Re: PC's Class B..
After rejecting Sony HP, I enquired at several labs got Dell as preferred for emi host cpu. Dell recommended the MCM. After evaluating 1, we bought 3 more have been happy over the last year. Mike Harris/Teccom -Original Message- From: k...@i-data.com k...@i-data.com To: emc-p...@majordomo.ieee.org emc-p...@majordomo.ieee.org List-Post: emc-pstc@listserv.ieee.org Date: Friday, September 15, 2000 4:38 AM Subject: RE: PC's Class B.. Here are my results from test performed 14/9 2000: PC: Dell Dimension L566CX ; Model MCM Monitor: Dell 15 Model E770p FCC and CE approved all components The PC cabinet is very good, but CD-ROM had to be grounded by EMC/Cu gasket arround the front. The it was very good with a margin of more than 5dB for Class B. The Monitor did not comply. It faild by up-to 6 dB at 130 - 160 MHz (switch mode noise). We then used a HP monitor Conclusion: PC, mouse and keyboard is very good (with modification) Monitor is bad. Best regards, Kim Boll Jensen i-data international --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
RE: PC's Class B..
Here are my results from test performed 14/9 2000: PC: Dell Dimension L566CX ; Model MCM Monitor: Dell 15 Model E770p FCC and CE approved all components The PC cabinet is very good, but CD-ROM had to be grounded by EMC/Cu gasket arround the front. The it was very good with a margin of more than 5dB for Class B. The Monitor did not comply. It faild by up-to 6 dB at 130 - 160 MHz (switch mode noise). We then used a HP monitor Conclusion: PC, mouse and keyboard is very good (with modification) Monitor is bad. Best regards, Kim Boll Jensen i-data international --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: ANNOUNCE - FAQ: Sources of EMC Safety Compliance Information, 52nd Issue
FAQ: Sources of EMC Safety Compliance Information This is to let you know that I have just posted in two parts the 53rd issue of the above FAQ to the newsgroup for regulatory/compliance matters and EMC and safety specifications and testing, sci.engr.electrical.compliance (s.e.e.c). The message IDs are: Part 1: 2915.0609.41472...@lyons.demon.co.uk Fri, 15 Sep 2000 07:09:27 +0100 (BST) Part 2: 2915.0612.41473...@lyons.demon.co.uk Fri, 15 Sep 2000 07:12:52 +0100 (BST) Courtesy of Martin Rowe, the FAQ is archived at the following URL: http://world.std.com/~techbook/compliance_faq.html and the Japanese version, courtesy Tom Sato, at: http://member.nifty.ne.jp/tsato/seec-faq/ The latest version should appear there in the next few days. The textfiles may be accessed at: Part 1: http://www.lyons.demon.co.uk/seecfaq1.txt Part 2: http://www.lyons.demon.co.uk/seecfaq2.txt Hope you find the FAQ useful: suggestions for additions or corrections are welcomed. Technical comments/queries to me, b...@lyons.demon.co.uk, please. Comments re web implementations only to the respective webmasters, Martin martin.r...@alum.wpi.edu or Tom vef00...@nifty.ne.jp. -- Bill Lyons - b...@lyons.demon.co.uk / w.ly...@ieee.org Maintainer of the sci.engr.electrical.compliance (s.e.e.c) FAQ = Claude Lyons Limited Brook Road Waltham Cross Herts EN8 7LR England Voltage and Power Control - Precise Electrical Instrumentation Tel: +44 1992 768 888 Fax: +44 1992 788 000 email: i...@claudelyons.co.uk URL: http://www.claudelyons.co.uk = --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
schematic
Low level halogen and Xenon lighting make use of electronic transformers. Does anyone have a typical circuit of one of these transformers? I attempt to do suppression of devices such as these that generate considerable broad band noise at broadcast as well as short wave frequencies and need to know what is causing the conducted distortion to feed back to the powerline. I am told by producers of these noise generators that most producers use the the same or a similar circuit. I believe SCRs or unstabilized switch mode supplies are the culprits. Any help would be appreciated. Ralph Cameron EMC Consultant for Suppression of Consumer Electronics ( after sale)
RE: PCB fuse trace
Thank you all for responding to my inquiry thus far. Here is an update on my findings. I have since had the opportunity to discuss this issue with a few different NRTLs in regards to particular standards. The uniform concensus thus far from these agencies are that they test to standards, not necessary impose restirctions that are not in the standards. Thus many agencies have agreed that a fuse trace, although discouraged, can be used as a primary means of protection, unless specifically referenced not allowing such use. But once again, this comes down to the particular standard that you apply too. Some may require abnormal tests, etc... -Original Message- From: Jim Freeman [mailto:free...@broadcom.com] Sent: Thursday, September 14, 2000 11:38 AM To: Peter Tarver Cc: Matsuda, Ken; emc-p...@ieee.org Subject: Re: PCB fuse trace In all of this discussion, no one has mentioned the possibility of fire from blowing a PCB trace fuse. I know that there are flame retardants in the PCB material that protect to a certain flashpoint but to rely on that mechanism for fire prevention is a bit far fetched. From my limite experience with fuses, there is generally a large structure that is enclosed in sand to prevent a fire from spreading. Jim Freeman Peter Tarver wrote: My experience with safety agencies is they do not want to rely on traces opening to act as fuses and no standards have been developed, that I am aware of, to address this issue. Fuses certification gets involved in the metallic alloys used, to the fraction of a percent, the conductor size, additional construction features, such as heat sinking elements for time delay characteristics, tension loading for fast action, blah, blah, blah. Most of these issues are far too difficult to control for pwb traces, especially considering the etching processes don't lend themselves to the level of control necessary to be a reliable fuse of specific ratings. Additionally, the heat sinking from pwb layout of one product to another or varying copper thicknesses in a product line, adding or subtracting ground planes for emc, the variability of soldering processes and location/thermal capacity of components on the pwb make this seem far too cumbersome to want to work with. BTW, this is a very different world from repeated twice, same result single-fault testing, where a pwb trace opens. Regards, Peter L. Tarver, PE ptar...@nortelnetworks.com -Original Message- From: Matsuda, Ken [ mailto:matsu...@curtisinst.com mailto:matsu...@curtisinst.com ] Sent: Thursday, September 14, 2000 7:02 AM To: emc-p...@ieee.org Subject: PCB fuse trace I was wondering if anyone knew a standard for the US, Canada, and Europe that covers PCB board traces that can be used as fuses? Thanks for the help, Ken --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: Immunity measurement uncertainty
