Re: UL legal requirement
At 02:55 PM 9/17/99 -0400, Bailey, Jeff wrote: Hello group, I am trying to find a basic document from UL and or CSA regarding the legal requirement of UL or CSA listing. I am thinking along the same lines as the European LVD. Can anyone offer insight as to whether this documentation exists? I'm going to stick my neck out and say, no you aren't going to find a *legal document* that requires UL or CSA testing. Why? Because private commercial companies aren't written into law. It's against fair trade. The day the state of California requires me by law to go to Midas to get my emissions taken care of is the day I leave. Likewise I doubt you'll find anything like that in the LVD that says NEMKO testing is required. What I think you'll find are references to NRTLs and that isn't restricted to UL or CSA. There's other NRTLs out there approved by OSHA for doing product approval. The NRTLs fall second in line to what the requirements of NEC call for. In other words, even in the event of a dispute with an electrician and an NRTL tested and approved product, the electrician can win of course depending upon what he or she is calling out in the Code. In such an event, UL or whoever has to request a clarification from the NEC. The real question is: Is there a legal requirement to obtain UL or CSA listing on a product that operates at a low voltage (below 50VAC or 75VDC), does not have a circuit that would be classed as a TNV circuit, does not operate in hazardous explosive environments, and does not consume a high amount of power? The product is also not connected to the mains supply, it is specified to require power from a safety listed supply. Well, I had on occasion to be in the same situation as you. I was reminded that in the case of a CO which is compliant to the Bellcore specs, GR-499 defines the supply voltages as Nominal Voltage 48vdc Minimum Voltage 42.5vdc Maximum Voltage 56.5vdc Transient Voltage 75.0 A 75.0 volt transient is understood to be a voltage excursion from 48 vdc up to 75 vdc and back to 48 vdc within 10 ms with a rate of rise and fall at 10V/ms. The 75 volt level, even though an excursion, was enough, in the specific situation I was in, to require UL-1950 testing. Regards, Doug - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: EMC and Safety Requirements for Mexico
At 03:01 PM 9/13/99 +0100, carlos.perk...@eu.effem.com wrote: Hello Group, Can anyone tell me if CE marking of electrical and electronic products is acceptable to the Mexican authorities? What tests in addition to the ENs would be necessary? Many thanks. Carlos Perkins. CE marking doesn't carry any weight in Mexico with their NOM standards. Nor do they accept as a memorandum of acceptability, the results of tests already performed. Although they are based on the same tests as Europe emissions and safety, the EN series is not recognized. Nor is testing for said standards accepted by labs outside Mexico. That includes the E1 telephone stuff that has to be done down there. There is no immunity as far as I know, but my information is about a year old. To get approval, which means getting a stamp on a box, one must test in Mexico and have someone with a Mexican ID number to sign for it all. In other words, you have to have someone whose residence is Mexico. Again, my information is about a year old so I'll gladly stand corrected. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Doubt on household equipment interference
At 04:54 PM 9/1/99 -0300, Muriel Bittencourt de Liz wrote: Dear Members I'd like to solve a doubt.. suppose the following: I have an electrical installation in a house. The feeding is with three-phase and one neutral conductors. If I connect a TV and a blender in the same phase, the blender generates interference (lines) in the TV screen. If I connect the TV in one phase, and the blender in another, the TV will have interference??? The neutral conductor is the same for all (of course!) Seems very plain, but I'd like to know... :) As I read the responses, I realized I was assuming a cable TV hookup. That may not be the case. I was involved with a product that used a 1 1/2 HP router motor as part of it's workings. You could see the sparking of the brushes when it operated. But, I was surprised to see very little interference up in the radiated range for FCC. What does impress me is that this interference may have something to do with the frame rate of the TV, since the NTSC is based on the 60 Hz and PAL is based on the 50 Hz line frequencies. In that sense, my guess is that it's most likely conducted interference. And I'd suspect you'd get interference even plugged in another phase. One simple test would be to put the blender in the oven with the oven door shut and turn it on. The blender, NOT the oven. grin If you get almost the same interference, then it's conducted. Doug - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: FCC 47 CFR Part 18
At 12:37 PM 8/31/99 -0600, JENKINS, JEFF wrote: Does anyone know if there are laws that require semiconductor processing equipment and other types of industrial equipment to conform to FCC 47 CFR Part 18? From time to time we get inquiries about this and we're wondering what is behind it. Thanks, Jeff Jenkins Advanced Energy Industries, Inc. Jeff, Go to http://www.access.gpo.gov/nara/cfr/ The correct title of what you're asking is CFR Title 47, Part 18. CFR is an acronym for Code of Federal Regulations. In other words, it IS Federal law. And if your equipment correlates to any of the criteria contained therein, then ye shall test. Regards, Doug - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Concrete as an insulator???
At 03:39 PM 8/20/99 -0600, POWELL, DOUG wrote: Hello all, I have a very innovative engineer who has come up with a design idea that uses concrete as an insulating compound in a very large inductor for a 200 kW switching power supply. Yup, this is the stuff you buy down at the local building supply company. He was very proud of the idea, but until he came up with it I think he was pretty desperate. I'm thinking I should make him desperate again but would like to be able to give him a clearly reasoned-out explanation. Has anyone ever had experience with using concrete or mortar in a high voltage application? What are the concerns here? It is my understanding that it does not actually dry but it cures with all the water contained inside. Been following this interesting discussion, and I have a few concerns to raise. Maybe someone could possibly set me straight since that seems to be happening a lot lately. cough First as has been stated, concrete floors are great for conductive areas. But I believe with the quality checks I did at another company, we're talking in the megohms. But there's a lot of buts that go along with that. Second, I was surprised to find that concrete has nearly the same linear expansivity as copper! Glass on the other hand is way off. So that turned out to be not a concern. Third, is the obvious thermal insulation properties. I'd be concerned about that at elevated temps. Fourth, is an odd thing that effects concrete structures. Apparently well known in civil engineering circles. Not me so don't ask. It's called Alkali Silica Reaction (ASR). Otherwise goes by the common name Concrete Cancer. Over time, concrete structures can eat themselves up from the inside. So I'd definitely get in touch with one of friendly Civil Engineers to find out more about it. Fifth, I believe that since concrete is alkaline in nature a low reactivity with rebar happens. So I don't think you'd have a problem there. Sixth, I believe that concrete is hydrophilic and loves water. And yes, it does not dry. I was making a stone wall along a brook long ago. A mason (who had been a friend in high school) came by to give me some pointers. I wanted to set some of the base stones in concrete but they were to be below the water level. Just do it he said, explaining it was chemical reaction taking place and not just a simple wet mixture drying. Lo and behold, it worked. So I'd be careful if this construction is to be subjected to high humidity. It would seem to me that the concrete would breath humidity at a certain rate much slower than expected. Seventh, concrete is excellent for compressive loads. Not tensive. Eight, vibration. Have not a clue on that one. If you're doing Bellcore, definitely check into that one. Ninth, properties of concrete depend greatly upon the aggregates used (cement) and it's proportion to water when mixed. If you want repetitive results, mixing may have to be an issue for strict procedural control. Otherwise, it's left wide open for anyone to assume. Regards, Doug - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
NEC 645-5(d)(5): ITE Power Cords and Raised Floors
I'm reading this thing and 1. Read 645-5 one way and it might be read to require ANY ITE equipment on a raised floor environment to have DP type cables. As in the second to last para that states Section 645-5(d)(5) requires interconnecting cables used under raised floors (other than branch-circuit conductors) to be listed as Type DP cables ... 2. Read 645-5 another way (which is the way I think I'm supposed to) and all ITE equipment on a raised floor environment are covered as long as they comply with 546-5(b)(1),(2),(3) prior to the above quote. -- Q; Could someone please provide their own *interpretation* as to how this section of NEC impacts ITE equipment on a raised floor environment with regard to SO or DP style power cables? Q: Does UL-1950 3rd Ed. in fact require DP style power cables for ITE equipment on raised floors? I thought this would be an issue if in fact an electrician was hard wiring the power cord of an ITE product that was on a raised floor. And as long as the electrician is NOT hard wiring the ITE product (even though in a raised floor environment), then compliance is covered under Section 546-5(b)(1),(2),(3). Regards, Doug McKean -- - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Product Safety Semantics
John, I can only try to relate safety with the extensive use of shall with ISO certification having gone through the lead auditor course nightmare. For ISO 9001, there's about 136 shalls listed. Get all your shalls right and you *will get* the certification. Miss a shall and you *will get* most likely what's called a major. Just one major and you could lose your certification. In order to keep the certification (pass inspections), one MUST have a compliant system in place. That being said, shall IMO indicates something inevitable in the future as in something to do. Must, also IMO, indicates something inevitable in the present as in something one must have now. In some respects, this is used in standards when one goes for agency testing, such as construction and performance. Once you've passed the shalls, you move into the musts since having passed the shalls you now obviously must have something compliant. Man, that sounds too much like legalize. Think I'll go soak my head ... Regards, Doug At 04:07 PM 7/16/99 -0400, John Juhasz wrote: Hi group. The subject here is regarding the words 'shall' vs. 'must' in various of product safety standards (including UL 1950 3rd Ed. and EN60950). Does anyone have any insight into the definitions of these as applicable to product safety? I have heard there are differences, but no one can seem to give me an answer. Comments please. John A. Juhasz Product Qualification Compliance Engr. Fiber Options, Inc. 80 Orville Dr. Suite 102 Bohemia, NY 11716 USA Tel: 516-567-8320 ext. 324 Fax: 516-567-8322 - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Off Topic Maybe: Hydrogen Fuel Cells
I apologize if this is really off topic ... Having a *friendly* discussion about hydrogen fuels cells replacing commercial power. I'm taking the you got to be kidden me! side. Okey. Sometime in the future, imagine this actually happens (stop laughing). Hydrogen is pumped out to everyone where in some shed, hopefully a quarter mile from my house, equipment uses the hydrogen for power conversion in the form of hydrogen fuel cells. Each residence has their own substation in a sense. Question - Besides from some obvious construction and engineering changes and JUST from a regulatory point of view, what's involved here? I'm thinking it would be a nightmare. Gotta be some power people out there that after they stop laughing might have something to say. There's gotta be some hefty building/construction requirements that are similar to ones that cover substations. Let alone what's involved with H2. Plus, if the cells are operating at a reduced voltage level, the ampacity of the wires used from the cells to the house would be unacceptably large in gauge. My thinking is 3kw or higher fuel cells to power a small house. Anyone care to take a shot? - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: 50 ohm 75 ohm
At 10:36 AM 7/13/99 -0700, Leslie Bai wrote: Dear members, Anyone there can share the experience to measure cables' impedance thus to identify whether a BNC is a 50 ohm or 75 ohm cable. Thanks, Leslie Quick and dirty method with a high amount of confidence that you have RG-58 or RG-59 in your hand but not an absolute method? Measure the OD of the cable. RG-59 is *more likely* to be fatter than RG-58. No guarantee though ... - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: EMC Detective and Flushing Toilet
Someone may have already suggested this but here goes ... (1) Fabricate an EMC story to relate the cause (Flushing toilet) to the effect (Rebooting PC). A major current draw from the same circuit to which the PC is connected appears to be happening at the same time the toilet is flushed. This may be caused by a sump pump that must pump waste up to an elevated septic tank. If this is indeed the case, a similar case such as yours has indeed happened. (2) Direct the customer to verify your speculation. Please verify if in fact a sump pump is being used to lift waste to a septic tank at a higher elevation than the bathroom. (3) Fix the problem. Sell house. Otherwise, have a licensed electrician redirect said wiring of sump pump to it's own dedicated circuit. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: ESRI
