Re: EMI Site Interference
It can be conducted overwhelming the spectrum analyzer (although unlikely) It could be large amplitude at an IF frequency (thus the broadband everywhere symptom) Might try a portable tuned receiver and start searching for the origin. - Robert - On Thu, 26 Mar 1998, Scott Douglas wrote: Hello Group - Here's a problem for you all to think about and hopefully help solve. I have a room in the corner of my building where I perform EMI pre-scans. Occasionally throughout the day I have a major interference show up on my analyzer. It does not come from the EUT. This is broadband, from 30 MHz to 1 GHz, at levels up to 70 or 80 dBuv. It is not like a flat carrier but rather more like PWM driven motor noise. It lasts from 15 seconds to 1 minute in duration. Then ambient returns to normal. We are a typical ITE manufacture. Our Genrad tester, wave solder, air compressors, motor generators, air conditioners, plumbing waste pumps do not appear to be the cause although none have been absolutely ruled out. The frequency and duration would seem to eliminate them however. We have swamp on one side, the interstate highway on another, fields on the third and the town on the last side. The only potential source I can find is a medical clinic about 350 meters away from us. They are the nearest building (the next being twice that far) and have an X-ray machine. Yesterday I went there at lunch and asked was the X-ray in use that day and they said yes but could not tell me a specific time that it was used. A software engineer here tells me that he has experienced radio problems in the parking lot outside my corner of the building. When he parks in a certain spot, his FM radio (the entire band) gets wiped out by a zhhzhhzhhh kind of noise. Move the car several feet any direction the problem goes away. This closely resembles what I see on the analyzer. Our analog guru suggests it is not the x-ray system as x-rays only last a few seconds. A one minute x-ray would burn you up he says. I never noticed this interference in another corner room of my building diagonally opposite my present location nor have I noticed the FM radio problem myself. Questions: 1.What are the possible sources of such interference? 2.Is the problem radiated or conducted? I suspect radiated as the signal goes away when you disconnect the antenna from the analyzer. 4.Why does this problem show up in only a small specific location on our property? 4.What are the potential solutions? I will be happy to answer any other questions you think of (if I can) and I look forward to the interesting comments I will receive from you all. Thanks in advance. Scott Douglas s_doug...@ecrm.com
Re: ITE vs Israel
I recently contacted Alan Clayman with Israel Testing Labratories web page: www.itl.co.il concerning another question and he was most helpful. There can be more involved than just meeting the regulations, once you find out what they are. There may also be other government approvals in order to ship to Israel. Based on my brief experience thus far, it appears that if you meet FCC UL/CSA requirements, you are at least well begun. -- George Stults HW Test Engr. CTS, Seattle WA
RE: FDA Modernization Program
Try http://www.fda.gov/cdrh/ode/parad501.html I think that will give you the complete information. You can also try www.aami.org. Mike Hopkins mhopk...@keytek.com -Original Message- From: sitar...@kodak.com [SMTP:sitar...@kodak.com] Sent: Thursday, March 26, 1998 3:51 PM To: emc-p...@majordomo.ieee.org Cc: 2203...@knotes.kodak.com Subject: FDA Modernization Program From Lotus Notes user: Michael J Sitarski Does anyone know about the FDA Modernization Program regarding Medical Devices? Does it pertain to EMC? Can you direct me to a source of further information? Thank you in advance for your responses.