You might try the IEEE EMC Symposium archives. There have been lots of papers over the years. I co-authored a paper with Dan Hoolihan on radiated immunity uncertainty for the 1997 symposium. Regards, Brent DeWitt Datex-Ohmeda Louisville, CO Leslie Bai leslie_...@yahoo.com on 09/14/2000 02:23:33 PM Please respond to Leslie Bai leslie_...@yahoo.com To: IEEE EMC-PSTC \(E-mail\) emc-p...@majordomo.ieee.org cc:(bcc: Brent Dewitt/US/D-O) Subject: Immunity measurement uncertainty Hello, members, Is there anyone who can direct me to somewhere I can find the method to derive the Immunity Test Uncertainties, e.g. ESD, RI, EFT/B, Surge, etc. Thanks, Leslie __ Do You Yahoo!? Yahoo! Mail - Free email you can access from anywhere! http://mail.yahoo.com/ --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org CONFIDENTIALITY NOTICE This e-mail communication may contain information that is proprietary, confidential and/or privileged from disclosure under applicable law. The information is intended to be for the use of the addressee only. If the reader of this e-mail is not the intended recipient, you are hereby notified that use, copying, dissemination or continued possession of this communication is strictly prohibited. If you have any reason to believe you are not the intended recipient of this e-mail, please delete all copies of this e-mail from computer memory or storage. Thank you. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: PCB fuse trace
Hi Peter, The simple metal tubes are a vacumn and the metal isn't surrounded by volatile material as it is in the PCN trace. Jim Freeman Peter Tarver wrote: Jim - Except for when a high breaking capacity fuse is needed, arc extinguishing fillers, like sand, are not generally necessary. I would also expect that such a fuse would not be in a primary circuit, where the US safety standard expects a fuse to see 10kA for miniature fuses. Even most of these fuses (again, in the US) don't use arc extinguishing fillers, but are simple glass tubes with metal ferrules (the 1 by 1-1/4 miniature fuses, and even several varieties of 5mm by 20mm fuses). The above is based on my experience testing fuses for about 4 years, during my tenure at UL. Regards, Peter L. Tarver, PE ptar...@nortelnetworks.com -Original Message- From: Jim Freeman In all of this discussion, no one has mentioned the possibility of fire from blowing a PCB trace fuse. I know that there are flame retardants in the PCB material that protect to a certain flashpoint but to rely on that mechanism for fire prevention is a bit far fetched. From my limite experience with fuses, there is generally a large structure that is enclosed in sand to prevent a fire from spreading. Jim Freeman Peter Tarver wrote: My experience with safety agencies is they do not want to rely on traces opening to act as fuses and no standards have been developed, that I am aware of, to address this issue. Fuses certification gets involved in the metallic alloys used, to the fraction of a percent, the conductor size, additional construction features, such as heat sinking elements for time delay characteristics, tension loading for fast action, blah, blah, blah. Most of these issues are far too difficult to control for pwb traces, especially considering the etching processes don't lend themselves to the level of control necessary to be a reliable fuse of specific ratings. Additionally, the heat sinking from pwb layout of one product to another or varying copper thicknesses in a product line, adding or subtracting ground planes for emc, the variability of soldering processes and location/thermal capacity of components on the pwb make this seem far too cumbersome to want to work with. BTW, this is a very different world from repeated twice, same result single-fault testing, where a pwb trace opens. Regards, Peter L. Tarver, PE ptar...@nortelnetworks.com -Original Message- From: Matsuda, Ken [mailto:matsu...@curtisinst.com] Sent: Thursday, September 14, 2000 7:02 AM To: emc-p...@ieee.org Subject: PCB fuse trace I was wondering if anyone knew a standard for the US, Canada, and Europe that covers PCB board traces that can be used as fuses? Thanks for the help, Ken
Re: Near Field Versus Far Field
Several excellent ideas have been put forward on this phenomenon. Here is my $.02 worth on the subject. I have often been able to reduce the far-field emissions, based on the reduction in near-field emissions. The important thing is to co-relate the far-field and near-field emissions, by comparing their frequency spectrums. It is possible that the 400 MHz clock you worked on with near field probe may not be the real culprit. Another trace may be coupling the 400 MHz clock noise to some cable, or one of the other signals, which is driven by the 400 MHz clock, may be the real source. Regards, Ravinder PCB Development and Design Department IBM Corporation - Storage Systems Division Email: ajm...@us.ibm.com *** Always do right. This will gratify some people and astonish the rest. Mark Twain marti...@appliedbiosystems.com@ieee.org on 09/14/2000 10:07:36 AM Please respond to marti...@appliedbiosystems.com Sent by: owner-emc-p...@ieee.org To: emc-p...@majordomo.ieee.org cc: Subject: Near Field Versus Far Field I am having a difficult time answering the following question for a non-technical person. Hopefully, someone can put the answer into a language that a non-technical person can understand. We have a 400 MHz clock and are failing radiated emissions at 10 meters by 10 dB at 400 MHz. We bring the product back to our lab and start making modifications on the clock circuit and taking measurements with a near field probe. With these modifications and measuring with a near field probe, we realize a 10 dB reduction in emissions at 400 MHz. Why would we not see the same reduction when taking the product back to a 10 meter site? Your help is appreciated. Regards Joe Martin marti...@appliedbiosystems.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: Homologations: Hong Kong / China Central Office Telecom Equipment
Jeffrey, Suggest to visit below site for your required information. http://www.ofta.gov.hk/index_eng.html Regards, Raymond Li Dixons Asia Ltd. Collins, Jeffrey jcoll...@ciena.com on 14/09/2000 08:44:44 p Please respond to Collins, Jeffrey jcoll...@ciena.com To: emc-p...@ieee.org cc:(bcc: Raymond Li/DixonsNotes) Subject: Homologations: Hong Kong / China Central Office Telecom Equipment Group, Any experiences with getting Central Office Telecom equipment (ITE) into Hong Kong and China? CB Scheme to IEC 60950 should address product safety. What about EMC? Has the Great Wall Mark (China's version of CE Mark) been implemented? What about environmental management issues Who would be the equivalent to the RBOC's in Hong Kong and China??? Thanks in advance, Jeffrey Collins MTS, Principal Compliance Engineer Ciena Core Switching Division jcoll...@ciena.com www.ciena.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: Near Field Versus Far Field