Hi George, A web search showed ... ESRI: Environmental Systems Research Inst., Inc. GIS: Geographic(al) Information System(s) Most likely a private thing for interfacing particular types of information. Regards, Doug McKean At 08:57 AM 7/7/99 -0400, geor...@lexmark.com wrote: Is anyone familiar with ESRI as a requirement or standard? I am fielding a question from our marketing folks as the person who usually handles what I call weird standards questions is on vacation. The requestor thought that ESRI has something to do with GIS. Neither acronym rings a bell for me. Regards, George Alspaugh Product Safety Lexmark International Inc. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: connectors that meet hipot requirements
Aren't there 0.156 connectors by Amp or Molex? At 01:21 PM 7/7/99 -0400, Beard, Susan wrote: Anyone know of any connectors with 0.1 spacings that survive a 2000 volt rms hipot requirement? Susan Beard - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Hipot requirements 4 TNV circuits
Hi George, After posting a similar question to Treg about a year or more ago, and doing some research, I maximized the spacings and incorporated them into the design practices at a former company. I believe these spacings will carry your product to just about anywhere in the world (which was my intention) you may wish to market. Basic: 3 mm Supplementary : 6 mm Inner layer:0.5 mm Regards, Doug McKean At 09:00 AM 7/1/99 -0400, sparaci...@andovercontrols.com wrote: Hello Once Again .. Everyone, I have a modem product that failed the hipot requirement defined in cls 6 of 950. My understanding is that an isolation xfmr between Telco SELV is needed and clearance from Telco gnd is to be 3mm minimum. Does anyone have any other general design guidelines that they can share on this topic ? Also, Can anyone point me to any manufacturers app notes for components used for telco isolation ? And if anyone can recommend any reading material, I'd like to read up on these and other issues relating to compliance design aspects of Telco circuits. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: NRTL Listing
Hi Joe, Personally, in my humble opinion, I'd have to question what would happen to my end user if for any reason what so ever the AC adapter shorted over to the 7vdc side. This is a personal opinion. I try to stand up on a soap box about matters like this and usually lose. But, in my opinion, I try to read the spirit of the standards rather than the black and white. I understand that what I'm suggesting is not really spelled out in black and white somewhere, but if given half the chance, I'd test. One of my jobs is safety whether it's written in some standard or not. I would think of the adapter AND the product to which it's attached as the system. Not only that, but a 115/230 VAC AC powered system and test it as such. Again, simply my opinion ... Regards, Doug McKean At 03:29 PM 6/25/99 -0400, Finlayson, Joe wrote: Hello Group, I am in the midst of evaluating the compliance status of a particular product for a potential OEM relationship. This product is a standalone box with Ethernet ports powered by an external AC adapter with an output of 7VDC. The adapter is NRTL Listed, IEC 950 CB report, etc. although the box itself has no safety certs whatsoever. My understanding is that there is no legal requirement to have an NRTL Listing, etc. for such a product although my policy has been to get that third party mark to minimize liability and such. Can anyone share some more info as to their reasons for listing or not listing such a product which is well below hazardous limits. Horror stories are definitely welcome as I would like ammunition to justify my case to force the issue. Thx, Joe * Joe Finlayson Compliance Engineering Manager NBase-Xyplex 295 Foster Street Littleton, MA 01460 Tel: +1 (978) 952-5887 Fax: +1 (978) 952-5054 Email: jfinlay...@nbase-xyplex.com - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: EFFECT
Hi Peter ... At 02:41 PM 6/28/99 +0100, PETER PHILLIPS wrote: Dear group, Has anybody heard about the term EFFECT relating to EMC and environmental testing combined. No. I believe there's an aircraft test that's titled something like Magnetic Effects. But I have no idea what that test entails and I don't know if it's a combination type test. Someone out there must know. I once suggested the idea of going into an environmental with a piece of equipment to do ESD testing at various RHs for a Bellcore style testing. That went over like a lead balloon. I'm sort a glad of that since the discussion went onto temperature testing with ESD at various temp levels below freezing. For some strange reason, standing in a 6x6x6 ft room in tropical conditions one minute then arctic conditions the next while recording something like 200 data points at various ESD levels just wasn't all that appealing. But if I thought of it, I'm sure someone else has ... I am looking for any information on the topic, also any views that people may have regarding the change in EMC performance due to adverse environmental conditions I had a PLL circuit giving me a bear of a time until I came back the next day after leaving at the site in below freezing temps. When it was turned on the next day, no PLL. Turned out the xtal froze up. But, it wasn't below the mfr's specs. Seems as though the mechanical impedance of the xtal was so high from low temps it wouldn't self start. That in turn started a routine test of prototype circuits using xtals in PLLs to be put into an environmental chamber at low temps. Looking forward to your comments Besides speculating with Paschen's Law, I'd also like to hear any testing that combines ESD + altitude. Also, ESD + humidity. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Capacitor Failure Analysis
At 03:30 PM 6/23/99 -0400, WOODS, RICHARD wrote: Can you recommend a lab in the USA that can perform failure analysis on an electrolytic capacitor? In a past life I've had caps analyzed. Usually the mfr of the cap is very willing to do the job. And they were very helpful. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: History Class ...
Thanks to all the responses. A suggested off line contact with one of the persons involved with the limits produced confirmation of much of what has been said. If I may take the liberty to paraphrase his response - it was determined to prevent radio interference at an agreed upon distance of 30 feet with an accepted *average* signal level for the average radio receiver. TVs on the other hand could be back to back in an apartment setting by as little as 6 feet. Additionally, the corresponding limits and method of testing for conducted interference also followed. Obviously, much more was involved than what my little summary explains, but the original motivation was what I was primarily interested. The great resource available here at EMC-PSTC proven once again. Thanks again. Regards, Doug McKean - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Transmission Line Theory
Alright, I'll take a stab ... At 02:30 PM 5/12/99 -0700, Allen Tudor wrote: Greetings group, I am trying to draw a parallel between transmission line theory and radiated emissions. From what I understand, a transmission line can be terminated at the source or the load with an impedance that equals the characteristic impedance of the transmission line itself. The important thing to remember is that once the signal energy has reached the far end of the trace, you want to dump that energy into a resistive load. Loading a line at the source end ... I'm not familiar with that. Even so, once the signal gets to the unterminated far end of the trace, there's an impedance mismatch and you will get reflection. Ideally, you will get 100% reflection. Tau(reflected) = E(reflected)/E(incidence) = (RLoad - RSource)/(RLoad + RSource) RLoad = infinity (unterminated) means 100% reflection. Tau(transmitted) = E(transmitted)/E(incidence) = (RLoad^2)/(RLoad + RSource) With this in mind, consider this scenario. A printed circuit card drives a clock signal down a trace on a backplane. The length of the backplane trace is long enough to be considered a transmission line. The driver on the printed circuit card is located within ½ inch of the edge connector (mating with the backplane) and is terminated with an impedance equal to the characteristic impedance of the backplane trace. However, the backplane trace is open ended (there is nothing connected to the end of the trace). Transmission line theory says the signal integrity will be maintained in this case. Forgive me on this, but I don't see how. I'm sort of a purist. You'll get 100% reflection under ideal conditions. Now for the questions: (1) How much, if any, of the energy will be radiated into free space when it gets to the end of the open transmission line? To me, this looks like a monopole antenna. I don't have a very good understanding of antenna theory, so this could very well be an invalid assumption. Of the cuff? Unknown. There's too many variables. Single wire antenna (monopole) embedded in FR-4 ... (2) If radiation does take place as stated above in question (1), which is better for reducing the radiation, termination at the source or termination at the load of the transmission line, or does it matter? Termination at load end. (3) If the characteristic impedance of the trace on the printed circuit card differs from the characteristic impedance of the trace on the backplane, how is this handled? Is a termination needed at each end in this case? I've seen small resistors put in series with the trace. Keep in mind that this characteristic impedance is not really a purely resistive thing. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Rodents, part II
Hope no one's offended with this ... I'm remembering a story a prof at school who worked at Bell Labs imparted on us one day in class. Seems as though, long ago, he was working on some system to be installed in some remote site way out in the mid-West. Someone suggested testing the cables to be Ground Hog Proof since there were a lot of Ground Hogs in the area. 'How do you test something to be Ground Hog Proof?' was the question. 'Guess you get some Ground Hogs.' was the obvious answer. A P.O. was cut for 4 full grown Ground Hogs, signed by the manager and sent to purchasing. About a week later, a crate marked Ground Hogs appeared in the lab. Cautiously, the lab guys opened up the box not knowing if these things were going to jump out and attack everyone after being cooped up for so long. What they found were 4 full grown Ground Hogs, packed in dry ice ... Be careful what you ask for, you just might get it ... - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Harmonics
My two cents intertwined below ...
At 01:38 PM 4/21/99 -0400, Scott Douglas wrote:
Hi All,
Recently an interesting discussion came up about harmonics. A general
disagreement followed. We hope you all can offer some insight and perhaps
help us settle the question.
The question is numbering of harmonics.
One side says that given a fundamental frequency of 200 MHz, the first
harmonic is 400 MHz, the second harmonic is 600 MHz and the third harmonic
is 800 MHz.
The other side says that given a fundamental frequency of 200 MHz, the
first harmonic is 200 MHz (or same as fundamental), the second harmonic is
400 MHz and the third harmonic is 600 MHz.
--
I've always referred to the integer number of the
harmonic as the number that's multipied to the
fundemental. The first harmonic in my scheme of
things would indeed by the fundemental. I have
never dealt with anyone who would tell me that the
third harmonic of 200 MHz would be 800 MHz.
And indeed, when the fourier expansion is done,
this is in fact the case. i.e.
Square Wave = a1*sin(wt) + a3*sin(3wt) + a5*sin(5wt) + ...
ANY Fields and Waves/Electromagnetics book worth
it's salt on fourier expansions will cover this.
--
The other part of the discussion revolved around even and odd harmonics.
One side says that even harmonics are lower amplitude than the odd
harmonics, the other side says odd harmonics are lower amplitude than even
harmonics.
All discussions assumed non-sinusoidal sources, generally our sources are
square- or modified-square waves.
Can someone shed some light on harmonic numbering and if possible, point
to a reference material that specifies this?
--
The even or odd being lower than the other
is certainly an odd observation. grin
In general weasel word alert, as the coefficients
decrease in an exponential manner (as long as the
factors include even and odd components), I don't
understand this observation.
If what's being observed is the sum of all wave energy
from the odds being higher than the sum of all wave
energy from the evens, then that's quite possibly true
since the odd sums will usually include the fundemental
which is highest anyway. But again, I don't understand
the observaton.
For instance, an absolutely perfect sawtooth wave
with peak values at +V and -V produces odd and even
harmonics. Such as
y-axis
|
/ +V| /
/ | /
/ | /
+- x-axis
/ | /
/ | /
/ -V| /
The fourier expansion of this is
f(t) = + (2V/pi)*{sin(wt) - 1/2sin(2wt)
+ 1/3sin(3wt) - 1/4sin(4wt) + ...}
Odds add in amplitude to be
(2V/pi)*(1 + 1/3 + 1/5 + ...)
Evens add in amplitude to be
(2V/pi)*(1/2 + 1/4 + ...)
The odds have it hands down since they
start with 1 and evens start with only 1/2.
Also, important to note is that an absolutely
perefect square wave produces nothing but odd
harmonics. Deviate the slightest from an
absolutely perfect square wave and the
expansion starts producing even harmonics of
amplitude related to how imperfect the
square wave ends up being.
Not sure if I answered your question.