Re: EMI Site Interference
Scott: Here's a couple of comments and suggested possibilities to investigate in tracking down the source of your problems. 1. Check the turn-on time (not X-ray operation time) for the X-ray equipment. The operator may turn on the unit, take one exposure, change film and set up for a second exposure, take the second exposure and then shut down the unit. That might account for the one minute (or so) duration. 2. Check out any low-power, automatic, motor-driven vent controls in your air conditioning system that may (only occasionally) come on during the day. Noisy, brushed motors may be used for such operations. 3. Don't rule out local sources generating power line conducted emissions yet. When the interference appears, quickly switch to a current probe and sense the AC line cord noise/current. Note the levels during and after the interference. Your AC line filter internal to the spectrum analyser may preclude detection when you disconnect the signal input cable. If suspicious current differences are noted, resume your search internal to the company. 4. Check to see if there are any pump controls nearby for storm drainage flow control (or other flow control, such as irrigation). These units are periodically polled from a remote control site (or operate on timers), and transmit a status to the remote site via RF links. I have such a slave valve site approximately 150 feet from my home and experience periodic bursts of interference (for 60 to 70 seconds) on multilple TV channels. Good luck, Mike Conn Owner/Principal Consultant Mikon Consulting
IEC 320 Cordset Lock
At one time I remember seeing a cordset lock to keep IEC 320 plugs connected to the receptacle. This was a formed wire assembly which attached to the mounting threads of the receptacle or filter and snapped over the cord. Does anyone know if these are still available and if they present any safety concerns. Thanks in advance Rick Busche rbus...@es.com rbus...@es.com
Re: EMI Site Interference
--- On Thu, 26 Mar 1998 13:14:35 -0500 Scott Douglas s_doug...@ecrm.com wrote: Hello Group - Here's a problem for you all to think about and hopefully help solve. I have a room in the corner of my building where I perform EMI pre-scans. Occasionally throughout the day I have a major interference show up on my analyzer. It does not come from the EUT. This is broadband, from 30 MHz to 1 GHz, at levels up to 70 or 80 dBuv. It is not like a flat carrier but rather more like PWM driven motor noise. It lasts from 15 seconds to 1 minute in duration. Then ambient returns to normal. We are a typical ITE manufacture. Our Genrad tester, wave solder, air compressors, motor generators, air conditioners, plumbing waste pumps do not appear to be the cause although none have been absolutely ruled out. The frequency and duration would seem to eliminate them however. We have swamp on one side, Not a likely source ;) the interstate highway on another, could be a very noisy vehicle ignition system which is driven past your location several times a day; do you see any schedule to the noise? (If you listen to ignition noise, you can actually hear the engine RPM, and you can tell an automatic from a manual transmission car. You can hear a vehicle as it slows for a curve, etc. Didn't Yogi Berra say that you can hear a lot when you listen?) fields on the third again, not likely and the town on the last side. Any complaints about EMI in the town? The noise spectra you are describing would create many gripes in an urban environment. Indeed, anything broadband enough to cover 30 MHz to 1 GHz is also likely has energy down to 1 MHz. This suggests you might be able to use a cheap loopstick antenna AM radio as a sniffing tool. The loopstick is quite directional. Practice doing a quick bearing sighting on a known location AM radio station. Then, be ready with the radio when the noise strikes again. The only potential source I can find is a medical clinic about 350 meters away from us. They are the nearest building (the next being twice that far) and have an X-ray machine. Yesterday I went there at lunch and asked was the X-ray in use that day and they said yes but could not tell me a specific time that it was used. A reasonable possibility. A software engineer (Uh Ohhh; these are guys who don't believe in harmonics and parasitics!) here tells me that he has experienced radio problems in the parking lot outside my corner of the building. When he parks in a certain spot, his FM radio (the entire band) does he ever listen to AM? What about that band? gets wiped out by a zhhzhhzhhh kind of noise. And