In message <00f201cb7737$825fe3a0$871faae0$@com>, dated Fri, 29 Oct 2010, Charlie Blackham <emcp...@sulisconsultants.com> writes:
>Testing a product to CISPR11 class B and seeing quite a difference in >results below 1 GHz when tested at two different labs. How much is 'quite a difference'? It's quite normal to find differences of 6 dB or so at particular frequencies, and this is just comparing OATS with OATS or SAC with SAC. The pragmatic crunch question is whether both sets of results give a PASS or give a FAIL by comparable amounts. > >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. I think it's futile to compare actual detailed results between OATS and SAC or FAC. You wouldn't even *expect* them to be very similar, given all the practical limitations of all the techniques. Just concentrate on PASS or FAIL by comparable amounts, on the one hand and PASS or FAIL by very different amounts on the other. The latter is almost always tracked down to significant differences in the test set up or the product's unusual characteristics (e.g. unusual cable configurations or significant directional emission from the body of the product). > >(The EUT is a small box with a single 2-core 24V dc/signal cable) If that's well-filtered, one might be optimistic about a PASS, so if it isn't achieved, look for gremlins, such as bad PC layout, 'ground' problems or emission from the product body. -- 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>
