Test and Measurement Forum

Hi,

I am new to programming in Labview and I need to write a software to automatically run the Picoscope and acquire data. I am basically scanning an object with a probe and recording the amplitude of the signal at a given frequency (plus harmonics). I have used the example programs given by Picoscope and made an attempt at writing the Labview program so that it does the above, using the Fast streaming functions. I basically open the Picoscope, set the channels, and then I loop over each position of the probe. At each iteration I ask the user whether the probe has been repositioned and once I have confirmation (by clicking 'OK' on a pop up message) I use StartPolling and then FastStreaming. I sample 8192 samples and perform an FFT and store the values. My problem is that if I wait a few minutes before clicking on 'OK' the sampling becomes chaotic. Do you know why?

Many thanks and apologies for the long explanation .

C

Hi

Which product do you have?

It's difficult to say what you are doing wrong. What do you mean when you say that the sampling is "chaotic"?

It sounds that block mode may suit your application better as you do not need to stream data continually.

Robin

Hi Robin,

I am using a Picoscope 3424.

What I meant by chaotic is that instead of sampling 8192 like expected, it starts sampling 1, then something like 100000 and the again 1 and then again 100000 etc..Also, if before pressing 'OK' (so in theory in between measurements) I vary the signal signficantly before putting it back to what it was before and then press 'OK', the time ordered data will show this variation even though in theory I haven't told the Picoscope to acquire data in between measurements (visibly it does, but I am not sure how and that is what I don't understand).

I did start with block mode but for some reason I changed to Fast Stream. I'll check it out again.

Many thanks for your quick reply,

Carolina.

Hi Carolina

I can't really tell what is happening without seeing your code.

However, I would go with block mode and call runblock when the user clicks on the button.

Robin

Thank you, I'll try that.