setting excitation voltage to 0 after stopping VI

[Bart_1987]

Hi

I am using a PXIe-4331 card to acquire data from strain gauges. I am using the AI Bridge DAQmx to collect data (we want bridge ratio data at the moment - see attached for my VI) for data acquisition and have noticed (using a voltmeter to check), that even after the VI is stopped, the excitation voltage is still supplied to the active channels.

I have found two previous posts in other forums that question this. The first had a reply that said to set the excitation source to "none", which is not possible when using the AI Bridge DAQmx. The second said that the best that could be done was to set the excitation voltage to the minimum (0.625V). Is it in fact the case that the only way for the excitation voltage to my gauges to be dropped to zero is to shut down my DAQ each time the VI is stopped (and then restart it each time I want to perform another test)?

Also, if the continuous supply of excitation to the channels is unavoidable (without switching the DAQ off), does this mean that the module continues to actively supply the previously specified excitation (as in maintain said voltage) after the VI is stopped, or is it just whatever was being supplied when the VI was stopped (so not actively adjusting to maintain the voltage at the original level)?

Thanking you in advance for any help that can be provided.

If I'm not being clear enough about what I'm asking, please let me know and I will try and think of a better way to ask.

Cheers

Bart

[MaggieAggie · Accepted solution]

Hello Bart, 

If the device has power there will be an excitation. An excitation of zero is not supported, so there will always be at least 0.625V. If you reset the device, it will go to the default excitation, but it will not be zero. 

Software is not required to actively monitor the excitation output. The excitation will maintain the last excitation voltage that was set in software. The excitation voltage may vary slightly, but it will stay within its accuracy specifications. 

I hope this answers your question! 

[ClaireJ]

Delete. I answered in the wrong account. Sorry.

B

[Bart_1987]

Awesome. Thank you for clarifying that for me.

Cheers

Bart