myDAQ analog reading fluctuation

[slasuc]

Hello,

I've prepared a simple application using myDAQ to read voltage from DC amplifier for strain gauges. The amplifier gives a signal between +10V and -10V, I've connected the positive output to AI0+ and the negative to AI0-. During usage, everything works normally and I get a nice graph but I've experienced problems when the strain gauge is not loaded. Instead of 0V (or a slightly different but constant value), I'm reading values changing from 0V to ~-0,2V (pic attached). 

I've tried another myDAQ with the same result BUT with USB 6009 board there are no fluctuations.

Could you give me any advice?

[Bob_Schor]

I'm tempted to say "I'm sending my response in a picture", and then not attaching the picture (as you seem to have done), but I'm wearing my "Good Professor" hat right now ...

What is the exact configuration of the myDAQ "when the strain gauge is not loaded"?  Specifically, describe what wires are in AI0+, AI0-, and AGND.  If they are all unwired, find any student who has taken any Electrical Engineering course and she (or he) will explain the problem to you (mention "high-impedance inputs" (and I'm not even an Engineer ...).

Bob Schor