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Re: Excessive smoke
At 08:43 AM 4/19/99 -0800, ed.pr...@cubic.com wrote: But Lou, it would be safe smoke! Ed As long as you don't *inhale* ... grin - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Conductive Paint
Well, here's some basic stuff from my experience. Conductive paint cannot be used for earth bonding. It can be used only for shielding purposes. In other words, don't expect to either a. pass large amounts of current through it, b. assume it will always be a reliable ground path, c. be able to act similar to the ground path a metal chassis provides. Conductive paint is usually good for *one time* use. In other words, don't expect the paint to survive repeated removals and installations of the cover to which it's applied. So use it carefully in places where it's a Fit and Forget type application. I've dealt with two types of conductive paint, nickel and copper. Both are somewhere around 1 to 1/2 ohm per square depending upon a lot of factors: 1. Composition of the paint - Acrylic based paint or oil based paint. Oil based being the higher ohms per square. 2. Manufacturability - Depending upon how thick or how many layers of the paint are applied. Research these topics very carefully with the paint maker and the vendor who will apply it. IF the decision to use conductive paint is made, the following information is necessary for safety: If the enclosure to which the paint is applied is plastic - a. Need UL-94V) rating of specific plastic used. b. Need UL approval of conductive paint. c. Need UL approval of specific plastic mfr to mold plastic. d. Need UL approval of marriage between specific plastic and specific conductive paint. e. Need UL approval of mfr to do marriage of plastic and paint. Regards, Doug At 10:06 AM 4/13/99 -0600, JENKINS, JEFF wrote: Hello Group, My company is proposing to use conductive paint on our enclosures, and I would like your input as to the acceptability of this vis-a-vis protective earth bonding of enclosure panels. I am interested in the perspective of both European and North American requirements. This should be a generic question, but if it helps, here are the standards we use: EN 60950 / IEC 950 / UL 1950 / CSA 950 EN 50178 UL 1012 CSA C22.2 No. 107.1 Regards, Jeff Jenkins Senior Regulatory Compliance Engineer Advanced Energy Industries, Inc. Fort Collins, CO USA 80525 - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: explanation of ESD events with coins in baggie.
Lou, It is impressive and my boss Doug Smith uses it during some of his seminars. I have tried hitting the coins in the bag with a hammer several times very near the antenna - nothing. I even smacked two big screwdrivers together on the metal near the antenna for several minutes - nothing. The piezoelectric effect is an interesting note, and I'll have to do more digging around about it. But for now, I not sure it is the mechanism. Whatever the mechanism, it is an elusive little bugger. And thanks about the info on the front end of an SA. Doug McKean At 09:03 AM 3/12/99 -0500, Lou Gnecco wrote: Doug, Despite the sampling window, the spectrum analyzer has a wide open front end. It is easily saturated by broadband signals, even though you think you are only looking at say, 100 to 200 MHz, the front end amplifiers see everything. A lot of things have a piezoelectric effect, including bone and ice. Maybe you are seeing that? Whatever it is, it's broad band. You are seeing some extremely narrow impulses which have a wide range of frequency components. I have GOT to try this! Lou - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Component vs Listed European Style ...
To whom it may concern, Sorry, rather lengthy. I tried to cut it down. I've finally realized I don't think I fully understand European approvals and I'll discuss why with two examples. The first example will go from the *system level* down to the *sub-system level*. The second example will go from the *system level* up to a *super-system level*. In other words, I don't think I fully understand how the stateside concept of component approval versus listed gets translated over into the CE mark, or VCCI, or BCIQ for that matter ... I believe this was touched on a while back but I can't find it. System Configuration - Let's say we have product. It's *model number* is System 1. System 1 is composed of two sub-systems. Sub-systems have in turn the *model numbers* Sub-system A and Sub-system B. System 1 has a mains input of 115/230vac to a power distribution unit (PDU). The PDU inputs the 115/230vac to a power supply. The power supply outputs 48vdc to sub-systems A and B. System 1 is NOT a telco product. First - System to sub-system: System 1 has been successfully tested to the appropriate emissions, safety, and immunity requirements. It is declared that System 1 complies to have the CE mark applied. System 1 is marketed. It is shipped overseas to our friends in Europe. No problems. Now, marketing comes along and wants to sell Sub-systems A and B of System 1 on their own. In other words, the Sub-systems A and B will NOT necessarily be in configurations that will use anything from the original configuration of System 1. And they will be advertised and sold as Sub-system A and Sub-system B. Question: Is any retest of the sub-systems by themselves required? If so, why so? If not, why not? Second - System to Super-system: Marketing decides to incorporate two or more System 1's into a configuration using a product, let's call that Product A, from another company that itself has been through all required emissions, safety, and immunity requirements and is itself CE marked. And has also been marketed and sold in Europe with no problems. *** Marketing also decides to advertise and sell this super-system under a new *model number* Super-system 2. There is a high amount of confidence that this entire system Super-system 2 will never be shipped as one piece. The Bill of Lading that would come through Customs though would show Super-system 2 with parts System 1 and Product A. Question: Is any retest of Super-system 2 required? If so, why so? If not, why not? - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Awards for Worst EMC/PS qualities
At 08:03 AM 3/8/99 PST, Bailin Ma wrote: Hi Group, We have already seen awards for the most misleading ads, worst attire, worst films, . Why not awards for worst EMC and PS qualities? Barry Ma Morgan Hill, CA 95037 Long ago in another company, I was completing the testing for a large rack mounted device, i.e. emissions, immunity, safety, some parts of Bellcore. We got a call from one of our customers complaining about how sensitive our equipment was and how susceptible it was to ESD events during their own testing of our equipment. This was deemed unacceptable by them. This decision of theirs jeopardized a sale of several million dollars. The finger was duly pointed by everyone right to yours truly. My head was literally in no uncertain terms put on the block. I contested producing repeatable and acceptable ESD test results that were BELOW the BER levels specified by Bellcore with ESD test levels ABOVE that specified by the test standard. I wanted as much margin as possible for our product. Well, it ended up that if you stood three to four feet in front of the rack and jingled change in your pocket or jangled a set of keys in front of it, the product would RESET. Jingling change in a ziplock bag produces very high levels of super fast transients up into the GHz range. Worse, slamming the metal door to the lab in which the equipment was setup would also reset the product. The lab door was say 20 or so feet from our equipment under test. It took six months of a redesign cycle to straighten out that one, but it was finally done. I always wanted to find out who in God's name could have come up with such an insidious ESD test by simply putting some change in a zip lock bag and jingling it in front of equipment. But, I figured he, whoever he was, was lost in time. And wouldn't you know it? ... I now work for that man. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: UL 1950 Requirements for Operational Insulation
At 09:30 AM 3/3/99 -0800, Allen Tudor wrote: Clause 5.4.4 of UL 1950, Third Edition specifies that in lieu of creepage and clearance distance requirements for operational insulation, the electric strength test for operational insulation (Table 18) can be used. Does anyone know how to calculate minimum distances between traces on a printed circuit board that would allow one to pass the dielectric test at a given voltage? Or has anyone taken any empirical data that would shed light on this topic? Also, would trace width have an impact on the dielectric test results? This is highly empirical and best done with a hi-pot tester and some bare boards. You're talking about Paschen's Law. Paschen's Law: Breakdown Voltage (BV) for uniform gaps V(kV)= 24.2Sh +6.1(Sh)^0.5 where V is the breakdown voltage in KV S=(293p)/760T h is electrode spacing in cm. p is pressure mm of mercury T is temperature in degrees Kelvin At STP, S = 1 so 30KV/cm is pretty good This relationship does not work for all values of pressure. This is all greatly dependent upon the geometry of the two test points of concern. I believe Paschen came up with this empirical equation with point probes. I like to remember that 3M volts for 1 meter at STP (roughly). That still works with the above equation. But remember that the field about two *point charges* varies inversely with the square of the distance. The field about two *line charges* varies inversely only with distance. So be careful fudging distances with traces. If we have 3MV @ 1m, then 3KV @ 1 mm which is roughly 40 mils. Double it for a x2 safety factor to 2 mm or 80 mils. For reinforced insulation, it's a x2 yet again so that now you have a 4 mm or 160 mil separation. Pick the safety factor that you want. I'm just suggesting this. I seem to remember something about wire mfrs build in a safety factor of x7 into the insulation, but I'm not sure about that. Now, take a look at UL-1950, Table 3, Minimum Clearances for insulation i primary circuits, and between primary and secondary circuits ... In the column for 150V, = 300V with a transient of 2.5KV, you get a rough idea (agreed very rough idea) of how these numbers work out ... Vrms = 300V, Op = 1.7, B/S = 2.0, R = 4.0 Some of those clearance numbers look familiar when compared to working it out long hand in my paragraph above? You can bet they do. The trace width does not have an impact on dielectric testing if you're talking about two traces horizontally adjacent on the same layer of the board. Traces vertically adjacent to each other will be a different story since the old standby FR-4 with a Dk = 4.7 will increase the BV by a factor of roughly 4.7. But, again, do your own empirical evaluations on your own boards. It will prove to be invaluable information. Hi-pot testing is one of the most common areas of safety testing failure. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: T1/E1 equipment
How about any lasers, Steve? Regards, Doug At 09:38 AM 2/17/99 -0600, Steve Grobe wrote: I have already had one response asking where we intend to sell the product, I know I should have thought of that. To start with the product would market to the U.S. and Europe. The product will convert signals on the copper interface (RJ-45 or coax) to either multimode or single mode fiber for longer runs. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Radio Frequency - Definition
At 09:30 PM 1/4/99 -0500, Kevin Richardson wrote: I am trying to find definitions for two terms: a) Radio Frequency ie what is radio frequency, and what frequencies are recognized as being RF rather than what may be practical for transmission purposes ?; and b) radio frequency energy (used in the first paragraph of the scope of CISPR 14 and on a few other occasions throughout the standard) Can anyone provide a pointer to what could be recognized as an official definitions for these terms? Any input would be most appreciated. For the *any input* department: Radio Frequency - I've worked with RF well down below the audio range. Actually around the 1 Hz range, so I have a little trouble with the 20K Hz to 100 GHz or so range for an absolute definition of Radio Frequency. Radio Frequency Energy - Isn't that just the old E^2 normalized to one ohm? - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: UL1950 Overvoltage Tests
Isn't this a variation of using the traces as a fusing element instead of using a real fuse? It's been done, there's nothing wrong with it until you start *claiming* the traces as a fusible device. I'm not sure about this, but if you are, don't the traces themselves have to be tested as if they're a fuse? I've talked with some test engineers at some test houses about this and it can get involved claiming traces as fusible links. To get around this, I had the equip modified to include fuses. Doug At 11:36 PM 1/4/99 +0200, Peter Merguerian wrote: Happy New Year to All, I would like to ask the opinion of all members regarding compliance criteria for the Overvoltage Tests in on TNV lines connected to exposed plant. UL1950 states that after the OV Tests, unit must comply with the Dielectric Voltage Withstand Tests or Leakage Current Tests. Assuming that after the OV Tests, some internal traces of the board opened and caused slight charring on the PCB and the unit passed all applicable Dielectric Voltage Withstand Tests, would this be considered an acceptable result? Looking forward to hearing from all members on this sensitive issue.