Hi Joe. You asked for an explanation as to why the difference between the near and far field results. I think the replies so far have probably answered that question. I've tried here to give some help with the real problem of solving the excess emissions. From my own experience and discussions with colleagues, I've found you definitely need to do some (if not most) of the trouble-shooting while at the test site. Finding a problem then just returning to the lab to solve it usually leaves you with a lot of questions unanswered. That might not be much help this time but perhaps next time? The following is how I'd go about tackling the problem. I'm curious to see if there's anyone in the group who disagrees with my approach. As with any EMC problem, you've got to consider the source, the transmission medium and the victim. Obviously there's nothing you can change about the victim (the test antenna) but you should be able to narrow it down to work out the real source, and the means by which it is being radiated. For clues to the problem's cause to begin with I usually ask: (1) For the problem frequency, what's the most likely source? (2) For the problem frequency, what's the most likely source antenna? At 400MHz the wavelength is a bit under 1m (3x10^8 / 400x10^6 = 75cm) so any short cables (or at this frequency, maybe even long PCB track - like back-plane tracks?) that might make nice 1/2 wavelength or 1/4 wavelength dipole antennas would be the first I'd check out. Could also be a slot antenna effect in your enclosure - any seams or gaps in the box that are in this ball-park? Usually I'd try isolating the source by either disconnecting cables, turning off or unplugging cards, attenuating cable emissions with copious amounts of ferrite clamps etc and get the test engineer to do a spot check at the problem frequency as I tried eliminating each suspect. This is where the buckets of ferrite cable clamps, rolls of aluminium foil, shielding mesh and earthing straps come in to play. Here's where that near-field probe might come in handy too. This kind of troubleshooting though often requires a fairly intimate understanding of the way the equipment under test works so you can be confident about your assumptions and the conclusions you draw from the observed results. If the design engineer isn't actually at the test site, she/he should at least be accessible by phone to discuss the problems and make suggestions as to what to try. Using this technique, you can usually narrow it down fairly quickly to the source and antenna. If there's time, and its practical then I'd try some quick modifications to the problem circuit that's the source of the noise in order to get some reference of what changes cause what kind of reduction in the emission levels. Quite often though, you have to be aware that a change may solve the emission problem at the frequency you're working on, but result in the energy appearing elsewhere in the radiated spectrum causing the equipment to exceed the limit at some other frequency, especially if you've just modified the source antenna and not the signal causing the emission. Also note - although its difficult when you're rushing to get the problem fixed, it pays to make good records of what you change and what the results are - can help a lot later on. If you have the time at site to try a few different options (that are repeatable later), and get the highest 3 or 4 emission levels for each option at site, then if you can't find a solution you're happy with at the test site, it gives you a reference to work with back in the lab. For example, say that you found that: Design Change #1 resulted in 6dB reduction in the emission at 400MHz with other peaks (below the pass/fail limit) at 200MHz (3dB under), and 800MHz(8dB under) Design Change #2 resulted in 20dB reduction in the emission at 400MHz but caused the peak at 200MHz that went over the limit by 6dB with the peak at 800MHz reducing to 10dB under the limit. Design Change #3 resulted in 3dB reduction in the emission at 400MHz with other peaks (below the pass/fail limit) at 200MHz (9dB under), and 800MHz(7dB under) Then when you get back to the lab to try and find a good permanent fix, by repeating the changes you made at site, and comparing the emissions levels you observe for each in the lab with the results at the test site, you can get a reasonable feel to tell if your measurements in the lab are going to be indicative of what you'll see at site. If you have access to a spectrum analyser and an antenna that covers the frequency range you're interested in you can probably get a better feel for the effect of your changes than when using a near-field probe. If the emissions are high enough to fail the test, there's a good chance you can get a reasonable indication of the result of changes by comparing the emission results measured in someone's back yard(know anyone
RE: Near Field Versus Far Field
I might add that the BEST way to do this is to only change one thing at a time, then retest. It's hard to tell what single change of the multiple changes attempted actually did the change. Michael Sundstrom Nokia Mobile Phones, PCC EMC Technician cube 4E : 390B phone: 972-374-1462 mobile: 817-917-5021 michael.sundst...@nokia.com amateur call: KB5UKT -Original Message- From: EXT Peter Poulos [mailto:pet...@foxboro.com.au] Sent: Friday, September 15, 2000 1:38 AM To: marti...@appliedbiosystems.com; emc-p...@majordomo.ieee.org Subject: Re: Near Field Versus Far Field Hi Joe. You asked for an explanation as to why the difference between the near and far field results. I think the replies so far have probably answered that question. I've tried here to give some help with the real problem of solving the excess emissions. From my own experience and discussions with colleagues, I've found you definitely need to do some (if not most) of the trouble-shooting while at the test site. Finding a problem then just returning to the lab to solve it usually leaves you with a lot of questions unanswered. That might not be much help this time but perhaps next time? The following is how I'd go about tackling the problem. I'm curious to see if there's anyone in the group who disagrees with my approach. As with any EMC problem, you've got to consider the source, the transmission medium and the victim. Obviously there's nothing you can change about the victim (the test antenna) but you should be able to narrow it down to work out the real source, and the means by which it is being radiated. For clues to the problem's cause to begin with I usually ask: (1) For the problem frequency, what's the most likely source? (2) For the problem frequency, what's the most likely source antenna? At 400MHz the wavelength is a bit under 1m (3x10^8 / 400x10^6 = 75cm) so any short cables (or at this frequency, maybe even long PCB track - like back-plane