Phantom analog voltages

[oemex]

Hello All,

I'm new to using NI products and hoping someone else has seen this problem. I'm using the following modules and DAQExpress.

NI-9215 BNC

NI-6216 USB

When measuring the analog voltages of any of the paired pins, I get a 'floating' phantom voltage on any remaining analog inputs that aren't connected to anything. In other instances, I'll read the same voltage across all other inputs even though I'm only connected to 1 pair. Example; I have a waveform generator on input , but I'm reading the same waveform on other other inputs via DAQExpress that I'm not connected. I have the modules set up for differential input. In reviewing the manuals I came across some explanations about using resistors to solve this or that a BNC type would resolve it, but it hasn't. Any insight would be helpful.   

[altenbach]

---

@oemex wrote:

In reviewing the manuals I came across some explanations about using resistors to solve this or that a BNC type would resolve it, but it hasn't.

---

Correct termination resistors (even with BNC) will solve it if you follow the manual. If it hasn't tell us what you did. (Of course it also does not make a lot of sense to read disconnected terminals ;)).