Re: Company Name Change
Obvious primary but there could be some secondary effects ... Primary: Reports, DoCs, TCFs, User manuals, Technical Manuals, etc ... Secondary: OEM agreements - that alone could be a huge biggee, Distributors - exactly what is their role overseas(?), ISO documents - documentation documentation documentation, Open Purchase Orders with labs - unexpected delays depending upon how strict your company or the lab is with accounting, ... It gets worse if you're one division of many in a huge corporation. Regards, Doug At 08:12 AM 12/22/98 -0500, Allan, James wrote: My company is in the process of undergoing a name change. Is there any advice from the board as to pitfalls and oh-oh's that have been experienced as I begin the process of having product safety, EMC and Telecomm registration certificates changed over to the new company name. What I am looking for are unexpected surprises that come from out of nowhere. Thanks Jim - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: 1000Base-T (IEEE 802.3ab) vs. EMI on UTP (Unshielded Twisted Pairs)
At 07:42 AM 12/11/98 -0600, Mike Mayer wrote: [...] =Coding Scheme for Gigabit Ethernet = PAM-5 (Pulse Amplitude Modulation 5 Levels) = 2 Bits per symbol ( = 4 bit combinations or levels) = Symbol Rate 125 Mbaud/sec = Bit Rate per pair 250 Mbits/sec = Bit Rate using 4 pairs 1000 Mbits/sec = 5th coding level used for control and management = Simultaneous Bi-Directional Transmission = I haven't read the spec, but I am confused in what I have read about the data rate. Is it 250 Mbits/sec per pair in each direction simultaneously? Some things I have read imply 1000Base-T is 500 Mbits/ sec transmit + 500 Mbits/sec receive instead of 1000 Mbits/sec and 1000 Mbits/sec receive simultaneously. Good call Mike. That one went right by me. Egg all over my face ... But the more I read this, the more I think they should get their units correct for bit rate, baud rate, data rate, transfer rate. The following is a shakedown of some notes I have. 1000BaseT is full duplex. It sends and receives data over four pairs from both ends of each pair at the same time. Each pair carries a full duplex of 250 Mb/s data. The data is encoded PAM 5. A 1000BaseT physical layer has 4 identical transceivers (receiver and transmitter). Each transceiver sends 250 Mbits/s. Since it's 2 bits per symbol, it's really 125 MBaud/sec. 4 transceivers operating at 250 Mbits/sec equals 1000 Mbits/sec BEFORE and AFTER the line coding/decoding. I'll explain why I emphasized this further below. 1000BaseT with PAM 5 was created to be compatible with 100BaseT. This allowed a dual data rate 100/1000BaseT transceiver to be developed. The baud rate of 1000BaseT equals 125 MBaud/sec. 100BaseT has the same baud rate. Thus the reason for why some people are convinced that the same CAT5 cable used for 100BaseT can also be used for 1000BaseT. Now, to explain why the emphasis above. Strictly speaking, by using PAM 5 line coding, there is no 1000 Mbits/sec total transferred on the cable itself. The 1000 Mbits/sec is before and after the coding. The PAM 5 coding turns it into a baud rate and is 125 Mbaud/sec for each line. There are no bits being sent down the line. So my concern about a contiguous on/off bit stream generating a square wave burst at 500 MHz is unfounded. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: 1000Base-T (IEEE 802.3ab) vs. EMI on UTP (Unshielded Twisted Pairs)
At the following webpage, http://www.scope.com/whitepap/white19.htm it is briefly discussed the concern over pushing 1000BaseT down Cat5. This concern has raised the possibility of introducing another version of Cat5 cable indicated as Cat5-E. I quote ... Can Better Cabling Help? Since most of the noise in a category 5 channel is due to the crosstalk and return loss properties of the cable, improving the performance of these parameters improves the SNR margin of gigabit Ethernet. TIA is currently in the process of developing a specification for enhanced cabling - category 5E. Category 5E offers 2 dB of improvement in the return loss and ELFEXT performance and 4 dB of improvement in the NEXT performance (figure 12) over category 5. Category 5E is specified by an addendum to TIA-568-A [5], which is under ballot as of this writing. This was written sometime in 1998 by Scope Communications. The use of PAM-5 for pushing 1000BaseT down a 100BaseT line reminds me of an excellent discussion by John C. Bellamy in his book _Digital Telephony_ (I highly recommend getting it). He compares energy spectral density merits of differing line coding and digital modulation techniques to shrink the width of power envelopes thus being able to increase higher data rates into a narrower bandwidth. Using the proper coding techniques, one could conceivably push a very high data rate that would otherwise require a wide bandwidth down a very limited bandwidth medium that would normally respond terribly to such a data rate. At http://www.bicsi.org/shariff/tsld001.htm an excellent presentation is given complete with eye diagrams when viewing the graphic version for Gigabit Ethernet tutorial. And again, some discursion is mentioned concerning the cable. Mr. Shariff presents the following Coding Scheme for Gigabit Ethernet PAM-5 (Pulse Amplitude Modulation 5 Levels) 2 Bits per symbol ( = 4 bit combinations or levels) Symbol Rate 125 Mbaud/sec Bit Rate per pair 250 Mbits/sec Bit Rate using 4 pairs 1000 Mbits/sec 5th coding level used for control and management Simultaneous Bi-Directional Transmission I still concur with Don. But, my gut feeling is that a 1000 Mbits/second data rate is capable of producing a data stream such as 10101010 ... or simply a square wave operating with a fundamental of 500 MHz. Or at least a 500 MHz burst. In any event, things will be interesting ... Regards, Doug - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: 1000Base-T (IEEE 802.3ab) vs. EMI on UTP (Unshielded Twisted Pairs)
I'll concur with Don, but as discussed at the IEEE 802.3z Gigabit Ethernet Task Force meeting in Irvine, California on March 10-14, 1997, this was apparently briefly discussed. The full text is at http://grouper.ieee.org/groups/802/3/z/public/minutes/Irv0397.txt I quote only the important part cough ... Cable shielding was discussed and it was explained that two shields are required to meet radiated emissions requirements. This configuration easily passes Class B. At another site, http://www.anixter.com/techlib/vendor/cabling/lan1000.htm it is suggested/hinted/implied that compliance either for emissions and/or especially with balance on UTPs, the burden of compliance rests not on thy humble standard when considering all possible applications. Compliance rests with thee. strictly my own interpretation Regards, Doug At 12:05 PM 12/7/98 -0800, Donald Kimball wrote: The IEEE 802.3ab defines the new Gigabit Ethernet Standard (i.e. 1000Base-T). This Local Area Network (LAN) can use 4 twisted pairs of unshielded copper cable (Category-5) at 100m maximum operating at 250Mb/s per pair in full-duplex bi-directional mode. This standard is designed to utilize existing LAN cables such as older 10Base-T and 100Base-T networks. The signaling (i.e. baud) rate is 125MHz per pair using 5-level Pulse Amplitude Modulation (PAM) . This probably results in the fundmental energy at 62.5MHz given that the signal must be bipolar to be compatible with transformers. Vendors such as Broadcom Corp. have developed single chip copper cable interfaces for this new standard. In the past, standards using unshielded cables, such as 100Base-T, 10Base-T, T1, E1, etc, have had signaling rates less than 30MHz, so that the fundamental frequency was below the 30MHz FCC and CISPR starting frequency for radiated emissions. However, 1000Base-T has a 125MHz signaling rate. A common mode current of less than 10uA at 30MHz at 1/2 of wavelength can yield an emission level equal to or greater than the Class B level. In addition, the 4 twisted pairs are all phase locked to each other. The intentional differential mode current is about 10mA, so the trans hybrid balance needs to be better than 60dB. This is achievable with the hybrid at the component level, but not at the system level with 100m of Cat 5 cable attached. Conclusion, I think that 1000Base-T (IEEE 802.3ab) on unshielded Category 5 cable is doomed to fail EMI. Anybody ever try a test? Any other opinions? Don Kimball - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: TNV-1 vs SELV for unit with Outdoor Coaxial Cable Connection
At 11:26 PM 12/1/98 -0600, Mel Pedersen wrote: Anyway, the intent here is that the insulation not be damaged from an overvoltage from the TELECOMMUNICATIONS NETWORK, and I believe that the overvoltages in mind included lightning strikes. Well, just my 1 cent worth would be that the intent of the standard would also include power lines crossing over telephone lines on a toppled telephone pole. Or, as we recently saw, even 16.6KV in the case of some druggie. I think the post was extremely appropriate for this forum. I've seen the aftermath of a transformer taking down most the wires around it on it's way to the ground. Not a pretty sight. The TNV circuits are certainly within the product. But, I'm sure I could give a good argument over the definition of exposed regarding to what they attach and what potential hazard could occur. Telephone lines on a power pole are certainly more exposed than buried telephone lines. *** This is _strictly_ my own interpretation *** Regards, Doug - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: High Voltage Exposure
At 12:39 PM 11/30/98 -0800, ed.pr...@cubic.com wrote: Hi Listmembers! I recently came across a Lineman's Web site which has a series of three pictures showing the near electrocution of a man who climbed a power pole topped with a 16.6KV 3 phase power bus. I think the content is reasonably on-topic for our group, considering the implications of shock hazard and safety. Just curiosity question for our high power people - At the beginning of the article it says the overhead 16.6KV line is a WYE? Thought they were mostly DELTA. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Flammability in Oxygen
Sorry this is long, buuut ... I recommend going to http://www.northland.cc.mn.us/Terry_Wiseth/gas%20transport%20part%201/index. htm Keep in mind that there are all sorts of hyperbaric chambers available. There are others that are smaller but not capable of great pressures. The only one I was in was a large one on City Island NY which took us down to the equiv of 160 ft under the ocean. It was capable of going much deeper. Assuming 33 ft of depth in salt water for every 1 atmospheric pressure, 160 ft is roughly 4.8 atmospheres or 71 lbs/in^2. They were doing alot of work with fire fighters who had succumbed to smoke inhalation. Depending upon the medical case involved, they can go as high as 4 atmospheres. One case there involved a motorcycle accident victim with a crushed knee. Had he remained in the hospital, he would have lost his leg. In the chamber, the partial pressure of O2 was high enough so that the little amount of blood that got around the injury managed to keep the tissue alive and eventually saved his leg. Oh, yea, the doc got stuck in there with the victim for the duration. On another note - Look up Pashen's Law to get a rough idea what you're up against. It goes roughly like this - Paschen's Law: breakdown for uniform gaps V(kV)= 24.2Sh +6.1(Sh)^0.5 where V is the breakdown voltage in KV S=(293p)/760T h is electrode spacing in cm. p is pressure mm of mercury T is temperature in degrees Kelvin At STP, S = 1 so 30KV/cm is a pretty good approximation for 1 cm. At 1, 2, 3, and 4 atmospheres for 1 cm it goes something like this ... Atmospheres separation (cm) Breakdown voltage (KV) 1 1 30 KV 2 1 57 KV 3 1 83 KV 4 1 109 KV The reason for the increase in voltage threshold is due to more charge carriers being present for charge transportation across the gap. Neon lights won't work at elevated pressures inside the tube. The inside has to be evacuated to a partial vacuum get the light to glow. You may also want to check for the flammability of materials at elevated percentages of O2. Side Note: The use of pure O2 during Apollo 1 and the earlier space flights like Mercury was merely a copy of using pure O2 in planes before the space program. Up until that point in time, there was nothing unique nor unusual about using pure O2. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Medical Devices in Hyperbaric Chamber
At 12:16 PM 11/24/98 -0800, ed.pr...@cubic.com wrote: Massimo: Further complicating the issue is that the Apollo 1 fire ocurred with a partial pressure O2 rich environment. My guess(!) is that a 1ATM O2 rich environment would be even more hazardous. Maybe you can find some hints on this via NASA or a hyperbaric chamber manufacturer? Just for the record, Apollo 1 had a pure O2 atmosphere. The disaster halted that practice. And I believe medical oxygen tanks run about 40% O2. I remember during dive training we were told medical O2 tanks weren't 100% O2. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Where We Do It
At 09:01 PM 11/20/98 GMT, Patrick Lawler wrote: On Thu, 19 Nov 1998 11:15:26 -0800, Ed Price ed.pr...@cubic.com wrote: big snip 11.) Douglas McKean dmck...@corp.auspex.com The most er ... challanging site where I had products tested was at an OATS run by Xx when they were just on the other side of the fence (literally) from Manchester Airport in Manchester New Hampshire. I think they've moved. big snip ... they've moved. Manchester Airport or the test house? chuckle The test house. No matter how carefully I try to write something, there's always something. And I might add, they were a very reputable place. Ummm ... the test house that is. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Laser Pointers
