RE: FW: [Fwd: [SI-LIST] : Copper balance] {Venting of PCBs}
Larry,
I had no idea there even WAS such a standard.
Interesting, the things it's possible to learn
here; an assemblage of experts, indeed!
Thanks!
Cortland
== Original Message Follows
>> Date: 24-Jan-01 15:19:07 MsgID: 1078-329 ToID: 72146,373
From: Larry Merchell >INTERNET:lmerch...@t-yuden.com
Subj: RE: FW: [Fwd: [SI-LIST] : Copper balance] {Venting of PCBs}
Chrg: $0.00 Imp: Norm Sens: StdReceipt: NoParts: 1
From: Larry Merchell
Subject: RE: FW: [Fwd: [SI-LIST] : Copper balance] {Venting of PCBs}
List-Post: emc-pstc@listserv.ieee.org
Date: Wed, 24 Jan 2001 15:10:35 -0800
Reply-To: Larry Merchell
Cortland,
The holes or slots may also be required to
meet the "Maximum unpierced conductor area"
requirement of UL796 Standard for Printed-
Wiring Boards for your particular PWB supplier.
In the UL Recognized Component Directory (vol.
3, ZPMV2) it is listed as Maximum, Area,
Diameter, Inches.
Regards,
Larry Merchell
Taiyo Yuden (USA), Inc.
San Marcos, CA
== End of Original Message =
---
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: IEC 606010-1-2
It is the same as 60601-1-2; 1993, i.e. CISPR 11, class A or B depending on the environment. Best regards, Jim owner-emc-p...@ieee.org wrote on 1/25/01 2:34 pm: Any advance info on conducted emissions for the new standard? thnx Brian O'Connell Taiyo Yuden (USA), Inc. --- 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 Jim Conrad P.O. Box 25 Hamilton, M.A. 01936 Phone: 978-468-3909 <>
RE: Decoupling Capacitors
Chris, Thank you for the interesting story. Unfortunately this case is not all that unusual. About a decade or so ago (names have been changed to protect the guilty) I was working in the hardware engineering group at a company that had just instituted an aggressive cost-reduction program. Thanks to a lucky break, we managed to hear about the latest cost reduction "victory" before any product was shipped. Manufacturing had decided to save money by eliminating those useless decoupling caps - ALL of them! They removed all the decoupling caps from 2 boards and re-ran the ATE tests. The boards passed, so they got an engineer to sign off on the ECO. This (mechanical) engineer had always wondered if those darn caps were really needed so he was more than pleased to sign off. We put an immediate halt to the cost reduction. I still have nightmares about what could have happened to our customers if that one had sneaked through. The product was buggy enough as it was! A couple of things need to be mentioned. One is that there were generous cash bonus awards for cost reductions. This caused a gold-rush mentality to take hold. People had strong incentives to cheat by making endruns around the normal review process. Another is that, due to politics, the Mechanical Engineering group had almost total control over the entire PCB process. A PCB is not just a mechanical object. It is a complex electronic component. I have seen great designs ruined by lousy layouts and mediocre designs rescued by careful layouts. Again, Thank You Chris for taking the time to relate this experience to us. Scott Lacey -Original Message- From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf Of Chris Maxwell Sent: Friday, January 26, 2001 9:38 AM To: 'EMC-PSTC Internet Forum' Subject: Decoupling Capacitors Just a little personal experience I want to relate. The EMC people can really appreciate this. Sorry about the long, conversational tone, but I think it will help people appreciate how much effort could have been prevented by following simple EMC design rules. One of our products has a motherboard with an ISA bus with 7 standard connectors. Over the past 7 years or so, we have taken advantage of this flexibility to use processor, VGA, ethernet and serial extender cards from numerous third party vendors with quite a bit of success. About a month ago, we started having troubles with an 8 port serial expansion card that we buy from a third party vendor. Some of the units would fail the serial comm test during the final quality test before shipping the units. We started testing samples extensively and set up some overnight tests to exercise the cards. We found that some cards would run indefinitely, others would fail. Sometimes they would fail after 1 minute, sometimes after 10 hours. We considered interrupt servicing (software) problems, bad chips, faulty connectors ... We then did about two weeks' worth of "isolation" testing, where we would shift boards between units, trying different software, firmware, hardware, processors (cookware?) configurations. We found only one common thread. That was, "bad" boards would always fail, although the time to failure was random. "Good" boards were always good. We then started swapping chips between "good" boards and "bad" boards. We swapped RS-232 drivers... no change. Uarts... no change. Processors ... no change. Memory... no change. Firmware... no change. We then swapped 3each 74LS374's and 2each 74LS373's all at once Aha! the "bad" board became good and the "good" board became bad. We thought we were narrowing in. So, we put the 373's back so that only the 374's were swapped. Suddenly, neither board would fail after an entire day's testing. Both boards became good? This brought our isolation testing to a screeching halt. We thought we were on the trail of finding a bad chip either by date code, manufacturer ... something. But when both boards went "good" this hypothesis went out the window. (For those who are curious, we did put the chips back so that all 5 were swapped and got our "good" and "bad" boards back.) We then sent one "good" and one "bad" board back to the manufacturer. They couldn't duplicate the problem. Their owner talked to our software guy and suggested changes in interrupt handling, handshaking, initialization ... None of this worked. About three weeks ago, my boss was sitting down with us evaluating the boards, we were looking for differences in manufacturers, date codes, bad solder joints ... He made a casual comment that the board didn't have many decoupling caps. ( You know, those $1 per ton, ubiquitous, little yellow gumdrop, 0.1 uF capacitors). At the time, we all agreed, but thought nothing of it. This product has been "stop-ship" for about a month. We have customers screaming, marketing is asking for daily updates. The guys in manufacturing are renting hotel rooms to store backed up units (that part's
