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DSOX 3000 series (and 4000 series) - waveform record length

Question asked by dprmorris on Jun 6, 2013
Latest reply on Jun 18, 2013 by chris_felder
Hi All,

I'm using the Agilent DSOX 3000 series scopes and controlling via labview. 

In my application, I need to acquire an averaged waveform from the scope. This in itself is easy enough, but I'm running into an issue with the number of points returned by the scope. 

To acquire my waveform I:
:STOP
:ACQ:COUN
:ACQ:MODE RTIM
:ACQ:TYPE AVER
:DIG
*OPC?
:WAV:POIN:MODE MAX
:WAV:POIN 5000
:WAV:BYT MSBF
:WAV:FORM WORD
:WAV:XOR?;XIN?;XREF?;YOR?;YINC?;YREF?
:WAV:DATA?

and then carry on essentially. The issue I have is that I seldom (if ever) get the number of points requested. Today, when I run my code I'm getting a 4444 point waveform returned. But I have seen it vary even when the scope setup is the same!

If I use the same basic code, but set :ACQ:TYPE NORM it works fine and I get 5000 points every time.

Anyone come across this before? Any ideas what I can try to solve this? The reason its a problem is that I need to FFT the code once I have it back on the PC and I want to ensure I get consistent delta F out of my FFT. I know I could cludge it by zero padding to a certain length, but I don't really want to do that. Additionally I'm trying to maintain compatibility with some other code down the line which was written for waveforms coming off a Lecroy scope which behaved much better in this respect and always returned the right record length.

Any thoughts gratefully received!

Thanks

Paul  

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