graphing isolated analog inputs, drift occurs even with bias resistors

[Zack Casella]

I have three analog signals I am trying to graph, all have a maximum 5.5V (5V ideally).  Two of these signals have a ground that is isolated from the third, so I assume I need Differential connections because they cannot share a common ground (as per the "Field Wiring and Noise Considerations for Analog Signals tutorial").  I have bias resistors of 10k between the AI:1, AI:2, AI:3 and AI GND on all three.

I initially and incorrectly set the "internal measurement configuration" to NSME when I did not have any signals connected just to test, and I did not experience any drift.  Now, with my signals connected, my signals drift up to and past 10V.  The data that I receive from looping this .vi is used in another main .vi, so I don't want to change it's type.

I am fairly new at data acquisition, so I am hoping someone can see a quick fix?

Thanks kindly,
-Z

[Ayman K]

Hello Zack,

The VI that you attached is missing a subVI (LO Linx Motor and other I_O Testing.vi). However, to be able to help you I want to understand couple of things. What is the signal sources that you are trying to measure? Are these differential signals and that is why you are using bias resistors. Also, What did you mean by NSME? Were you referring to NRSE mode of operation. Please post the subVI along with further explanation and screenshots of the drift so that I can better assist in resolving the issue.

The signal source you are trying to measure along with any transducers used is very important to note here for better understanding on my side.

Best Regards,
Ayman Kabire