RE: Chip noise halts Intel 820 motherboard
In defense of Intel (please wait a moment while I don my full body armor), this is probably one of those things that only occurs on alternate rainy Tuesdays when using certain specific brands of SDRAM. Scott Lacey -Original Message- From: David Spencer [SMTP:dspen...@oresis.com] Sent: Thursday, May 11, 2000 12:52 PM To: EMC-PSTC Subject:RE: Chip noise halts Intel 820 motherboard Filed under Things that make you go hmmm. Was this a major Product Verification screw up? Or a carefully crafted marketing plan to increase demand for RDRAM? Have a Great Day, Dave Spencer Oresis Communications -Original Message- From: Paul J Smith [mailto:paul_j_sm...@notes.teradyne.com] Sent: Thursday, May 11, 2000 7:21 AM To: Barry Ma Cc: EMC-PSTC Subject: Re: Chip noise halts Intel 820 motherboard Barry, Thanks for the heads-up. Article was also published by AP in today's Boston Globe. The following excerpt is from the site you noted Regards, Paul J. Smith Teradyne, Boston Chip maker will replace motherboards using its 820 chip set due to noise caused by simultaneous switching of signals. Intel Corp. has acknowledged another setback for PCs using its 820 chip set. The company announced Wednesday morning that it will replace motherboards using its 820 chip set that are exhibiting symptoms of a problem with a related component -- called a memory translator hub, or MTH -- with synchronous dynamic RAM (SDRAM). While the hub is not part of the 820 itself, it is required on a motherboard that uses SDRAM. It enables the chip set, which was designed to work with Rambus dynamic RAM (RDRAM), to use less expensive, more readily available SDRAM. We have found that some systems ... may be sensitive to system board noise, an Intel spokesman said. Hangs and reboots The MTH problem, which manifests itself by system hangs and intermittent system reboots, is due to noise caused by simultaneous switching of signals on the MTH buses, Intel officials said. Intel is working with PC and motherboard makers to notify computer users of the problem and to offer a replacement motherboard. Intel plans to replace all the 820 motherboards with SDRAM support that it sold directly to customers with an Intel 820 chip set motherboard with RDRAM memory. Computer users who believe they are affected should contact their manufacturers, or they can check Intel's Web site, where they can download the MTH ID Utility to test for the presence of the hub. The MTH support site also includes additional information on the problems. We believe less than 1 million boards with the MTH have been shipped to customers, an Intel spokesman said. However, since we have determined no root cause on this issue, we have decided to offer a replacement. Barry Ma barry...@altavista.com on 05/10/2000 07:12:33 PM Please respond to Barry Ma barry...@altavista.com To: EMC-PSTC emc-p...@ieee.org cc:(bcc: Paul J Smith/Bos/Teradyne) Subject: Chip noise halts Intel 820 motherboard http://dailynews.yahoo.com/h/zd/2510/tc/chip_noise_halts_intel_820_produ ction_1.html INTEL will replace motherboards using its 820 chip set due to noise caused by simultaneous switching of signals. Can anybody be more specific or just make a speculation by using EMC language? Another question is irrelevant to EMC. I am wondering why it took so long - five months from field failure report to recreating the problem inside INTEL? See quotation below: First noted in November Intel began shipping the MTH last November. The problem was brought to light by an Intel customer who observed the problem Intel followed up on the report and observed the problem in its own tests earlier this month. Barry Ma b...@anritsu.com ___ Why pay when you don't have to? Get AltaVista Free Internet
RE: Millivolt drop tests
Mark, If such a table exists, it was probably generated by one of the power companies. If you can not obtain the information, your best bet would be to measure several examples of each type of properly prepared joint. Measuring new, clean, carefully torqued joints should give you a reasonable idea of what the millivolt drop should be for each size/type. You can then decide how much percentage increase is acceptable for aging. Any joint over that limit in the field will need to be serviced. Scott Lacey -Original Message- From: m...@cjbdev.demon.co.uk [SMTP:m...@cjbdev.demon.co.uk] Sent: Friday, May 05, 2000 8:32 AM To: emc-p...@ieee.org Subject:Millivolt drop tests Dear All, As part of our production safety tests, we check the millivolt drop across a connection in a 300A dc supply to a cell stack. In the past, we have only done that to one of the connections, and our maximum allowed limit for the drop has been based on results we've had in the past plus a bit of lee-way. However, because of experience of our equipment in the field, we feel we should test all the connections in the 300A line rather than just the risky one. But I have no previous results to go on for all the different types of connection. I was told that there is a table somewhere of current/material/cross- sectional-area/tightening-torque/temperature etc etc against mV drop. Can anyone point me in the right direction, as I have exhausted my Standards, text books and company library! All pointers very gratefully received. Regards, Mark -- Mark Hone Wellman CJB Limited Email: m...@cjbdev.demon.co.uk Airport Service Road Tel: +44 (0)2392 629239 (Direct) Portsmouth, HampshireTel: +44 (0)2392 664911 PO3 5PG, ENGLAND Fax: +44 (0)2392 697864 --- 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: Mains Color Codes
Robert, I have always found the European color codes (brown/light blue/green w/yellow) to be best for dual market use. UL and CSA seem to have no problem with the use of these. You will need to provide some kind of legend plate or tag explaining the color codes, as many U.S. electricians are still not familiar with these. Scott Lacey -Original Message- From: Mavis, Robert [SMTP:rma...@pelco.com] Sent: Tuesday, April 04, 2000 5:33 PM To: emc-p...@ieee.org Subject:Mains Color Codes I know this was kicked around a while back but here we go again. What are the allowable color codes for pigtails that come from a permanently connected apparatus to be connected to mains for US and Europe? Is there a color code that is allowable for both? Thanks in advance for any help.. Robert L. Mavis Agency Compliance Coordinator Engineering Department, Compliance Engineering Group Pelco 300 W. Pontiac Way Clovis, CA 93612 Phone: (559) 292-1981 x2309 Toll Free: (800) 292-1981 x2309 Fax:(559) 291-3775 email: rma...@pelco.com URL:http://www.pelco.com http://www.pelco.com - Note: If you are not the intended recipient of this e-mail, contact administra...@pelco.com or call (559) 292-1981. Information contained may be confidential. Dissemination, distribution or copying of this e-mail is prohibited if you are not the intended recipient. --- 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: Mars Lander EMC problem?
Barry, Insufficient testing. They have been able to duplicate the problem in the lab, using another Mars Lander. The problem occurs some percentage of the time. Other times it does not. Scott -Original Message- From: b...@anritsu.com [SMTP:b...@anritsu.com] Sent: Thursday, March 30, 2000 7:05 PM To: Lacey,Scott; Tony J. O'Hara Cc: emc-p...@majordomo.ieee.org Subject:RE: Mars Lander EMC problem? Scott and Tony, That means the sensor was unable to tell the leg jolt from the landing shock. Did the NASA report explain why the sensor couldn't implement its function properly? Was it another design mistake omitting transition unit of propelling force from Pound to Kilogram? Barry Ma b...@anritsu.com -- Original Text -- From: Tony J. O'Hara tonyoh...@compuserve.com, on 3/30/00 11:41 AM: Tony, I don't think it was actually EMC. The report I saw on CNN said the legs opened with a jolt, fooling the sensors which were supposed to cut the retro rockets when they detected the shock of landing. Scott Lacey It looks like Scott Lacey is right, thank you! I made the assumption that spurious signal was electrically generated. It appears it was mechanically or magnetically generated! Is a Hall effect sensor microphonic? Well, I guess another lesson for me not to jump to conclusions before all the data is available! Tony Colorado Below is an excerpt from the complete NASA report. Premature shutdown of descent engines. PLAUSIBLE. A magnetic sensor is provided in each of the three landing legs to sense touchdown when the lander contacts the surface, initiating the shutdown of the descent engines. Data from MPL engineering development unit deployment tests, MPL flight unit deployment tests, and Mars 2001 deployment tests showed that a spurious touchdown indication occurs in the Hall Effect touchdown sensor during landing leg deployment (while the lander is connected to the parachute). The software logic accepts this transient signal as a valid touchdown event if it persists for two consecutive readings of the sensor. The tests showed that most of the transient signals at leg deployment are indeed long enough to be accepted as valid events, therefore, it is almost a certainty that at least one of the three would have generated a spurious touchdown indication that the software accepted as valid. The software - intended to ignore touchdown indications prior to the enabling of the touchdown sensing logic - was not properly implemented, and the spurious touchdown indication was retained. The touchdown sensing logic is enabled at 40 meters altitude, and the software would have issued a descent engine thrust termination at this time in response to a (spurious) touchdown indication. MOST PROBABLE CAUSE OF LOSS OF MISSION --- 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: Fires from Electric Fans
Mr. Wiederhold, About a year and a half ago, I installed a whole-house fan for a relative. The unit was clearly labeled inspect and lubricate annually. In addition, there was a warning marked on the motor end bell about not attempting to defeat the thermal cutout . Most locked rotor situations with fans occur from a lubrication failure. I have actually seen people try to wedge the thermal cutout reset button to prevent operation while troubleshooting. Not a safe practice at all. Scott Lacey Test engineer -Original Message- From: rbus...@es.com [SMTP:rbus...@es.com] Sent: Thursday, March 30, 2000 10:30 AM To: emc-p...@ieee.org Subject:Fires from Electric Fans Posted on behalf of Mr. Wiederhold... -Original Message- From: eric wiederhold [mailto:ecwiederh...@hotmail.com] mailto:[mailto:ecwiederh...@hotmail.com] Sent: Thursday, March 30, 2000 8:22 AM To: rbus...@es.com mailto:rbus...@es.com Subject:Fires from Electric Fans Mr. Busche, I am assisting others in doing research on the potential for a fractional horsepower electric motor to catch fire after a locked rotor situation occurs. In the course of my internet research I came across the Virtual Conference Hall live compliance talk that occured in early 1996, the web address being (http://www.rcic.com/cnf/emc-pstc/1996/list401.htm) http://www.rcic.com/cnf/emc-pstc/1996/list401.htm) . Some of the things posed in that talk were of interest and in line with the research being performed. In general, we have a situation in which a fractional horsepower electric motor was the driving force in a powered attic ventilator that was itself manufactured in the early 1980's. The PAV was installed within a residential structure for a number of years, approximately 13-15. We believe that a locked rotor situation occured, caused the motor to overheat, (during which time the thermal protective device was either bypassed or was otherwise caused to fail), thus causing components within the motor and PAV to achieve a state that ultimately began the fire. The fire itself was contained to the attic area of the residence in question but,unfortunately, serious burn injuries were inflicted upon at least one individual as a result of this fire scenario. I would like to exchange with you further on the subject of the situation, if you would be so kind. I am looking into any possible leads that could help in our understanding of the possibilities. Any specific knowledge of a substantially similar sitation would be of use. If this in not something that you can do but you know of another or others that could share advice, please feel free to pass that information along also. It would be appreciated if you would respond to this message. My name is Eric. Thank you for your time Mr. Busche. __ Get Your Private, Free Email at http://www.hotmail.com http://www.hotmail.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: modest proposal
Muriel, As you are one who has studied Esperanto, I wonder if you would be kind enough to list the Esperanto equivalents of the following words in English: Freedom Liberty rightsprotesttyranny justice property privacy This is not simply curiosity, as I was unable to find these in any Internet Esperanto dictionary. I am very aware of the warning given by Eric Blair (writing as George Orwell) to be cautious about adopting any language which does not contain words for such concepts. Scott Lacey -Original Message- From: Muriel Bittencourt de Liz [SMTP:mur...@grucad.ufsc.br] Sent: Monday, March 27, 2000 12:25 PM To: EMC-PSTC List Cc: Lou Gnecco Subject:Re: modest proposal Group, I think this discussion of language is very important. Why? I'll speak for myself... During the last centuries/years, most of the third-world or developing countries (as you prefer) has adopted the idea of buying technologies instead of developing its own. Together with that, has come the imposing of the product's manufacturer language, that is the english, german, etc... As you can see, we don't use english because it is simple or easy to write/talk. We use it because most of the industrial world has adopted it as a universal language. Lou wrote: I certainly agree that the world does not need another artificial language like esperanto. I'm studying esperanto for some time, and I don't think esperanto is artificial at all! Esperanto was made to be easy for people from all nations. It's made of pieces from various languages (most radicals resemble latim language, the grammar is very similar to english, because of its simplicity). The original purpose of the esperanto language is to be a nation-free language. A language that someone learns because someone wants to talk with people from other nations, without any prejudice of race, language or faith. We are in entering the third millenium. I think it's time to begin thinking/acting different. Why couldn't we all talk a language that everybody has to learn, instead of only the non-english countries? It can be esperanto, universal language, etc... Well, all of these may seem only dreams from a brazilian engineer... but I think that's the way we create our world! Best Regards, Saudacoes, Salutojn! Muriel --- 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 - Declaration of Incorporation?
