Connecting Differential Voltage Signals to the NI 9207 avoiding use 1M resistor for each channel.

[eddy2121]

I was measuring voltages directly only connecting NI9207 (AI0+ and AI0-) and voltage source (+ and -), I got wrong readouts. I tested using a know voltage source and comparing multimeter value with NI-MAX task (see Ni-MAX task.JPG) for checking.

Using the configuration like wiring.JPG the problem was resolved. But I have to use a 1M resistor for each voltage channel for getting right measurements.

Is there any solution for improve this scenario? I mean avoid using 1M resitor for each voltage channel

[Henrik_Volkers]

You need at least one 1M  (or another bias current path). All depends on your source(s), how are they related to COM? 

Or: What are your sources and how are they supplied and connected related to COM of the DAQ?

(See my signature: Ground is ...)