Analog signal: wrong reading in the test panel

[fgjdgf]

Dear All,

I am writing since I am facing a quite strange problem.

I connect a sensor to my DAQ. If I read with the tension at the terminals on my DAQ with a multimeter, I read 3 V (and that is the correct value).

The point is that on the test panel I read a smaller value (1,2 V) and I can not understand why.

I also tried to use a different analog input, but nothing change.

Thanks,

Samuele

[crossrulz]

What DAQ?  How is the sensor wired to your DAQ?  How is the channel configured?

[fgjdgf]

Sorry, I forgot some details:

DAQ: USB-6212

Sensor: data sheet attached

Channel configuration like in the picture.

Thanks

[crossrulz]

Are both sides of the differential signal already referenced to the AI GND?  If they are floating, you need to add a couple of large resistors (1MOhm usually works) on each side to AI GND.

For more information, read this article: Field Wiring and Noise Considerations for Analog Signals 

[santo_13]

You have not shared any connection diagram or information about your sensor.

[fgjdgf]

Sorry,

I forgot the data sheet.

[crossrulz]

Attached is the English version of the datasheet.

Now I see your issue on page 6 of the datasheet.  This sensor's output is not a simple voltage; it outputs a 4-20mA signal.  What this means is that it will output 4mA for the lower range and 20mA for the higher range.  You cannot directly measure voltage because its output is a current.  A simple way to handle this is to put a 500 Ohm resistor across your DAQ inputs.  This will allow you to use the 10V scale for the DAQ.

20mA*500 Ohm = 10V

4mA*500 Ohm = 2V