Hi:
I read the tutorial for differential mode.
I am measuring a DC voltage and my test fixture is a very low impendance. So I should only use AI- to AIGND to setup differential mode.
The question I need to ask is I don't need to put any wire from AI+ to AIGND. Is this correct?
The second question is if I then add a BNC cable from my test fixture to 5112 board. the voltage starting changing from 758ohm to 18kohm resistor. The voltage seems starting going down. I don't understand why it is happening like this. Could you explain to me? Attached is my graph.
The third question is I use DMM to test the current from AI- to AIGND, AI- to the negative node of 100ohm and AI+ to the postive node 0f 100ohm. I got 0mA, 0mA and 0mA. I also got no voltage across 10kohm resistor. Could you please tell me why?
If so, how does it remove common mode voltage and noise in this config? I don't understand. Could you pls explain to me?
I would appreicate if you can reply to me promply. I am in a very urgent.