Indeed. The lower 5mW lasers used in some optical transport systems may seem low. BUT, the beam is concentrated into an area only a few mm^2 before it manages to get dispersed. That's an amazing amount of energy for eye tissue to receive. A laser rated somewhere just above 20mW can ignite cleaning alcohol spilled on a workbench into flame. Not that I would know from personal experience. Heard it from someone. I think a friend did it ... I don't think there has to be any worry about a technology being banned. Maybe the public use of it due to some jerk. But then again, that's how some laws get started. At 02:53 PM 11/11/98 -0500, Lacey,Scott wrote: RE: Laser Pointers Laser pointers can indeed be dangerous. However, every one that I have seen offered for sale in the U.S. comes with prominent safety warnings about potential eye damage. The retina of the eye is very sensitive to light in the middle of the 600 nanometer range (bright red). The damage is related to exposure time vs. intensity at the surface of the retina. Fortunately, beam spread of the typical lower cost pointers provides some protection at a distance. The eye should NEVER be exposed to one of these devices at close range, such as arm length. Aiming one of these at another person's eyes would constitute assault, and would be prosecutable under both criminal and civil statutes. I am very concerned by the modern tendency to ban new technology in its infancy due to potential or actual misuse by some individuals. I am sure - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Laser pointers
Sign on the wall of a lab ... ** ** *- WARNING - * * DO NOT LOOK INTO BEAM * * WITH REMAINING GOOD EYE * ** ** - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Laser pointers
Hi Rick, The Classes are I (Roman numerals) thru V, I believe. The lower the better. Chemical lasers are way up there. To be precise, I think those pointers are rated Class IIIb. You have to check the laser regs controlled by the FDA to get the precise limits. It's based on power and frequency. This is a gross overstatement but Class III lasers constitute the point where tissue can begin to occur. Very rough is that Class IIIb lasers can cause tissue damage if continuous exposure is allowed for something like 1,000 seconds. Check the regs yourself for exact numbers and DO NOT rely on my post. Look at CFR Title 21, Part 807 (subparts as required) CFR Title 21, Part 1000 (subparts as required) CFR Title 21, Part 1010 (subparts as required) CFR Title 21, Part 1040 (subparts as required) Personally, I would not let the scouts play with them. But, that's because I'm just a hard ass. Regards, Doug At 08:21 AM 11/10/98 -0700, rbus...@es.com wrote: As a tie to this discussion, could someone clarify the Laser pointer classes? Are all of them Class 3 or higher or are there Class 2 and below. Interestingly enough, I took a group of scouts on an activity last week and several kids pulled out Laser pointers and had Light Battles between themselves. What is the consensus of the group on potential hazards from misuse of these devices? Should Class 3 and higher be banned? Thanks Rick Busche rbus...@es.com mailto:rbus...@es.com - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: CE+ CE = CE
I've been getting that same reaction for years from mangers in regard to domestic Safety Component Recognition versus a system testing. Same thing for domestic emissions testing. I've got all the approvals for everything. Whaddaya mean I have to get it all tested AGAIN! They hear component approval and think I'm done. You ought to see what happens when you put an approved modem into a product. Let's see ... There's approx 154 countries in the world. Fortunately, that doesn't *necessarily* mean a grand total of 154 approvals. Gets almost amusingly predictable with this Lego style thinking that project managers have ... Doug At 09:00 AM 11/5/98 -0800, Knighten, Jim wrote: Group, I think we all understand that there is no basis in the physics of EMI to support CE+CE=CE. However, this is a difficult concept for the lay person, I think. I know that managers in my company have difficulty with this (but,...I'm using subsystems that are CE marked!!!). Also, CE+CE not necessarily = CE is very inconvenient for the integrator. I suspect business pressures will continue encourage integrators to press for certification by legislation, rather than the pesky system level tests. Jim - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Heat Warning
At 02:33 PM 10/28/98 +0100, andreas.tho...@toshiba-teg.com wrote: Dear All, I like to ask you for your comment regarding following case: If there is a portable IT product which bottom surface can become hot (around 49°C) during use, would you recommend to put a warning label onto the product or would you consider a warning in the operator's manual as sufficient ? Thank you for your comments Kind regards Hi, Andreas, Personally? Both. But, what I find interesting is that by affixing a heat warning label to the product, one would be prompted to put it on the surface of concern, i.e. on the bottom, i.e. where the end user cannot see it, i.e. defeating it's purpose. Doug - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
[no subject]
Ok, you guys got me. I didn't think it's take this long. I confess. The gig's up. I'm the one ... About 15 years ago in another company far away, I brought a product into a reputable lab to be tested. It passed, if I remember correctly, by -0.5 dB. The confidence acid test back then was (and I'm not joking) if it can pass with the - worst case configuration - being the monitor on it's side placed on top of the EUT with a topping of cables tied in a bow-tie, then it should pass in any other reasonable configuration. Well, too many people (like me) screamed about these crazy configurations. Now, you can't do that type of cable manipulation/configuration anymore. So, the confidence test had to change. And well it should. How that boss I had to answer to back then thought that every single product would be rock steady at -0.5 dB with no distribution of data was and still is beyond me. We aren't talking about a single car on the highway going the speed limit, we're talking about a whole herd of cars on the highway. The current calculation of error is fairly applied without having to resort to tying everything up into a bow-tie. Doug - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: LVDS technology
Massimo, 1) I have a small amount of experience with this. Symmetry will play an important part. In some bus designs, designing in added lengths to various traces may be necessary to keep an equal prop delay among the traces of the bus. 2) EMI behavior depending on unequal signal paths is dependent upon the frequency. Unequal signal paths will form simple loops. Loop antennas respond directly to the square of the frequency. Wires on the other hand respond directly to the frequency. 3) I always advise shielding cables. But, this can also cause more problems if a few things aren't considered: a) Make sure the shield is making 360 degree contact when connecting to the body of the connector. b) At high frequencies, do not use small drain wires for ground connection. Especially long lengths of small ground wire. c) Use braid style shielding for wires that may be subjected to a moderate amount of movement during their use. Use foil as a last choice and when it's fairly certain it will be subjected to almost no movement during it's use. 4) Discontinuities in transmission lines cause reflections. This will smear digital signals. How much is theoretically calculated by the different reflection coefficients: a) For the one that is coming back at you from the discontinuity: Tau(reflected) = E(reflected)/E(incidence) = (RLoad - RSource)/(RLoad + RSource) b) For the one that is traveling on beyond the discontinuity: Tau(transmitted) = E(transmitted)/E(incidence) = (RLoad^2)/(RLoad + RSource) Interesting to note: 1) When RLoad RSource, the reflection back to the source is inverted in polarity. 2) When RLoad = 0, theoretically, the reflection back to the source is 100% and inverted. 3) When RLoad RSource, theoretically, the reflection is 100% and not inverted. And the transmitted wave is proportional to the load. Just my two cents worth, Doug At 08:39 AM 10/14/98 +0100, Massimo Polignano wrote: We are about using LVDS (Low Voltage Differential Signaling) technology to transfer high speed video data to a XGA display 1 m from the driver board. Differential signaling is very good to improve EMC characteristics of the link, but in my opinion is also very critical in actual layout: any lack of symmetry can jeopardize its performances. Has anybody esperience with these circuits? How much EMI behaviour depends on equal signal paths? Is it advisable to shield cables? What does a discontinuity on the transmission line (change in characteristic impedence) produce? - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Ozone...
All I found was the following from 1996 ... http://www.ssnewslink.com/html/governme.html At 09:44 AM 10/9/98 -0400, Matejic, Mirko wrote: Can somebody confirm information I picked on the radio that each Shuttle launch causes a major damage in the Ozone layer? Mirko Matejic - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: teleco 48 volt specifications
Gary, I'm not exactly sure what it is you're looking for but TR-499 is the generic spec and states 48vdc nominal, high, low, and transients. As to how the 48vdc is supplied within a CO, I *believe* that's up to the individual CO. Case in point, the COs I've seen (and I haven't seen many) use grasshopper fuses all over the place anywhere the supply branches. This prevents the failure of one product, shelf, rack, even bay from effecting anything else in the CO. I believe it has to do with seperation of failures between or among other pieces of equipment in the CO. That certainly makes common sense, but as to where that criteria is within the Bellcore specs, I don't know. Doug Gary McInturff wrote: Can anybody direct me to the requirements and specifications that described the -48 volts supplied inside Telco or Bell company offices? Thanks Gary McInturff - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: EN 55022 vs. Telecommunications -48Vdc DC Powered Equipment, Conducted Emissions AC side or DC side?
Don, Until I contested this arrangement, I routinely had 48vdc equipment tested for the conducted emissions on the AC side (input side) of a seperate AC-to-DC power supply (an HP if I remember correctly) that powered the shelf. That HP supply was part of the test equipment setup and not part of the system. Doug Donald Kimball wrote: I work for Qualcomm, and we EMC test -48Vdc powered telecommunications equipment, especially cellular and PCS base stations. The -48Vdc power is usually shared with other equipment at the same location (eg. an Alcatel Switch, Cisco Router, etc.) We have always tested for conducted emissions on DC side of the power line, since we do not control the AC to DC power converter, and we share the DC power with other equipment. Recently, we integrated another vendor's E1 inverse multiplexer into our base station controller racks. The vendor claimed CE mark compliance and sent us a test report. This equipment is powered by -48Vdc, but they tested for conducted emissions on the AC side of the AC to DC power supply that powered the E1 inverse multiplexer. When questioned, they said that the test facility told them they must test on the AC side of the line, and not the DC side of the line. The test facility said they would not issue a declaration of conformity based on testing the DC side of the power line. In fact, they went through several AC to DC power supplies before they found a power supply that was EN 55022 compliant by itself. This makes no sense, since the DC power is shared, and the choice of AC to DC power supply cannot be controlled by Qualcomm. Moreover, a well chosen AC to DC power supply can filter out the noise on the DC side of the line. In fact, one version of the inverse multiplexer fails on the DC side of the power line, but passes on the AC side of the line. If the emissions on the DC side of the power line are compliant with EN 55022 Class A limits, the those same emissions should be below the limit on the AC side. What is the correct answer in this case? Do you test the AC side or the DC side? Don Kimball - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Liability of OEM
You could probably spend the rest of your life trying to get a correct answer from this question since litigation *usually* follows the deep pocket method with recovering a settlement. I've seen some pretty wierd (IMHO) cases that didn't seem to follow logic until the deep pocket theory is applied. What I try to impress upon corporations where I've worked is product liability *usually* follows (not always) the cause of the fault and that amounts to essentially only three areas - 1) if it was designed wrong, then it defaults to the designer or who owns the design function. 2) if it was put together wrong, then it defaults to mfr-ing or who owns the mfr-ing function. 3) if it's been sold wrong (misapplication), then it defaults to marketing (misrepresentation). or who owns the marketing function. Whether or not your company applies your company name on the product or not can get sticky. And OEM-ing a porduct for some else can also get sticky. But, it's always best to follow the spirit of the standards as they are written. I find that I get rather leary of people who want to follow a reg as it is written in black or white. If your product or design is robust enough, the regualtion will end up being a guide rather than a leash. And, IMHO, that's the way things should be done rather than throwing a wrench every time some standard raises it's head. I'll get off my soap box now ... Best to consult an attorney who specializes in product liability. Disclaimer - I am neither a legal expert nor an attorney, so don't count on my opinion as fact. Regards, Doug - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: CB SCHEME
Well, this has been rather informative, but the CB scheme as I understand it is specific about exactly what test data is involved. Right now, it's mainly safety related testing, no? In other words, you could be testing a product in country A who participates in the CB Scheme. The tests may involve emissions, immunity, safety and telephone. Submitting your product to country B who also participates in the CB Scheme may mean that country B will accept ONLY the tests involved with safety and none of the other tests. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
FR-4 Dielectric Constant Used in Simulations ...