Ray, The answer depends on whether your compressor is a component or a finished product. Component = yes, product = no way. Scott Lacey -Original Message- From: Russell, Ray [SMTP:ray_russ...@gastmfg.com] Sent: Friday, March 24, 2000 10:14 AM To: 'IEEE PSTC' Subject:EMC - Declaration of Incorporation? Greetings, We sell an air compressor with a DC motor. This motor requires a capacitor across the DC supply lines to meet the EMC requirements. Of course management does not want to supply the capacitor, they want to describe it in the documentation, and add a note on the Declaration of Conformity that a capacitor is required. Is this acceptable for European customers? In that scenario, I would like to issue a Declaration of Incorporation, but after reviewing the directives, I can only find a reference to the Declaration of Incorporation in the Machinery Directive. Can this be used for the other directives? Thank you once again for your assistance, Ray Russell Regulatory Compliance Engineer --- 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: The wisdom behind all these standards
Martin, While I may disagree with some of the technical content of various standards (I think they need to add more details to accommodate smaller, more distributed systems), I heartily agree with the need for them. The immunity tests in particular represent real-world threats to equipment, and a lot of electronics out there are only marginally compliant, in spite of the approvals marked on the case. I've had several instances where third party devices failed permanently when used as part of setups for immunity tests. They probably passed testing only in certain ideal configurations that don't represent actual field installations. Scott Lacey -Original Message- From: Martin Rowe (TMW) [SMTP:m.r...@ieee.org] Sent: Friday, March 24, 2000 9:54 AM To: emc-p...@majordomo.ieee.org Subject:The wisdom behind all these standrads I've been reading messages from this list for several months, and I see many questions about how to comply with the long list of EMC standards. Yet, I can't recall anyone ever questioning the appropriateness of any standard. That is, should the standand add value to a product or to those who use it? Is it that the EMC engineer's place is not to question the wisdom of a standard's value, but simply to make products with those standards, whether or not we agree with the intent of those standards? That's not to say that these regulations are bad. Maybe they're good because they make the world a better place for those who use electronic products. Just wondering. /\ | Martin Rowe | / \ | Senior Technical Editor | /\ /\ | Test Measurement World | / \/ \/\ | voice 617-558-4426 |/\ /\ / \/ | fax 617-928-4426 | \/ \/ | e-mail m.r...@ieee.org | \ / | http://www.tmworld.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: Ambient Cancellation Device for OATS
Exactly. Scott Lacey -Original Message- From: Brumbaugh, David [SMTP:david.brumba...@pss.boeing.com] Sent: Thursday, March 23, 2000 11:19 AM To: emc-p...@majordomo.ieee.org Subject:RE: Ambient Cancellation Device for OATS I would like to add that one must be careful when it comes to using such a system. I apologize if this has been pointed out already, but it can't be emphasized enough. When using a system like this, you take the risk that the ambient environment will mask significant emissions from the EUT. You may never see these emissions under such conditions, and it will bite you later. I am particularly concerned when I hear this being touted as a panacea for testing in traditionally noisy environments, such as development labs. Be careful folks. My 2 cents. DB -- From: Price, Ed[SMTP:ed.pr...@cubic.com] Reply To: Price, Ed Sent: Thursday, March 23, 2000 9:01 AM To: 'Doug'; emc-p...@majordomo.ieee.org Subject: RE: Ambient Cancellation Device for OATS Doug: As I understand the process, there isn't actually cancellation AT the OATS. They have a monitor antenna nearby, but relatively far from the EUT on the OATS. A real EUT signal should fall off considerably by the time it reaches the monitor antenna, but an ambient emission will be relatively constant at the monitor and measurement antennas. All you have to do is sample the ambient, invert it, and sum it with the measurement antenna voltage. This should delete the ambient from the measurement data. (Easy to say! All you need is enough computing power and sufficiently capable processing algorithms.) The cancellation takes place as a data operation within the Cassper hardware (or it's controlling computer), and not as an energy cancellation of the propagating fields actually on the OATS site. And yes, I would also like to know more about how Cassper manages to do this. But, I also realize they can't give away their trade secrets either. Ed :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military Avionics EMC Services Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) -Original Message- From: Doug [SMTP:dmck...@gte.net] Sent: Wednesday, March 22, 2000 11:38 PM To: emc-p...@majordomo.ieee.org Subject:Re: Ambient Cancellation Device for OATS Perhaps it's because I've never understood ... How exactly does one do ambient cancellation at an OATS? --- 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: Sharp edges
To the group, After monitoring the discussion for a while, I thought that I would share my experiences. As a person who bears scars from encounters with sharp edges inside equipment, I can state with certainty that outside CORNERS are by far the worst offenders. Knocking off these corners at 45 degrees will eliminate a large percentage of cut hazards, especially on small brackets. Most of the remaining problems with edges will be caused by burrs from manufacturing problems. Properly adjusted and sharpened punches and dies will not leave large burrs. A punched piece of metal will have smooth edges on one side and a sharper edge on the other. This is a normal result of the process. The sharper edge is usually only capable of causing superficial scratches on skin. Metal alloys that tend to develop larger burrs are generally put through a surface sanding process after being punched. A good sheet metal vendor can help a great deal. As for testing edge sharpness, women's stockings (and pantyhose) are often ruined by snags. Some brands are more susceptible than others. A piece of this material stretched over cardboard, with thin foam or felt padding between, would make a good tester. Scott Lacey --- 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: Dithered clocks and EMC - BEWARE
Paolo, Thank you for the information. I suspect that you are correct as to the critical nature of the frequency modulation method. The design engineer picked the device, probably as the cheapest vendor. The device did not behave as I expected, based on some Internet research of dithered clock technology. We were very pressed for time, but I hope someday to spend some more looking at this technology. Perhaps my experience explains the digital TV set interference, since all such devices are obviously not the same. Scott Lacey -Original Message- From: paolo.ronc...@compuprint.it [SMTP:paolo.ronc...@compuprint.it] Sent: Monday, March 20, 2000 5:21 AM To: emc-p...@ieee.org Subject:RE: Dithered clocks and EMC - BEWARE I have a very succesfull experience with SSCG (Spread Spectrum Clock Generation) that is a patented technology used to intentionally spread the energy of oscillators and clock signals and any signal derived from the clock. I am sure Keith Hardin knows it first-hand because he is one of the developers ! We have been using an SSCG chip since 1995 on most of the electronics of our printers - most of them class B devices, with oscillator frequencies in the range 24 - 32 MHz. We even managed to get significant cost reductions by switching from 4-layer to 2-layer boards and still passing CISPR22 and FCC class B limits for radiated emissions. One point that seems not to have come up in this discussion is the kind of dithering we are talking about. In SSCG the main clock frequency is modulated, but just ANY frequency modulation is not enough ! Key is the wave-shape of the modulating function, and that is the crucial point in the SSCG patent (Keith, correct me if I'm wrong). The trick is to maximize the rate of change of the function representing the frequency modulation, so that the oscillator spends the minimum time on any given frequency within the modulating range, thus avoiding additional peaks in the emission spectrum. The modulating function in the SSCG technique does just that. This is best explained in the first (to my knowledge) publication on the subject (here, too, Keith knows much more !!) : K.B.Hardin, J.T.Fessler, D.R.Bush (Lexmark Intl.): Spread Spectrum Clock Generation for the Reduction of Radiated Emissions - 1994 IEEE Intl. Symposium on EMC, August 1994 Chicago (Symposium Record page 227) I suspect an explanation to Scott's problem may be that he didn't use the SSCG technique but another form of dithering that was not controlled in such a way as to get the flat frequency distribution that you get with SSCG. Also the amount of frequency deviation can be important. The attenuation you get in quasi-peak (QP) readings is dependent on that. I hope Scott can give us more details. As to the problems with digital TV, I honestly don't have any knowledge about that, but I remember the same inventors of SSCG did a study on interference potential of this technique : K.B.Hardin, J.T.Fessler, D.R.Bush (Lexmark Intl.): A Study of the Interference Potential of Spread Spectrum Clock Generation Techniques - 1995 IEEE Intl. Symposium on EMC Atlanta ( Symposium Record page 624). Hope this helps. Paolo Roncone Compuprint s.p.a. - Italy --- 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 mailto: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 mailto:jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org mailto:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org mailto: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: Dithered clocks and EMC - BEWARE
Robert, and the group, Although I have only limited experience (1 instance) with dithered clocks, I thought that I might share that experience with the group. I had a product that was failing radiated emissions at one particular frequency with a vertical antenna orientation. I tracked the problem down to a particular cable and circuit card. Use of a near field probe identified the oscillator package as the source of the emissions (the second harmonic). The device was located near the card edge, insufficient decoupling, etc. All the textbook layout errors. A check of the oscillator specifications showed that it was a standard TTL device with a fanout of 10 inputs. I had already found some fixes that would reduce emissions, clamp-on ferrites, additional shielding, etc., but thought it made more sense to reduce the emissions at the source. I suggested to the design engineer that a low-power TTL oscillator, with a fanout of 2 inputs, would reduce currents through the offending etches. Someone else suggested a dithered clock device instead. When we tested the dithered clock, emissions were actually worse. We had simply spread the problem over a wider spectrum. I have heard some success stories for these devices, but results in this case were disappointing. I still think a lot depends on the layout. I strongly suspect that real-world disruption to nearby devices is generally going to be worse, since the idea behind these devices is to fool quasi-peak measurements in order to pass. Caveat Emptor! Scott Lacey -Original Message- From: Robert Macy [SMTP:m...@california.com] Sent: Friday, March 17, 2000 9:38 AM To: emc-p...@ieee.org Subject:Fw: Dithered clocks and EMC - BEWARE Of interest, so I forward this to the group: - Robert - Robert A. Macy, PEm...@california.com 408 286 3985 fx 408 297 9121 AJM International Electronics Consultants 619 North First St, San Jose, CA 95112 -Original Message- From: John Woodgate j...@jmwa.demon.co.uk Newsgroups: sci.engr.electrical.compliance,sci.electronics.design Date: Tuesday, March 14, 2000 11:55 PM Subject: Dithered clocks and EMC - BEWARE About a year ago we had a thread on this subject, concluding that some research was needed to see whether dithered clocks were better or worse in terms of conforming to EMC requirements. I learned very recently that some reliable but as-yet unpublished research has found that digital TV receivers are some 40 dB (!!) more sensitive to dithered clock emissions than to unmodulated carriers. This is likely to lead to changes in EMC limits within maybe as little as three years, since the authorities certainly don't want to be deluged with complaints of interference from people who have just opted for digital TV. So, if you are thinking of using a dithered clock, think again! -- Regards, John Woodgate, OOO - Own Opinions Only. Phone +44 (0)1268 747839 Fax +44 (0)1268 777124. http://www.jmwa.demon.co.uk I wanted to make a fully-automated nuclear-powered trawler, but it went into spontaneous fishing. --- 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: broad band EM noise
Giuseppe, First, a question. What ill effects (to him or to household appliances) are being caused by this EM noise? Scott Lacey -Original Message- From: Rossi Giuseppe [SMTP:g.ro...@crf.it] Sent: Friday, March 10, 2000 10:19 AM To: 'emc-pstc' Subject:broad band EM noise Dear collegue I've got a question to which I'm not able to responde: A friend of mine is complaining about the EM radiated (not conducted) noise coming from a electrical generation power plant ( I do not know the exact translation , hope that is anyway clear) He told me that the phenomena is particulary annoying in case of dry weather and that there is no noise in case of rain or fog. Could you give me any hint or point me toward something to read ? Thank you Giuseppe Rossi --- 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: Disconnect Device
Richard, Readily accessible means not obstructed by furniture or equipment. The shutoff will be wall mounted, in a visible location, at a height where persons of short stature can reach it, but not so low as to require crouching to reach it. Local codes may specify a height range. It should also have padlock holes so that lockout/tagout procedures may be employed for maintenance. Scott Lacey -Original Message- From: owner-emc-p...@ieee.org mailto:owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org] mailto:[mailto:owner-emc-p...@ieee.org] On Behalf Of wo...@sensormatic.com mailto:wo...@sensormatic.com Sent: Thursday, March 09, 2000 5:08 PM To: emc-p...@majordomo.ieee.org mailto:emc-p...@majordomo.ieee.org Subject: Disconnect Device Clause 1.7.2 of IEC 60950 and its clones requires the installation instruction to state that permanently connected equipment must have a readily accessible disconnect device incorporated in the fixed wiring if the equipment does not have a disconnect device. What is the criteria for assessing if the disconnect device is readily accessible? Richard Woods --- 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 Test Conditions
