RE: [PSES] Different Radiated Emissions results at different labs
Hi, One of the other problems that cause different emission levels can be put down to cyclic times. Many digital devices (and I have nothing to say if yours is or is not digital) have cyclic times where logic switching happens at a high clock speed but subsequent divisions of the clock only switch - say - once per second. This then gives a dwell time for the receiver, so that this switching is captured. I do not know exactly how this type of time varying emission profile is captured when using the CISPR weighting but I expect there will be a difference in reading if the emission is captured as opposed to not captured. I recently made some comparison measurements and there was 15dB difference between sweep one and sweep 2 of the same unit until I increased the dwell time. It ended up as 8.383 seconds before the results were of equal emission levels across the plot. This was a peak measurement. Regards, Tim Tim Haynes Electromagnetic Engineering Specialist SELEX Galileo, A Finmeccanica Company 300 Capability Green Luton LU1 3PG (Phone () +44 (0) 1582 886239 (Mob )) +44 (0) 7540629920 (Fax 7)+44 (0)1582 795863 (Email *) t mailto:tim.hay...@selexgalileo.com im.hay...@selexgalileo.com www.selexgalileo.com http://www.selexgalileo.com/ P Please consider the environment before printing this email. There are 10 types of people in the world-those who understand binary and those who don't. J. Paxman From: Bill Owsley [mailto:wdows...@yahoo.com] Sent: 29 October 2010 23:26 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Different Radiated Emissions results at different labs *** WARNING *** This message has originated outside your organisation, either from an external partner or the Global Internet. Keep this in mind if you answer this message. Like this notes says... +/- 8 dB per NSA between all qualified sites. Then there is the uncertainty part of the equipment to add in. Then if you have cables hanging off the EUT, all bets are off, unless you can ensure that those are NOT radiating. Not likely, so Mr. Murphy conspires to bedevils you with apparent random measurements. Welcome to the world of EMC Test! Find the reports on line of round robin tests of various labs using a small well defined source, one without cables, and most labs will be within +/- 4 dB. Still rough if you are into cutting that close to the limit. Aim for Class B, probably make Class A. Note that is targeting a 10 dB margin. Bill In the event of a national emergency, click on the following links to provide directions to your duly elected mis-representatives. http://www.usa.gov/Contact/Elected.shtml or... https://writerep.house.gov/writerep/welcome.shtml http://www.senate.gov/general/contact_information/senators_cfm.cfm if really desperate... http://www.usa.gov/Contact/Elected.shtml --- On Fri, 10/29/10, Derek Walton lfresea...@aol.com wrote: From: Derek Walton lfresea...@aol.com Subject: Re: Different Radiated Emissions results at different labs To: emcp...@sulisconsultants.com, EMC-PSTC@LISTSERV.IEEE.ORG Date: Friday, October 29, 2010, 10:33 AM HI Charlie, you point out one of the problems in EMI testing that always plagued us. The response by some has been to levy all sorts of controls on the measurement. While this has enabled a more accurate measurement, it hasn't improved correlation one bit. The whole premise of EMC measuring is full of holes, some are addressed with a huge effort, the rest are gaping. A friend once said to me it's like measuring with a vernier gauge and hitting with a sledge hammer. If you want to do EUT comparisons, you must have identical sites: ground plane size, edge termination, tables, masts, antennas, cables, instruments, software and people. Finally, and critically, the EUT MUST be set up exactly the same, with power derived from the same impedance. Take a simple example of NSA on a ground plane, the criteria is +/- 4 dB. On two different sites the NSA may read up to 8 dB different at the same frequency and both sites comply. I'm not sure you can quantify exactly what that would do to your results, but I'm sure the variation will show itself in your results. Forget the SA/Receiver argument, different antennas offer just as much if not more variation. I'd look more to the test software, EUT set up and the operators technique. Sincerely, Derek Walton L F Research -Original Message- From: Charlie Blackham emcp...@sulisconsultants.com To: EMC-PSTC@LISTSERV.IEEE.ORG Sent: Fri, Oct 29, 2010 2:04 am Subject: Different Radiated Emissions results at different labs Group Testing a product
RE: [PSES] Different Radiated Emissions results at different labs
Some products are very sensitive to interconnecting cable placement. I don't know of many labs that actually go through cable manipulation at each frequency being measured, along with rotating the product and scanning the antenna height, to make sure the emissions measured are truly maximized. I think this is one factor that may contribute to lack of repeatability. Jim Hulbert Pitney Bowes From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Larry Stillings Sent: Friday, October 29, 2010 9:23 AM To: 'Amund Westin'; EMC-PSTC@LISTSERV.IEEE.ORG Subject: RE: [PSES] Different Radiated Emissions results at different labs You should be using a different test lab. We have never had that much of a variation on the same EUT. I attribute that to using a true EMI receiver, which has much better amplitude accuracy then a spectrum analyzer. But that is a whole different discussion. I have seen products leave the lab and come back and have the same profile within 1 dB or less. Larry Stillings Compliance Worldwide, Inc. From: Amund Westin [mailto:am...