PXI-6704 Analog Out not going to commanded values

[Gary_MavSysInc]

I'm driving all 32 channels of the PXI-6704. I have noticed that that outputs do not go to the commanded values every time. They do most of the time but they are messing up on a random basis. I have two PXI 6225 boards monitoring the output of the PXI-6704 to verify my conclusion. The DAQ Write VI is sitting in a while loop waiting on a cmd from a Shared Variable. On receiving the new cmd, the DAQ Write VI outputs the new cmd'd values (doubles) to the analog output board. I can leave the new cmd values the same, all zeroes, and I still see the random anomalies. The board is 4+ years old and I am beginning to wonder if I have leaky capacitors on the sample and hold circuit. The loop is running at 10 Hz.

[gaving]

Hey Gary,

I have a suggestion to try...

follow this example (if you have the DSC toolkit for LabVIEW) to set up an "event structure" that will "fire" when the value of your shared variable changes.

    -you can do this twice, once for ao0:15 (make two separate loops) and once for ao16:31.

If you do this then you won't be writing the same value over and over again, you will only be writing a value to the AO channels when the value of the shared variable changes.

If you do not have DSC you can just use an inner while loop to read the value and watch for it to change, then continue on to write the new value

Let me know what you experience...

-gaving