His attached image shows a single DAQ Assistant, which would correspond to a single task.
Anyway, I think what you're saying is that you are seeing the same measurement on disconnected channels as your other channels. You might want to check out NI's article on ghosting.
The DAQ card you are using is multiplexed, so the ADC is shared by all of the channels. When the multiplexer switches to a disconnected channel the accumulated charge from the previous channel has nowhere to go (input impedance is in the GOhms) and you will measure a very similar voltage between the two channels.
Connecting unused channels to ground would ensure that you read back 0V if that is what you are looking for. If the goal is to determine whether or not a connection has been broken, you might need to get a little more clever (use resistors to pull the line to a known voltage or ground, or perhaps incorporate a unity-gain buffer on each of your inputs).
Best Regards,
John Passiak