this observation is not time dependent? You can repeat this at any time? This would sound more like a multipath wave cancellation node; the direct signal plus a reflection cancells the field strength at an unlucky location. Move a few feet, and the cancellation goes away. The signal magically emerges from the noise. This may be a distraction from your problem. Move the car several feet any direction the problem goes away. This closely resembles what I see on the analyzer. And just what do you see on the analyzer? Maybe you could set the analyzer up to a normally quiet freq, set the span to zero, trigger on video, and capture the time domain view of the signal. Is it random, or do you see pulse modulation? Does the PRR suggest anything? Our analog guru suggests it is not the x-ray system as x-rays only last a few seconds. A one minute x-ray would burn you up he says. Yes, the actual X-ray emission. But maybe the HV power supply runs for a minute before the tube is gated on. You may be seeing the spectra of an HV insulation breakdown. I never noticed this interference in another corner room of my building diagonally opposite my present location nor have I noticed the FM radio problem myself. Questions: 1.What are the possible sources of such interference? Still many; more data is needed. Work with that clinic; at least you should try to rule that very likely source. 2.Is the problem radiated or conducted? I suspect radiated as the signal goes away when you disconnect the antenna from the analyzer. About all that eliminates is an internal spurious in the SA. The path could be totally radiated, from far away directly to your test antenna. It could come into your building on the powerlines, only to be radiated locally. I could be generated locally, with radiated AND conducted components. 4.Why does this problem show up in only a small specific location on our property? You need more data to substantiate this. 4.What are the potential solutions? Find the source. Fix the source (if the source owner will let you). Break the path. Work 3rd shift. Move out of Dodge. Live with it. Fix it in software with a -60dB correction factor. Retire. Get promoted. I will be happy to answer any other questions you think of (if I can) and I
Re: Technical Papers
--- On Thu, 26 Mar 1998 08:27:28 + Paul Smith smi...@stranduk.com wrote: Hello all, Does anybody know where I could get hold of the papers presented at the EMC International Symposium, Sendai, Japan from 1994 ? Any information greatly appreciated, Regards, Paul Smith EMC Engineer ---End of Original Message- Paul, what a lucky request!! You can buy a full set of all symposia records, from 1955 to 1995, on four CD-Roms, from either the IEEE (908-981-0060) or Applied Microfilm Corporation (617-893-7863)(may be 781-893-7863 now), email at a...@bx.com or their web site at amc.bx.com. The cost is $40 for an IEEE member, a bit higher if not. -- Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 619-505-2780 List-Post: emc-pstc@listserv.ieee.org Date: 03/26/98 Time: 12:11:32 --
Re: EMI Site Interference
The duration, and your location could point to a vehicular source, for example a high power CB, or radio telephone in a vehicle. __ Reply Separator _ Subject: EMI Site Interference Author: s_doug...@ecrm.com at PMDF List-Post: emc-pstc@listserv.ieee.org Date:3/26/98 13:14 Hello Group - Here's a problem for you all to think about and hopefully help solve. I have a room in the corner of my building where I perform EMI pre-scans. Occasionally throughout the day I have a major interference show up on my analyzer. It does not come from the EUT. This is broadband, from 30 MHz to 1 GHz, at levels up to 70 or 80 dBuv. It is not like a flat carrier but rather more like PWM driven motor noise. It lasts from 15 seconds to 1 minute in duration. Then ambient returns to normal. We are a typical ITE manufacture. Our Genrad tester, wave solder, air compressors, motor generators, air conditioners, plumbing waste pumps do not appear to be the cause although none have been absolutely ruled out. The frequency and duration would seem to eliminate them however. We have swamp on one side, the interstate highway on another, fields on the third and the town on the last side. The only potential source I can find is a medical clinic about 350 meters away from us. They are the nearest building (the next being twice that far) and have an X-ray machine. Yesterday I went there at lunch and asked was the X-ray in use that day and they said yes but could not tell me a specific time that it was used. A software engineer here tells me that he has experienced radio problems in the parking lot outside my corner of the building. When he parks in a certain spot, his FM radio (the entire band) gets wiped out by a zhhzhhzhhh kind of noise. Move the car several feet any direction the problem goes away. This closely resembles what I see on the analyzer. Our analog guru suggests it is not the x-ray system as x-rays only last a few seconds. A one minute x-ray would burn you up he says. I never noticed this interference in another corner room of my building diagonally opposite my present location nor have I noticed the FM radio problem myself. Questions: 1. What are the possible sources of such interference? 