@westin-emission.no] Sent: Friday, October 29, 2010 4:34 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: SV: [PSES] Different Radiated Emissions results at different labs Quite often I see 4-5 dB variation on the same EUT and on the same lab. Day 1: Make measurement. Take down the test setup. Day 2: New measurement. Same EUT. Tries to recapitulate the test setup with same EUT position on the table and cables. This is a challenge J #Amund Fra: Charlie Blackham [mailto:emcp...@sulisconsultants.com] Sendt: 29. oktober 2010 09:04 Til: EMC-PSTC@LISTSERV.IEEE.ORG Emne: [PSES] Different Radiated Emissions results at different labs Group Testing a product to CISPR11 class B and seeing quite a difference in results below 1 GHz when tested at two different labs. I don't wish to discuss why this is being done, but would be very grateful for any Quantitative data people have on differences between different OATS or between OATS and semi-anechoic or anechoic chambers. (The EUT is a small box with a single 2-core 24V dc/signal cable) Regards Charlie Charlie Blackham Sulis Consultants Ltd Tel: +44 (0)7946 624317 Web: www.sulisconsultants.com http://www.sulisconsultants.com/ Registered in England and Wales, number 05466247 - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher j.bac...@ieee.org David Heald dhe...@gmail.com - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher j.bac...@ieee.org David Heald dhe...@gmail.com - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher j.bac...@ieee.org David Heald dhe...@gmail.com - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc
Re: [PSES] Different Radiated Emissions results at different labs
In message B5113F712514D611BC3C00D0B76954220122312F@cw-server.complianceworld, dated Fri, 29 Oct 2010, Larry Stillings la...@complianceworldwide.com writes: I have seen products leave the lab and come back and have the same profile within 1 dB or less. It's reasonable to think that the repeatability is dependent on the fine details of the product and its AEs and cables. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK If at first you don't succeed, delegate. But I support unbloated email http://www.asciiribbon.org/ - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
RE: [PSES] Different Radiated Emissions results at different labs
You should be using a different test lab. We have never had that much of a variation on the same EUT. I attribute that to using a true EMI receiver, which has much better amplitude accuracy then a spectrum analyzer. But that is a whole different discussion. I have seen products leave the lab and come back and have the same profile within 1 dB or less. Larry Stillings Compliance Worldwide, Inc. From: Amund Westin [mailto:am...@westin-emission.no] Sent: Friday, October 29, 2010 4:34 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: SV: [PSES] Different Radiated Emissions results at different labs Quite often I see 4-5 dB variation on the same EUT and on the same lab. Day 1: Make measurement. Take down the test setup. Day 2: New measurement. Same EUT. Tries to recapitulate the test setup with same EUT position on the table and cables. This is a challenge J #Amund Fra: Charlie Blackham [mailto:emcp...@sulisconsultants.com] Sendt: 29. oktober 2010 09:04 Til: EMC-PSTC@LISTSERV.IEEE.ORG Emne: [PSES] Different Radiated Emissions results at different labs Group Testing a product to CISPR11 class B and seeing quite a difference in results below 1 GHz when tested at two different labs. I don't wish to discuss why this is being done, but would be very grateful for any Quantitative data people have on differences between different OATS or between OATS and semi-anechoic or anechoic chambers. (The EUT is a small box with a single 2-core 24V dc/signal cable) Regards Charlie Charlie Blackham Sulis Consultants Ltd Tel: +44 (0)7946 624317 Web: www.sulisconsultants.com http://www.sulisconsultants.com/ Registered in England and Wales, number 05466247 - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher j.bac...@ieee.org David Heald dhe...@gmail.com - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher j.bac...@ieee.org David Heald dhe...@gmail.com - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher j.bac...@ieee.org David Heald dhe...@gmail.com
SV: [PSES] Different Radiated Emissions results at different labs
Quite often I see 4-5 dB variation on the same EUT and on the same lab. Day 1: Make measurement. Take down the test setup. Day 2: New measurement. Same EUT. Tries to recapitulate the test setup with same EUT position on the table and cables. This is a challenge …. J #Amund Fra: Charlie Blackham [mailto:emcp...@sulisconsultants.com] Sendt: 29. oktober 2010 09:04 Til: EMC-PSTC@LISTSERV.IEEE.ORG Emne: [PSES] Different Radiated Emissions results at different labs Group Testing a product to CISPR11 class B and seeing quite a difference in results below 1 GHz when tested at two different labs. I don’t wish to discuss why this is being done, but would be very grateful for any Quantitative data people have on differences between different OATS or between OATS and semi-anechoic or anechoic chambers. (The EUT is a small box with a single 2-core 24V dc/signal cable) Regards Charlie Charlie Blackham Sulis Consultants Ltd Tel: +44 (0)7946 624317 Web: www.sulisconsultants.com http://www.sulisconsultants.com/ Registered in England and Wales, number 05466247 - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher j.bac...@ieee.org David Heald dhe...@gmail.com - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher j.bac...@ieee.org David Heald dhe...@gmail.com