Just a suggestion, but would it be too much to ask people who did some of the tremendous studies in simulations and analysis scenerios with printed circuit boards to do best case and worst case scenerios with a RANGE of FR-4 values and then to have the Dk of the board for the frequencies of interest actually MEASURED? I found that ALL simulations presented used the typical Dk = 4.7 value that can vary with great latitude from mfr to mfr (dependent upon mfr-ing techniques) and can vary with frequency. I even took one person aside after their presentation, (a very good one I might add) and discussed this point with them. They hadn't thought of this. We're talking at the Ph.D. level. Now maybe that isn't such a big concern for them, but it is for me. The 4.7 value is at best a fantasy. Also, my understanding is that Dielectric Constant is done with DC voltage while the more general Permittivity is done with frequency. Am I being to overly something-or-other? Discussion? Ideas? Flames? Regards, Doug - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.com with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, ri...@sdd.hp.com, or roger.volgst...@compaq.co (the list administrators).
Re: Who's responsibility.....
Hi Ron, Answers below ... Wismer, Ronald S. wrote: Our company(In the US) wishes to purchase an AC/DC power supply from an outside vendor(From overseas). We then, plan to add some fusing circuitry, an enclosure, and a terminal block so that it mechanically meets our needs. The vendor claims to meet the EMC and LV directives, but no claims to FCC approval. Our market of interest is the US only, thus the problem. I'm assuming here a simple open frame power supply. My question is, if the vendor can not produce proof that that they tested to, and comply with, the FCC requirements, is it allowable for our company to qualify the device and label it accordingly? No UL approvals? Are there any risks involved in doing so? Yes, there are three important ones I can think of: 1) You won't be in control of any changes to the power supply. 2) The power supply mfr is under no obligation to inform you of any changes except through maybe some contractual arrangement. 3) If such changes result in non-compliance, you will have to answer for them. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.com with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, ri...@sdd.hp.com, or roger.volgst...@compaq.co (the list administrators).
Re: AST Tutorial on the Use of Tempature to increase Acceleration Factor
Richard Haynes wrote: Doug, Thanks for adding your important two cents. Could you show us an example with the necessary conversions numbers. Also there is the concept of equilivalents/mole where the number of equivalents is effectively the valence, i.e. 2 for Cu(+2). There are some cases where n is not an even intergal. All is all a dimensional analysis must yield a dimensionless number in the exp(E or H or F). Thanks Richard Haynes Sure, and I would certainly invite any corrections. One over-riding theme when using equations is to be sure of the assumptions by which they have been deduced. The Arrhenius equation is a good approximation for simple atoms/molecules. As one moves away from simple atomic structures to more complex molecules, the idea of heat has to change. Complex atomic structures no longer bang into one another more so at higher temps than lower. They begin to do all sorts of strange things like twist, bend, longitudenally vibrate, etc ... In other words, different modes of displaying heat come about. Alright, now that everyone's gone to sleep, here we go. Using Arrhenius Equation = exp[ (Ea/R)*(1/T1 - 1/T2) ] where Ea = Activation Energy * Note: The less the value, the less sensitive to temp; the greater the value, the more sensitve to temp. R = Gas Constant T = Temperature in degrees Kelvin How we pick the units of R determines everything else as far as units go. One form of the gas constant is: R (Gas Constant) = 8.3144 J/mol*K and 1/R = 0.1203 Thus, AE = exp[0.1203*Ea*(1/T1 - 1/T2)] This means that if Ea is divided by R, the units K must remain in the numerator to cancel the K in the denominator from the (1/T1 - 1/T2) factor. This will leave the final exponent dimensionless. Thus, Ea should be in the units J/mol. This form (J/mol) is very different in implications than simply Joules. Changing this constant to units that have calories involves 1 calorie = 4.184 Joules R (Gas Constant) = 1.9872 J/mol*K and 1/R = 0.50322 Thus, AE = = exp[0.50322*Ea*(1/T1 - 1/T2)] This means Ea is now in the units cal/mol. The form of Arrhenius with which I'm familiar uses electron volts (eV's) as units. So, using the conversion 1 eV = 96.485 kJ/mol leaves R = 8.6172E-5 and 1/R = 11,604.56557 Thus, AE = = exp[11,604.5656*Ea*(1/T1 - 1/T2)] This means Ea is now in the units eV/mol. Ea = 0 eV/mol - temp has no effect. Ea = 1 eV/mol - temp has alot of an effect. Some semi-mfrs use 0.4 or 0.5 for estimates with CMOS and higher numbers for 0.6 or even 0.7 for BJTs. It is important to note that since there is such a mix of semi-conductor material in any device, it is better to estimate, then empirically derive (as long as you have enough sampling) the Ea specific to the product. That will take some time. Here's a sample of how they all work out so that the same AF (acceleration factor) comes out the same no matter which version of Arrhenius you choose to use. --- INPUTS *** --- Test time at T1 = 16,006 hours 666.92 days (interesting) 95.27 weeks 1.83 years T1 = 30C (equation converts to K) T2 = 50C Ea eV/mol = 0.6 J/mol = 57891.00 cal/mol = 13900.00 --- *** OUTPUT *** --- AF = 4.1490 : 3857.79 hours 160.74 days 22.96 weeks 0.44 years --- --- Regards, Doug
Re: AST Tutorial on the Use of Tempature to increase Acceleration Factor
Hope you guys don't mind my two cents but I hope you're assuming something here which I don't see. The units for the Gas Constant used in the Arrhenius' equation is R (gas constant) = J/mol*K or cal/mol*K That means Ea (activation energy) must be in units J/mol, or cal/mol. If the units of eV's are being used, then all the constants must have their corresponding units changed also to eV's so that R = eV/mol*K and Ea = eV/mol To say that H is simply the units of calories is a little misleading. It's units are cal/mol. Very different concept than simple cals. Regards, Doug Richard Haynes wrote: Paul, Thank you for your suggestion. I hope these comments will be useful. Richard Haynes Applications of the Arrhenius type equation include chemical and electrochemical reactions and many other systems such as bipolar and MOS infant mortality. Both temperature and voltage are accelerating factors(D. Cook, Method of Determining Reliability Screens for Time Dependent Dielectric Breakdown , Proceedings of the International Reliability Physics Symposium, IEEE, 1979, p. 1.). When using the Arrhenius type equation several variations of representations of the energy of activation are being used, such at E( energy of activation with eV units), H and F( heat and free energy of activation, both in cals or kcals-kilocals, 1,000 cals). Each means the same measure of energy, that is, the energy necessary to be supplied so the system can reach the final state. -Original Message- From: Parker, Thomas P (Paul) tppar...@lucent.com To: 'Richard Haynes' vale...@pluto.njcc.com Date: Friday, July 24, 1998 8:54 AM Subject: RE: AST Tutorial on the Use of Tempature to increase Acceleration Factor Richard - Most people are used to seeing Ea for activation engery in electron volts, vs H in the Arrhenius equation. I would suggest explaining that. Many failure modes do not necessarily follow Arrhenius, especially workmanship defects and other mechanical defects. Can you be discuss the types of failure modes that this equation applies to as well as what it does not apply to. Actual experimental examples would be great. Paul -- From: Richard Haynes[SMTP:vale...@pluto.njcc.com] Sent: Friday, July 24, 1998 3:02 AM To: emc-pstc; accelerated-stress-testing Subject: AST Tutorial on the Use of Tempature to increase Acceleration Factor File: Temparrt.doc Greeting Groups, I hope this tutorial will clear up some aspects of using the temperature to increase the acceleration Factory. Please let me know if this was helpful so I can tell my boss. Thanks and have a good day. Richard Haynes PS The attached file is in Word 6.0
Re: Power transformers, certification, etc...
Peter E. Perkins wrote: Brian PSNet... Regarding your question as to whether certification is required on products 'over there' or not... In the USA, since the publication of the OSHA CFR 1910.303 Certification requirements, there has been such for electrical equipment. Specifically, 'Every electric utilization system and all utilization equipment installed after March 15, 1972, and every major replacement, modification, repair, or rehabilitation, after March 15, 1972, of any part of any electric utilization system or utilization equipment installed before March 15, 1972, shall comply with the provisions...'. Yes, you read it correctly 1972... Further, it calls out: 'Suitability of equipment for an identified purpose may be evidenced by listing or labeling for that identified purpose'... Careful ... Telcos being public utilities are exempted. Telcos are also state controlled, not federally controlled. Interpretation of this point is not uniform.
Re: Looking for Horror Stories
knigh...@exchange.sandiegoca.ncr.com,Internet writes: RE: my request of a couple of weeks ago for EMC compliance horror stories: Thanks to all who shared humorous and real horror stories. I have shared most of them with my management. While the stories of good intentioned designs gone bad were helpful, I just wish I had more accounts of manufacturers/integrators getting into legal difficulties over non-compliance with EMC rules. Well, while taking evening classes in the early 80's, my prof got involved with a terrible incident down in New Jersey. Seems a hospital had a high incidence of infant deaths in the intensive care ward in the maternity ward. Late at night, the alarms would go off for no apparent reason. Annoyed, the nurses would turn them off and do the rounds on foot. After some prelimenary investigation, my prof found out that a nearby tv transmitter was allowed by license with the FCC to increase their output wattage by some enormous amount after say midnight but had to reduce it prior to 6 am or some such arrangement. The cables interconnecting the nurses station to the various monitors sang like a lark with these freqs and set off alarms with induced voltages. Not sure of all the specifics except what I've related above nor the name of the hospital but they lost something like 6 kids before fixing it. Personally, the only EMC issue that's come up no matter where I've worked has to do with surges on the power grid even with compliant equipment. If you're in an industrial grid, seems as though powering up and powering down things things like an electric foundry or large numbers of air conditioning equipment can unbalance the line or phase eonough to reset equipment or cause a burst of bit errors either over the weekend or late at night. Never really zeroed in on the cause. Does tend to upset people to be running some Bellcore test over the weekend only to find the equipment in STANDBY mode halfway through a 3 day test. Regards, Doug
Re: Reliability Tests
Richard, You're absolutely correct. I was making quite a few assumptions here. I'm using a pure Arrhenius equation for acceleration of the tests. And in fact, I'm using 0.6 for activation energy. If the system is predominantly CMOS, maybe that should be higher - that's good. If the system is predominantly BJTs, than it should be lower - that's not so good. Now, I'm not so sure that I'm in agreement with using multiple systems the number of which gets divided into the total time. If I test 1,000,000 cars by idling them for 1 hour without a failure, I can only claim 100% confidence that any car will operate at idle with no failure for 1 hour. If on the other hand I continue to test the 1,000,000 cars at idle till 1/2 of them fail say after 1 year, I can only claim a 50% confidence that none will fail at idle after 1 year. Or am I all wet about this one? Regards, Doug Richard Haynes wrote: Doug, What distribution did you use for the calculation. This may be a major assumption and the AF can vary by several times? Richard Haynes From: Douglas Mckean dmck...@corp.auspex.com Not sure I have this right but why not just do some accelerated temp testing with a sample quantity? I calculate that 16,006 hrs (95.27 weeks) at 20 degrees C reduces to just 6.01 weeks at 65 degrees C. Regards, Doug Jon Ilseng wrote: For the reliability engineers out there, I am looking for ideas on how to perform a reliability test for a Base Transceiver Subsystem with a predicted MTBF of 16,006 hours. Researching the MIL-HDBK-781 test plans, the shortest test time is Test Plan XXID. Test Plan XXID has a test duration of 17,606.6 hours (1.1 X 16,006 hours). This is equivalent to 733 days or 2 years just to conduct a reliability test. Plus, Test Plan XXID allows no relevant failures. There has to be a smarter and more cost effective method to perform a reliability test to verify this 16,006-hour MTBF. Any ideas would be greatly appreciated.
