Help with a pressure transducer connected to NI USB-6000 (Single ended)

[ppaulade]

HI,

Please I need help with a 3 -wire transducer. This is the first time setting it up and I am trying to get some measurements in bar. 

The transducer is from 0-400barS (sealed gauge) and from 0-5V. So the volt value multiplied by 80 will give the pressure in bar.

I have attached my connection diagram and picture of set up.

Yellow wire is connected to the power supply +ve.

Ground of power supply (Red Wire) is connected to AI GND

Ground of pressure transducer is connected to power supply ground and AI GND

Blue wire is the AO from the pressure transducer connection to AI of DAQ.

I Guess this is correct.

Now my issue is, I am getting negative voltage values in my readings although the pressure transducer outputs voltage from 0V to 5V.

Attachments 5, 6 and 7 are screenshots of the output voltage graph from software.

Attachment 8 contains a screenshot from the datasheet of the transducer. See Code B, Voltage Mode. I also noticed there is PE and also 0V. is there two grounds? 

I do not understand.

Also, what kind of graph should I expect to know my values are correct.

[santo_13]

When close to 0V, it is normal for a bipolar input AI to swing around 0V (yes, even negative) due to noise and errors. You can handle it in software by coercing the value between 0 and 400 bar. Thereby, you don't see the negative values.

[ppaulade]

Okay thanks