock.lexmark.com To: emc-pstc%ieee@interlock.lexmark.com cc:(bcc: George Alspaugh/Lex/Lexmark) Subject: NEC Question Colleagues: The question was asked if all products sold in the US, specifically industrial products, that plugged into the mains had to be UL Listed. The answer was that not necessarily UL Listed, but according to the NEC they did have to be listed, labeled, certified, classified, etc., by a 3rd party. The answer went on to say that this was only applicable if the locality in which the product were to be used, and their AHJ, adhered to the NEC and that not all areas of the country adopted and adhered to the NEC. 1. Do you agree with the above responses? 2. How long has the NEC required products to be listed, labeled, certified, classified, etc.? Your comments and feedback would be appreciated. Thanks in advance, Steve Brody sbr...@prodigy.net --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
EN60950 Special National Conditions
Group, Does any one know the specific technical reason for the spanish special national condition 3.2.1 that says that equipment up to 10A shall be provided with a plug according to UNE20315? As Spain use the standard European CEE7 (schuko) plug (which I am assuming UNE20315 refers to) then why is this National requirement specific to Spain and not all other continental countries that use this same plug/socket and power system? Many thanks, Duncan. Hobbs. -- The contents of this communication are confidential to the normal user of the email address to which it was sent. If you have received this email in error, any use, dissemination, forwarding, printing or copying of this email is strictly prohibited. If this is the case, please notify the sender and delete this message. -- --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Fw: Conductive Coatings/Conductive Plastic
John another possibility. I have seen screen matterial put inside the plastic. the screen can come to the surface where needed. It tends to warp the plastic part due to cooling issues. Can be very fine and cover LED openings letting light through - Original Message - From: Chris Wells cdwe...@stargate.net To: John Juhasz jjuh...@fiberoptions.com Sent: Tuesday, March 19, 2002 4:57 PM Subject: Re: Conductive Coatings/Conductive Plastic John some comments We use a Stainless Steel loaded Polly carbonate to control ESD in the faceplates of our user interfaces. For ESD control it works very nicely! The CC ohmic resistance over metal helps in slowing down the ESD discharge current. A coated inner surface would be good for RF but defeat the ESD advantage. Grounding Contact has been reliable in adverse conditions with pressed in inserts over many years (sorry don't know the metal used - looks like brass). I believe the pressed in approach helps bond to the SS fibers. RF filtering is not very good in the 400-500 MHz range. I can picture the coating bonding the various fibers together and working well in RF but... Plastic had to get a special UL recognition - the coating would add more UL issues as others attest. Note that the Poly Carb is brittle compared to the Poly carbonate with out SS. This can lead to cracking problems with inserts screws or other mechanical attachments. The SS aditive creats a surface texture/color that has an uncontroled glossy shine to it. We had to texture the surface to tone it down and have used grey or black pigments to dominate the blotchness. Also the SS fibers can come off into the skin sort of like fiberglass and cause iritation to the skin if you rub your hand against. Wear on the molds has been an issue but controlable for medium volume usage of ~ 10K/year and simple designs. If the tooling is very expensive I would think twice. Chris Wells Senior Design Engineer Cutler-hammer Pittsburgh Pa. - Original Message - From: John Juhasz jjuh...@fiberoptions.com To: emc-p...@ieee.org Sent: Tuesday, March 19, 2002 5:42 AM Subject: Conductive Coatings/Conductive Plastic Seeking comment on Conductive Coatings vs. Conductive Plastic Having dealt with metal (primarily steel) enclosures, my knowledge of conductive coatings/conductive plastics is strictly based on what I have been able to gleen from simple research and some conversation. It is my understanding the conductive plastic (metal fibers mixed with the plastic) is less effective at high frequencies ( 200MHz) than plastic with a conductive coating (i.e. electroless plating). Further, from a processing perspective (notwithstanding the shielding effectiveness), if good contact between mating pieces is required, conductive plastic is not a top ranked choice - the amount of fiber that is actually exposed to make contact is difficult to control and filing during product assembly may be required to expose sufficient fiber. And in both cases - SE and physical contact - the preparation (mixing) of the plastic/metal fiber needs to be tightly controlled (and is more difficult to control), with potential for greater variances from to batch to batch than there is for plated plastic. Comments please. GE Interlogix John A. Juhasz Product Qualification Compliance Engr. Fiber Options Div. Bohemia, NY 11716 --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/
NEC Question
Colleagues: The question was asked if all products sold in the US, specifically industrial products, that plugged into the mains had to be UL Listed. The answer was that not necessarily UL Listed, but according to the NEC they did have to be listed, labeled, certified, classified, etc., by a 3rd party. The answer went on to say that this was only applicable if the locality in which the product were to be used, and their AHJ, adhered to the NEC and that not all areas of the country adopted and adhered to the NEC. 1. Do you agree with the above responses? 2. How long has the NEC required products to be listed, labeled, certified, classified, etc.? Your comments and feedback would be appreciated. Thanks in advance, Steve Brody sbr...@prodigy.net --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: FCC Part 68 and prototypes
