usb6008 analog voltage input giving strange readings

[otg]

I am trying to get a voltage via a USB-6008 into LabView. The voltage input is via BNC, so one wire goes to hole #1 (GND) and the other to hole #2 (ai0).

I have measured the voltage input on the wires going into the USB-6008, and it seems ok (for the moment 1.6V so it's not that much) but when I put the wires into the USB-6008 the output looks as in the attached picture.

Any ideas?

[Henrik_Volkers]

Your signal looks like a 50Hz line noise/ground loop/bad supply ???

Please provide a connection diagram including the power supply of your signal source.