Don, We also have a PVC rack with the 16 positions (20, actually, counting the 40cm positions). It does speed things up considerably. Would still love to have a probe positioner, though (I am a gadget freak). :-) Bob R.
--- On Thu, 2/2/12, [email protected] <[email protected]> wrote: From: [email protected] <[email protected]> Subject: RE: IEC 61000-4-3 Field Uniformity Measurement To: [email protected] Date: Thursday, February 2, 2012, 5:05 PM I use a 16-position rectangular probe stand made from PVC pipe to do my uniform field calibration. Once it is set up, it takes maybe 90 minutes to do both polarizations. I have to open and close the chamber door a lot, but it is not that big of a deal. BTW, I use the constant forward power method. After doing the calibration the first time, I discovered where the null field locations are, so I simply avoid using those locations as the first point. For me, any of the 4 center points work well. Donald Borowski EMC Compliance Engineer Schweitzer Engineering Labs Pullman, WA, USA From: Bob Richards <[email protected]> To: [email protected] Date: 02/02/2012 01:50 PM Subject: RE: IEC 61000-4-3 Field Uniformity Measurement Sent by: [email protected] Brian, That is a sweet setup. I can only dream of having a probe positioner. I've tried selling the idea that we can get one and share it among the labs in our company, but getting them to spend that kind of money is like pulling teeth. Bob R. --- On Thu, 2/2/12, Kunde, Brian <[email protected]> wrote: From: Kunde, Brian <[email protected]> Subject: RE: IEC 61000-4-3 Field Uniformity Measurement To: "[email protected]" <[email protected]> Date: Thursday, February 2, 2012, 4:10 PM I must admit we have a sweet setup. We do radiated immunity in our 10 meter semi-anechoic chamber which when the floor panels are rolled into place makes a 3 meter fully anechoic setup. We also have one of those automated probe positioners so when we do calibration, we just set it up, start up the software, and go on break for a couple hours. Not really that fast, but what used to take us most of a week we can do in less than a day. The positioner makes it very quick and saves wear and tear on the chamber door. Worth the $22K we paid for it. I do understand your situation. A good friend of mine has a lab only a few miles from me with a small 3 meter chamber lined with ferrite tiles. I went to help him with his calibration testing and we had all kinds of trouble. Basically with the same equipment I have, at some points we couldn?t even hit 10V/m let alone 18V/m. We were pulling our hair out and never did get anything that resembled ?uniformity?. The best we could do is a 0.75 meter square unified field at 7V/m. It was like the power was just getting sucked into the wall tiles. Anywhere except right down the center of the chamber was highly attenuated. Maybe if we try some of your techniques we will have better luck. The Other Brian From: [email protected] [mailto:[email protected]] On Behalf Of Bob Richards Sent: Thursday, February 02, 2012 1:26 PM To: [email protected] Subject: Re: IEC 61000-4-3 Field Uniformity Measurement --- On Thu, 2/2/12, John Woodgate <[email protected]> wrote: Hopefully, there is much more 3rd harmonic (and upwards) than second, so it might be out-of-band. If there is more second, buy another amplifier! I have had to use an amp where the second harmonic was only about 13 dB down at the required test level. The antenna gain from the fundamental to the second harmonic changed by 15dB, so the second harmonic in the field was 2dB over the fundamental. Of course, when I tried to explain this to the bean counters, their eyes just glazed over. Unfortunately, "buy another amplifier" was not an immediate option. :-( I had to move the antenna in closer and start all over. I am beginning to think the grass must be way greener where you guys work!!! LOL. Bob R. - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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Thank you. - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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