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Mutiple PXI-6143 boards pretrigger problem

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Hi All,

 

I am re-posting this from the Multifunction DAQ discussion panel as suggested by an NI aplication engineer. Hope it's ok to cross-post since I apparently went to the wrong place since this question may be more PXI-related than Multifunction DAQ. The questions is the following:

 

I am running into some strange pretrigger problem on using multiple PXI-6143 cards and hoping you can give some help!

 

I am using 4 PXI-6143 boards in a PXI-1033 chassis to do 32-channel simultaneous analog input acquisition. I used the DAQmx functionality to configure a pretrigger task using reference digital trigger externally fed into a PFI line. The program will acquire those data and save into a TDMS file (through DAQmx Configure Logging.vi) and then finish. I found that the pretrigger works well if I only select channels from a single board (say Slot2 ai0:7, or Slot3 ai0:5, somthing like this). When I fire up the trigger, the program finishes almost right away. The program is basically configured using DAQmx utilities.

 

However, if I select channels from more than one board (say Slot2 ai0 + Slot3 ai0), no matter how many channels I selected, after firing up the trigger, the program will keep going for approximately the amount of time required for all pretrigger samples to be acquired, and then finish. So then in the resulting file the desired signals right before the pretrigger happens were not there.

 

This is very strange... Can anyone recommend a fix, please?

 

Thanks a lot!

 

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boto,

 

Would you be able to post your code?

 

 

James K.
National Instruments
Applications Engineer
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Solution
Accepted by topic author boto

See here.

 

 

Best Regards,

John Passiak
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Hi James, please see my code attached below.

 

Hi John, thanks and I will do the update today and report back if it solves the problem.

 

Thanks both of you very much!

 

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It does seem like that updating the DAQmx driver to 9.5 solved the problem.

 

Thanks very much!

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