Hi,
For a project a proportional-pressure regulator (MPPES by Festo) is used. By changing the voltage (0 to 10 V), it is possible to control the air pressure in a pipe (0 to 10 bar). Also, the regulator provides the actual pressure value (0 to 10 V). This signal (actual value) is measured analog with an USB-6008 in combination with Labview 2018 at one of the AI ports. For measuring the voltage signal, I connected one cable with the AI+ port and the other cable (ground) with GND. Regarding the manual, I chose "RSE" (0 to 10 V) during setup the voltage measurement with DAQ assistant. Almost everything works: If you enter a set pressure e.g. 2 bar, 2 Volts are generated and the actual value, which is send from the regulator is also 2V. A manometer that is installed for visual check also shows 2 bars.
The problem is, that the measured voltage is constant around 0,35 V in the range from 0 to 0,35 V. I measured manually the Voltage with a voltmeter between the cables and everything is fine, values below 0,35 V are shown. So there is no problem with the regulator. Also these 0,35 Volts aren't an offset. Values above 0,35 V are measured correctly. So it seems that the USB-6008 measures the voltage not correct in this range? I tried a different AI port, but nothing changed. I also connected the cables to the AI+ and AI- ports and chose "DIFF", with the same results.
If you guys can give me a solution for this, it's greatly appreciated,
Cheers,
Lars