RE: Lights for 3-meter Chamber
I should have been a bit less negative about fluorescent lights. Certainly, you can wire several fluorescent fixtures in your room to a switch, so that you can take advantage of their inherent glare-free quality and the fact that they produce much less heat. When the power is switched off, they will be completely harmless to your chamber environment. The down side to this is that, sooner or later, you will forget to turn them off and will ruin a data scan or two. Regarding fire hazards in general (even from the EUT frying itself). I always like to add a honeycomb RF vent panel next to the location of the test technician's station. There are times when it's very handy to be able to hear the EUT in operation, to hear warning signals, and simply to be able to smell the inside of the chamber. It's also a handy place to route a fiberoptic cable or two, and a good place to route a string (I like waxed cable lacing cord) if you need to be able to "push" a reset button. (One of my recent programs involves a combat helmet-mounted electronics pack, which shuts itself off after 45 seconds if it doesn't detect any physical movement of the soldier. So we have to keep "waking it up" throughout the testing program.) Regards, Ed -Original Message- From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Thursday, January 25, 2001 11:15 PM To: Price, Ed; 'marti...@appliedbiosystems.com'; emc-p...@majordomo.ieee.org Subject: Re: Lights for 3-meter Chamber One caveat. If you are on a budget for a room, fluorescents can be very handy in that they don't add nearly to the heat load that needs to be removed like incandescents. You need enough incandescents to light the room sufficiently when the fluorescents are turned off during an RE test. -- >From: "Price, Ed" >To: "'marti...@appliedbiosystems.com'" , emc-p...@majordomo.ieee.org >Subject: RE: Lights for 3-meter Chamber >Date: Thu, Jan 25, 2001, 9:23 AM > > > > > > -Original Message- > From: marti...@appliedbiosystems.com > [mailto:marti...@appliedbiosystems.com] > Sent: Wednesday, January 24, 2001 6:15 PM > To: emc-p...@majordomo.ieee.org > Subject: Lights for 3-meter Chamber > > > > We are setting up a 3-meter chamber to do some pre-compliance measurements. > What are the best low emissions lights to purchase for this chamber. > Please be specific as to manufacturer and models. > > Thanks > > Joe Martin > Applied Biosystems > > > --- > > The choice for internal chamber lighting is still simply incandescent bulbs. > Avoid anything that uses fluorescent lights, and also avoid any electronic > ballast or driver circuitry. > > Incandescent lamps within chambers have a reputation for burning out > quickly. This is because they are turned on and off so much (I turn mine off > whenever I close the chamber door), and also because the lights are operated > off of filtered power. When the lights are off, there is often very little > load on the output side of the room filters, causing a slight voltage rise. > Thus, the lights are turned on usually with a slightly high nominal voltage > condition. > > You can use expensive "traffic light" lamps, or you may find some industrial > bulbs rated for 130V or so. My position is ordinary light bulbs are cheap. I > just keep a case handy, and I bought one of those extension wands so that I > can change a bulb without even getting a ladder. > > I also installed a couple of 150W floodlights, so that I can switch them on > to help my digital camera's flash when I take pictures. (The anechoic wall > treatment really soaks up the available light; I usually force the camera up > the equivalent of two "f-stops", even with the floodlights.) > > Regards, > > Ed > > Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Services Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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
Safety in Oregon
Dear colleagues, I would like to know if UL mark (or other certification mark) is required, or mandatory in Oregon state, for safety purpose. This applies to a laboratory equipment (spectrometer). If you know some web links, I'll appreciate them. Thanks a lot for your cooperation, Pierre SELVA 2 route de la Grobelle 73000 JACOB BELLECOMBETTE Tel : 33 (0) 6 60 52 04 96 Fax : 33 (0)6 61 37 87 48 e-mail : pierre.se...@worldonline.fr
Periphery ESD ground rings on high speed interface cards
Greetings all. I have a general question about the use of isolated ground rings at the periphery of rack type optical interface cards (so maybe it's specific). My understanding is that isolated (fully moated) ground rings are often placed around the edges of high speed interface cards in an attempt to keep ESD out of critical areas on the board (or to hold in edge radiation is another more suspect reason I have heard). This just seems like a bad idea to me, but I must admit that I am not on the design end of things. I ran this by a microwave specialist I know and he shared my opinion. There just seem to be too many opportunities for arc-over or induced voltages that could cause the same or more damage to the board. My question is this: does anyone have a concrete reason why such a ground ring would be a good idea? I would like to keep this discussion in the 1+GHz range, but anyone with experience please feel free to chip in. Thanks in advance David Heald Senior EMC Engineer/ Product Safety Engineer Curtis-Straus LLC NRTL Laboratory for NEBS, EMC, Safety, and Telecom Voice:978.486.8880x254 Fax:978.486.8828 www.curtis-straus.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