tracks?) that might make nice 1/2 wavelength or 1/4 wavelength dipole antennas would be the first I'd check out. Could also be a slot antenna effect in your enclosure - any seams or gaps in the box that are in this ball-park? Usually I'd try isolating the source by either disconnecting cables, turning off or unplugging cards, attenuating cable emissions with copious amounts of ferrite clamps etc and get the test engineer to do a spot check at the problem frequency as I tried eliminating each suspect. This is where the buckets of ferrite cable clamps, rolls of aluminium foil, shielding mesh and earthing straps come in to play. Here's where that near-field probe might come in handy too. This kind of troubleshooting though often requires a fairly intimate understanding of the way the equipment under test works so you can be confident about your assumptions and the conclusions you draw from the observed results. If the design engineer isn't actually at the test site, she/he should at least be accessible by phone to discuss the problems and make suggestions as to what to try. Using this technique, you can usually narrow it down fairly quickly to the source and antenna. If there's time, and its practical then I'd try some quick modifications to the problem circuit that's the source of the noise in order to get some reference of what changes cause what kind of reduction in the emission levels. Quite often though, you have to be aware that a change may solve the emission problem at the frequency you're working on, but result in the energy appearing elsewhere in the radiated spectrum causing the equipment to exceed the limit at some other frequency, especially if you've just modified the source antenna and not the signal causing the emission. Also note - although its difficult when you're rushing to get the problem fixed, it pays to make good records of what you change and what the results are - can help a lot later on. If you have the time at site to try a few different options (that are repeatable later), and get the highest 3 or 4 emission levels for each option at site, then if you can't find a solution you're happy with at the test site, it gives you a reference to work with back in the lab. For example, say that you found that: Design Change #1 resulted in 6dB reduction in the emission at 400MHz with other peaks (below the pass/fail limit) at 200MHz (3dB under), and 800MHz(8dB under) Design Change #2 resulted in 20dB reduction in the emission at 400MHz but caused the peak at 200MHz that went over the limit by 6dB with the peak at 800MHz reducing to 10dB under the limit. Design Change #3 resulted in 3dB reduction in the emission at 400MHz with other peaks (below the pass/fail limit) at 200MHz (9dB under), and 800MHz(7dB under) Then when you get back to the lab to try and find a good permanent fix, by repeating the changes you made at site, and comparing the emissions levels you observe for each in the lab with the results
RE: PCB fuse trace
Ken, From my experience with UL, if a trace opens during a fault test, the first test you must pass is the hipot, then UL will jump the portion of the trace that opened and perform the same test. If the trace opens in another location the same process is repeated (I guess until there is no longer a trace to open or if another device fails and protects the unit). If some other device (unapproved) protects the unit, you will have to repeat the fault 3 times with the same result in order for it to be acceptable. If the trace opens up to the input, you may discover that you really should have designed in a protective device. Ed From: Matsuda, Ken matsu...@curtisinst.com Reply-To: Matsuda, Ken matsu...@curtisinst.com To: 'Jim Freeman' free...@broadcom.com,Peter Tarver ptar...@nortelnetworks.com CC: Matsuda, Ken matsu...@curtisinst.com, emc-p...@ieee.org Subject: RE: PCB fuse trace Date: Thu, 14 Sep 2000 17:09:07 -0400 Thank you all for responding to my inquiry thus far. Here is an update on my findings. I have since had the opportunity to discuss this issue with a few different NRTLs in regards to particular standards. The uniform concensus thus far from these agencies are that they test to standards, not necessary impose restirctions that are not in the standards. Thus many agencies have agreed that a fuse trace, although discouraged, can be used as a primary means of protection, unless specifically referenced not allowing such use. But once again, this comes down to the particular standard that you apply too. Some may require abnormal tests, etc... -Original Message- From: Jim Freeman [mailto:free...@broadcom.com] Sent: Thursday, September 14, 2000 11:38 AM To: Peter Tarver Cc: Matsuda, Ken; emc-p...@ieee.org Subject: Re: PCB fuse trace In all of this discussion, no one has mentioned the possibility of fire from blowing a PCB trace fuse. I know that there are flame retardants in the PCB material that protect to a certain flashpoint but to rely on that mechanism for fire prevention is a bit far fetched. From my limite experience with fuses, there is generally a large structure that is enclosed in sand to prevent a fire from spreading. Jim Freeman Peter Tarver wrote: My experience with safety agencies is they do not want to rely on traces opening to act as fuses and no standards have been developed, that I am aware of, to address this issue. Fuses certification gets involved in the metallic alloys used, to the fraction of a percent, the conductor size, additional construction features, such as heat sinking elements for time delay characteristics, tension loading for fast action, blah, blah, blah. Most of these issues are far too difficult to control for pwb traces, especially considering the etching processes don't lend themselves to the level of control necessary to be a reliable fuse of specific ratings. Additionally, the heat sinking from pwb layout of one product to another or varying copper thicknesses in a product line, adding or subtracting ground planes for emc, the variability of soldering processes and location/thermal capacity of components on the pwb make this seem far too cumbersome to want to work with. BTW, this is a very different world from repeated twice, same result single-fault testing, where a pwb trace opens. Regards, Peter L. Tarver, PE ptar...@nortelnetworks.com -Original Message- From: Matsuda, Ken [ mailto:matsu...@curtisinst.com mailto:matsu...@curtisinst.com ] Sent: Thursday, September 14, 2000 7:02 AM To: emc-p...@ieee.org Subject: PCB fuse trace I was wondering if anyone knew a standard for the US, Canada, and Europe that covers PCB board traces that can be used as fuses? Thanks for the help, Ken --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Share information about yourself, create your
RE: Near Field Versus Far Field
