I would use 6 dB as the correction factor for small EUTs. The 1 dB variance was after taking into account the 6 dB difference identified with the REFRAD.
As you had pointed out, the 1 dB left over is a function of "luck", i.e.,, the set up similarity between the EUT and the REFRAD and the repeatibility of any measurement. In addition, I have just started the correlation study. I have a first pass, but not a detailed data base by any means. I am not really at a point to describe a correction factor. Don > ---------- > From: Gorodetsky, Vitaly[SMTP:[email protected]] > Sent: Wednesday, January 12, 2000 5:24 PM > To: '[email protected]'; [email protected] > Cc: [email protected]; [email protected] > Subject: RE: Chamber and OATS Correlation > > Don, > > I would not use 1dB as the correction factor. You have not collected > sufficient statistics to consider this 1dB as "systematic error", it is > rather within the accuracy of your measurements. > > > -----Original Message----- > > From: [email protected] > [SMTP:[email protected]] > > Sent: Wednesday, January 12, 2000 12:19 PM > > To: [email protected]; [email protected] > > Cc: [email protected]; [email protected] > > Subject: RE: Chamber and OATS Correlation > > > > > > 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:[email protected]] > > > Reply To: Barry Ma > > > Sent: Wednesday, January 12, 2000 1:00 PM > > > To: [email protected] > > > Cc: [email protected]; [email protected] > > > 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, [email protected] 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:[email protected]] > > > Reply To: Barry Ma > > > Sent: Tuesday, January 11, 2000 5:55 PM > > > To: [email protected] > > > Cc: [email protected] > > > 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 [email protected] > > > with the single line: "unsubscribe emc-pstc" (without the > > > quotes). For help, send mail to [email protected], > > > [email protected], [email protected], or > > > [email protected] (the list administrators). > > > > > > > > > > --------- > > This message is coming from the emc-pstc discussion list. > > To cancel your subscription, send mail to [email protected] > > with the single line: "unsubscribe emc-pstc" (without the > > quotes). For help, send mail to [email protected], > > [email protected], [email protected], or > > [email protected] (the list administrators). > > > --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