Re: Reliability Tests
Not sure I have this right but why not just do some accelerated temp testing with a sample quantity? I calculate that 16,006 hrs (95.27 weeks) at 20 degrees C reduces to just 6.01 weeks at 65 degrees C. Regards, Doug Jon Ilseng wrote: For the reliability engineers out there, I am looking for ideas on how to perform a reliability test for a Base Transceiver Subsystem with a predicted MTBF of 16,006 hours. Researching the MIL-HDBK-781 test plans, the shortest test time is Test Plan XXID. Test Plan XXID has a test duration of 17,606.6 hours (1.1 X 16,006 hours). This is equivalent to 733 days or 2 years just to conduct a reliability test. Plus, Test Plan XXID allows no relevant failures. There has to be a smarter and more cost effective method to perform a reliability test to verify this 16,006-hour MTBF. Any ideas would be greatly appreciated.
Re: Desiging Openings for EMC Compliance
At recent symposium in Santa Clara, I talked to some length with one of the speakers about round holes in shielding for ventilation. For all the equations I've seen and tried to verify, they really don't pose a problem with the work I've done. But, that's strictly my experience and that in itself is limited to some others here. Slots are the things to watch out for because in my experience they have caused alot of problems. Now, mechanical types I find are the best to teach EMI issues. Why? Because they aren't all cluttered up with Maxwell and integral vs. differential forms ... Just remember: Slots are wires incognito. Regards, Doug WOODS, RICHARD wrote: I am about to give a short seminar to our Mechanical Engineers and Designers on enclosure design for EMC compliance. There is only one problem - I have no faith in the theory I have for the attenuation through openings. The following formula is from the EMC Handbook, Vol 3, by Don White. Assuming the frequencies of interest are below the waveguide cutoff frequency, the formula is A(dB) = KL/G - 20 log N where, K = 32 for round holes or 27 for square holes L = thickness of panel G = hole diameter N = number of holes. According to this formula, one 1/4 inch hole in a 0.090 inch panel would have an attenuation of 11 dB, and ten holes would have no attenuation whatsoever. This does not match my experience in typical ITE. Does anyone have any usable rules of thumb for Mechicanical types? Richard Woods Sensormatic Electronics wo...@sensormatic.com Views expressed by the author do not necessarily represent those of Sensormatic.
Re: Dual names on regulatory labels
chasgra...@aol.com wrote: Hello!! I have a question regarding dual manufacturers names on a regulatory label. From an EMC perspective: The situation is that Company A wishes to buy product from Company B and resell using Company As name and model number. In order to save time, Company A wishes to use BOTH sets of model numbers on the SAME label as well as using company B licence numbers etc. Is this legally acceptable?? Yes, as long as the appropriate paperwork from the agencies concerned shows both company names and both model numbers in the reports. If Company B did the testing, then Company A must make arrangements with Company B to have the documentation changed accordingly. It gets trickier if Company A doesn't want any reference or mention of Company B in any of the documentation to include Company B's model numbers. For instance, FCC Part 15 Class A reports may be changed to reflect only Company A's name and model numbers. The change only requires a change to documentation fee. But, FCC Part 68 reports require a registration on the part Company A with the FCC. I think I have that correct ...
Re: Majordomo results: Re: odd immunity
Well, someone said they saw this on tv and I don't doubt them. How do they grab codes off the air for phones? Regards, Doug Flinders, Randall wrote: My question is. . . . Even with the keystrokes, how could they access the account without possession of the the ATM card? Regards, Randy Flinders EMC Test Engineer Emulex Network Systems Chairman Orange County Chapter IEEE EMC Society -- From: Douglas Mckean Sent: Tuesday, July 07, 1998 6:57 PM To: emc-pstc Subject: Re: Majordomo results: Re: odd immunity problems ? How about ... The one where some creative types got some EMI(?) equipment to monitor the keystrokes of people at an ATM? Story goes that they sat in a van in a parking lot by the bank with antennas focused on the ATM. Once you entered in your numbers, they could translate the EMI signature to keystrokes on the keypad. After you left the scene, they drained your account. Never knew if that was UL or fact. -- __ Begin of Forwarded Material __ End of Forwarded Material The comments and opinions stated herein are mine alone, and do not reflect those of my employer.
Re: Majordomo results: Re: odd immunity problems ?
How about ... The one where some creative types got some EMI(?) equipment to monitor the keystrokes of people at an ATM? Story goes that they sat in a van in a parking lot by the bank with antennas focused on the ATM. Once you entered in your numbers, they could translate the EMI signature to keystrokes on the keypad. After you left the scene, they drained your account. Never knew if that was UL or fact.
Re: Odd immunity problems.
Yes, Chris. Quite amusing. Then, of course, there's the famous fly in the microwave debate ... ducking quickly Chris Dupres wrote: Hi Keith. As we wander round this world of Electro-fizz, pop and 2dB-over-limit, we come across all sorts of strange EMC behaviour, some directly witnessed, some without an actual source (I heard of a friend of the wife of the chap who reads the gas meters - etc.) A few more amusing ones have slippped into Urban Legend, or latterday Folklore, some are much more recent. 1. There is the story of the lady on the ninth floor of a block of flats who whenever she heated her milk for her bedtime drink, twenty seconds later there was a loud 'Donk' noise from the wall. Subsequent investigation showed that whenever the ladies Microwave was started, the lift was called from the ground floor and stopped at the ninth. The ladies kitchen was against the lift shaft and the noise was that of the lift doors closing. - Unattributed 2. There is the story of the short-term car park gates at Gatwick airport being opened simply by holding an electronic cigarette lighter up to the exit card reader, and flicking it a few times. This was discovered by careful TV surveillance, and the surveillance technician using his lighter to see the time! Indirectly attributable to the BAA. 3. A metal detector on a coffee packaging plant dumping 50 lbs of instant coffee into the scrap-sack whenever a CelNet phone was used within 20 metres. Witnessed by Chris Duprés. 4. A Tissot Two-Timer digital/analogue wrist watch which went into time travel mode (about x 60 )whenever a particular Motorola Micro-Tac portable phone nearby had someone actually speaking into the mouthpiece. Witnessed by Chris Duprés. It was my damn watch! 5. Motor Vehicles with Capacitor Discharge ignition systems stranded, unable to run, parked on the A5 at Clifton-on-Dusmore, near Rugby, UK. The fact that this road goes right through the middle of the NATO 16kHz transmitter may have been significant. ( Is this EMC, or just total overload?) Attributable to an AA patrol in The Halfway House Inn, Crick, Northants, UK. 6. And there is the one where the flame on the gas cooker flared up red and then went out whenever the phone rang... This was found to be due to the telephone extension bell up the garden being fitted to the gas supply pipe, such that whenever the bell rang the rust was shaken off the inside of the pipe which got carried through to the flame causing the flare up and then blockage. OK, this is not EMC per se, but it seemed funny anyway. This was culled from a UK magazine, probably Readers Digest, while waiting for the Dentist. 7. Lot's of other examples at home, including: - The TV changing channels or turning off whenever the central heating came on. - The TV presenting us with the Gatwick Airport Meteorology transmissions, albeit at very low level, when the Microwave was running. (we are about 2 miles from Gatwick). - A Ceramic firing kiln in the garage going up 10 degrees whenever a switchmode battery charger was running in the garage. - The outside Quartz Halogen security light comes on whenever my office lights (fluorescent) or the bathroom ventilation fan are switched off. There must be many, many weirder and funnier ones out there :-) Regards, Chris Dupres Surrey, UK. -- __ Begin of Forwarded Material __ End of Forwarded Material The comments and opinions stated herein are mine alone, and do not reflect those of my employer.
Re: Energy Star (?)
Energy Star is a program setup by the EPA. Originally, urban legend has it that some beaurocrat somewhere in the bowls of the US government multiplied the number of PCs to be bought for Federal Employees by the wattage of the average device and concluded that it was unacceptable. The monitor and pc mfrs were required to put in the option of the screen and pc going to sleep after a period of time. That's if the system is setup to do that in the first place. Go figure ... Usually on first bootup, the monitor will show a little energy star logo. It has since expanded into other devices. See the whole preview at http://www.epa.gov/energystar.html Regards, Doug Bill Lyons wrote: This is definitely a FAQ, and perhaps a little off-topic, but can someone kindly remind me what Energy Star is? A colleague said he thought it was a (US) standard for household electrical wiring. I said my recollection was that it was a US marking of a green product (such as a computer monitor) with automatic energy- saving standby mode. Clarification, and ideally a reference, greatly appreciated by both of us. -- Bill Lyons - b...@lyons.demon.co.uk / w.ly...@ieee.org
Re: EMC in motors and drives
I'd have to underscore Keith's responses with just a few of my own - Q: Finding the EM in a circuit using network analysis: About 2 years ago I looked into software for EMC work. I was interested in loading in artwork of a pcb (gerber files, Orcad, whatever) for analysis - not system level modeling. I soon found out there were basically three categories of software: 1) Expensive mainframe level software at a university. You contract out their services. 2) Not so expensive $5K to $12K pc loadable stuff. 3) Inexpensive less than $5K pc loadable stuff. I was concentrating on #2 and #3. I uncovered that the software in its attempt to streamline the number chrunching for a pc makes some assumptions with which I didn't agree. For instance, some of the software makes the assumption that ANY ground is a perfect ground. NOT ALL software makes this assumption, so you have to be very careful as to YOUR specific application. Please do not take my word for it. Best to dicuss this with several of the vendors who would be more than willing to out there to provide much help with your needs. Q: Why does EM happen in motors and drives? Usually it has to do with high current and usually has to do with unintended consequences of that current not going where you think it should nor doing what you think it should. Remember that EMC doesn't cover just emissions. If you're drawing alot of current across a board one one ground plane with a mixed layout of digital and analog circuits, then ground bounce, crosstalk, etc ... will freely rain upon your parade.
