Question in reading differential measurement

[Anson Wong]

Hi,

I am a new user in Labview and DAQ. I am trying to read pressure data from a Dynisco PT160 pressure transducer (Output vdc: 0 - 10V, 16-32 vdc excitation) via a USB6009. I tried to connect the positive and negative output from the transducer to AI 0+ and AI 0- of the USB6009 (Differential mode), respectively. I set up AI 0+ as differential input in labview. However, the reading of AI 0+ in labview is incorrect even after I did proper scaling and connected a pair of resistors to ground for bias currents. Then, I tried to connect the positive and negative output to AI 0 and GND, respectively (Single-Ended Mode) and the reading in labview is correct. However, the reading is noisy, which I somewhat expected after reading the "Field Wiring and Noise Considerations for Analog Signals" document. I want to know if I have done something incorrectly when I was using the differential/RSE mode? Also, any other advice in pressure reading will be greatly appreciated.

Thanks in advance for your information.

Regards,

Anson 

[Broken_Arrow]

If you are using a split power supply (negative and positive V), then I'd expect that you'd have to use GND referencing (single ended). If you're using a single ended power supply (GND and positive V), then I'd expect either one to work.

Are you sure it is noisy, as in electrical noise? If you have (for example) a 0 - 10,000 PSI transducer, there's going to be more perceived bouncing around of the signal than a 0 to 10 PSI, given the same full scale output.