2. Is the problem radiated or conducted? I suspect radiated as the signal goes away when you disconnect the antenna from the analyzer. 4. Why does this problem show up in only a small specific location on our property? 4. What are the potential solutions? I will be happy to answer any other questions you think of (if I can) and I look forward to the interesting comments I will receive from you all. Thanks in advance. Scott Douglas s_doug...@ecrm.com Received: from 192.168.190.1 by ALPHA.CORP.SCIATL.COM (PMDF V4.3-13 #7203) id 01iv4iq96rw0003...@alpha.corp.sciatl.com; Thu, 26 Mar 1998 14:21:40 -0500 (EST) Received: from [199.172.136.3] by gatekeeper.sciatl.com for doug.kea...@sciatl.com id OAA13141; Thu Mar 26 14:28:19 1998 Received: (from daemon@localhost) by ruebert.ieee.org (8.8.8/8.8.8) id NAA21778; Thu, 26 Mar 1998 13:11:59 -0500 (EST) List-Post: emc-pstc@listserv.ieee.org Date: Thu, 26 Mar 1998 13:14:35 -0500 From: s_doug...@ecrm.com (Scott Douglas) Subject: EMI Site Interference Sender: owner-emc-p...@majordomo.ieee.org Reply-to: s_doug...@ecrm.com (Scott Douglas) Message-id: fc.0064b57bb98c0064b57bb98c.b...@ecrm.com X-Envelope-to: Gasque, Bruce%SA-MEL-420@ccmail.corp.sciatl.com, Kealey, Doug%SA-B08@ccmail.corp.sciatl.com, Schultz, Charlie%SA-CHICAGO@ccmail.corp.sciatl.com, Waters, George%SA-MEL-420@ccmail.corp.sciatl.com MIME-version: 1.0 Content-type: text/plain; charset=us-ascii Content-transfer-encoding: 7bit Priority: normal Precedence: bulk X-Resent-To: Multiple Recipients emc-p...@majordomo.ieee.org X-Listname: emc-pstc X-Info: Help requests to emc-pstc-requ...@majordomo.ieee.org X-Info: [Un]Subscribe requests to majord...@majordomo.ieee.org X-Moderator-Address: emc-pstc-appro...@majordomo.ieee.org
FDA Modernization Program
A lot of info is on the web, search for FDA. Then after you are completely confused call Walter Snesko at the FDA. He has a toll free number 800 638 2041, extention 120. Rgds Lou Begin Forwarded Message Return-Path: owner-emc-p...@majordomo.ieee.org From: sitar...@kodak.com To: emc-p...@majordomo.ieee.org Cc: 2203...@knotes.kodak.com List-Post: emc-pstc@listserv.ieee.org Date: Thu, 26 Mar 1998 08:02:02 -0400 Subject: FDA Modernization Program Reply-To: sitar...@kodak.com From Lotus Notes user: Michael J Sitarski Does anyone know about the FDA Modernization Program regarding Medical Devices? Does it pertain to EMC? Can you direct me to a source of further information? Thank you in advance for your responses.
Fwd: Re: Yellow-green ground wire
I am re-posting this message because my email address has been changed. emc-pstc did not post this message because it came from my new address which was not in the member list. Ed, Here are the ones I use: For 14 AWG, 41 x 30 str., Grn/Yel, PVC, UL 1015, CSA Type TEW, 600V, 105 deg. C. Alpha 3079-28 Belden 8916-189 Carol Cable C2105-189 They also make other AWG in the UL 1015 class. Have been using these for over 10 years now, Once they were special order but now the color is a standard. For a distributor try: Pacer Electronics 1-800-969-6156 Regards, Scott s_doug...@ecrm.com
Fwd: Re: IEC 825-1
I am re-posting this message because my email address has been changed. emc-pstc did not post this message because it came from my new address which was not in the member list. Steven, There is no FCC equivalent to IEC 825-1. By FCC I presume you mean Federal Communications Commission here in the US. If you want the US equivalent to IEC 825-1 then you want the A.N.S.I. standard Z136.1. This is a voluntary standard. If you want the US law regarding lasers then you want 21 CFR 1040.10. Hope this helps. Regards, Scott s_doug...@ecrm.com
ITE vs Israel
Hello, Does anyone have experience or knowledge of the Israeli regulation applicable to an notebook ITE? Please differentiation between the AC/DC adapter requirements and the computer itself would be appreciated. Thanks Regards Guy Benjamin XL Computing (Canada) Inc.
