If MU is only for audit purpose, it won’t help at all. If you are using MU for your benefit, there are always some improvement opportunities in your test setup.
If you can’t quantify how inaccurate you are, how do you improve anything? <quote> I'm amused to read you make adjustments for your MU being larger. Keep in mind were kind of measuring jello...</quote> Uncertainty and measurement errors are different. Systematic error can only be compensated, not MU You should not make any adjustments based on MU. It is an uncertainty not a correction factor (don’t get amused) Plain EMC may be still measuring a jello. But more accuracy is necessary in “Radio” certifications. It will be really odd if your measurements are +/- 4 dB off for the radiated power J MU is a nice tool if you know/want how to use it OOO (Own opinions only) Best regards, Deniz Demirci National Technical Systems (NTS Canada) Phone: 403-568-6605 ext 244 fax: 403-568-6970 email:[email protected] <mailto:[email protected]> web: http://www.ntscorp.com/about/locations <http://www.ntscorp.com/about/locations> From: [email protected] [mailto:[email protected]] Sent: Thursday, August 12, 2010 5:43 PM To: Deniz Demirci; [email protected]; [email protected] Subject: Re: Calibration supplier for signal generator with pulse modulation Again, how do you guarantee / justify what you are doing if you don't care about the MU. I don't see how MU helps improve any measurement. How does it? Does it make the instrument magically more accurate? Does VSWR magically get lower? etc etc etc... No, it doesn't, nor will it ever. I'm amused to read you make adjustments for your MU being larger. Keep in mind were kind of measuring jello... I am strongly disagree with the “I did it and it is correct” attitude in EMC discipline. Maybe it explains the overall situation and measurement deviations between the laboratories Ironically, the "studies... round robins etc " that reported differences of 20 dB and up, included acredited labs, with MU budgets... So much for that. Quite simply, the only way for good consistent results is a good test technique, a competent operator, and good equipment. Please notice, MU is not mentioned here... Now, just for the record, I'm not being flippant. I prefer to focus where its worth the effort. I keep going back to measuring some limit, which I still maintain is somewhat arbitrary. If you fail by a few dB, so what... In real life you should be held accountable for your products performance. If you get calls because it malfunctions, then you don't have a good design. If you never get a call, then it's probably fine. We need to forget about MU and address the other low hanging fruit first... Sincerely, Derek Walton From: Deniz Demirci <[email protected]> To: Bob Richards <[email protected]>; [email protected] Sent: Thu, Aug 12, 2010 2:51 pm Subject: RE: Calibration supplier for signal generator with pulse modulation I've been performing in-house calibrations of LNA's, LISN's, CDN's, Current clamps and they have been accepted by the auditors. There is no restriction in terms of 17025 if you follow the requirements such as dedicated calibration instrumentation and MEASUREMENT UNCERTAINTY assessment. I admit my MU figure for calibration is larger than a calibration laboratory and it is accounted in EMC measurements. Again, how do you guarantee / justify what you are doing if you don't care about the MU. I am strongly disagree with the “I did it and it is correct” attitude in EMC discipline. Maybe it explains the overall situation and measurement deviations between the laboratories OOO (Own opinions only) Best regards, Deniz Demirci National Technical Systems (NTS Canada) Phone: 403-568-6605 ext 244 fax: 403-568-6970 email:[email protected] web: http://www.ntscorp.com/about/locations From: [email protected] on behalf of Bob Richards Sent: Thu 8/12/2010 7:51 AM To: [email protected] Subject: Re: Calibration supplier for signal generator with pulse modulation --- On Thu, 8/12/10, Ken Javor <[email protected]> wrote: And similarly, not because of MU but because of 17025 or perhaps ISO 9000, I've seen test equipment that could easily have been calibrated in house, such as current probes, LISNs and a 41 inch rod antenna have to be sent to the calibration lab. This is totally unproductive, except for the calibration lab. And I would argue further that it is detrimental to the discipline, because if you do your own calibration, you understand better how things work. This is a subject near to my heart. I've performed in-house calibrations of cables, LISNs, CDNs, current probes etc, and I agree 100% with what you said. Knowing the procedure helps to understand how things work and, just as important, gives a person the knowledge of how to perform quick verifications of a test setup in case there is ever any question as to the proper operation of that equipment. Every so often, a conversation comes up in the lab about whether we should do in-house calibrations. The issue is never about MU, cost or validity of data, it usually hinges around 17025 and what auditors will say. IMHO, shipping LISNs and/or CDNs to have calibrations performed by a cal lab is less reliable than in-house calibrations. This has little to do with the cal lab's ability, but from the possibility of damage during shipping. I've had CDNs come back with stuff rattling around inside (possibly chips off of ferrites?). If I can't perform an impedance verification in house, then what should I do to insure it is not damaged - send it back to the cal lab? Bob R. - 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]>