Re: EMC in 19 rack
Oh, ok, have had experience with both styles with power supplies end mounted and middle mounted. Personally, from a noise reflection point of view as far as the backplane power traces, I would prefer a middle mounted PS system. But, that's debatable. The middle mounted rack did far better EMI-wise (Class B device) than the side mounted rack ... Bt, that's also debatable. I was able to do a serious amount of board layout for the backplane with regard to actual printed circuit board construction of the middle mounted shelf. But above and beyond EMI, both suffered from the issue of thermal problems. The side mounted was a little better than the middle mounted. Both were convection cooled devices and not forced air. And in both cases, the PS's were in the 50 to 75 watt range. I don not know the specifics of your product but for what it's worth, just from the experience of both of these products, I learned the the following two hard lessons and would recommend reviewing them to see if they apply: 1) As far as covection cooled rack mounted shelf products, there seems to be a trade-off between emi and thermal. IOW, if you want a really good robust thermal shelf, emi may have to be sacrificed. Likewise, if you want a really good robust emi shelf, then thermal may be a problem. 2) Everyone seems to forget that marketing likes to sell these things as much as possible. So, there may be a good chance that these shelves will get stacked on top of one another in the rack adding to a really terrible thermal issue at the customer site. As such, there's a Bellcore requirement concerning watts per square foot in a CO. I believe that may be in TR-499 (TSGR) Transport Systems Generic Requirements. Just my two cents ... Regards, Doug Gary Allen wrote: Doug, I mean what we have been calling a 'subrack': that is a double Eurocard high shelf in a 7' high rack. Not dumb when the terminology is mixed. I think shelf is probably a better term - and I've just seen that I typed rack and not subrack in error. Gary.
Re: dstrbtd Vs centrl pwr in 19rak
Hi Gary, Have to ask a dumb question. Do you mean a rack as in a 7 foot 19 inch style floor standing rack that is part of a bay in something like a CO, or do you mean a shelf that's mounted in 7 foot high 19 inch wide rack? Sorry, confused ... Regards, Doug Gary Allen wrote: Hi EMCers, For PSUs for each of say 17 cards in a telecoms 19 rack, an alternative is one PSU card at the end of the rack. However this means long (backplane?) busses of supplies. I suspect that EMI would be worse for the alternative central PSU solution. Is this the case in anyones experience? And are there solutions offerable with such a brief brief? And any literature on WEB or elsewhere?
Re: Altitude
Well, Just for my two cents, 40,000 ft equates to roughly 1/5 the pressure at sea level or almost 3 lbs/in^2 absolute compared against 14.7 lbs/in^2 at sea level absolute. That leaves any type of plug or wall structure of the capacitor having to withstand 11 lbs/in^2 across it. Also, the capacitor or even a transformer may have fluid inside and leak. It also may involve a chip ingassing humidity once it's back on the ground. Why? Assume typical temp at 40,000 ft is nominally -70 degrees F. Within a matter of minutes the plane could be on the ground in some tropical area. Condensation occurs on the chip, water forms, ingassing occurs and now you've got a saturated chip. Regards, Doug geor...@lexmark.com wrote: There is also an FAA? limit on the magnetic properties of air shipments. The gauss from the package must be within a stated maximum to avoid interference with navigational instrumentation. Even a concentrated shipment of small motors can exceed the limit due to the magnetized elements within. It has been five years since I was in EMC so I can't cite the actual standard or regulation. Don't know if this is what you were looking for.. George Alspaugh Product Safety Please respond to rbusche%es@interlock.lexmark.com To: emc-pstc%ieee@interlock.lexmark.com cc:(bcc: George Alspaugh) bcc: George Alspaugh Subject: Altitude This is not a safety or EMI question, but because this group has such broad backgrounds and diversity I am hoping that someone can comment. I have been asked by one of our customers to ensure that our equipment is capable of being shipped in an un-pressurized aircraft for altitudes of 30K to 40 K feet. This is a non operational requirement, but are there other concerns I should be aware of? I recall hearing that some commercial grade electrolytic could explode at high altitudes. Any comments or suggestions greatly appreciated. Rick Busche Evans Sutherland Salt Lake City, Utah rbus...@es.com
The Santa Clara EMC Colloquim
I'd just like to say that it was nice to finally put some faces to the names. Thought it went very well.
Re: Twist on Connectors
An electrician told me by word of mouth the proper way to apply wire nuts is: 1) Twist the wires in the direction of twisting on the wire nuts. 2) Twist the wire nut onto the wires. 3) Wrap electrical tape around the wires and nut in the direction the wire nut was twisted to secure the wire nut. I have no idea if this is standard practice, but it sounds as though something you should look for in high vibration environments if wire nuts are used. Regards, Doug Jack Cook wrote: There is one factor which I haven't seen mentioned in the discussion. I believe the original query stated that the connector(s) would involve a motor. If so, wouldn't there be some concern about vibration? This isn't my field but I'd be reluctant to use wire nuts under those conditions unless I could find expert assurances that such connections are still safe. Regards, Jack Cook, Xerox Corp
Re: Twist on Connectors
Could I ask a more general question? Twist-ons are typically used alot by electricians in all sorts of wiring applications within the US. Are electricians outside the US allowed to use twist-ons when wiring to local code? Regards, Doug -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of Russell, Ray Sent: Thursday, May 28, 1998 6:58 AM To: 'IEEE PSTC' Subject:Twist on Connectors Greetings, Here in the US, twist on connectors or wire nuts are commonly used for all type of wiring applications. We have a product where the AC primary line cord connects to the winding of a motor. We are currently using crimp type connectors. But some bean counter found that he could save a penny and wants to change to twist on connectors. My previous experience (at another company), during a product review by a European notified body required us to replace twist on connectors with crimp on type. To further complicate matters there is an IEC standard for twist on connectors, IEC-60998-2-4. My question is: are twist on type connectors allowed for this type of equipment in Europe? Is there any standard or guide lines that I could refer to? Most standards that I have reviewed, only state that the connection must be reliable. So if there is an IEC standard for twist on connectors, and these connectors meet that standard, would not they be considered reliable? Thank you for your consideration, Ray Russell ray_russ...@gastmfg.com
Re: Coated Printed Boards
When analyzing printed circuit boards, BOTH clearance AND creepage are issues. The flat pcb fab (no parts installed or soldered) would most likely have nothing but creepage issues - distances along the surface of the board (as the crow walks). An assembled pcb with parts that could compromise creepage (parts laid down on the board for example or wires added as a mod after assembly or maybe even a piggyback board) would have clearance issues as well (as the crow flies). Thus, the reason why both clearance and creepage are included in all the IEC-950 based standards that I've seen: UL-1950, EN-60950, ... Regards, Doug Alan Booth wrote: Dear Treggers, I am having a problem with clause 2.9.5 of EN60950 regarding Coated Printed Boards. The second paragraph, second sentence reads : 'Between any two uncoated conductive parts and over the outside of the coating, the minimum distances in tables 3, 4 or 5 apply.' Tables 3, 4 and 5 only deal with clearance distances. I would have thought that table 6 for creepage was a more appropriate application in this instance. Can anyone explain the reasoning behind this? Many thanks, Alan Booth. Equipment Engineering Group Fujitsu Telecommunications Europe Limited Solihull Parkway Birmingham Business Park Birmingham B37 7YU Telephone +44 121 717 6492 FAX +44 121 717 6014/6018 e.mail- a.bo...@ftel.co.uk
Re: NRTL Value
George, Can't say I have had the same experience. But, I have had experience with two different safety NRTLs each with their own label. Anytime something did come up I always referred the issue to the supervisor of the test engineer of the approval to make the call. My experience was that the NRTLs were very helpful. I did have issue with one rather famous factury inspector, but it was obvious that he went beyond the scope of the factory inspection report. Regards, Doug geor...@lexmark.com wrote: Here's a situation that I find very frustrating. Suppose a (leading) National Recognized Test Laboratory (NRTL) assesses a product and issues an authorization letter for the use of their mark. Suppose a year or so later, during a routine follow up service inspection, a dozen or so variation notices are generated by the NRTL inspector. Suppose that many of the VN's state that changes to the design are required, although it is the same design approved by the NRTL in the first place. Suppose that the VN's include changing the power rating label to Listed Accesory, which is exactly opposite the labelling requirement as described in the NRTL's own guidelines. Suppose one VN requires moving the power rating label, or adding a new label, nearer the convenience outlet. A reasonable request, but never raised during the approval process or prior FUS visits. Do you: A. Register a complaint with the Better Business Bureau (ha) B. Notify OSHA, who authorizes all U.S. NRTLs C. Take future business to an alternate NRTL D. Argue each point in a reasonable manner with the inspecting engineer E. All of the above Has anyone had a similar experience with a U.S. NRTL? George Alspaugh Lexmark International
Defibrillators
Has anyone worked on defibrillators? My slight reading on the subject has found widely differing limits. And the milli-amp spec is from the hand only. Especially the right hand. One reason why long ago, I was taught to work on tubes with one hand - if current was to pass through you from your hand to your feet, better that it's with the right hand than the left hand. Current entering the left hand could cross the heart easier than the right. Direct contact with the heart muscle as in patient implanted defib devices require only micro-amps to work. A third condition, pulses, end up being another story altogether based on the amount of energy with I^2*t. This allows for people to survive a higher level current spike in a transient state that would otherwise kill in a static state. But, these spikes must be less time in duration than the period of a natural pulse in the heart muscle. Defibrillators work how? Certain number of pulses for a certain length of time? And there's more than one type of defibrillator then the capacitive, right? I have found very little on the subject and would be interested in sources. Thanks in advance. Doug
Re: Fingers for Anechoic EMI Chamber Doors ...
Thanks for all responses both on and off-line. Some very funny, but all very informative.
Re: Best multi-layers backplane layout
Initially the stack up looks alright without knowing anything else. Just some curiosity questions: 1) Are there any signal layers in this backplane? 2) Which power plane has the most current/family of ICs/noisy? From this, you might want to consider assigning layer 1 as the outside layer of the backplane and layer 12 as the inside layer. Then, make the least noisy/least current draw power plane as layer #1 and maybe bury the noisiest or hottest power plane in the middle of the board. 3) Board to be plain old FR-4? 4) Someone mentioned symmetry. Good point. Unless you stand over the board mfr during routing, they may add or subtract Cu layers as they see fit. 5) Also, you may need to know that 1 oz Cu is about 4.848*10^-4 ohms per square 2 oz Cu is about 2.424*10^-4 ohms per square Regards, Doug Jim To wrote: Hello fellow engineers. I have 7 power planes and 5 ground planes. 6 of the power planes are +5V, +12V, and +3.3V; 1 of the planes has AC voltage. 2 of the grounding planes are low voltage return planes for DC; 3 of the planes are chassis ground planes. I was asked to provide a way to layer these planes to minimize EMI. My first attempt on the design on this plane is as followed: Layer 1:Chassis Gnd Layers 2 3:+5V Layer 4: Logic Gnd for +5V, +3.3V, +12V return, and supply signals Layers 5 6: +3.3V Layer 7: Logic Gnd for +5V, +3.3V, +12V return, and supply signals Layers 8 9: +12V Layer 10:Chassis Gnd Layer 11:AC power plane Layer 12:Chassis Gnd I would appreciate any comments you may have on this design. I took the approach of inserting ground plane in between power planes, but I am concerned about large ground loops caused by logic gnd planes since they behave as the return path for all DC. Many thanks. Jim To Force Computers, Inc. jim...@fci.com -- The comments and opinions stated herein are mine alone, and do not reflect those of my employer.
Re: Optical Multiplex Carrier System
CTL wrote: What are the EU requirements for EMC on Optical Multiplex Carrier Systems that provide for capacity upgrades? What about Safety? There are no copper connections to any network. System components are transponders, passive optical multiplexers, optical amplifier, and wavelength demultiplexers. I've worked on some metal-to-fiber/fiber-to-metal ECL/TTL products with Class III-b laser systems at DS3/OC1 rates with PAL, SECAM, and NTSC formats for video transport in Central Office and strand mounted environments. Safety? I used EN-60950 but would have had to eventually use EN-50083. I was gone before that happened. Lasers? IEC-825/EN-60825 There are plenty of labs out there to help. Not really sure if I gave you any worth while info. Regards, Doug