Derek, The points you make are extremely valid. Product testing should not be merely a paper chase, with a certificate as the only goal. I agree that if your product always gets bolted to a large metal structure, it should be tested in a simulated condition. However, and I am guessing here, if the structure is outdoors and painted, ground bonding through the structure may be poor in an actual installation. I guess it depends on what you are trying to accomplish. If the product will not pass without the metal structure, I would be highly skeptical of results obtained by the simulation. If, on the other hand, you are trying to simulate the worst case, I say press your case with the test lab. It has been my experience that problems experienced in testing, especially immunity, ALWAYS show up sooner or later in the field. That is why we try to bias tests towards failure. Scott Lacey -Original Message- From: lfresea...@aol.com [SMTP:lfresea...@aol.com] Sent: Tuesday, March 07, 2000 10:27 AM To: emc-p...@ieee.org Subject:EMC Test Conditions Folks, the testing of a product at a MAJOR Compliance lab has me concerned. I have two main concerns, they are: 1) The test item is designed to be bolted to a large metallic structure which cannot be part of my set-up, it costs way to much ( $2,000,000 each ). So I have a fixture, which mounts all the components as they would be mounted, using wiring as it would be wired etc. etc. etc. Because this fixture is only about a cubic metre, the lab is telling me I should test as table top equipment. I don't think this is correct. IMHP, table top equipment is meant to be EUTs like PC, printers, coffee makers, TVs etc. In most cases, the location in which they reside has very little metal in the proximity. OTOH, control systems like ours, are almost always fastened to metal objects. It is important to have this metal, or a simulation of it present, because I've found that otherwise, there is little correlation to the final installation. I also feel strongly that lifting this metal structure 80 cm off the ground plane is a stupid thing to do. So, my opinion is that there needs to be a third testing consideration added to table top and floor mounted equipment, that of simulated installation testing. OK, so this would require additional work. But if this is not considered, then results from all these system will vary dramatically. We worry at great length about the setup for table top equipment, and floor equipment. But if systems don't fit in this category, it's open season! 2) Since my device can be installed almost anywhere, it is supplied with a 3 foot length of flying lead. The intent is for final customers to extend this cable as needed. Here the lab tells me I'm OK testing with just 3 feet of lead My product standard is EN 61326, which allows me if my cables are under 10' in length, to blow away FTB and CI testing. This is ludicrous! I know now how some of my competitors can claim EMC compliance when they fail in my lab. I feel very strongly about issue 1, enough that I would offer to draft guidelines to present to whoever makes the rules. On issue 2, there has to be some education, at the moment the playing field is not level. I do not want to play the same games as others, because I feel the EMC protection we incorporate is really needed. Anyone got any constructive comments? Derek Walton --- 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
FW: Product Safety Certification School
Forwarded for John Lindstrom: -Original Message- From: Linstrom, John (IndSys, GEFanuc, CDI) [SMTP:john.linst...@cdynamics.com] mailto:[SMTP:john.linst...@cdynamics.com] Sent: Monday, March 06, 2000 12:48 PM To: 'Lacey,Scott' Subject:RE: Product Safety Certification School I have an old copy of a Design Data Digest , based on Mil-Std-1472, that quantifies all sorts of human capabilities - reach, height, seating positions, knobs and rotations, etc. John Linstrom Computer Dynamics PH 864.281.7768 x266 FX 864.675.0106 john.linst...@cdynamics.com mailto:john.linst...@cdynamics.com -Original Message- From: Lacey,Scott [ mailto:sla...@foxboro.com mailto:sla...@foxboro.com ] Sent: Monday, March 06, 2000 10:41 AM To: 'Paul J Smith' Cc: 'emc-p...@ieee.org' Subject: RE: Product Safety Certification School For those just looking for ergonomics information, there is an excellent MIL-STD that covers nearly every aspect of human/equipment interface, with reference dimensions for various percentages of a sample population. It covers everything from desk height to strength required to turn knobs. I lost my copy some years ago so I can't supply the document number. Scott Lacey -Original Message- From: Paul J Smith [SMTP:paul_j_sm...@notes.teradyne.com] mailto:[SMTP:paul_j_sm...@notes.teradyne.com] Sent: Monday, March 06, 2000 9:59 AM To: Rich Nute Cc: dan_mitch...@condordc.com; mailto:dan_mitch...@condordc.com; emc-p...@majordomo.ieee.org mailto:emc-p...@majordomo.ieee.org Subject:Re: Product Safety Certification School I found the following website http://ergo.human.cornell.edu/ http://ergo.human.cornell.edu/ at Cornell that is reasonably close to describing some of the areas of interest for the typical product safety professional. Site includes the following text. CUErgo presents information from Ergonomics research studies and class work, conducted by the Cornell Human Factors and Ergonomics Group in the Department of Design and Environmental Analysis at Cornell University, on ways to improve usability, comfort, performance and health, through the ergonomic design of hardware, software, and workplaces. Paul J Smith, Teradyne, Boston Rich Nute ri...@sdd.hp.com mailto:ri...@sdd.hp.com on 03/03/2000 06:01:08 PM Please respond to Rich Nute ri...@sdd.hp.com mailto:ri...@sdd.hp.com To: dan_mitch...@condordc.com mailto:dan_mitch...@condordc.com cc: emc-p...@majordomo.ieee.org mailto:emc-p...@majordomo.ieee.org (bcc: Paul J Smith/Bos/Teradyne) Subject: Re: Product Safety Certification School Hi Dan: Last year, sometime, reference was made about the possible creation of a University program to teach Product Safety. I was wondering if anybody has heard anything further about this program? I probably was the one who mentioned that engineering schools should include a 1-term course in product safety. Its on my wish-list. I'd like to find even one engineering school that would consider such a course, and then I'd volunteer to help create the course. But, I believe that no engineering school currently has such a course. Best regards, Rich --- 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 mailto: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 mailto:jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org mailto:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org mailto: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 mailto: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 mailto:jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org mailto:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org mailto:ri
RE: Product Safety Certification School
For those just looking for ergonomics information, there is an excellent MIL-STD that covers nearly every aspect of human/equipment interface, with reference dimensions for various percentages of a sample population. It covers everything from desk height to strength required to turn knobs. I lost my copy some years ago so I can't supply the document number. Scott Lacey -Original Message- From: Paul J Smith [SMTP:paul_j_sm...@notes.teradyne.com] Sent: Monday, March 06, 2000 9:59 AM To: Rich Nute Cc: dan_mitch...@condordc.com; emc-p...@majordomo.ieee.org Subject:Re: Product Safety Certification School I found the following website http://ergo.human.cornell.edu/ at Cornell that is reasonably close to describing some of the areas of interest for the typical product safety professional. Site includes the following text. CUErgo presents information from Ergonomics research studies and class work, conducted by the Cornell Human Factors and Ergonomics Group in the Department of Design and Environmental Analysis at Cornell University, on ways to improve usability, comfort, performance and health, through the ergonomic design of hardware, software, and workplaces. Paul J Smith, Teradyne, Boston Rich Nute ri...@sdd.hp.com on 03/03/2000 06:01:08 PM Please respond to Rich Nute ri...@sdd.hp.com To: dan_mitch...@condordc.com cc: emc-p...@majordomo.ieee.org (bcc: Paul J Smith/Bos/Teradyne) Subject: Re: Product Safety Certification School Hi Dan: Last year, sometime, reference was made about the possible creation of a University program to teach Product Safety. I was wondering if anybody has heard anything further about this program? I probably was the one who mentioned that engineering schools should include a 1-term course in product safety. Its on my wish-list. I'd like to find even one engineering school that would consider such a course, and then I'd volunteer to help create the course. But, I believe that no engineering school currently has such a course. Best regards, Rich --- 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 --- 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: Surge Testing per EN 55024/EN61000-4-5
Jim, You do in fact have a potential ground connection - at the phone line. In the static (on-hook) state you will have -48 Vdc, referenced to earth. If you look at your home phone service you will see a wire running to a cold water pipe, with a tag that says something like Telephone Company Ground - Do Not Remove. PBX systems at work will be different. I have little knowledge of whether they ground or not. I have learned the hard way to look for these non-obvious ground connections. Best wishes, Scott Lacey -Original Message- From: Jim Hulbert [SMTP:hulbe...@pb.com] Sent: Thursday, March 02, 2000 8:52 AM To: Lacey,Scott; emc-p...@ieee.org Subject:RE: Surge Testing per EN 55024/EN61000-4-5 Scott, The product I'm currently looking at uses a 2 -prong AC mains plug. Actually the supply is small direct plug-in type with DC leads that connect to the product. The product itself is encased in plastic and the only other connection is through an internal modem board to a standard analog telephone line. The connection to the phone line is a simple 2-wire (tip and ring) configuration. As I see it, surge tests with reference to earth ground are pointless. Others have pointed out that an ungrounded product may in the real world actually have a reference to ground depending on how it is installed or what other equipment it is connected to. That is a good point which I hadn't thought about. However, I don't think that in my particular situation that's that case. Thanks to all who responded with their opinions. Jim Lacey,Scott sla...@foxboro.com on 03/01/2000 01:31:46 PM Please respond to Lacey,Scott sla...@foxboro.com To: 'Jim Hulbert' hulbe...@micro2.pb.com cc: 'emc-p...@ieee.org' emc-p...@ieee.org (bcc: Jim Hulbert/MSD/US/PBI) Subject: RE: Surge Testing per EN 55024/EN61000-4-5 Jim, I'm not quite sure from the description what your product looks like, but, here are a few things to keep in mind. If you use a 3-prong ac mains plug you absolutely should do the line-to-ground test. If you use a 2-prong ac mains plug you still might want to perform the test anyway, depending on how your product is used. For example, if your plastic housing may be DIN rail mounted or screwed to a wall, you may have a leakage or arc path to earth. Your customer may have deliberately grounded the DIN rail to satisfy the requirements of other vendor's equipment already mounted. Even if it only gets screwed to a plasterboard wall, it still may get grounded by accident. I have seen two such scenarios over the years. In the first instance one mounting screw went through the wallboard and touched the grounded sheath of a BX cable in an older building. In the second instance a screw penetrated a metal stud used to frame the wall. An outlet box was attached to another stud. Bingo - instant ground. I'm sure there are many who will disagree with me, but we test products not only to conform to a standard, but also to ensure a more robust product. I want to find any vulnerability first, before the product gets to a customer. Customers tend to get VERY angry when their new product hiccups, and the nasty stuff tends to flow downhill real fast when their CEO calls yours. Scott Lacey -Original Message- From: Jim Hulbert [SMTP:hulbe...@pb.com] Sent: Wednesday, March 01, 2000 10:32 AM To: emc-p...@ieee.org Subject: Surge Testing per EN 55024/EN61000-4-5 Colleagues, EN 55024 calls for surge pulses to be applied line-to-line and line-to-earth on the AC mains port and line-to-ground on signal and telecommunications ports that connect directly to outdoor cables. However, if my EUT is encased in plastic covers and has no direct earth ground connection (class 2 power supply), is the line-to-line test on the AC mains the only surge test that I need to apply? It seems to me that performing a line-to-earth test on either the AC mains port or on signal/telecommunications ports is not warranted since the basic standard EN 61000-4-5 does not specify placing the EUT over a reference ground plane. With no reference ground plane and no direct ground connection how can a test be applied with respect to ground? Jim Hulbert Pitney Bowes - This message is from the IEEE EMC Society Product Safety
RE: Surge Testing per EN 55024/EN61000-4-5
Chris, In the case you mention, setting the CD player in its normal position on a grounded steel plate should do. The unit may end up sitting on a steel shelf unit along with other equipment with grounded chassis. I used such a setup at home for years. Scott Lacey -Original Message- From: Colgan, Chris [SMTP:chris.col...@tagmclarenaudio.com] Sent: Thursday, March 02, 2000 4:41 AM To: emc-p...@ieee.org Subject:RE: Surge Testing per EN 55024/EN61000-4-5 Let's say I'm testing a Class II double insulated CD player - no reference to earth. If the product were stand alone, line to earth testing would be pointless, at least as I see it. It is conceivable that the CD player could be connected to a Class I, earthed amplifier. Through the interconnects, the chassis of the CD player could become grounded (there would probably horrendous hum problems but that's another story). Line to earth tests are now valid but how would I set this up in the lab? A lead from the CD player chassis to the nearest socket outlet earth? A lead to the chassis of my Keytek surge tester? A thin lead, a thick lead? I guess the test should be representative of the real world and repeatable. Any suggestions? Regards Chris Colgan EMC Safety TAG McLaren Audio Ltd mailto:chris.col...@tagmclarenaudio.com -Original Message- From: Mike Hopkins [SMTP:mhopk...@keytek.com] Sent: 01 March 2000 18:32 To: 'Jim Hulbert'; emc-p...@ieee.org Subject: RE: Surge Testing per EN 55024/EN61000-4-5 As long as there is no other path to ground, a line to line test would be all thats required, but keep in mind, if you have other I/O, telecom, control lines, or anything else coming out of that plastic box, you then have a potential path back to ground, and in fact, will likely have REAL ground connections. For example, many television sets have two wire power plugs, are in plastic cases, but if you have cable tv, the odds are that coax cable is grounded. Same thing applies if there is a telecom line involved -- very likely one of the telecom lines is ground. .. Mike Hopkins mhopk...@keytek.com -Original Message- From: Jim Hulbert [SMTP:hulbe...@pb.com] Sent: Wednesday, March 01, 2000 10:32 AM To: emc-p...@ieee.org Subject:Surge Testing per EN 55024/EN61000-4-5 Colleagues, EN 55024 calls for surge pulses to be applied line-to-line and line-to-earth on the AC mains port and line-to-ground on signal and telecommunications ports that connect directly to outdoor cables. However, if my EUT is encased in plastic covers and has no direct earth ground connection (class 2 power supply), is the line-to-line test on the AC mains the only surge test that I need to apply? It seems to me that performing a line-to-earth test on either the AC mains port or on signal/telecommunications ports is not warranted since the basic standard EN 61000-4-5 does not specify placing the EUT over a reference ground plane. With no reference ground plane and no direct ground connection how can a test be applied with respect to ground? Jim Hulbert Pitney Bowes - 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 adminstrators: Jim Bacher: jim_bac...@mail.monarch.com, or 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:
RE: Copper braid
Ron, Try to find a supplier to the marine electrical industry. Commercial fishing boats require heavy-duty bonding. They usually use copper straps or large braid. By the way, if the ground connection does not have to be flexible, thin copper sheet works better than braid. The earth ground rod connection to our Lindgren chamber is 6AWG stranded wire. Again, marine suppliers sell flexible (dc) mains cable by the foot, in sizes down to 00AWG. Scott Lacey -Original Message- From: ron_cher...@densolabs.com [SMTP:ron_cher...@densolabs.com] Sent: Tuesday, January 25, 2000 5:51 PM To: emc-p...@majordomo.ieee.org Subject: Copper braid I am looking for 2 inch plus tin coated copper flat braid to ground screen rooms and a ground plane with. All I can find is it by the 100' roll. I don't need that much. Does anyone have a good source?? Thanks, Ron Chernus, Denso - 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). - 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: dBu
Dave, I have always seen this used for micro, as in dBuV = decibel microvolts. It may also stand for decibel units. If so, a unit is most likely 1 volt rms, a common unit in professional audio. The formula would be 20 X LOG(input voltage/reference voltage), with LOG referring to LOG 10. Scott Lacey -Original Message- From: Dave Wilson [SMTP:dwil...@babtps-us.com] Sent: Thursday, January 20, 2000 4:16 PM To: emc-p...@ieee.org Subject: dBu Has anyone come across this unit before? It's referenced in EN55103-2 (Professional Audio/Video Immunity) for audio frequency common mode immunity testing. I realise it may be a misprint, but I thought someone else may have already looked into it. Dave Wilson BABT Product Service - 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). - 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: Looking for tunable dipole antenna.
