6289 DAQ - AI_SENSE

[BeanBoy]

Is it possible to wire a digital line into the AI_SENSE. That is wire PO.1 into AI_SENSE.

I ask because I need to Verify the levels for a control line on a DUT that is capable of producing +12V(+/-0.5V), +5V(+/0.1V), 0V and High Impedance (Hi-Z).

I was planning on wiring the PO.1 to AI_SENSE and use the AI_0 to measure the signal in NSRE mode to measure the +12V level and verify the High Impedance mode.

The NI6289 USB DAQ measure up to 10V on the AI lines and accepts upto 11V.  By applying a offset on AI_SENSE I should be able to read the 12V signal with the +5V offset provided by digital IO line.

The worries I have are (1) the stability of the 5V level on the Digital line (2) do I need to put a current limiting resistor between PO.1 and AI_Sense to limit the current should the High Impedance mode switching leave the DUT control level at 0V.

Any help would be appreciated.  

[crossrulz · Accepted solution]

If you read the spec carefully, you will see that the 11V input is referenced to COMMON, not the AI Sense.  So this won't work.

It seems like you need a voltage divider.  Two 100k resistors would work well to divide the voltage in half.  You can setup a DAQmx scale to account for this divider.