Helmholtz Coils
Surely, someone out there has the vector equations describing the magnetic field iof a classic Helmholtz coil. My vector equations class, being 30+ years ago, is just too dim. I keep getting the derivation wrapped around the axle. The centerline equation, H=0.716NI/r, is readily available; however, I want to analyze the interior volume and, if practical, the exterior volume. Jim Sketoe Boeing Company (314)925-4735 james.g.ske...@boeing.com
Re: FDA Modernization Program
Michael, Try the FDA website at www.fda.gov Joe Martin marti...@perkin-elmer.com __ Reply Separator _ Subject: FDA Modernization Program Author: sitar...@kodak.com at INTERNET List-Post: emc-pstc@listserv.ieee.org Date:3/26/98 12:40 PM From Lotus Notes user: Michael J Sitarski Does anyone know about the FDA Modernization Program regarding Medical Devices? Does it pertain to EMC? Can you direct me to a source of further information? Thank you in advance for your responses.
Re: any insight appreciated
Lisa, The 10 ohms per square seems high to be critically connected with EMC directly..(maybe ESD ONLY???). I would have to say that the move to 20 ohms won't have much of an effect Now, the retest debate is interesting... If you have a TCF, I would recommend submitting your changes to the outfit holding your TCF, and letting them determine the extent of testing If not, (not knowing much about your product), I would have to say you would have to seriously consider retesting a whole spectrum of tests. Furthermore, if you only tested to old versions of standards, other tests may have to be done anyways Hope this helps, Regards, Bob Tims Compliance Engineer Ericsson Messaging Systems Inc.
RE: Required number of pulses per minute
There is actually another issue regarding repetition rates: MOV's, which are typically used for AC power mains protectors, have a very low average power rating. If you surge a MOV at rates of 1 shot/20 seconds continuously, many of the smaller varistors commonly used will get warm -- some will get hot. For this reason, most surge specifications don't require surge testing at rates faster than one per minute - this keeps the average power very low, won't affect MOV performance, and keeps the MOV cool! Mike Hopkins mhopk...@keytek.com -Original Message- From: Ing. Gert Gremmen [SMTP:cet...@cetest.nl] Sent: Thursday, March 26, 1998 10:02 AM To: Dudek, John; emc-p...@majordomo.ieee.org Subject: Re: Required number of pulses per minute Hello John and group, All Surge standards do stop at maximal 1 pulse per minute, BTW most surge generators for compliance to this standard cannot generate much more then 1 pulse per 25-35 seconds. IEC 1000-4-5 at page 19 lists the req. for surge generators. Open circuit voltage0,5 -- 4.0 kV Tolerance 10% Waveform: surge 1.2/50 and 8/20 uS voltage/current resp. SC current : 0.25 kA to 2.0 kA Tolerance 10% Polarity pos/neg Phase shifting : 0-360 degrees from LINE Output impedance 2 ohm Repetition rate : at least 1 per min So a generator giving 1 pulse per minute suffices for testing acc. to this standard. Standards can be bought at every standardization institute in Europe. Try f.i. the Dutch NNIhttp://www.nni.nl Regards, Gert Gremmen Ing. --- == Ce-test, Qualified testing == Consultants in EMC, Electrical safety and Telecommunication Compliance tests for European standards and ce-marking Our Web presence: http://www.cetest.nl -Oorspronkelijk bericht- Van: Dudek, John jo...@cor.com Aan: 'emc-p...@majordomo.ieee.org' emc-p...@majordomo.ieee.org Datum: woensdag 25 maart 1998 7:08 Onderwerp: Required number of pulses per minute Hello everyone, Maybe someone in the group knows the following information. IEC 1000-4-5 (and the European Norm EN 61000-4-5) prescribes tests for simulating the effects of voltage surges caused by switching disturbances in the power station. I am trying to identify the number of pulses per minute when applying test surges to industrial equipment. My searching has resulted in the following answers: 1. at least one per minute 2. 6 pulses per minute 3. 10 pulses per minute 4. 12 pulses per minute I have also been told that there is a new edition of EN 500082-2 (issued 1997) that might provide this information. However, the usual documentation sources only have the 1995 edition of this standard. My two questions are: 1. Where can I find the number of pulses per minute defined for industrial equipment when applying IEC 1000-4-5 or EN 61000-4-5 ? Or does anyone know this number? 2. Does anyone have a 1997 edition of EN 500082-2 ? If you do, where were you able to purchase it?? Thanks to anyone that can offer their input. John F. Dudek Manager, Product Safety Engineering Corcom Inc. Libertyville, Ill. USA voice: 847-680-7400, ext. 134 fax: 847-680-8169 (general) or 847-680-0340 (direct) Mailto:jo...@cor.com Visit us at http://www.cor.com
