PCI-6251 into LABVIEW DAQ Assist block interruptions and resets

[peter_mizza]

Signals being received from PCI-6251 into a LABVIEW DAQ Assist block interrupts and resets every 10 seconds after 1 minute of data acquisition. Would this be a memory buffer problem or is it something related to the hardware? I am using a BNC-2110 hardware connector. Please view the attached image.

[Erik_J]

Hi Peter,

There could be something going on with the memory buffer, I have a couple of questions for you.

Are you running an Analog Input or Digital Input task?  Are you doing Finite or Continuous acquisition?  How many samples are you trying to read?  And at what rate?  If you are doing Continuous Acquisition, what does your code look like?  Is it simply a DAQ Assistant inside of a While Loop?

Thanks,
Erik

[peter_mizza]

Hi Erik,

thanks for your fast reply.

- all incoming channels are Analog inputs (AC current, AC voltage, DC current, DC voltage)
- continuous data acquisition
- sample rate: 5 k Hz
- samples to read: 1000
- clock setting: internal
- DAQ assistant is located within a while loop in a SubVI; the outcoming data of this SubVI feeds other SubVI's.


Peter

[Erik_J]

Hey Peter,

What do you mean by block interrupts?  The picture isn't too clear to me, I can see the spike after 1 min, then another one after 10 secs, but could you explain the graph a bit more please?

Thanks,
Erik

Message Edited by Erik J on 12-04-2006 02:24 PM

[peter_mizza]

Hi Erik,

the spikes are not the problem. These are current injections of the inverter for an anti-islandig test, so they are intentional.

The problem is that the graph displays the incoming current signal continuously for only about 1 minute after starting the program. After this minute the signal is interrupted frequently in an intervall of 10 seconds (image shows one interruption), although the DAQ assistant is setted on continuous.

I hope, it's clearer now.

Peter

[Erik_J]

Hey Peter,

Ahh, I understand the graph now!  Hmm, this is very strange behavior.  Instead of using the DAQ Assistant, try to use the explicit DAQmx VIs (see picture).  You have more explicit control over what is going on with the DAQmx VIs and keep as much as you can out of the loop.

Regards,
Erik

[peter_mizza]

Hi Erik,

thanks for your help.
I figured out that the interruptions don't appear, if the samples to read are setted on 1000 and the sample rate is 5 kHz. I'm still using the DAQ assistant. When I try to increase the samples to read, the interruptions will appear. But I'm not sure what's the reason.

Peter

[Erik_J]

Hey Peter,

That is very strange behavior.  I could take a look at your code if you like, it sounds like something my not be synchronizing properly.  If you're happy with 1000 samples to read at 5 kHz and it's working, I would declare success!

Regards,
Erik