I'm fairly inexperienced using DAQs and have a hopefully simple problem. I have a BNC breakout to alligator clips connected to a channel. When the alligator clips aren't connected to anything, I see a 60 Hz signal oscillating between about 30 mV and -30 mV. I know 60 Hz noise is typical of ground loops, but I don't see how this could be a ground loop when the clips aren't attached to anything (I also could be wrong on this).
That noise could be coming from all kinds of places. My first thought is the signal is being induced onto your cable from machines, florescent lights, near by power cables, etc. What do you get if you just tie your two clips together?