IEC 1010, clearance switching power supllies
OK, I admit, i'm confused. trying to figure out clearance on a switching power tranformer using IEC 1010 according to Annex D2, D4. 120/240Vac input goes thru rectifier comes out at max 390 Vdc into switching tranformer. Assuming Overvoltage III and Pollution 2 using Table D.6 at 600V, clearance is 5.5mm. Paragraph D.2 allows for interpolation which would bring the 5.5 mm down some. But para. D.2 refers you to para D.4. The first sentence is straight forward bit the next sentence that begins with However is where my mind goes numb, and then to get referred to D.5 is the icing on the cake. So the question basically is - am I stuck using the 600V value from table D6 or can I interpolate a value between 300 and 600V on Table D6? thanks for any insight that may unstick my brain and get the blood circulating again. eric henn...@fp.com
FW: Safety Requirements in SA.
More official information. -- From: LYONSWM Wimpie Lyons[SMTP:lyon...@mail.sabs.co.za] Sent: Thursday, March 26, 1998 3:56 PM To: WOODS, RICHARD Subject: Safety Requirements in SA. Dear Mr. Woods It is of great concern to me that you did not receive my E-mail message which was sent to both you and your SA agent. Please confirm receipt of this message. We accept both the IEC and EN specifications as proof of compliance. In the case of a product being tested against EN60 950 we require from the company to apply for a sales permit due to the SABS adopting the IEC set of specifications. It is a matter of administration only. This covers both the importer and the SABS. * Government Gazette no. 17548, Notice no. R1792 of 8 November 1996. Please supply me with your fax number. * The only deviation is the plug. We adopted the document as is. * It is a precondition for import. We want to get rid of the fly by nights. * Factory surveillance is not a requirement. We issue a letter of authority based on the test report. * No mandatory compliance marks are enforced. * The letter of authority will be presented at Customs through your company's Clearing agent. * The local agent will forward the documents for my attention upon which we will issue the letters if the test reports were found to be proof of compliance. The contact person at the SABS is myself. Please do not hesitate to contact me should you require further information. Yours faithfully Wimpie Lyons Manager: Electronic Engineering and Physics: Inspection Services Division. E-mail: lyon...@sabs.co.za
Re: Measuring the Noise level of an ITE PC or Workstation
Are you speaking of audio or rf noise? -Original Message- From: Kamran Mohajer kamran_moha...@netpower.com To: EMC-Pstc (E-mail) emc-p...@ieee.org; TREG (E-mail) t...@world.std.com List-Post: emc-pstc@listserv.ieee.org Date: Wednesday, March 25, 1998 7:21 PM Subject: Measuring the Noise level of an ITE PC or Workstation Fellow Engineers, I would like to find out what standard is being used for measuring noise levels for ITE equipment these days. In particular, I am interested in noise level measurement for PCs and workstations. Are there any labs in the northern California or in California that could do this test? I would appreciate your input on this matter. Regards, Kamran Mohajer, M.Sc. Staff Engineer NeTpower Inc., 545 Oakmead Parkway Sunnyvale, CA 94086 Tel:408-522-5185 Fax:408-522-4135 kamran_moha...@netpower.com
FDA Modernization Program
From Lotus Notes user: Michael J Sitarski Does anyone know about the FDA Modernization Program regarding Medical Devices? Does it pertain to EMC? Can you direct me to a source of further information? Thank you in advance for your responses.