Joe, It's been a few years, but Compliance Engineering used to sell Roberts Antennas - Telescoping dipoles with coax baluns. The telescoping elements were adjusted (by hand) using a tape measure. We used to mark a standard inch tape measure with a permanent marker for convenience. They also sold a preamplifier for use with the antenna. They published plans in their magazine for those who would build their own. Construction is fairy simple except for machining the phenolic parts. I imagine it could be done using woodworking equipment if you had to. Perhaps Jon Curtis might know who to contact? Scott Lacey -Original Message- From: hoban...@racalcomm.com [SMTP:hoban...@racalcomm.com] Sent: Wednesday, January 19, 2000 8:53 AM To: emc-p...@majordomo.ieee.org Subject: Looking for tunable dipole antenna. Does anybody have any idea on where I can purchase a set of dipole antennas that have tunable baluns? I need them for performing pre-compliance antenna gain tests on some of the antennas that are used on the various Racal handheld radios. The frequency range I am interested in is the 30 MHz to 1 GHz frequency range. I am interested in either used or new antennas. I had a set of them about 20 years ago but don't remember whether they were home made or something we purchased from some manufacturer. If you have any ideas for a source please let me know. Thanks, Joe O'Banion - 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). - 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: Lead Banned in Europe Japan?
My, how public spirited of them. Scott -Original Message- From: simon_...@emc.com [SMTP:simon_...@emc.com] Sent: Tuesday, January 18, 2000 10:24 AM To: emc-p...@ieee.org Subject: RE: Lead Banned in Europe Japan? A little research on the Internet showed that the proposal comes from a tin manufacturers association. I cannot give you a direct sourse at the moment, but it was not difficult to find. The association's goal is to replace lead with tin. Leo Simon -Original Message- From: ron_well...@agilent.com [mailto:ron_well...@agilent.com] Sent: Tuesday, January 18, 2000 9:39 AM To: emc-p...@ieee.org; mpeder...@midcom-inc.com Subject: RE: Lead Banned in Europe Japan? Mel, It would be interesting to know who your Customer is that is making this request. We have had similar requests for material content, including lead, specifically in the components we manufacture. You have already heard from people concerning the WEEE Directive in Europe. As for Japan, there is no ban on lead but a law regarding disposal of waste into landfills. Some Japanese manufacturers are imposing lead elimination requirements on their suppliers, mostly component suppliers, to comply with this landfill law. Regards, +=+ |Ronald R. Wellman|Voice : 408-345-8229 | |Agilent Technologies |FAX : 408-345-8630 | |5301 Stevens Creek Blvd.,|E-Mail: ron_well...@agilent.com| |Mailstop 51L-SQ |WWW : http://www.agilent.com | |Santa Clara, California 95052 USA| | +=+ | Common sense is the collection of prejudices acquired by age | | eighteen. - Albert Einstein | +=+ -Original Message- From: mpeder...@midcom-inc.com [mailto:mpeder...@midcom-inc.com] Sent: Monday, January 17, 2000 3:46 PM To: emc-p...@ieee.org Subject: FW: Lead Banned in Europe Japan? Hello: I periodically recieve inquiries on the quanitity of various materials (including Lead) in our product. A customer of ours recently claimed that Lead has been banned in electronics in Europe Japan. They are asking what we are doing about this. Is there any basis in truth for this? Thanks Mel Pedersen Midcom, Inc. Homologations Engineer Phone: (605) 882-8535 mpeder...@midcom-inc.com Fax: (605) 882-8633 - 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). - 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). - 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). - 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: LVD voltage range.
John, With a 12V battery system, you will have to address the issues of hazardous energy - ie.the heating effects of battery current under short-circuit conditions. Even a small battery pack can heat a wedding ring nearly white hot. Scott Lacey -Original Message- From: fwhitfi...@rheintech.com [SMTP:fwhitfi...@rheintech.com] Sent: Thursday, January 13, 2000 9:44 AM To: emc-p...@ieee.org Subject: LVD voltage range. Hello all, Does a hand-held field device that operates mainly on 12Vdc from a group of batteries and alternatively uses an AC/DC adapter need to be assessed for safety according to the LVD? I read somewhere that for LVD the DC voltage should be between 75 and 1500V. Does this mean that such a device does not need to be evaluated for safety at all ? A client is awaiting a response from me in a couple of hours so I would appreciate any views on this matter. Thanks for your usual co-operation. John Whitfield Safety Engineer Rhein Tech Labs - 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). - 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: Surge Test Performance Criterion
Jim, The situation you describe would be criterion C, because there is a temporary loss of function and it is recoverable. Scott Lacey -Original Message- From: Jim Hulbert [SMTP:hulbe...@pb.com] Sent: Wednesday, January 12, 2000 3:08 PM To: emc-p...@ieee.org Subject: Surge Test Performance Criterion A product has a switched mode power supply with a current sensing circuit that causes the supply to shut down when a surge pulse is applied to the AC mains in accordance with EN61000-4-5/IEC1000-4-5. After about 10 minutes, the supply can be turned back on and normal operation of the product can be resumed by the operator. Does this product conform to criterion B of the EN 50082-1 or EN 55024 standards? I believe it does because the sensing circuit is specifically designed to protect the product against this kind of voltage/current surge and the product operation is fully recoverable by the operator afterward. However, I would like to hear how others who do this testing would interpret this. Jim Hulbert Senior Engineer - EMC Pitney Bowes - 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). - 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).
Tiger Tail for 27 MHz?
Fellow Listmembers, I have a question regarding tiger tails used to improve transmission characterisics of a hand-held transmitter (HHT). The HHT is basically a dipole, with the chassis as the bottom element. The tiger tail is a quarter-wave length of wire that connects to the shell of the coaxial connector and is allowed to hang downwards, effectively increasing the electrical length of the chassis. They are commonly used with higher frequency HHT's where a quarter wavelength is relatively short compared to a standing man. I want to fabricate one for use with a 27 MHz (CB) HHT. I need a length of wire more than nine feet long. My question is this: If I wind the nine feet of wire spirally around a length of polypropylene rope, will it still work properly? Also, should I use Litz wire? Thanks in advance for any help. Scott Lacey - 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: Buying a VCR
Max, I think you have either a bad cable or poor internal connection in the VCR. There should be no effect on signal when the VCR is off - the signal is bypassed straight from the input connector to the output connector. Your local Radio Shack sells an inexpensive adapter which couples two cables together. Connect this in place of the VCR - if the problem remains the VCR is not at fault. The F connectors used for TV use the center conductor of the coax as a pin. They are often damaged by banging against a chassis. Another thing to pick up at the Shack is their connector cleaner pen. It will lubricate the threads and prevent galling, another source of problems. Scott Lacey -Original Message- From: mkel...@es.com [SMTP:mkel...@es.com] Sent: Monday, January 10, 2000 12:39 PM To: emc-p...@majordomo.ieee.org Subject: Buying a VCR I recently bought a VCR. After connecting it up to cable, I noticed interference on all the broadcast channels. In addition, the pictures on non-broadcast channels lacked the brightness, color and crispness I am accustomed to. This was, of course, true even when the VCR was turned off. I imagine this (immunity?) problem could occur with any device connected to your cable. My advice: Connect these products up right away--right after you buy them and check all your channels carefully. Max Kelson Peripherals Engineer Evans Sutherland 600 Komas Drive, Salt Lake City, UT 84158 http://www.es.com/ http://www.es.com/ Telephone: 801-588-7196 / Fax: 801-588-4531 mailto:mkel...@es.com mailto:mkel...@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, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - 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: Ground lugs
James, In our lab, I just spotted a tin-plated lug of the type you seek. It is marked BURNDY SCRULUG, and is tin plate over copper, with a clamping plate between the screw and the wire. I have no idea how old this lug is, or if Burndy still makes them, but it might be a good idea to contact them. Scott Lacey -Original Message- From: goedd...@sensormatic.com [SMTP:goedd...@sensormatic.com] Sent: Friday, December 17, 1999 2:09 PM To: emc-p...@majordomo.ieee.org Subject: Ground lugs Happy Holidays group, In getting agency approval on our I.T.E. product, the safety ground terminal has come into question. When hard wiring a product, Para. 3.3.7 indicates that the conductor is to be clamped between metal surfaces, and the terminal shall not damage the conductor. This has been interpreted as the terminal must have a metal plate that clamps down on the conductor, and no rotational stresses from the screw are applied to the conductor. In Europe, I understand that a rail terminal block, where one of the terminals is shorted to a rail, is generally used, and accepted, but somewhat costly. There may also be alternatives, but we haven't found an off the shelf one yet. I am looking for a grounding terminal that accepts #14-#18 AWG wire, has a clamping plate, is tin plated, and has a mount or hole for direct connection to a chassis. Since this has been so difficult a component to find, we had one designed. Now my question is, How is everyone else dealing with this ground lug requirement? Is there a common component available that meets these specs? The ground lugs in common use in the electrical industry do not have the plate, and are copper or copper alloy. Thank you for your assistance. James Goedderz Sensormatic - 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). - 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: Ground lugs
James, Most equipment today uses crimp-on ring terminals, secured to a ground stud using a star washer and hex nut. The ground wire from the power inlet goes on first, and other safety grounds are stacked on top, each with its own star washer and nut. I have never had agency approval problems with this type of construction. You must use a double crimp ring terminal, one that grips the wire insulation securely. If, for some reason, you must use the setscrew type lug, your best bet would be to have a batch of the commercial lugs tin plated. They are easy to dismantle once the setscrew is removed, and most large cities have plating houses. Tin is one of the easier (and cheaper) plating processes. I completely agree that you must have a plate between the screw and the wire. I have seen wires almost cut in two by the other type. Scott Lacey -Original Message- From: goedd...@sensormatic.com [SMTP:goedd...@sensormatic.com] Sent: Friday, December 17, 1999 2:09 PM To: emc-p...@majordomo.ieee.org Subject: Ground lugs Happy Holidays group, In getting agency approval on our I.T.E. product, the safety ground terminal has come into question. When hard wiring a product, Para. 3.3.7 indicates that the conductor is to be clamped between metal surfaces, and the terminal shall not damage the conductor. This has been interpreted as the terminal must have a metal plate that clamps down on the conductor, and no rotational stresses from the screw are applied to the conductor. In Europe, I understand that a rail terminal block, where one of the terminals is shorted to a rail, is generally used, and accepted, but somewhat costly. There may also be alternatives, but we haven't found an off the shelf one yet. I am looking for a grounding terminal that accepts #14-#18 AWG wire, has a clamping plate, is tin plated, and has a mount or hole for direct connection to a chassis. Since this has been so difficult a component to find, we had one designed. Now my question is, How is everyone else dealing with this ground lug requirement? Is there a common component available that meets these specs? The ground lugs in common use in the electrical industry do not have the plate, and are copper or copper alloy. Thank you for your assistance. James Goedderz Sensormatic - 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). - 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: CFR's
