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. 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