I see I omitted an important phrase in my previous response -- EUT emission.
I tested a small EUT in the chamber and found the correlation to be off by as much as 7 dB when measured again at the OATS. When I compared the REFRAD data of the OATS to the REFRAD data of the chamber, I found a 6 dB variation at the same frequencies where the EUT emissions were off by 7 dB. Thus if one were to compare the emissions of the EUT to the correction factor of the REFRAD, there would be a 1 dB variation. Of course this is a small EUT with 4 cables. As the evaluation has just begun, I can only assume that the correlation will fall off as the size and complexity of the EUT increases. Don > ---------- > From: Barry Ma[SMTP:barry...@altavista.com] > Reply To: Barry Ma > Sent: Wednesday, January 12, 2000 1:00 PM > To: umbdenst...@sensormatic.com > Cc: mmate...@foxboro.com; emc-p...@majordomo.ieee.org > Subject: RE: Chamber and OATS Coorelation > > > Is it possible that the correction factors you got from RefRad* cannot > give the same good results when measuring real EUT? In other words, > different EUT would probably need different correction factors. I'm just > curious. > > *RefRad is a comb generator produced by EMCo - a part of ETS now. > > Barry Ma > --------------- > On Wed, 12 January 2000, umbdenst...@sensormatic.com wrote: > > Barry, > > Thank you for your comment. What we are trying to do is establish better > correlation between the chamber and OATS so we minimize our time in the > heat, humidity, rain and bugs (South Florida) at the OATS. We are not > trying to replace the OATS with the chamber. > > We have recently been evaluating a REFRAD for correlation purposes. So > far the results with the REFRAD factors have been very good. The > emission in the chamber was 7 dB off from the OATS value, but this > correlated to within 1 dB of what was predicted by the REFRAD. I admit > our sample universe is small at this time with only a handful of > emissions to compare to. But these first results are promising. > > Don Umbdenstock > Sensormatic > > ---------- > From: Barry Ma[SMTP:barry...@altavista.com] > Reply To: Barry Ma > Sent: Tuesday, January 11, 2000 5:55 PM > To: mmate...@foxboro.com > Cc: emc-p...@majordomo.ieee.org > Subject: RE: Chamber and OATS Coorelation > > > Mirko, > > I happen to have a copy of CISPR 16-1 at hand. Clause 16.6 "Open area > site validation procedure" reads: > > ... The deviation between a measured NSA value and the theoretical value > shall not be used as a correction for a measured EUT field strength. This > procedure shall be used only for validating a test site. ... > > The above statement is not followed by any explanation. What do you think > the reason is? My guess is that there are lot of factors causing > inaccurate E-field measurement. The collective result of those factors > cannot be simply corrected by changing antenna factors. > > At the end of your message, however, you stressed on "for a specific test > setup". May we try this "illegal" correction procedure with caution only > "for a specific test setup" and for a specific frequency range? Hopefully > it might be worthwhile to try. > > Barry Ma > Anritsu Company > Morgan Hill, CA > ----------- > On Tue, 11 January 2000, "Matejic, Mirko" wrote: > > Richard, > > You could improve correlation by adjusting chamber antenna factors for a > correlation differences which you can get from NSA measurements one at > OATS the other in the chamber with a fixed antenna height. You could also > determine correlation differences by comparing measured field strength > levels from battery powered comb generator. > > Fixed vs. 1-4m antenna height among other factors will always create > unpredictable correlation for a specific test setup. > > Mirko Matejic > > > > ______________________________________________________________ > > Free Internet Access from AltaVista: Get it, share it & win! > http://freeaccess.altavista.com/pika/www/initweb.jsp > > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to majord...@ieee.org > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to ed.pr...@cubic.com, > jim_bac...@monarch.com, ri...@sdd.hp.com, or > roger.volgst...@compaq.com (the list administrators). > > --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