Dick, Try http://law.etext.org Scott Lacey -Original Message- From: Dick Grobner [SMTP:dick.grob...@medgraph.com] Sent: Friday, December 17, 1999 1:09 PM To: 'emc-p...@ieee.org' Subject: CFR's Does anyone out there know if you can download Code of Federal Regulations (CFR's) at no charge. If so does anyone have the site address. I know you can purchase them for a fee from the people who sell standards, etc. Any input would be appreciated. Thx Happy Holidays! - 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). - 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: Measuring ESD
Ned, Any calibrated static charge meter should work ok. They run about $400 to $600 dollars from many vendors (ACL, 3M, Ion Systems, etc.). You probably will want to test worst case - dry pump, gloved hand, unit sitting on an insulated surface. One person pumps while the other holds the meter. Have them pump as fast as possible. Check the body of the pump, the plunger, and the surfaces of the plastic container for charge. I would use a dry wooden platform, and secure the container to it, to prevent charges caused by movement of the container against the insulated surface. Do not use polyethelene for the support, as it is well known for generating static when a poly container is moved across it. There have been several nasty fires at gas stations when people try to fill containers sitting on a bedliner during winter. A charge is generated when the container is dragged toward the tailgate, the nozzle is brought near, and a fire results from the discharge. A quick check to be sure that the meter is ok is to hold it near a tape dispenser (clear office type tape) while rapidly pulling a couple feet off the roll. Hope I've been of some help. Scott Lacey -Original Message- From: Ned Devine [SMTP:ndev...@entela.com] Sent: Thursday, December 16, 1999 9:42 AM To: 'IEEE, EMC/Product Safety' Subject: Measuring ESD Hello, I need some help from the ESD experts. I am trying to find a way to measure the electro-static build-up on a hand operated pump. The device is used to suck out the gas from small gas engines before the service. Obviously, an ESD event would not be a good thing. We are trying to validate some design concepts for the customer. The pump is a piston type. It sort of looks like a giant syringe with a one way valve. The pump has integral threads and is screwed to a large 2-3 gallon plastic tank. The pump is used to create a vacuum in the tank. You need to pump, really pull, it 10-15 times to get the necessary vacuum. A siphon hose is attached to the tank. You open a clamp on the hose to suck the gas into the container. I think I need a static monitor or field meter. Does anyone have any ideas on test equipment or test methods? I did a search and I came up with John Chubb Instrumentation, model JCI 140 Static Monitor. Does anyone have any experiences with this meter or others? Ned Devine Entela, Inc. Program Manager III Phone 616 248 9671 Fax 616 574 9752 e-mail ndev...@entela.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). - 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: Common Mode Choke
Derek, We stock a 16 amp line filter which we have used on lower current products specifically to prevent saturation of the choke when used as a protective device for external events such as EFT. I put one on a product containing an industrial computer supplied by a business partner to solve a problem with Ethernet communications during EFT testing. Interestingly, although the computer was CE marked, EN61000-4-4 was absent from the list on the compliance label. I had a tough time convincing the engineering manager that the larger device was needed. He wanted to use a smaller filter that replace the IEC cord inlet. The answer to your question is that, in the absence of reliable data from the vendors, you must either devise a quick test or deal directly with a good custom magnetics house that will build a part to your specs. Unfortunately, today we often find ourselves dealing with puppies after the old dog engineers have either retired or been laid off. A lot of these kids don't know, don't care, and think truthfulness is an impediment to sales. It can be difficult tell stupidity from malice as they both cause similar problems. Scott Lacey -Original Message- From: Derek Walton [SMTP:l...@rols1.net] Sent: Thursday, December 02, 1999 2:47 PM To: IEEE EMC Discussion Group Subject:Common Mode Choke Good day all, I'm refining the input filter of a 150 watt SMPS. Nothing flashy, just a few caps and a common mode choke. The current is drawn by the supply in short bursts as the DC link cap is charged. I've shown that peak current reaches 6 amps for up to 2 ms. I've also demonstrated that the CM choke, while rated for the RMS current ( a 2 amp device ), does saturate when the current exceeds about 4 amps. I've been trying to find out from the vendors, what current it takes to saturate the CM choke. I've had answers from CM chokes can't saturate to that's not an important parameter, use the rms figure My question is, with over 20 potential vendors of this type of component, is there any way I can find out saturation performance without buying one of each type and testing it. I've played with 3 so far, the most expensive was NOT the best! I guess, I'm curious why more folks don't know about this effect also. Thanks, Derek Walton Owner L. F. Research EMC Design and Test Facility 12790 Route 76, Poplar Grove, IL 61065. www.lfresearch.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). - 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: Ground Fault Current Interruptors
David, Try National Semiconductor. I believe they manufacture most of the ICs used. Scott Lacey -Original Message- From: david_l_tarnow...@email.whirlpool.com [SMTP:david_l_tarnow...@email.whirlpool.com] Sent: Tuesday, November 30, 1999 3:34 PM To: emc-p...@majordomo.ieee.org Subject:Ground Fault Current Interruptors EMC Safety Colleagues, Does anyone know where I could get information about the bandwidths of ground fault current interruptors; that is, has there been a study that shows what the statistical lower and upper current limits are as a function of frequency? David Tarnowski Whirlpool Corp. St. Joseph, MI - 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). - 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: Shielded Enclosure Fire Hazard - Wrong Scott
Egon (and fellow list members), I think you meant to reply to Scott Douglas. Lately, I have received several emails which were replies to him. Since most of them were probably initiated by clicking on the Reply button, I suspect some internet glitch is at fault. Scott's company is located about 40 miles north of us, so our email probably follows similar paths. List members: When replying, double-click on the alias (the name which appears on the To line) to bring up the Properties dialog box. The email address for Scott Douglas is: s_doug...@ecrm.com mailto:s_doug...@ecrm.com My email address is: sla...@foxboro.com mailto:sla...@foxboro.com Ain't computers wonderful :-) Scott Lacey -Original Message- From: Egon H. Varju [SMTP:e...@varju.bc.ca] Sent: Wednesday, November 17, 1999 8:06 PM To: EMC-PSTC Subject:RE: Shielded Enclosure Fire Hazard Scott, I presume you mean Halon, not halogen. Sorry, but Halon systems are neither invisible nor odourless. When you set one off, the room fills with a smoky haze that has quite a strong odour. I presume that this is due to additives that are included for the very purpose of making it obvious. By the way, when you set one of these things off, there is a very loud, explosive noise. Not sure if this is due to an explosives charge opening the pressurized cylinder, or just the explosive expansion of the gas. Regardless, you'd have to be deaf (and blind) to not realize that the system had deployed. In a previous incarnation, I used to work on oil rigs in the Arctic Ocean. I once had the dubious distinction of setting one of these things off (due to a tantalum cap on one of my PWBs). Just imagine sitting there in the middle of winter, in that complete silence of the Arctic, and all of a sudden there is this incredible explosion and smoke ... Needless to say, a change of underwear was in order. No, there is no danger of missing the fact that there is halon in the air. As for breathing the stuff, I'm not aware of any actual harm. Yes, it displaces the normal oxygen, so you obviously can't live on it, but it's not poisonous, just neutral. I'm sure I got quite a lungfull of the stuff, but there was no harm done. No big deal. Egon :-) At 12:25 PM 17/11/1999 , you wrote: - 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: Shielded Enclosure Fire Hazard
Scott, I beg to disagree, ... but, Halon, along with Freon and other compounds was banned by the Montreal Protocol, ostensibly to protect the ozone layer. Interestingly, the Freon replacements must, per the treaty, be phased out in 20 years - by coincidence about the time when the international patents expire. No suitable replacement for Halon has yet been found, and the U.S. military has bought up much of the existing stocks for vehicle and shipboard fire protection systems. If I remember correctly, Halon can cause suffocation by displacing oxygen, rather than causing toxicity. When I worked in a Halon protected room, our instructions were to take a couple of deep breaths before the system fired, and hold our breath during escape. Scott Lacey -Original Message- From: Scott Douglas [SMTP:s_doug...@ecrm.com] Sent: Wednesday, November 17, 1999 1:53 PM To: geor...@lexmark.com; emc-p...@majordomo.ieee.org Subject:RE: Shielded Enclosure Fire Hazard George, I once worked in a laboratory that developed the Doppler weather radar we all see on TV today. In our just built (in 1979) control room, they put a halogen extinguisher system. Halogen works by displacing the oxygen and thus the fuel for the fire. No fuel, no fire. The system could fill the entire control room, 50' x 80' in less than 30 seconds. We had big klaxon alarms and a disable mechanism, but strict rules to just run like hell. We had a 10 second warning bell that went off just before the gas came down. Point is, it wasn't so much the ozone layer that made halogen fall out of favor, it was the severe threat to human life. The gas is odorless, tasteless and invisible, so if it went off you wouldn't know until too late. I recall they told us that you would not live 30 seconds in a room filled with halogen. The several false alarms caused us to evacuate and we had to call the fire department to ventilate the building for 60 minutes before we could get back to work. Halogen is certainly an extremely effective means of suppressing fire, but operating costs and impact on operations play a big part in its use (or lack thereof). The gas is expensive and, while there is little damage to facilities or equipment from its use, there can be human consequences to deal with. Scott s_doug...@ecrm.com ECRM Incorporated Tewksbury, MA USA - 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: 60 Hz Power Line Impedance
Muriel, The usual method of measuring the impedance of a component is to insert a non-inductive resistor in series with the component and measure V1 vs. V2, where V1 is the voltage across the resistor and V2 is the voltage across the component under test. At any frequency, the voltage ratio will be determined by the reactance of the component. A vector impedance meter or differential input oscilloscope is normally used. An ordinary oscilloscope and probe may be used in a pinch, by measuring Vt (V total) vs. V2. What you do is connect one probe, with the ground lead at the circuit return, and move the probe from Node 1 to Node 2, measuring and recording the peak values at each frequency. Node 1 is the point where the signal source connects to the resistor, Node 2 is the junction of the resistor and component, and Node 0 is the point where the component connects to the signal source return. One probe is used to eliminate the errors caused by non-matched probes. It is possible to determine inductance or capacitance by working the reactance formulas backwards. Scott Lacey -Original Message- From: Muriel Bittencourt de Liz [SMTP:mur...@grucad.ufsc.br] Sent: Friday, November 12, 1999 4:52 PM To: david_l_tarnow...@email.whirlpool.com Cc: Lista de EMC da IEEE Subject:Re: 60 Hz Power Line Impedance Group and Mr. Tarnowski, I don't know the answer for this question, but it lead me to other doubt I have... When read in my Receiver/Spectrum Analyzer: 50 Ohms, what is the frequency range on which this impedance is valid? This question also applies to impedance of loudspeakers (generally 8 or 4 ohms)?? And the impedance of my network? How do I determine? Thanks in advance for those who answer... Good Weekend!! Muriel - 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: Is Your Head Clamp CE Marked?
