wrong voltage vaules when I use NI9244 and electrical power Suite 2017

[The_NewOne]

Hello, 

I measure voltage 3 phase with NI9244 and I have some problems to understand the values.

When I have a signal between AI0 and ground, AI1 and ground and A2 and ground, I measure the right value like 230V RMS at every Port. Ok!

But when AI1 and AI2 are not connected and just Ai0 is connected - I measure in my vi the same value as on Ai0 on the other ports. And the graph looks the same Ai0, Ai1 and Ai2. When I checked the signal by MAX without my vi the graph looks same on every port, too. 

Can anybody explain me why?

Thank you.

Gregor

[ThreeLions]

Hi,

As I know, this is the configuration of NI-DAQmx. if there is no signal, the simulation waveform appears on NI MAX.

Thanks!

[Dave@RPS]

This might be simple, we had a similar issue on an SBRIO in the past.  It was due to floating inputs.

You mentioned funny reading when a couple of channels were disconnected.  Try tying those channels to ground and see if that doesn't fix it.

[James_McN · Accepted solution]

Hi Gregor,

When I look at the pinout for the 9244 there is no ground. The Analog inputs are referenced to a common neutral point. Is this what you are connecting? (Pinout at https://www.ni.com/docs/en-US/bundle/ni-9244-specs/page/specs.html).

The issue with open connectors normally only impacts multiplexed signals but this is a simultaneous card. I think more likely the issue in this case is that the signal is coming through the neutral or you are reading it as a delta system. I don't have one in front of me so I'm not sure if MAX would allow you to select a Delta or Wye connection for this module.

Cheers,

James