Hello Joe, Consider the following -- in the far field (3 or 10 meters), a plane wave is monitored. In the near field, using either commercial or lab built near-field probes, either E field or H field emissions will be monitored separately. The E, H components will be isolated. The emission may be identified with a probe, but the effective radiator (culprit antenna) for that emission might be missed. The above is an answer to the question. If you would like a real life experience describing the difference, read the example that follows. On a recent product we had a band of frequencies of non-compliant emissions that were somewhat polarity sensitive. We observed a particular signature of the emission (modulation on a pulse) at 3 meters using a bilog antenna. Using a direct contact E field probe, the pulse frequency showed up at high levels around the processor and DSP chip, but not with the signature. We were able to find a trace of the corresponding polarity that was suspect and had a similar signature, and at a lower level than we found around the processor and DSP chip. Looking at the schematic, we identified a reasonable fix. But that only helped part of the profile. We then sniffed with a non-contact magnetic loop probe and found another viable culprit. The fix implemented brought the product into compliance with reasonable margin. Neither fix by itself brought the product into compliance. Both were necessary, required a minimum amount of components and contributed to rationale source suppression. We did not introduce balloon squeezing, i.e., beat down an emission at one frequency and see it pop up at another frequency. This kind of isolation is more effective than monitoring the far field emission, hypothesizing the culprit antenna while analyzing the schematic. We have done it both ways. The near field approach takes a little more time to set up but saves time in the long run. Or maybe we were just lucky! Best regards, Don -- From: marti...@appliedbiosystems.com[SMTP:marti...@appliedbiosystems.com] Reply To: marti...@appliedbiosystems.com Sent: Thursday, September 14, 2000 1:07 PM To: emc-p...@majordomo.ieee.org Subject: Near Field Versus Far Field I am having a difficult time answering the following question for a non-technical person. Hopefully, someone can put the answer into a language that a non-technical person can understand. We have a 400 MHz clock and are failing radiated emissions at 10 meters by 10 dB at 400 MHz. We bring the product back to our lab and start making modifications on the clock circuit and taking measurements with a near field probe. With these modifications and measuring with a near field probe, we realize a 10 dB reduction in emissions at 400 MHz. Why would we not see the same reduction when taking the product back to a 10 meter site? Your help is appreciated. Regards Joe Martin marti...@appliedbiosystems.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re:RE: PCB fuse trace
Ken, I would suggest using caution in using a PCB trace as a fuse. The agencies typically test at what is perceived as worst case, which may not be the right thing to test a PCB trace fuse with. It will be very important to keep the power supply return as far away from the fuse as possible. The reason being that the PCB material could start to burn if the trace becomes hot instead of blowing. If it does and it is able to create a carbon path to ground, it will continue to burn. Rich Nute wrote an article years ago that was published in the PSTC news letter that covers how it burns. At the very least get a copy from Rich or someone who still has a copy, before you proceed . Jim Jim Bacher, Senior Engineer Paxar - Monarch e-mail:jim_bac...@monarch.com voice:1-937-865-2020 fax:1-937-865-2048 --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
RE: EN 61000-3-3
One could follow the guidelines in the standard but the alternatives are sometimes as costly as buying the test equipment that does this automatically. The alternatives are labor intensive except in the simplest of products. Look at the web site www.ergonomicsusa.com for test equipment. They also rent equipment for the occasional user. Dave George Unisys Corp. 2476 Swedesford Road Malvern, PA 19355 Tel: 1-610-648-3653 Fax: 1-610-695-4700 -Original Message- From: Brooks, Barbara [mailto:bbro...@hnt.wylelabs.com] Sent: Tuesday, September 12, 2000 10:10 AM To: EMC Post Cc: joe.ross...@avocent.com Subject: EN 61000-3-3 Does any one have any information regarding how you determine if equipment will not product significant voltage fluctuations or flicker with out performing the tests of EN 61000-3-3 per Paragraph 6.1? EN 61000-3-3 Paragraph 6.1 states Test shall not be made on equipment which is unlikely to product significant voltage fluctuations or flicker. Barbara Brooks Wyle Laboratories 7800 Highway 20 West Huntsville, AL 35807- (256) 837-4411 ext 595 (253) 721-0144 Fax bbro...@hnt.wylelabs.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: EMC/EMI Training
Hello Keith, I've been selling Tim Williams' books for a couple of years and have received no complaints. The newest one, published this year, is titled, EMC for Systems and Installations. Check it out at www.safetylink.com/bookshop.html where you will find a description of this book (and others). Regards, Art Michael Int'l Product Safety News A.E. Michael, Editor 166 Congdon St. East P.O. Box 1561 Middletown CT 06457 U.S.A. Phone : (860) 344-1651 Fax: (860) 346-9066 Email : i...@connix.com Website: http://www.safetylink.com ISSN : 1040-7529 - On Fri, 15 Sep 2000, Keith Zell wrote: What training classes and/or books would you recommend for the best practical EMI/EMC training from a systems approach? I am particularly interested in grounding/shielding issues and fixes. Any help would be appreciated. B. Keith Zell Electrical Design Engineer PMI Food Equipment Group Troy, OH 45374 (937) 332-3067 (ph) (937) 332-3007 (fax) zell...@pmifeg.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: EMC/EMI Training
Keith, My two favorite books are Noise Reduction Techniques in Electronic Systems by Henry Ott, and Controlling Radiated Emissions by Design by Michel Mardiguian Regards Joe Martin Product Safety/EMC Engineer Keith Zell zell...@pmifeg.com on 09/15/2000 07:25:31 AM Please respond to Keith Zell zell...@pmifeg.com To: emc-p...@ieee.org cc:(bcc: Joe P Martin/FOS/PEC) Subject: EMC/EMI Training What training classes and/or books would you recommend for the best practical EMI/EMC training from a systems approach? I am particularly interested in grounding/shielding issues and fixes. Any help would be appreciated. B. Keith Zell Electrical Design Engineer PMI Food Equipment Group Troy, OH 45374 (937) 332-3067 (ph) (937) 332-3007 (fax) zell...@pmifeg.com What training classes and/or books would you recommend for the best practical EMI/EMC training from a systems approach? I am particularly interested in grounding/shielding issues and fixes. Any help would be appreciated. B. Keith Zell Electrical Design Engineer PMI Food Equipment Group Troy, OH 45374 (937) 332-3067 (ph) (937) 332-3007 (fax) zell...@pmifeg.com