Richard, Under the old Part 68 regime, there was a thing called a Limited field trial administered by the Telcos. This was primarily used to do test prototypes and do early field trials while you were waiting for the FCC to issue the approval. You had to have a compliant product, i.e. have all your testing completed, before you coud go to field trial. This process has now gone the way of the Dodo, as there is no longer any approval by an agency (FCC, ACTA) required; you self declare as a manufacturer. Under the self declaration scheme, all you have to do is test your product (can be inhouse), issue a Declaration of Conformity, and send the application to ACTA. You do not have to wait for any form of approval from ACTA, but you can ship the product in any quantities you wish, as soon as you have signed the declaration and posted it on your company website . All the details are on the ACTA website (www.part68.org). Regards Doug Beckwith --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Surge test on a loop
I read in !emc-pstc that am...@westin-emission.no wrote (in LFENJLPMMJB mhpeibnilieiocdaa.am...@westin-emission.no) about 'Surge test on a loop', on Wed, 20 Mar 2002: Assume a fire alarm detection system. 10 smoke detectors are connected in series on a loop and both ends of the loop is connected to the fire alarm panel. Shielded cable is used and the shield is connected through the whole loop. So, how do we carry out the surge test on the loop? The alarm panel and the detectors are all EUTs. As far as I understand IEC61000-4-5:1995 chapter 7.5, I will insert an extra 20 meter shielded cable between each detectors and then I will drive the surge pulse onto the shield in order to test one of the detectors. Then I move the extra 20m cable to the next detector and surge test it. If this is correct, why can't we just put the surge pulse onto the shielded loop and assume that the whole loop was tested at once? You haven't said which product EMC standard you are applying. This matter should have been made clear in that standard. If it isn't, you should press for an amendment to clarify it. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Surge test on a loop
Amund Westin write: If this is correct, why can't we just put the surge pulse onto the shielded loop and assume that the whole loop was tested at once? I've not done this test. But thinking about it, failure at anything in the loop can prevent the surge from stressing the rest of the EUT's. What if the wrong one fails? I don't have the standard here at home, but I suspect you would do as well to test each of the EUT's on a short test loop, alone, that being arguably more severe. Cortland --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: Conductive Coatings/Conductive Plastic
Thanks to all who responded to my message (below)regarding conductive coatings/conductive plastics. Everyone made some good points. GE Interlogix John Juhasz Fiber Options Div. Bohemia, NY -Original Message- From: John Juhasz [mailto:jjuh...@fiberoptions.com] Sent: Tuesday, March 19, 2002 8:42 AM To: 'emc-p...@ieee.org' Subject: Conductive Coatings/Conductive Plastic Seeking comment on Conductive Coatings vs. Conductive Plastic Having dealt with metal (primarily steel) enclosures, my knowledge of conductive coatings/conductive plastics is strictly based on what I have been able to gleen from simple research and some conversation. It is my understanding the conductive plastic (metal fibers mixed with the plastic) is less effective at high frequencies ( 200MHz) than plastic with a conductive coating (i.e. electroless plating). Further, from a processing perspective (notwithstanding the shielding effectiveness), if good contact between mating pieces is required, conductive plastic is not a top ranked choice - the amount of fiber that is actually exposed to make contact is difficult to control and filing during product assembly may be required to expose sufficient fiber. And in both cases - SE and physical contact - the preparation (mixing) of the plastic/metal fiber needs to be tightly controlled (and is more difficult to control), with potential for greater variances from to batch to batch than there is for plated plastic. Comments please. GE Interlogix John A. Juhasz Product Qualification Compliance Engr. Fiber Options Div. Bohemia, NY 11716 --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: Surge test on a loop
As you say, you have several types of EUTs, and each type must be tested as the EUT. Any other equipment connected to the EUT with cables are considered to be auxiliary equipment. The standard is clear on how to test the EUT when auxiliarly equipment is attached. In your case, the procedure has no knowlege that there is a loop and does not care. All it knowns is that a surge is being applied to a cable. I am sure that there are many ways one could devise to test one or more EUTs at the same time; however, in the end, if you are claiming compliance to a standard, you must test according to the procedure in the standard. If you wish to do otherwise, then you will have to peruse the Technical Construction File route. Richard Woods Sensormatic Electronics Tyco International -Original Message- From: am...@westin-emission.no [mailto:am...@westin-emission.no] Sent: Wednesday, March 20, 2002 4:59 AM To: emc-p...@majordomo.ieee.org Subject: Surge test on a loop Hi all, Assume a fire alarm detection system. 10 smoke detectors are connected in series on a loop and both ends of the loop is connected to the fire alarm panel. Shielded cable is used and the shield is connected through the whole loop. So, how do we carry out the surge test on the loop? The alarm panel and the detectors are all EUTs. As far as I understand IEC61000-4-5:1995 chapter 7.5, I will insert an extra 20 meter shielded cable between each detectors and then I will drive the surge pulse onto the shield in order to test one of the detectors. Then I move the extra 20m cable to the next detector and surge test it. If this is correct, why can't we just put the surge pulse onto the shielded loop and assume that the whole loop was tested at once? Best regards Amund Westin, Oslo/Norway --- This message is from the IEEE EMC Society Product Safety Technical Committee
