Measuring Fewer Channels Than Configured Using NI-DAQmx and NI-SWITCH

Updated Jul 6, 2018

Reported In

Hardware

  • PXIe-6368
  • PXI-2527

Driver

  • NI-SWITCH
  • NI-DAQmx

Issue Details

I have an application that involves NI-SWITCH and NI-DAQmx functions, and it is used to acquire up to 15 channels. However, I´m only acquiring from 5 channels now. I´m also using DAQmx Flatten Channel String VI.

How can I fix this?

Solution

First verify that this is not an NI-SWITCH problem:
  • Use NI-SWITCH shipped examples.
  • Use NI-DAQmx shipped examples, i.e Voltage - Continuous Input, to test if your hardware can acquire from all channels. If unsuccesfult, try to debug channel by channel using this shipped example or NI MAX. If succesful, continue with next steps.
If you are able to acquire from all your channels using shipped examples or NI MAX (used for debuging) then:
  • Verify the list of physical channels before DAQmx Create Channel (VI) is the correct list.
  • If using DAQmx Flatten Channel String (VI) verify that the elements outputted are correct.
  • If all of this is correct, then verify the data outputted in DAQmx Read is correct.

Additional Information

Isolate individual channels and use example programs or NI MAX to eliminate the possibility of a hardware problem.

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