RE: Near Field Versus Far Field/Troubleshooting
I wanted to throw in an emissions trouble shooting technique that I saw Jon Curtis do one time when I was at his lab. I'd like to call it the Jon Curtis Wet Finger Test We had a signal failing at 200Mhz. We had narrowed the problem down to either the GPIB cable or the GPIB interface circuitboard connected to the GPIB cable. We were able to open up the unit and gain access to the GPIB board while it was running. Jon wet his finger and ran it over the pins of a few suspect IC's. When his finger touched one particular pin, the spectrum analyzer reading changed radically. It was a 40Mhz clock line. We reduced our emissions by cutting the run and putting a resistor in line with it. OK being a compliance guy, the lawyer in me is saying the following: 1. Please don't try this on AC or hazardous voltages (for obvious reasons). 2. Also, know your IC's. As you run your finger over some IC's, shorting adjacent pins may cause trouble. In our case it didn't. 3. Also, be careful of any hot IC's or heatsinks. 4. Wash your hands afterwards. (Lead's poisonous you know.) What I'm trying to say is: it's a neat technique and may be helpful, but I don't want someone to electrocute themselves, hurt their DUT or burn a finger trying it. Please use caution See ya's later Chris Maxwell, Design Engineer GN Nettest Optical Division 6 Rhoads Drive, Building 4 Utica, NY 13502 PH: 315-797-4449 FAX: 315-797-8024 EMAIL: chr...@gnlp.com -Original Message- From: michael.sundst...@nokia.com [SMTP:michael.sundst...@nokia.com] Sent: Friday, September 15, 2000 8:59 AM To: pet...@foxboro.com.au; marti...@appliedbiosystems.com; emc-p...@majordomo.ieee.org Subject: RE: Near Field Versus Far Field I might add that the BEST way to do this is to only change one thing at a time, then retest. It's hard to tell what single change of the multiple changes attempted actually did the change. Michael Sundstrom Nokia Mobile Phones, PCC EMC Technician cube 4E : 390B phone: 972-374-1462 mobile: 817-917-5021 michael.sundst...@nokia.com amateur call: KB5UKT -Original Message- From: EXT Peter Poulos [mailto:pet...@foxboro.com.au] Sent: Friday, September 15, 2000 1:38 AM To: marti...@appliedbiosystems.com; emc-p...@majordomo.ieee.org Subject: Re: Near Field Versus Far Field Hi Joe. You asked for an explanation as to why the difference between the near and far field results. I think the replies so far have probably answered that question. I've tried here to give some help with the real problem of solving the excess emissions. From my own experience and discussions with colleagues, I've found you definitely need to do some (if not most) of the trouble-shooting while at the test site. Finding a problem then just returning to the lab to solve it usually leaves you with a lot of questions unanswered. That might not be much help this time but perhaps next time? The following is how I'd go about tackling the problem. I'm curious to see if there's anyone in the group who disagrees with my approach. As with any EMC problem, you've got to consider the source, the transmission medium and the victim. Obviously there's nothing you can change about the victim (the test antenna) but you should be able to narrow it down to work out the real source, and the means by which it is being radiated. For clues to the problem's cause to begin with I usually ask: (1) For the problem frequency, what's the most likely source? (2) For the problem frequency, what's the most likely source antenna? At 400MHz the wavelength is a bit under 1m (3x10^8 / 400x10^6 = 75cm) so any short cables (or at this frequency, maybe even long PCB track - like back-plane tracks?) that might make nice 1/2 wavelength or 1/4 wavelength dipole antennas would be the first I'd check out. Could also be a slot antenna effect in your enclosure - any seams or gaps in the box that are in this ball-park? Usually I'd try isolating the source by either disconnecting cables, turning off or unplugging cards, attenuating cable emissions with copious amounts of ferrite clamps etc and get the test engineer to do a spot check at the problem frequency as I tried eliminating each suspect. This is where the buckets of ferrite cable clamps, rolls of aluminium foil, shielding mesh and earthing straps come in to play. Here's where that near-field probe might come in handy too. This kind of troubleshooting though often requires a fairly intimate understanding of the way the equipment under test works so you can be confident about your assumptions and the conclusions you draw from the observed results. If the design engineer isn't actually at the test site, she/he should at least be accessible by phone to discuss the problems and make suggestions as to what to try. Using this technique, you can usually narrow it down fairly quickly to the source and
Re: EMC/EMI Training
Clayton R. Paul, Introduction to Electromagnetic Compatibility, John Wiley and Sons, ISBN 0-471-54927-4. Henry W. Ott, Noise Reduction Techniques in Electronic Systems, John Wiley and Sons, ISBN 0-471-85068-3. - Original Message - From: Keith Zell To: emc-p...@ieee.org Sent: Friday, September 15, 2000 10:25 AM Subject: EMC/EMI Training What training classes and/or books would you recommend for the best practical EMI/EMC training from a systems approach? I am particularly interested in grounding/shielding issues and fixes. Any help would be appreciated. B. Keith Zell Electrical Design Engineer PMI Food Equipment Group Troy, OH 45374 (937) 332-3067 (ph) (937) 332-3007 (fax) zell...@pmifeg.com
synchronous bus clocks on PCI backplanes
Hi All, This is a question regarding systems which use CompactPCI bus architecture. On a cPCI backplane the PCI clock is routed to every slot on the backplane with up to 7 peripheral slots possible on a normal backplane. My question is this: With the cPCI specification calling out specific trace lengths for clock traces on both the backplane itself and on peripheral cards, have other people experienced any unique EMI problems in trying to meet the design constraints associated with this synchronous bus; especially where there are unpopulated slots on the backplane? Thanks in advance, Bill Fleury ***Artesyn Communication Products, LLC** Bill Fleury Email: bi...@artesyncp.com Compliance Engineer Phone: 608-831-5500 8310 Excelsior DriveFax: 608-831-8844 Madison, WI 53717 The difficult can be done immediately, the impossible takes a little longer (Army Corp of Engineers) *** Visit us at www.artesyn.com/cp ** Bill Fleury (E-mail).vcf attachment: Bill_Fleury_(E-mail).vcf
PCB fuse trace
