Measuring ground refernced signals with differential configuration

[portal6]

I am measuring pressure with a differential tranducer with up to 5V output excited by a regulated power supply. It is then supposed to be a ground-referenced signal source. I chose the differential configuration for my DAB. I am conecting the Vout of the transducer to the AI+ and the COM (that is the COM of the power supply aswell) to the AI-. I thought it was the correct configuration but instead when conecting AI- with the AIGND of the board I get a better signal. I didn´t expected that because measuring grounded signal sources with ground referenced measurement systems have usually a groun loop problem. I would like to have an explanation to this behaviour.

[Salvador_Santolucito]

Just to be sure... did you explicitely set your DAQmx task to use differential input?  The default configuration for AI is typically RSE (referenced single ended).  If your software is set to use RSE and you wire your signal differentially, then you won't get good data.  You can explicetly set the input signal configuration on the DAQmx Create Channel VI in LabVIEW.

-Sal

[portal6]

Hello Sal,

I changed  from singled ended to differential the DAB configuration . I changed this via software aswell. I don´t know it doesn´t performe as it should ¿? Thank you very much for your help anyway.

Cheers