Re:Yellow-green ground wire
Dear Ed, Try; Belden Montreal 4150 Ste. Catherine Ouest, Suite 420 Westmount, Quebec H3Z 2Y5 Phone 514-935-6372 Fax: 514-935-5706 or Carol cables Best regards, Mr. Kim Boll Jensen ScanView, Denmark
Technical Papers
Hello all, Does anybody know where I could get hold of the papers presented at the EMC International Symposium, Sendai, Japan from 1994 ? Any information greatly appreciated, Regards, Paul Smith EMC Engineer Strand Lighting Ltd, Mitchelston Industrial Estate, Kirkcaldy. Fife. KY1 3LY Tel: 01592 652333 Fax: 01592 653528 e-mail: smi...@stranduk.com
Re: any insight appreciated
-Oorspronkelijk bericht- Van: Cefalo, Lisa cefa...@mksinst.com Aan: emc-p...@ieee.org emc-p...@ieee.org Datum: donderdag 26 maart 1998 3:25 Onderwerp: any insight appreciated Hello all, I was wondering if any of you may have some insight or experience or recommendations about the following dilemma: We use a rather complex keypad/front panel on one of our pieces of equipment. This panel, in it's manufacture, consists of several different layers, polycarbonate, adhesive. etc.. One of these layers is a shielding material spec'd at 10ohms per square. This is very high compared to a metal enclosure: you can expect that it does not contribute very much to total screening fo EMI. From EMI point of view this is almost an opening. We would like to go to a 20 ohms per square material but are cautious about the potential effects on the EMC characteristics (emissions, esd, etc.). For ESD this is not bad too. Goal in ESD is to get rid of fieldstrength esp. for LCD displays, and to reduce discharge current. Both are met for 10 and 20 ohms per square, the latter even better. Immunity is always better when no direct discharge can take place on the conductive part of the foil. The window itself is grounded by contact with a silver mesh which in turn is grounded via conductive cement to studs that attach to the metal bezel. I expect in comparison with the actual resistance of the ground path the change from 10 to 20 ohms is small. In the interest of time and money, the debate is to re-test or not, and which tests... Any comments or help would be appreciated. Thank you, Lisa If you EMI performance is close to the limit (say within 6 dB), you better re-test. Consider ESD retesting too if direct discharge on the conductive part can take place. If you want to be safe, or follow the EMC-directive: RE-TEST everything. Hope i've been of any service to you. --- == Ce-test, Qualified testing == Consultants in EMC, Electrical safety and Telecommunication Compliance tests for European standards and ce-marking Our Web presence: http://www.cetest.nl cefa...@mksinst.com
US-CA-PETALUMA-COMPLIANCE ENGINEER
DSC's Access Products Division, in Northern California (Petaluma), is looking for a Compliance Engineer. BSEE with at least 5 years of industry related Compliance experience. Direct exposure to Bellcore GR-1089-CORE and GR-63-CORE is desired. We are also looking for a Hardware Verification Engineer. BSEE with at least 5 years of telecommunications experience. Solid background in electronics, digital design, and communications theory. Experience with telecommunications test equipment, specifications, and requirements. ADSL, ATM, and SONET experience is desirable. To apply, please forward a letter of introduction, resume (email preferred), and salary history to: Dave Lorusso david_loru...@optilink.dsccc.com 707-792-7807 (fax)
