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U848xA Sensors and Averaging

Question asked by FrancisSmall Employee on Jun 19, 2015
Latest reply on Feb 7, 2016 by bejstam
I'm trying to make measurements while manually setting the filter length and using the U848xA USB power sensors when connected to a N1914A power meter. So far, no luck. The U848xA sensors are exhibiting different behavior than other sensors - I'm wondering if this is a defect in the power meter, or if this is something the USB sensors are inherently capable of. (The manuals don't seem to indicate that they can't do this, so... ???)

To recreate the situation, I have a 'standard' power sensor connected to Channel A of the N1914A (f/w A2.01.10 - Sep 2014), in this case it's a E9304A, and a U8488A connected to Channel C. They aren't hooked up to any signals - not that it really matters in this case.  Here are the SCPI commands I then send to the power meter:

* *RST
* INIT1:CONT ON (automatically transition from idle to waiting-for-trigger)
* INIT3:CONT ON
* SENS1:AVER:COUN 100 (or about 2.5 sec at 50ms/sample)
* SENS3:AVER:COUN 100
* TRIG1:SOUR BUS
* TRIG3:SOUR BUS
* *TRG

Note that, after *RST, averaging state defaults to On (SENSx:AVER:STAT ON) and auto trigger delay defaults to on (TRIGx:DEL:AUTO ON). You also can't use the immediate trigger if you want to make use of the trigger delay and filter length to average the reading.

After sending the *TRG command, Channel A updates after the expected 2.5 sec. Likewise, a FETCH1? command will block until the 2.5 sec have completed, then return the value. However, Channel C with the USB sensor never updates, and a FETCH3? command simply times out. (I have also tried this with f/w revisions A.01.01, A.01.06, and A.01.08 installed in the sensor but the behavior is the same for all.)

So, it sounds like defective behavior to me, but I wondered if anyone else had ideas about this.

Edited by: Francis Small on Jun 19, 2015 4:54 PM

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