Scott, CE compliant? I'm not even sure that my brain is Y2K compliant! :-) Scott Lacey -Original Message- From: Scott Douglas [SMTP:s_doug...@ecrm.com] Sent: Monday, November 15, 1999 11:18 AM To: EMC-PSTC (E-mail) Subject:Is Your Head Clamp CE Marked? Hi All, Happened to see the X-Files last night and noted that the clamp used to hold Multer's head still during brain surgery had a CE mark prominently displayed on the forehead section. Makes me wonder, is CE marking of brains coming next? Would mine pass? Or will it need a major re-design to become compliant? Not sure I want the answers to those questions. Scott s_doug...@ecrm.com ECRM Incorporated Tewksbury, MA USA - 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). - 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: Please Help with drawing Symbols of L and R
Barry, Instead of drawing in Word, why not try the Paint program that comes with Windows. The version that comes with Win95 and later actually has some nice features, such as multi-size zoom, cut and paste with mirror, rotate, flip, etc. If you hold down the SHIFT key while drawing with the mouse, you will get circles instead of ovals, squares instead of rectangles, and lines at 45 and 90 degrees only. I do all my sketch type drawings in Paint, then open them in Microsoft Photo Editor, and save as a GIF (Graphics Interchange Format) file. The later versions of Word will allow you to paste GIF and JPG graphics (InsertPicture...From File). I use JPG format for digital photos of test setups, etc. One other hint: If you have a Windows schematic program, you can paste into Paint, Word, or Excel. In the schematic program select the area desired, COPY, open the other program, and paste. By separate email I am sending an example of an Excel spreadsheet done this way. Scott Lacey -Original Message- From: b...@anritsu.com [SMTP:b...@anritsu.com] Sent: Friday, November 05, 1999 6:14 PM To: emc-p...@majordomo.ieee.org Subject:Please Help with drawing Symbols of L and R Hi, I'm writing a Word file. It is difficult to draw symbols of L and R. Can anybody please help me with drawing inductors and resistors in MS Word file? Thanks. Barry Ma - 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). - 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).
Source for semi-rigid coax?
To the group, Does anyone know of a source that will sell small amounts of semi-rigid coax (hardline), preferably by mail? I have a few small projects in mind. Scott Lacey - 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).
Conduit Knockout Dimensions - OOPS!
After reading Bill Lawrence's posting, I realized I made a typo error. The last two numbers should have been 1 3/8 and 1 3/4. The dimensions would then be: 7/80.875 1 1/8 1.125 1 3/8 1.375 1 ¾1.750 These are nominal values - the min and max values would be those which Bill reported. I apologize for any mixups - when typing, my brain outruns my fingers. Scott Lacey - 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: EN60950 - conduit entry dimensions
Jim, I took a few quick measurements of workboxes, isolation transformers, etc. in the lab, as well as the knockout openings in the cast housings of some of our flow transmitters. 7/8 and 1 1/8 seem to be the most common for the smaller circuits, with 2 3/8 and 2 3/4 used for the heavier stuff. Check a Hubbell catalog for required sizes for cable grips, etc. Scott Lacey -Original Message- From: Jim Eichner [SMTP:jeich...@statpower.com] Sent: Wednesday, October 06, 1999 5:49 PM To: 'EMC-PSTC - forum' Subject:RE: EN60950 - conduit entry dimensions I have received very little response to this one, so I thought I'd post it again. Aren't there any permanently connected ITE equipment mfr's on this forum?! What do you provide in the way of knockouts or ...??? Thanks, Jim Eichner Senior Regulatory Compliance Engineer Statpower Technologies Corporation jeich...@statpower.com http://www.statpower.com Any opinions expressed are those of my invisible friend, who really exists. Honest. -Original Message- From: Jim Eichner [SMTP:jeich...@statpower.com] Sent: Thursday, September 23, 1999 10:49 AM To: 'EMC-PSTC - forum' Subject: EN60950 - conduit entry dimensions Greetings all: In clause 3.2.2 allows the provision of knockouts, cable entries, etc. in lieu of a non-detachable power cord for permanently connected equipment. In Table 10, it lists the overall diameter of conduit based on the number of conductors involved, up to 16A. In my particular application, there are 2 wires plus earth, and the current (and the branch circuit protection) is less than 16A, so the table tells me I need a knockout that can accommodate a 16.0mm O.D. conduit. If things are done there anything like they are done here, this 16mm conduit will be secured in a fitting of some sort, and the knockout needs to be matched to the fitting, not the conduit (i.e. a 16mm hole is likely too small). Is there a reference, or can anyone tell me, what the appropriate sized hole will be? Is this standardized somewhere? Thanks in advance for your help, Jim Eichner Senior Regulatory Compliance Engineer Statpower Technologies Corporation jeich...@statpower.com http://www.statpower.com Any opinions expressed are those of my invisible friend, who really exists. Honest. - 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). - 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). - 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: Temperature probe
Leslie, The Fluke Model 51 or 52 should be adequate for your needs. These are battery operated thermocouple instruments, single and dual input models. They are relatively inexpensive, and I would strongly recommend the dual input model for the extra features, as well as the ability to measure E.U.T. internal temperature and chamber ambient simultaneously. Scott Lacey -Original Message- From: Leslie Bai [SMTP:leslie_...@yahoo.com] Sent: Wednesday, October 06, 1999 2:29 PM To: emc-p...@ieee.org Subject:Temperature probe Hello, group: Seems that my question is not relavent to this group but hope someone there could help. I am looking for an ACCURATE temperature probe ( accuracy is about +/- 1 degree C from -50 to +80 degree C). It will be used to measure the microwave frequency drifting over the temperature. It will be put in a temperature chamber. Although the chamber has a temeprature display, it's not accurate as we expected (about +/-3 degree C), thus we need a more accurate probe to perform the measurement. If you have any info or similiar probe, pls kindly let me know - the brand, model, etc... Thanks in advance. Leslie http://biz.yahoo.com/prnews/991006/ca_digit_m_1.html = __ Do You Yahoo!? Bid and sell for free at http://auctions.yahoo.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). - 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).
Coatings for Ferrite Tiles?
To the group, Can anyone recommend a paint or other (light colored) coating that can be applied over ferrite tiles? The lighting in the bat cave (shield room) is rather grim. It can be very difficult to see when working inside of a cabinet. Photos of test setups would also look better if there were less contrast with the background. Scott Lacey - 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: Direct Contact Discharge into Vents to EN61000-4-2
Bill, I think that the only time that you would have to discharge to the interior metal is if the vents are large enough to admit the standard test finger. This has a much more blunt shape than the contact point on an ESD gun. Scott Lacey -Original Message- From: Jacowleff, Bill [SMTP:bjacowl...@vdo.com] Sent: Friday, September 24, 1999 4:03 PM To: Emc-Pstc (E-mail) Subject:Direct Contact Discharge into Vents to EN61000-4-2 -Original Message- From: Jacowleff, Bill Sent: Friday, September 24, 1999 3:53 PM To: EMC POST GROUP (E-mail) Subject: Direct Contact Discharge into Vents to EN61000-4-2 Greetings to all: I am testing a product that has small plastic modular housing with vents to EN61000-4-2. At 8 kV Air discharge I have discharge to the open vents which is fine, the PCB is protected on the perimeter and tolerates this well. However my question is with the Direct Contact Discharge to these vented areas. I am under the impression of where I have an air discharge I am to follow-up that area with a Direct Contact Discharge. In this particular case the vents are large enough to allow the tapered Direct Contact Discharge Tip to fit deep enough in the vents, passing the perimeter protection on the PCB and come in direct contact with one component on the PCB. So my question is How far should the Direct Contact Discharge Tip be inserted into a vent? As far as it will reach? Or shouldthe Direct Contact Discharge Tip be limited to touching the outside wall of the module near the vent? Thanks for your reponse in advance. Best Regards, Bill Jacowleff VDO Control Systems Airpax Instruments 150 Knotter Drive Cheshire, CT 06410 Phone: 203 271-6394 FAX:203 271-6200 bjacowl...@vdo.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). - 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: Immunity Problems ?? Insufficient Data
Joe, More data will be required before the group would be able to help with a diagnosis. You say that each instrument is on it's own line. Are you referring to an ac power line? Also: Is each instrument provided with it's own isolated ground receptacle? Are they networked? If so, is the connection copper or optical? Are the instruments microprocessor based? Is there a central device (PC) controlling them? Are all devices exhibiting these symptoms, or just a few? Do they shut down while doing something, or when sitting idle? I would suggest keeping a log of events, with each machine assigned a number, in order to create a matrix showing which machine shut down, when it shut down, what else was happening, etc. I understand the need to maintain confidentiality of proprietary information, but it should be possible to provide some generic data. Scott Lacey -Original Message- From: marti...@pebio.com [SMTP:marti...@pebio.com] Sent: Tuesday, September 07, 1999 5:04 PM To: emc-p...@majordomo.ieee.org Cc: marti...@pebio.com Subject:Immunity Problems ?? EMC Professionals, We have 42 of the same instruments installed in one laboratory. They are each installed on their own dedicated line. On a regular basis, an instrument will shut down during a run. The instrument that shuts down is different each time. These instruments are laboratory equipment that meet Class A radiated limits of EN 55011 and meet the immunity requirements of EN 50082-1. Any ideas as to the potential cause of the problem and possible ways to resolve the problem would be greatly appreciated. Regards Joe Martin EMC/Product Safety Engineer P.E. Biosystems marti...@pebio.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). - 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: Temperature Measuring of Magnetic Components
Kamran, The method used by most of the better magnetics houses is to embed thermocouples into the transformer during construction of a sample. The resulting temperatures will be higher than external measurements. Scott Lacey -Original Message- From: Kamran Mohajer [SMTP:kmoha...@cisco.com] Sent: Tuesday, August 24, 1999 5:50 PM To: emc-p...@ieee.org Subject:Temperature Measuring of Magnetic Components Hello EMC-PSTCers, I wonder if anyone knows of the method of measuring temperature limits on magnetic components. I happen to get involved in this and found that my results are different than the vendors result by as much as 10-15 degrees on measuring on a same magnetic component. Even applying the thermocouple to different location on a coil seems to give you different results. Is there a method that I should be following to measure temperature with thermocouples methods, not change of resistance, on magnetic parts such as transformers, coils, etc.? Thanks, *** Kamran Mohajer DSL Compliance Lead Cisco Systems, Inc. Phone(408)-525-6121 Fax(408)527-0495 kmoha...@cisco.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). - 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???