Surge test on a loop
Hi all, Assume a fire alarm detection system. 10 smoke detectors are connected in series on a loop and both ends of the loop is connected to the fire alarm panel. Shielded cable is used and the shield is connected through the whole loop. So, how do we carry out the surge test on the loop? The alarm panel and the detectors are all EUTs. As far as I understand IEC61000-4-5:1995 chapter 7.5, I will insert an extra 20 meter shielded cable between each detectors and then I will drive the surge pulse onto the shield in order to test one of the detectors. Then I move the extra 20m cable to the next detector and surge test it. If this is correct, why can't we just put the surge pulse onto the shielded loop and assume that the whole loop was tested at once? Best regards Amund Westin, Oslo/Norway --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Relative merits of various logic families in not generating RFI
Thank you for the prompt reply. Yes, faster rise time would lend the signal and its generation to create energetic RFI, but just in case there were some internal states that blew power out, or high impedance return paths through the substrate that caused all the outputs to dance in common mode horror would be examples of the gotchas I was looking for. - Robert - -Original Message- From: peter.pou...@invensys.com peter.pou...@invensys.com To: Robert Macy m...@california.com List-Post: emc-pstc@listserv.ieee.org Date: Tuesday, March 19, 2002 8:23 PM Subject: Re: Relative merits of various logic families in not generating RFI Robert, I suggest you have a look at the logic selection guides and application notes from the major semiconductor logic manufacturers. As a starting point, check out page 13 to 15 of http://www.fairchildsemi.com/ms/MS/MS-520.pdf for a rule-of-thumb guide on how to assess EMI generation from the manufacturer's specs for the logic. Generally the slower the rise fall time, the lower the emissions. Robert Macy m...@california.com To: emc-p...@ieee.org Sent by: cc: owner-emc-pstc@majordomFax to: o.ieee.org Subject: Relative merits of various logic families in not generating RFI 20/03/02 08:49 Please respond to Robert Macy Group, What are the relative merits of the various logic families HCT, HC, AC, ACT with regard to generating RFI? I remember one time we replaced an HCT which made more noise than Schottky TTL due to an internal overlap in the switching causing a power rail shorting spike. I'm sure by now that most IC vendors have addressed the EMC problems associated with poorly designed chips, but what's the status on these now? What's the order of preference? Which one's best? - 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 --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
RE: CE - the abbreviation
This is old news, and of no real consequence. Only for those that like to compile lists: I just realized that in addition to all the others (caveat emptor, conducted-emissions, [Windows] CE, conformité européenne, etc.) there is now yet another, somewhat obscure, usage of the letters C E (this one seems to have an all important s p a c e separating the two letters: OJ C E!). Of course, the OJ C E is _not_ the portion of the OJ dealing with CE marking (that would be too easy!). EXTRACT FROM: http://europa.eu.int/eur-lex/en/help-about.html#OJCEnotice quote The Official Journal, published daily in 11 languages, consists of two related series, the L series (Legislation) and the C series (Information, notices and preparatory EU legislation), a supplement and an annex. EUR-Lex [ http://europa.eu.int/eur-lex/en/oj/index.html ] provides free access to the C and L series of the Official Journal for a period of 45 days following publication (after which they can be found on the monthly CD-ROM). The EU Institutions have decided to add an exclusively electronic section to the Official Journal C Series, known as the OJ C E. Documents published in the OJ C E will ONLY be published electronically. From now on, the OJ C E, structured as the current OJ C, will appear in the 11 official languages on the EUR-Lex site (http://europa.eu.int/eur-lex) under the Official Journal heading, where texts are currently available for 45 days. The full OJ C E texts will also be available on the OJ LC monthly CD-ROM, and in the Celex database. Some documents previously published in the OJ C may be transferred to the OJ C E. An index of all documents published in a given OJ C E will be printed in the paper edition of the OJ C of the same day. As is presently the case with the Annexes to the OJ C, the two OJs will bear the same number (e.g. the OJ C195 on paper will correspond to the electronic OJ C 195 E). The frequency of publication of the OJ C E series will depend on the frequency and volume of documents sent for publication by the EU Institutions. end of quote So now that's clear!! best regards, glyn -- TUV Rheinland of North America, Inc. Product Safety Quality Industrial Machinery Division (Chicago Office) Glyn R. Garside Senior Engineer 1945 Techny Rd, Unit 4 NORTHBROOK, IL 60062-5357, USA Tel (847)562-9888 ext 25 Cell (847)612-1574 Fax (847)562-0688 email ggars...@us.tuv.com http://www.us.tuv.com _ The information included in this e-mail is intended only for the person or entity to which it is addressed. Any use of this information by persons or entities other than the intended recipient is prohibited. If you receive this transmission in error, please delete this email and destroy any copies of it. Any opinions expressed in this email are those of the individual and not necessarily those of TUV Rheinland of North America, Inc. _ --- 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: Ron Pickard: emc-p...@hypercom.com 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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
