Check when AO current is not in compliance

[ebutler]

I have an NI-9265, which is an AO current device with a compliance voltage of 12V. Is there a way (apart from measuring the output voltage/current with a separate channel) to interrogate the device to determine if the output is below the compliance voltage?

[cbwestl]

Hello ebutler,

If you are using DAQmx, you can specify maximum voltage to 12V in the initial DAQmx Create Virtual Channel VI. If output voltage exceeds this, you will receive an error.

Or are you using cRIO?

Your suggested approach of measuring will also work of course.

[ebutler]

I am using DAQmx.

Thanks for your answer, but, there isn't a terminal on Create Virtual Channel for the maximum/minimum output voltage, only for the output current.

[cbwestl]

Sorry, my bad. I was looking at AO Voltage, not current.

Unfortunately, I can not find a way for you to internally check the voltage output of the 9265.

However, the maximum current output of the module is 20mA, so could you please explain why the compliance voltage matters?

If you set maximum current output to 20mA, you will receive an error that you can handle if you try to source more current.

Otherwise, you will probably need to compare actual current to set current, and manually find any difference.

[ebutler]

I'm driving a load that can vary, sometimes to the extent that driving 20mA of current would require more than 12V. It would be useful to know when this is the case.

It seems that there is no other solution but to measure with a separate AI channel, then.

[cbwestl]

If I understand your application correctly, then yes unfortunately you will need to measure separately.

Keep in mind that the module is specified to 20mA, 12VDC, 600Ohm maximum limits.

I would try to see if I can figure out the load somehow. Or limit it to 600Ohm. Do not know which options you have related to this.

Anyway, good luck!