Don, We have made correlation between our chamber and OATS using the CNE meter at several positions in the "uniform field" of the chamber. Chamber antenna fixed, Oats antenna scanned. We have created a correction table whereby one point or an average of several points can be used depending on the particular EUT you are testing. If you have knowledge of where the EUT is emitting, maybe a top slot of a 6ft cabinet, you can elect to apply a specific correction. Or if the EUT is small, then the average of 4 points may cover the area of the EUT. We have gotten very good results. However, when cables are involved, correlation goes down. Our next run will include the several positions on the OATS also.
Best Regards, Dale Albright. ----- Original Message ----- From: <[email protected]> To: <[email protected]>; <[email protected]> Cc: <[email protected]> Sent: Wednesday, January 12, 2000 8:16 AM Subject: RE: Chamber and OATS Coorelation > > 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).