Hi group, I am sure that Ken appreciates all the pointers, but no one is answering his question. He is asking for a reference to a standard that allows him to do this. If I knew one I would certainly tell him. Josh -Original Message- From: mr...@ix.netcom.com [mailto:mr...@ix.netcom.com] Sent: Friday, September 15, 2000 8:30 AM To: E Eszlari Cc: matsu...@curtisinst.com; free...@broadcom.com; ptar...@nortelnetworks.com; emc-p...@ieee.org Subject: Re: RE: PCB fuse trace Keep in mind the possibility of the trace shorting to dead metal parts before vaporizing creating a momentary high leakage current. Bob E Eszlari bosesaf...@hotmail.com wrote: Ken, From my experience with UL, if a trace opens during a fault test, the first test you must pass is the hipot, then UL will jump the portion of the trace that opened and perform the same test. If the trace opens in another location the same process is repeated (I guess until there is no longer a trace to open or if another device fails and protects the unit). If some other device (unapproved) protects the unit, you will have to repeat the fault 3 times with the same result in order for it to be acceptable. If the trace opens up to the input, you may discover that you really should have designed in a protective device. Ed From: Matsuda, Ken Reply-To: Matsuda, Ken To: 'Jim Freeman' ,Peter Tarver CC: Matsuda, Ken , emc-p...@ieee.org Subject: RE: PCB fuse trace Date: Thu, 14 Sep 2000 17:09:07 -0400 Thank you all for responding to my inquiry thus far. Here is an update on my findings. I have since had the opportunity to discuss this issue with a few different NRTLs in regards to particular standards. The uniform concensus thus far from these agencies are that they test to standards, not necessary impose restirctions that are not in the standards. Thus many agencies have agreed that a fuse trace, although discouraged, can be used as a primary means of protection, unless specifically referenced not allowing such use. But once again, this comes down to the particular standard that you apply too. Some may require abnormal tests, etc... -Original Message- From: Jim Freeman [mailto:free...@broadcom.com] Sent: Thursday, September 14, 2000 11:38 AM To: Peter Tarver Cc: Matsuda, Ken; emc-p...@ieee.org Subject: Re: PCB fuse trace In all of this discussion, no one has mentioned the possibility of fire from blowing a PCB trace fuse. I know that there are flame retardants in the PCB material that protect to a certain flashpoint but to rely on that mechanism for fire prevention is a bit far fetched. From my limite experience with fuses, there is generally a large structure that is enclosed in sand to prevent a fire from spreading. Jim Freeman Peter Tarver wrote: My experience with safety agencies is they do not want to rely on traces opening to act as fuses and no standards have been developed, that I am aware of, to address this issue. Fuses certification gets involved in the metallic alloys used, to the fraction of a percent, the conductor size, additional construction features, such as heat sinking elements for time delay characteristics, tension loading for fast action, blah, blah, blah. Most of these issues are far too difficult to control for pwb traces, especially considering the etching processes don't lend themselves to the level of control necessary to be a reliable fuse of specific ratings. Additionally, the heat sinking from pwb layout of one product to another or varying copper thicknesses in a product line, adding or subtracting ground planes for emc, the variability of soldering processes and location/thermal capacity of components on the pwb make this seem far too cumbersome to want to work with. BTW, this is a very different world from repeated twice, same result single-fault testing, where a pwb trace opens. Regards, Peter L. Tarver, PE ptar...@nortelnetworks.com -Original Message- From: Matsuda, Ken [ mailto:matsu...@curtisinst.com ] Sent: Thursday, September 14, 2000 7:02 AM To: emc-p...@ieee.org Subject: PCB fuse trace I was wondering if anyone knew a standard for the US, Canada, and Europe that covers PCB board traces that can be used as fuses? Thanks for the help, Ken --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send
EU Equivalent Standard
Group: Can anyone advise what the European equivalent standard to UL 1431, Personal Hygiene and Health Care Appliances is? The product I have been questioned about is a cosmetic device (non-medical) that temporarily reduces the appearance of cellulite using a vacuum process. Many thanks in advance to those that respond. Sincerely, Robert Loop Engineering Supervisor Wyle Laboratories Product Safety ph - (256) 837-4411 x313 fax- (256) 721-0144 e-mail: rl...@hnt.wylelabs.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: EMC/EMI Training
Hello to all, IMO, three of the most informative books from a practical intro approach into the world of EMC are (not in any particular order): 1. Henry W. Ott, Noise Reduction Techniques in Electronic Systems, John Wiley and Sons, ISBN 0-471-85068-3, 2. Mark Montrose, EMC and the Printed Circuit Board - Design, Theory and Layout Made Simple, IEEE Press, ISBN 0-7803-4703-X, and 3. Michel Mardiguian, Controlling Radiated Emissions by Design, Van Nostrand Reinhold, ISBN 0-442-00949-6. As for instruction, try Kimmel Gerke's (www.emiguru.com) EMI Made Simple seminars. The material covered is complete, can be customized and can be presented in-house. Note: To all in the group. This message was, and should not be contrued as, an advertisement for any of the entities identified above. I am just relaying my own opinion. I hope this helps. Best regards, Ron Pickard rpick...@hypercom.com - Original Message - From: Keith Zell To: emc-p...@ieee.org Sent: Friday, September 15, 2000 10:25 AM Subject: EMC/EMI Training What training classes and/or books would you recommend for the best practical EMI/EMC training from a systems approach? I am particularly interested in grounding/shielding issues and fixes. Any help would be appreciated. B. Keith Zell Electrical Design Engineer PMI Food Equipment Group Troy, OH 45374 (937) 332-3067 (ph) (937) 332-3007 (fax) zell...@pmifeg.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: PCB fuse trace
