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failed channels? Diagnostic for PCI-6120

I use the PCI-6120 and the Traditional (legacy) NI software.  In the middle of an experiment one of the analog output channels apparently stopped working.  About 8 hours later, the second analog output channel apparently stopped working.  (We do very long experiments, but we have used the system for more than 24 hours in previous experiments without problems.)

I am trying to figure out if the analog output channels could have died or if there is another explanation.  Using the BNC accessory device, I looked for the signals on an oscilloscope, but there were no signals.  I also tried the sine generator function in MAX, but no sine was generated on either channel.  Digital trigger signals still work.  I am trying to locate a voltmeter with the proper pins to test the signals through the I/O cable from the PCI-6120 to the BNC.  Besides the methods I have already tried, is there anything else can I do to test the function of the channels?  Does it seem reasonable that the channels would simply stop working?  If so, can they be repaired, or is a new board the likely solution?

Any ideas would be appreciated.  Thanks.
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Those sound like the same troubleshooting steps that I would recommend.  You can try testing the Analog Inputs and DIO lines as well to see if the malfunction is isolated to the Analog Outputs only.  Also, were any errors generated by your program when the malfunction occured (I'll assume youre using LabVIEW)?  When you try to generate a sine wave on the analog output in MAX, do you just read 0V?

It sounds like during the course of the analog generation, an excessive voltage might have occured, causing damage to the board.  If that is the case, a new board can be purchased, or the board can be sent in to National Instruments for repair.


Nicholas B, National Instruments


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Thank you for your reply.  Today we tested the other lines.  One of the Analog Outputs is reading a constant voltage of about 5.5 V while the other is about 0 V.  The DIO lines that we use are fine.  The Analog Inputs seem to be ok as well, so the problem does seem to be isolated to the Analog Outputs.  When we generated the sine in MAX, there was no voltage.  I am not using LabVIEW, just Visual C++ and Visual Basic, and when the malfunction occurred there was no error in the program. 


We did not do anything differently at the time of the malfunction, but it does seem like the board is damaged.  Do you think that there is something on our software side that could have generated excessive voltage that I should try to check (to prevent problems from happening again)?  It sounds like the next step will be to call the company to inquire about repairs. 


Thanks again.

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Message 3 of 5
If you are not providing external sources, the board should not be able to exceed its own limits.  However, a short could damage the board as well...which can occur on the board.  I would double check the code to ensure its values are not exceeding limits and give our support line a call to inquire about an RMA.  Also make sure all of your ground lines are connected properly to ensure that you do not have ground loops. 
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Message 4 of 5
Thanks, Nicholas.  You have been very helpful.
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