pcie 6363 - voltage drift in SE recording

[balajisriram]

Hi, 

I am recording the output of a function generator (~15mV sinusoids at ~3000 Hz). I am using a BNC to direct the signal out of the function generator and into the BNC2090A and recording the analog signal in SE mode.  While the data starts out being close to 0 in diff mode (fig 1), it drifts towards -10V as soon as i shift the recording to SE mode (fig2 ). Finally after ~ 5 minutes, the voltage eraches its minimal value and levels off (fig 3)

Whats happening?

Board: PCIe 6363

PC: Dell optiplex running Windows 7

DAQ Interface: BNC 2090A

Only AI0 is connected. Every other BNC slot is empty

I checked the output of the function generator using an oscilloscope - it is pretty stable over many hours.

Balaji

[Dennis_Knutson]

When you switch to single ended mode, how are you connecting the gnd? Out sounds like you have a floating signal.

[balajisriram]

Thanks for the reply. 

I am recording in RSE mode(if that is what you are asking)

[Dennis_Knutson]

You already said that. I'm asking about the physical connection changes that you changed.

http://www.ni.com/white-paper/3344/en/

[crossrulz]

What Dennis is trying to get at is that if you are using RSE configuration, you need the ground of your signal to be connected to AI GND.