Hello all, In addition to all of the already mentioned reasons not to use a trace as a fuse, is that the fiberglass resin becomes conductive once it is molten, and a China syndrome meltdown can occur if the circuit energy is sufficient to maintain the molten state. Mike Harris/Teccom Co. -Original Message- From: Peter Tarver ptar...@nortelnetworks.com To: emc-p...@ieee.org emc-p...@ieee.org Date: Thursday, September 14, 2000 2:00 PM Subject: RE: PCB fuse trace Jim - Except for when a high breaking capacity fuse is needed, arc extinguishing fillers, like sand, are not generally necessary. I would also expect that such a fuse would not be in a primary circuit, where the US safety standard expects a fuse to see 10kA for miniature fuses. Even most of these fuses (again, in the US) don't use arc extinguishing fillers, but are simple glass tubes with metal ferrules (the 1 by 1-1/4 miniature fuses, and even several varieties of 5mm by 20mm fuses). The above is based on my experience testing fuses for about 4 years, during my tenure at UL. Regards, Peter L. Tarver, PE ptar...@nortelnetworks.com -Original Message- From: Jim Freeman In all of this discussion, no one has mentioned the possibility of fire from blowing a PCB trace fuse. I know that there are flame retardants in the PCB material that protect to a certain flashpoint but to rely on that mechanism for fire prevention is a bit far fetched. From my limite experience with fuses, there is generally a large structure that is enclosed in sand to prevent a fire from spreading. Jim Freeman Peter Tarver wrote: My experience with safety agencies is they do not want to rely on traces opening to act as fuses and no standards have been developed, that I am aware of, to address this issue. Fuses certification gets involved in the metallic alloys used, to the fraction of a percent, the conductor size, additional construction features, such as heat sinking elements for time delay characteristics, tension loading for fast action, blah, blah, blah. Most of these issues are far too difficult to control for pwb traces, especially considering the etching processes don't lend themselves to the level of control necessary to be a reliable fuse of specific ratings. Additionally, the heat sinking from pwb layout of one product to another or varying copper thicknesses in a product line, adding or subtracting ground planes for emc, the variability of soldering processes and location/thermal capacity of components on the pwb make this seem far too cumbersome to want to work with. BTW, this is a very different world from repeated twice, same result single-fault testing, where a pwb trace opens. Regards, Peter L. Tarver, PE ptar...@nortelnetworks.com -Original Message- From: Matsuda, Ken [mailto:matsu...@curtisinst.com] Sent: Thursday, September 14, 2000 7:02 AM To: emc-p...@ieee.org Subject: PCB fuse trace I was wondering if anyone knew a standard for the US, Canada, and Europe that covers PCB board traces that can be used as fuses? Thanks for the help, Ken
RE: PCB fuse trace
Doesn't it depend on the purpose of the fuse? If the circuitry is non-telco and voltages are 42V you have wide design latiitude. Even if the agencies do not care, you should characterize the performance under abnormal conditions. At least one company uses printed fuses on PC accessory cards to prevent runaway combustion (fires) when ceramic by-pass capacitors crack and short. The cards were recognized by well-known US and European safety agencies. Mains and telco have special IEC-950 rules and testing likely has poor ROI. Since the 'fuse' is not a recognized component, sufficient characterization may be a problem with most safety agencies. David Sterner Ademco, Syosset NY -Original Message- From: Joshua Wiseman [mailto:jwise...@printronix.com] Sent: Friday, September 15, 2000 2:42 PM To: Emc-Pstc (E-mail) Subject: PCB fuse trace Hi group, I am sure that Ken appreciates all the pointers, but no one is answering his question. He is asking for a reference to a standard that allows him to do this. If I knew one I would certainly tell him. Josh -Original Message- From: mr...@ix.netcom.com [ mailto:mr...@ix.netcom.com mailto:mr...@ix.netcom.com ] Sent: Friday, September 15, 2000 8:30 AM To: E Eszlari Cc: matsu...@curtisinst.com; free...@broadcom.com; ptar...@nortelnetworks.com; emc-p...@ieee.org Subject: Re: RE: PCB fuse trace Keep in mind the possibility of the trace shorting to dead metal parts before vaporizing creating a momentary high leakage current. Bob E Eszlari bosesaf...@hotmail.com wrote: Ken, From my experience with UL, if a trace opens during a fault test, the first test you must pass is the hipot, then UL will jump the portion of the trace that opened and perform the same test. If the trace opens in another location the same process is repeated (I guess until there is no longer a trace to open or if another device fails and protects the unit). If some other device (unapproved) protects the unit, you will have to repeat the fault 3 times with the same result in order for it to be acceptable. If the trace opens up to the input, you may discover that you really should have designed in a protective device. Ed From: Matsuda, Ken Reply-To: Matsuda, Ken To: 'Jim Freeman' ,Peter Tarver CC: Matsuda, Ken , emc-p...@ieee.org Subject: RE: PCB fuse trace Date: Thu, 14 Sep 2000 17:09:07 -0400 Thank you all for responding to my inquiry thus far. Here is an update on my findings. I have since had the opportunity to discuss this issue with a few different NRTLs in regards to particular standards. The uniform concensus thus far from these agencies are that they test to standards, not necessary impose restirctions that are not in the standards. Thus many agencies have agreed that a fuse trace, although discouraged, can be used as a primary means of protection, unless specifically referenced not allowing such use. But once again, this comes down to the particular standard that you apply too. Some may require abnormal tests, etc... -Original Message- From: Jim Freeman [ mailto:free...@broadcom.com mailto:free...@broadcom.com ] Sent: Thursday, September 14, 2000 11:38 AM To: Peter Tarver Cc: Matsuda, Ken; emc-p...@ieee.org Subject: Re: PCB fuse trace In all of this discussion, no one has mentioned the possibility of fire from blowing a PCB trace fuse. I know that there are flame retardants in the PCB material that protect to a certain flashpoint but to rely on that mechanism for fire prevention is a bit far fetched. From my limite experience with fuses, there is generally a large structure that is enclosed in sand to prevent a fire from spreading. Jim Freeman Peter Tarver wrote: My experience with safety agencies is they do not want to rely on traces opening to act as fuses and no standards have been developed, that I am aware of, to address this issue. Fuses certification gets involved in the metallic alloys used, to the fraction of a percent, the conductor size, additional construction features, such as heat sinking elements for time delay characteristics, tension loading for fast action, blah, blah, blah. Most of these issues are far too difficult to control for pwb traces, especially considering the etching processes don't lend themselves to the level of control necessary to be a reliable fuse of specific ratings. Additionally, the heat sinking from pwb layout of one product to another or varying copper thicknesses in a product line, adding or subtracting ground planes for emc, the variability of soldering processes and location/thermal capacity of components on the pwb make this seem far too cumbersome to want to work with. BTW, this is a very different world from repeated twice, same result single-fault testing, where a pwb trace opens. Regards, Peter L. Tarver, PE ptar...@nortelnetworks.com -Original Message-
