USB-6001 output voltage does not go above 0.8V

[Sorosham]

Thanks so much for your responses.

I drew a wiring diagram of the circuit and attached it below. 

I tried to measure current of the output signal but I got zero!! 

[RavensFan]

To clear up something, that 130 mA value you've been talking about all along has nothing to do with the current in the analog output connection.  It is the current being supplied by the power supply to power the pressure regulator.

I do see an error in your wiring diagram, and now I can actually see there is a wire missing in your picture.  Your analog input is a different signal.  You only have the + side of the analog input hooked up.  You need to wire the - side as well.  Since the device seems to not be differential, but control, power, and feedback all share a common ground, wire from AI0- to the ground of the power supply.

[Sorosham]

That didn't make any difference, since the feedback coming from the sensor was single ended (not differential).

It is clear to me that the problem is with output signal, not measuring it, because when I increase the output I don't feel any pressure change with my finger on the air tube. My time is limited and I need to fix this issue, 
Any other suggestions please?

[RavensFan]

It does make a difference when measuring that feedback.  Your DAQ assistant is set up for differential signals.  That means it takes the voltage of AI+ relative to AI-.  If nothing is connected to AI-, you cannot have a valid signal.

As for the analog output.  Just disconnect everything.  Verify your DAQ device is putting out a voltage by reading it with a multimeter.  Change the value in your VI and make sure the meter matches.

[Sorosham]

Thanks yes you are right. I tested it with only a multimeter and voltages matched! but again with wires connected to the pressure regulator the maximum is limited to 0.8V. 

[RavensFan]

Disconnect the DAQ card.  Use another power supply where you can adjust the voltage between 0 and 10 and connect that to the control input of the regulator.  See if it works using that.

Also, it looks like you can control it using their software and the USB port.  Does it work that way?

[Sorosham]

Actually when I use their software it worked fine, 

That software is not versatile in terms of controlling that's why I use Labview.

Best,

[Sorosham]

When I separated GND and (-) from the power and connected AO to the GND and pressure regulator, the voltages matched this time! but it actually doen not work! I mean the voltage changes accordingly but the real pressure does not change! 

[RavensFan]

Since it works via USB, but not with the voltage input, is it possible you need to change a setting in the device to tell it to follow the input wires?

[Sorosham]

There is no setting on the device. What if I use a differential amplifier?

Best,