Omega Pressure Transducer troubleshoot needed

[sashahid]

Hi, I am new to Labview and NI-DAQ device. I want to connect an OMEGA differential pressure transducer on a small pipe tube and acquire a voltage signal through DAQ assistant. The pressure transducer was provided calibrated by the company. The pressure transducer has a linear voltage output 0-10 VDC and the pressure range is 0-2.5 KPa. This means to get corresponding pressure signal I simply have to multiply the voltage signal by 0.25. The pressure transducer has 3 wires; black, white and red. The transducer requires 24 VDC excitation and I have connected the black wire to the –ve and red wire to the +ve of the 24 VDC power supply. I have connected the white wire to pin #31 of NI USB-6211. Additionally I have also connected –ve of the power supply to pin# 32.

Now when I use the DAQ assistant to acquire a signal on my computer and use a multimeter on pins 31 and 32 the voltage values do not match. Please if you could tell me what I am doing wrong here.

Thank you

Ali

[mjrivera]

Hello Ali,

It seems like you are configuring your application differential. In this case, I recommend you to configure your device in an (RSE) way, using the pin #28.

In the followed white paper you will find information on how to achieve this and also their differences, since as you mentioned you are starting this is a  good reference while working acquiring data.

Field Wiring and Noise Considerations for Analog Signals

http://www.ni.com/white-paper/3344/en/

[sashahid]

Thanks for sharing the reference paper. Its indeed useful for beginners, however as you said about configuring the device in RSE mode I tried that but it did not solve the problem. The voltage signal that I get in RSE is very unstable with high level of noise. Whereas the differential model gives a stable signal which only changes when the pressure on the higher end of the sensor changes. However it does not match with the voltage signal that I directly take from the pins (for other sensors that I am using besides this the signal matches perfectly). I am guessing the sensor is faulty and have contacted omega to get their advice. 

[justgene]

Have you posted your code?  I've recently worked with Differential vs. RSE with the DAQmx tools.  I found that the create channel vi required a "constant" be wired to the input terminal configuration terminal.  otherwise the vi would change to a "default" mode which I think is differential.

Gene