Doug, Concrete may be made to work as an insulator, but conditions will have to be carefully controlled. Most concrete tends to be somewhat hygroscopic, although this varies with mix variables including type of aggregate used. I have heard that large concrete pads are successfully being used as alternatives to ground rods in some RF applications. I believe that the military has done a lot of work in this area, using massive grids of welded rebar to distribute conductivity within the slab. Anyway, you will need to ensure that the cement used is a low moisture absorbing type. Your local masonry supplier should be able to help with this. Use only insulators, such as quartz sand, for aggregate. Some pre-mix may contain foundry slag and other metallic aggregate. If you are unable to purchase low moisture absorbing mix, and must use the stuff from the home center, I would suggest that you use bonding compound to replace much or all of the water in the mix. I have used 100 percent bonding compound with great success, the resulting concrete being much stronger and more water resistant. The only drawback is the higher cost. I would strongly recommend performing conductivity testing on samples before using a particular mix. A prolonged 95 percent humidity test would probably be wise. I am delighted to hear that there are others out there willing to try crazy methods and materials. Good Luck, Scott Lacey -Original Message- From: POWELL, DOUG [SMTP:doug.pow...@aei.com] Sent: Friday, August 20, 1999 5:40 PM To: EMC-PSTC (E-mail) Subject:Concrete as an insulator??? 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. thanks, -doug === Douglas E. Powell, Compliance Engineer Advanced Energy Industries, Inc. 1625 Sharp Point Dr. Fort Collins, Colorado 80525 USA --- 970-407-6410 (phone) 970-407-5410 (e-fax) mailto:doug.pow...@aei.com mailto:doug.pow...@aei.com http://www.advanced-energy.com http://www.advanced-energy.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). - 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: Equipment designed and manufactured for use in-house
Carlos, Over the years, I have designed and built a lot of this type of equipment. It is actually easier to build in safety with this type of equipment rather than a commercial product because component costs are not as much of a factor. Here are a few rules to follow: Identify and list all possible safety hazards - make a checklist Use appropriate connectors for the voltages and currents involved Use CE marked components wherever possible Make sure that all SELV wiring is physically separate from non-SELV wiring Use additional insulation over non-SELV wiring whenever possible Secure all wiring against coming loose inside the enclosure Securely fasten all hot or heavy components within the enclosure Clearly label any potential hazards - If necessary, label as For Use Only By Trained Operator Securely fasten all access covers with appropriate fasteners - use special tamper-resistant fasteners if required - label all covers Do Not Remove - Service To Be Performed Only By Specially Trained Personnel Finally, make sure that all safety issues on the checklist have been properly addressed If all of the above are properly done, you should have safe test fixtures which no safety inspector should have any problems with. One more thing, be sure to properly document all test fixtures, and keep copies on file. I hope this helps some, Scott Lacey - 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: new legal issues
Prop 65 sounds like another case of the technically illiterate creating convoluted laws which burden the productive sector and create more work for the bureaucrats. The entire electronics industry is tooled up for lead-tin solders. I doubt that the California market is large enough to justify the use of lead-free substitutes, and many manufacturers may simply decide not to expose themselves to potential future liability - the example of the State-financed tobacco megasuits looms large in corporate offices today. Massachusetts recently enacted a new victim disarmament law which goes so far as to regulate the technical aspects of firearm construction, including melting points of alloys and stringent drop test requirements. Many manufacturers have simply refused to ship certain firearms into the state, including current models of the M1911, which the U.S. military found safe and reliable enough to issue in World Wars I and II, Korea, and Vietnam. If individual states continue in this vein, either Congress will have to step in and deal with liability issues, or many of us will find ourselves living in landlocked islands where some technology is simply unobtainable. I shudder to think what the legal eagles (or is it vultures?) could find objectionable in the typical laser printer. LASERS! High Voltage! These things are too dangerous to be sold to consumers! As to the Lemelson patents, and barcodes, I can't help but wonder if he was a Patent Attorney by trade? The group is claiming that he invented barcodes, cordless phones, cassette players, camcorders, etc. Some years back one of the automotive magazines published an interesting story about a Patent Attorney named Selden who patented the automobile. He had every auto manufacturer in the country paying him royalties, until one by the name of Henry Ford decided to fight. In the final stages of the court battle plaintiff Selden, who had never built any autos, was challenged to actually build a working vehicle according to his patents. The finished vehicle was brought to a track where it was to race a production Ford in front of the judge. The Selden auto never got to race, due to numerous design defects. The patents were invalidated, and the auto industry thrived. Will history repeat itself? Scott Lacey - 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: cost effective EMC facility
Ed, I find your idea of a salt water ground plane very intriguing. I imagine the salts used would involve more than just table salt, and the chemistry would have to be checked and adjusted regularly, similar to a swimming pool. The problem of stratification could easily be solved with circulator pumps, which would be turned off just prior to actual use (those of you near fault lines might take advantage of natural agitation, your salt water pools would be shaken, not stirred). : ) On a related note, does anyone have any experience doing EMC scans below ground? It seems that the earth would be about the lowest cost shielding material available. Perhaps an updated and enlarged version of the early pioneers soddie (sod hut) might be just the ticket. It might even incorporate a salt water ground plane. A side benefit would be that EMC engineers might gain some useful exercise by swimming a few laps at lunch time (how many laps around the turntable/raft equals one mile?). : ) Scott Lacey -Original Message- From: Price, Ed [SMTP:ed.pr...@cubic.com] Sent: Monday, August 02, 1999 5:35 PM To: 'Arun Kaore'; 'emc-p...@majordomo.ieee.org' Subject:RE: cost effective EMC facility Arun: I was just struck by what you said about setup a Sea Plane or a salt water based site . Has anyone ever set up an OATS using salt water as the ground plane? Talk about excellent surface smoothness, easy to level and cheap material, plus simple repair! (Uhh, could we say it fixes itself?) Just what conductivity would be enough? Could we get enough conductivity before we reach salt saturation? I suppose the upper limit on surface area would be when we get to the point of the wind causing surface ripples. Or gravitational tides. Turntables might be a lot cheaper, too. Just a thin raft that floats. Seriously, has anyone tried this for an OATS? (I seem to recall the US Navy had a really big ship simulator here in San Diego, where they placed scale models of ships on a sheet-steel sea in order to model HF wire antennas.) Regards, Ed :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-): -):-):-):-):-):-):-):-):-):-):-):-):-):-):-) Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 619-505-2780 (Voice) 619-505-1502 (Fax) Military Avionics EMC Services Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-): -):-):-):-):-):-):-):-):-):-):-):-):-):-):-) - 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: Lightning and GFCI - OOPS!
OOPS! In my recent posting, I proved that human memory is a very fallible thing. I stated that in the failed GFCI outlet I examined, the sense coil measured current in the GROUND conductor. Thankfully, Jim Eichner pointed out that such a circuit would not fulfill the most important need for a GFCI. This forced me to sweep away some of the cobwebs and peer more closely into the gray matter filing cabinet. I now remember that the HOT and NEUTRAL leads both passed through the sense coil. Otherwise, the device was exactly as described. My apologies for posting incorrect information, and thanks to Jim for getting me back on track. Scott Lacey *** Jim Eichner responded: I was under the impression that the sense coil does NOT sense current in the ground wire, but rather it senses any imbalance between the currents on the Line and Neutral conductors. The difference is crucial, in that only the latter can detect fault current going directly to ground (e.g. by a water pipe) rather than back to the receptacle ground. *** - 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 or 75 ohm
Leslie, This is fairly simple using an RF signal generator and an oscilloscope terminated at 50 ohms. The RF generator must have an output impedance of 50 ohms. The trick is to first measure the amplitude delivered at the oscilloscope from a known 50 ohm cable at 5 MHz or greater. Then, without changing any settings, connect the unknown cable and observe the amplitude. The 75 ohm cable should exhibit a higher amplitude, and will probably vary with cable length. I once used a method similar to this to determine which end of a cable was shorted due to an improperly installed crimp connector. Before I set this up for him, the unfortunate technician had to cut one connector off and then check with an ohmmeter. This gave him a 50% chance of removing the good connector. By the way, I generally mark cables with colored tape - green for 50 ohm and violet for 75 ohm. Prevents a mix-up when working in a busy lab. Hope this helps. Scott Lacey 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 - 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: Current probe problem
In my opinion, letting the cable insulation touch the probe body is never a good idea. I always try to shim the cable and probe in order to center the cable within the probe opening. The trick is to keep the shims outside of the probe. A good trick is to make a V block out of wood, with a deeper center notch for the probe body. This insures good radial and axial alignment (for consistency) and also prevents the probe body from touching the ground plane. Scott -Original Message- From: Jim Eichner [SMTP:jeich...@statpower.com] Sent: Monday, June 21, 1999 1:10 PM To: EMC-PSTC Subject:RE: Current probe problem In his write up of the problem, Doug writes If possible, current probes should be positioned on the measured cable so as to minimize the potential between the cable and the current probe body. This usually means locating the probe near the ground/chassis end of a circuit. Following a tip from someone on this forum quite a while ago, I have observed significant variation in the spectrum of noise along the length of a cable. I have started doing my cable current measurements by sliding the probe over the length of the cable, with my spectrum analyzer in max hold mode. I assume I get a worst case sweep by doing this, as I pick up the worst of everything at any position on the cable. Following Doug's advice above, or any instance of using a current probe in a single fixed position, could result in the probe being positioned right at a null for a frequency of interest, sending you on a wild goose chase looking for some other source. Does Doug or anyone else have similar experience or a better way to overcome the problem? Regards, Jim Eichner Senior Regulatory Compliance Engineer Statpower Technologies Corporation jeich...@statpower.com http://www.statpower.com Any opinions expressed are those of my invisible friend, who really exists, but can only be seen by my dog. Honest. - 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: Request for Environmental Chamber Info for North American Mar ket
Kevin, I heartily second Jeff's endorsement of the Thermotron SE Series. We have several of the larger SE-1000-3-3 chambers in use. The integral 3.5 floppy drive is a tremendous idea. Test setups are easily archived for future reuse. The ability to capture a temperature log to disk for later graphing makes report writing easier. The network control capability (ThermoTrak) should really boost your productivity. Scott Lacey -Original Message- From: Kevin Harris [SMTP:harr...@dscltd.com] Sent: Wednesday, May 12, 1999 12:03 PM To: EMC-PSTC (E-mail) Subject:Request for Environmental Chamber Info for North American Market Hi Folks, Well it is time for me to get a new environmental chamber. I need a unit with temperature and humidity control and also automated control from a computer. We are looking for a capacity in the 8 cubic foot range. Does anyone have some manufacturer names and model numbers for a chamber they have used and liked or perhaps some info on units to stay away from (perhaps it would be better for the second part to be offline). Thank you Best Regards, Kevin Harris Manager, Approval Services Digital Security Controls 1645 Flint Road Downsview, Ontario CANADA M3J 2J6 Tel +1 416 665 8460 Ext. 2378 Fax +1 416 665 7753 email: harr...@dscltd.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). - 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: LFM test rig
Daniel, The key item which you should have is an anemometer probe. They are available at reasonable prices. This will allow you to measure airflow at the power supply under test. A simple box (length several times width and height to linearize flow) with fans mounted at the outlet end will be all that is needed, plus a variable supply to throttle back the fans until the correct LFM is measured. You will need a couple of holes in the side of the box for probe access. Keep the holes small - most hot wire type probes are less than half an inch in diameter. CFM (fans required) = LFM X Cross-sectional Area of box. Have Fun Scott ORIGINAL MESSAGE My company produces AC to DC Power Supplies. I have been directed to make a quick and dirty test rig that will allow me to put a predetermined airflow in LFM over the unit. Does anyone know of a website that describes something like this or have had experience building such a test rig and would be willing to share their expertise. Daniel W. Mitchell Product Safety Associate Engineer EOS Corp. - 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
Lou, The best way to deal with an angry water moccasin, as any good-ol-boy can tell you, is to dust them with a load of fine gauge shot. 100% effective, with no ricochet danger to bystanders. There are even special snake loads available in most revolver calibers. Fooling around with improvised methods is risking serious injury or even death. (my apologies to the politically correct) Scott -Original Message- From: Lou Gnecco [SMTP:l...@tempest-inc.com] mailto:[SMTP:l...@tempest-inc.com] Sent: Monday, May 03, 1999 10:06 PM To: emc-p...@majordomo.ieee.org mailto:emc-p...@majordomo.ieee.org Subject:Re: Rodents, part II Brent, When i worked for NASA we also had water moccasins. They liked to get in the cable trays and snuggle up next to the RG-9 coax cables, which were indistinguishable from them. Those snakes were highly poisonous and very aggressive. They were also BIG. they could strike clear across the ( 1 lane) road, and if you threw rocks at them, they would actually chase you. If you ever run into this problem, one way to get them is with a CO2 fire extiguisher. they hate the cold and it drives them off. Another way is to take a 10 ft piece of conduit, run a length of RG-223 thru it, leaving a loop at the far end. Then you ease up to the snake, slip the loop over its head and PULL, decapitating it. This takes nerve, because to do this you must be well within the snake's striking distance. I never did it, but I have stood there (aghast) and watched one of our technicians do it, several times. Do not try this at home. 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, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Refractory Ceramic Fibers (RCF)
Doug, Refractory Ceramic Fibers (RCF) look very much like white cotton fibers, except that they are stiffer. They are used as insulation for heaters, temperature chambers, etc. Look for them in your products around tanks, heaters, and the like. They will usually be either wrapped in foil or contained within a metal shroud. Another place they are used is around temperature stabilized (oscillator) crystals - referred to as a crystal oven assembly. The other applications you mentioned may possibly contain RCF. You should check with your suppliers. If it is whitish in color and won't melt or burn with a cigarette lighter, it should be suspected. Nomex is a pale brownish-yellow in color. I doubt that the transistor pads would contain RCF, an insulator, since their function is to transfer heat. Good Hunting Scott ==ORIGINAL MESSAGE== Recently one of our customers sent the email at the bottom of the page about RCF. To be perfectly honest I am not familiar with what types of materials or products might contain RCF. My understanding is that RCF are used for very high temperature insulation, much higher than regular fiberglass is able to support. Intuitively I believe that these fibers might be found in applications that use paper-like insulation, braided tubing, possibly transistor gap-pads or sil-pads. - 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: ? on EN 50140 - help!
