Hi Gert, I think you would be better saying MU muddies the water on what you might be measuring. IT DOES NOT GIVE YOU ACCURATE NUMBERS.
Anyone that thinks EMC is metrology, especially when they only focus on a small part of the big picture, is unnecessary adding cost and complexity to a measurement process. Can anyone put their hand on their heart and say +/-10 db on an OATS really makes a difference in use? What about complying with a limit when there's never going to be anything in the are to be interfered with? Before MU needs to be used in EMC, there are many other low hanging fruit to pick first with much better payback in cost reductions or reproducibility. I like the measure jello with a micrometer analogy.... Cheers, Derek. From: ce-test, qualified testing bv - Gert Gremmen <g.grem...@cetest.nl> To: lfresea...@aol.com; j...@jmwa.demon.co.uk; emc-p...@ieee.org Sent: Tue, Aug 10, 2010 12:34 pm Subject: RE: Calibration supplier for signal generator with pulse modulation MU is of course the only way of knowing what you do/measure and ultimately test. But if it need to be taken into account…. is another story. But if you do not know where your errors are, I guess you can better stop measuring. In most metrological approaches only the hardware measurement chain is evaluated (antenna-cabling-measuring device), and default value is used for the transfer between EUT through OATS/SAR/FAR. And –as all of you know- the EMC community itself came up with a MU criterion (sort of) for that: the Normalized Site Attenuation with it’s +/4 dB margins (using a well defined simple source) This can be combined with the standard uncertainty of your measurement chain to get a total MU value. Most calcs result in 4-6 dB of MU More can be found in the appropriate part of CISPR 16 (part -4-2) of which I don’t have the exact reference at hand… someone ?? Gert Gremmen ce-test, qualified testing bv Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org <mailto:emc-p...@ieee.org?> ] Namens lfresea...@aol.com Verzonden: dinsdag 10 augustus 2010 19:07 Aan: j...@jmwa.demon.co.uk; emc-p...@ieee.org Onderwerp: Re: Calibration supplier for signal generator with pulse modulation HI John, just stressing Ken's use of the word unwarranted. I'm personally vehemently opposed to MU in EMC measurements: the reason why is that end to end even 10 dB is a trivial error... Just because the Stds committee says so does not make it warranted. All MU contributes is an academic exercise and lines pockets of individuals/organizations pushing it. We as an EMC community need to push back and say enough already. Our efforts are needed to address more important problems. Just for the record, Automotive EMC does not require MU, US Military to not require MU. If MU wasn't needed to put a man on the moon it sure as heck isnt needed in washing machines, computers etc. I'm guessing this is more than 10 cents worth! Derek Walton L F Research. From: John Woodgate <j...@jmwa.demon.co.uk> To: emc-p...@ieee.org Sent: Tue, Aug 10, 2010 11:46 am Subject: Re: Calibration supplier for signal generator with pulse modulation In message <c886e31f.841a0%ken.ja...@emccompliance.com>, dated Tue, 10 Aug 2010, Ken Javor <ken.ja...@emccompliance.com> writes: >Uncertainty for modulation parameters of depth or pulse on-off ratio >and time >duration? Uncertainty applies to things like field intensity, >where the >construction of the room or OATS and near field effects >combine to provide >significant uncertainty. > >But something easily measured with an o'scope of modest (audio) >performance? >That is a totally unwarranted extension of the concept. > Unfortunately, it isn't. The metrologists have inflicted formal uncertainty assessment on us and it's like death and taxes - always with us. Everything has to have its uncertainty assessed. -- 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. 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