Hello,
I'm using an NI-9411 in a 9171 chassis, measuring a 5V differential signal @ < 100Hz but my frequency measurement jumps around a lot when I touch the bnc connector on the device I'm measuring (hand-held tachometer).
I was surprized to read that the input threshold for the 9411 is only 300mV. I think I'm introducing noise because the tachometer isn't pulling the signal are enough below 300mV in it's off state.
I don't have many options for external signal conditioning in this application so I'm wondering if I'm issing something in the DAQmx settings.
For instance, it looks like I can't specify the input termination (single-ended vs. differential) or the input thresholds/max range etc...
Any thoughts?