Lisa, We use software from Chase for this. At each frequency step the generator power starts off several dB below the level determined during calibration (using field probes). Actual forward power is measured using a directional coupler in the antenna feed. The modulation is turned on only after the final power level is reached. The amplifier gain is left at maximum. All equipment is allowed to warm up fully prior to use. Scott -Original Message- From: lisa_cef...@mksinst.com [SMTP:lisa_cef...@mksinst.com] Sent: Tuesday, April 06, 1999 1:59 PM To: emc-p...@majordomo.ieee.org Subject: ? on EN 50140 - help! Could someone please clarify the following : the test procedure for EN 50140 states the frequency range is swept from 80 MHz to 1000MHz, using the power levels established during the calibration process, and with the signal 80% amplitude modulated with a 1 kHz sinewave pausing to adjust the RF signal level or to switch oscillators and antennas as necessary Does this mean that the modulation is to be turned on and off during the stepping or sweeping of frequency? I have never heard of doing this but I have been asked to respond to the question. Can anyone shed some light as to why someone would interpret it that way?? thank you!!! Lisa - 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). - 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
While not quite as bad as the disaster Ed Price described, I once had to fix a shielded room built to the specifications of a self-described RF expert. This gentleman had convinced his management that he could build a cheap and easy facility. The intended site was an unused loft on the fourth floor of the building, a 100+ year old former hat factory. They started by removing most of the inch-thick dust and all of the dead bird carcasses. They never stopped to wonder why there were so many dead birds - more on that later. Sheet metal workers brought in a load of galvanized steel and dumped it onto the somewhat clean floor. The expert had them butt the (still oily) sheets together and screw them down over the beat up wooden floor. Then, three inch wide strips were fastened over the joints, with screws every foot or so. One of the mechanical techs was a carpentry expert, so he convinced the RF expert to hire him instead of a building contractor to install the frame for the screening. He framed the cage using two-by-fours on the flat, on four foot centers, to save on lumber. Then he ran one-by-fours horizontally to provide some support for the copper screening stapled over the whole mess. He used a cheap hollow-core door because it was easier to carry up the narrow stairs. The door, of course, was wrapped in copper screening. The screening on the outside wall was left with several horizontal seams over the windows. The first hint of trouble was that AM reception was pretty fair inside the room due to the long unsecured seams. The carpentry expert had given up by that point, so I was asked to solder the window seams by my boss, the RF expert. Anyway, to make a long story short, I eventually used several thousand sheetmetal screws, several cartons of staples, several rolls of three-inch copper tape, and over a dozen pounds of solder before the room was more or less usable. I worked on that nightmare for weeks, finally having to solder the seams between floor and walls to plug some of the worst leaks. The room was finally quiet enough to use for pre test site scans and diagnostic use. My boss demonstrated his gratitude by sulking for weeks. We soon learned to cover the equipment with plastic when it was not in use. Birds often flew into their former roost/toilet. None of the experts involved had bothered to check for access holes before starting work. There were several holes, some of them in inaccessible locations above the screen room, which was framed in such a flimsy manner that no one dared to climb onto it. It is amazing how effectively steel wool sprayed with instant foam can plug leaks when it is inserted using a long pole with a frustrated test engineer at the other end. Never, ever, again! Scott - 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: PCB coating questions
Arjen, For insulation over PCB traces, some types of dry film solder mask might be suitable. These films are manufactured to a consistent thickness, and then laminated to the PCB. You need to check with your board vendor as to types and approval ratings. These films are very tough, just ask anyone who has ever tried to scrape through one in order to expose a trace for rework. You will want to make sure that your PCBs are fabricated as SMOBC, or solder mask over bare copper.Tin coatings have a tendency to flow when boards are wave soldered or reflowed, and may weaken the integrity of solder mask. You will also get better performance at high frequencies. As to conformal coatings, there are several issues to consider. The first is cleanliness. No-clean flux leaves a thin film over the PCB surface which will prevent proper adhesion of coatings. Most conformal coatings are intended for protection against moisture and humidity, and voids under the coating won't matter. For arc prevention, the coating must adhere tightly to the board and components. The second issue is how much of the board to coat. Coatings tend to interfere with repairs. Even repairable coatings make the job more difficult, and more importantly, tend to create voids when heated with a soldering iron. If only certain portions of your boards require protection you might consider selectively applying an epoxy potting compound to those areas. I hope that this will be of some help. Scott - 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: New EMC requirements proposed for IEC60335
Chris Not to beat a dead horse, but: While your observations on the political side are very interesting and all too true, I still stand by my comments regarding immunity testing of fly-by-wire (100% electronic vs. electronic/electromechanical controlled) products. These products are potentially far more dangerous than most people realize. The tremendous flexibility of microprocessors is often abused by lazy or sloppy designers, who tend to mask out problems in software rather than correct very real and serious hardware problems. This is especially common at smaller firms, of which I have worked for many (under temporary contract). On many occasions I have had to go to the mat in design meetings in order to win a couple of days reprieve to find and fix problems prior to a software solution being implemented. The problems almost always were relatively easy to correct, once diagnosed correctly. Some could have been very dangerous under the wrong circumstances if left uncorrected. If all immunity testing requirements were struck down tomorrow, I would still want to perform some level of testing on this type of product. To not do so is to expose yourself to tremendous legal liablilities in the future. Many immunity tests may be improvised in order to get a feel for how the product performs under duress. The point is not that consumer products must always behave flawlessly, only that no dangerous conditions result. Scott -Original Message- From: Chris Dupres [SMTP:chris_dup...@compuserve.com] Sent: Wednesday, March 03, 1999 6:29 PM To: Lacey,Scott Cc: emc-pstc Subject: RE: New EMC requirements proposed for IEC60335 Hi Scott. You wrote: It's sometimes all too easy to forget WHY we perform these tests. While we are trying to comply with written requirements in order to pass, we are also trying to ensure product performance in the real world, Time for my favourite hobby horse again... Going back even further than your memory, back in fact to 1972, the Treaty of Rome in Europe. This was when the Euro Nations decided to get into a single trading bed and knock down barriers to trade within Europe. In Europe, we called it the Common Market. In the US it is often called 'Fortress Europe'. Whatever, as a result of this treaty, all Euro Nation States had to follow Directives, one of which was raised in 1989, the EMC directive, which sort to regularise EMC performance within Europe. The purpose of this Directive, I need not remind you, is to ensure that no Euro State, or any other state for that matter, couldn't steal a trading advantage by making their equipment cheaper by building to a lesser standard of EMC performance. I suppose it was levelling the playing field, such that everything had to meet a minimum standard. Since then the standard required is slowly getting stiffer, but whether this improves the lot of the Euro Proletariat or not, I have my doubts, but sure as hell the sales of filters, screening and EMC testing services has gone through the roof. I could ask, Who are the CISPR committees, who told them what constituted a suitable EMC performance? Who voted them into power, who let them put the price of my TV up? Who told the BS and DIN people to make my life more complicated and more expensive by constantly making the EMC requirements more difficult to meet? I don't remember voting for them... But as I earn my living supporting exactly that business, it would be churlish to do so, so I wont just now. If you read the Directive, you will note that terms like 'Removal of barriers to trade', and 'free movement of goods across borders' etc. are mentioned so often it gets boring. But not once does it say anything about making the world a less EMC active place, or anything about improvements to the environment or living quality by the reduction of interference. No, the EMC Directive is a financial/political package, the politicians who approved the Directive's publication wouldn't recognise an EMC if it fell on their foot. Our activities in trying to achieve Euro EMC standards is merely to meet the political aspirations of a European Economic Area, and so far that seems to at least stopped big wars in Europe for the last 50 years or so. Maybe that's the real reason for all this. Another self opinionated twopence worth from a tired, cynical, aging EMC hack. Chris Dupres Surrey, UK. p.s. Has anybody heard about the Bad Haircut Directive? - 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). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org
RE: New EMC requirements proposed for IEC60335
$0.02 I just thought I'd add my two cents worth. It's sometimes all too easy to forget WHY we perform these tests. While we are trying to comply with written requirements in order to pass, we are also trying to ensure product performance in the real world, which can be a very hostile place from an EMC standpoint. Having your new microprocessor controlled washing machine jump from Gentle/Hand wash to Industrial Clean mode due to an EMC event may not be life threatening, but it sure would be aggravating when a favorite garment was destroyed. Many consumer products are now 100% electronically controlled, fly-by-wire type designs. At the same time, more and more sources of interference are being brought into proximity with them. I think the Europeans are probably well aware of this, which is why they may be thinking of introducing new standards. It is far easier and more cost effective to design in immunity than to attempt to add it on later. A robust product has a huge marketplace advantage, especially in a global marketplace. \$0.02 Scott - 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: Questions on Plug Adapters
Craig, - 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).
Need Suggestions for Inducing Harmonic Distortion
To the group, I am hoping that someone has some good suggestions for inducing harmonic distortion to the ac line input of an instrument under test. The nominal input is 120Vac/60Hz. The distortion frequencies are 120, 180, 240, and 300 Hz, at 5% applied harmonic distortion. The plan is to place the secondary winding of a 10:1 step-down transformer in series with one phase of the instrument under test. The distortion frequency will feed the primary of the transformer. Both frequencies will be generated by variable frequency ac sources. One source will be adjusted + or - 0.5Hz away from the exact frequency in order to explore all possible phase relationships over time. I plan to use true rms meters to monitor voltages. I also intend to first measure the open-circuit secondary voltage of the transformer in order to determine the exact winding ratio. Another possible method might be to use a combination of 50 ohm attenuators and a splitter to sum the outputs of two oscillators into the external (50 ohm) input of an ac source. My question is: Will controlling voltage ratios be enough to guarantee 5% distortion, or must I obtain a distortion analyzer and actually measure the output? I hope one of the group has had some experience with this type of test. This test can not be waived as the instrument being tested uses the ac waveform as a reference signal. Thanks in advance for any help Scott B. Lacey sla...@foxboro.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: Laser Pointers
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 that the majority of these handheld pointers are used responsibly and safely. There are many legitimate uses for a compact, low cost, battery operated laser source such as these. Some uses are yet to be discovered. By the way, all of the following devices have the potential to cause eye damage or vehicle or other accidents if misused: Laser Pointers LED Keychain Lights (Hi-Intensity Versions) Cordless Spotlights Portable Flash Units for Photography Infrared RemotesInfrared Illuminators for Night Vision Equipment Hi-Intensity FlashlightsAuxiliary Vehicle Lighting Hand Held Mirrors Visible Infrared Fiber Optic Transmitters Infrared is especially dangerous, even at low power levels, because we can not see it. It is possible to look into an IR source for hours without even knowing it. For what it's worth, Scott Lacey sla...@foxboro.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: Burning Card Module
Peter, Excessive energy applied to the capacitors is the most likely culprit. Any of the following might be the cause: 1) Excessive power supply ripple. Especially with tantalum capacitors, this will exceed the voltage rating even though the apparent DC level measured with a meter appears to be within specification. The voltage rating is somewhat misleading in many applications. It is a DC rating based on typical usage. The Effective Series Resistance (ESR) of the capacitor determines its power handling capability at a particular frequency. This is determined by performing a reactance plot of the component. Many manufacturers are somewhat cagey with published specifications, and seemingly identical components will not perform the same. 2) Lightning or Electrostatic Discharge. Either one of these will raise havoc with internal components. That outside antenna should have a properly earthed protection device at the point where it enters the building. The earth at the antenna protective device must have a solid (copper) connection to the power line earth at the service entry or it may aggravate the problem. Soil alone is not a sufficient connection. 3) Unintentional RF pickup at the antenna. High powered mobile transmitters can and will cause RF burns to components in some instances. Sites where explosives are in use ban operation of mobile transmitters for this reason. RF energy sufficient to ignite a detonator will easily destroy smaller capacitors. Scott Lacey sla...@foxboro.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: Cable Shielding
You might try capacitively coupling the cable shield at one end. We had some success doing this at a company I worked at some years ago. We mounted the connector shell to a copper plane at the component side of a thin PCB. the bottom plane of the PCB was in contact with the chassis of the unit. The PCB functioned as a plate capacitor, with several small ceramic capacitors connected between the planes to increase coupling. It worked quite well in our application. I hope this may help Scott Lacey Test Engineer The Foxboro Company sla...@foxboro.com -Original Message- From: rbus...@es.com [SMTP:rbus...@es.com] Sent: Wednesday, November 04, 1998 10:56 AM To: emc-p...@ieee.org Subject:Cable Shielding My company manufacturers image generation equipment (large mainframe computer) which is typically placed at a significant distance from the display device. These may be as much as 50 to 150 feet apart. In my EMC tests, I have determined that due to common mode, harmonic noise, both ends of this shielded cable must be terminated to the respective device chassis. Unfortunately, this has the potential to create significant ground loops which severely compromise the quality of the video signal. To add insult to injury, the signals within the cable are twisted pairs, differentially driven. This eliminates (as I understand it) the possibility of terminating the signal return to chassis ground at the point at which the cable exits the enclosure. So, on the surface it appears that I have the choice of meeting EMC regulations or meeting equipment performance. My questions are as follows; 1. Is it reasonable to provide single end termination of the overall (outside) cable shield? 2. Can differentially driven signal grounds be successfully grounded to chassis return? Should they be? 3. Is it reasonable to request or demand that both devices are sourced from the same power AND/OR bonded to a common power grid? 4. Is it desirable for signal returns to terminate at the chassis ground at the point at which the cable exits the device. Thanks in advance Rick Busche Evans Sutherland 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). - 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).
