A single-ended earth grounded PCI data acquisition board's analog inputs and outputs are controlled by a PC. The daq board has also analog outputs. One of the analog output is controlling the motor speed. It does that by controlling the 0-10V VFD drive input via an isolation amplifier which isolates the grounds of VFD and the daq system. I tried to draw the system above. The mootor and VFD are close to eachother and the DAQ system is 20m far away.
The fan motor is a 3-phase (3-50Hz) 22kW AC motor prim delta: 380V. This is the VHD drive in use.
I'm trying to prevent noise or common mode noise.
Recently I've been told to check the potential difference between the daq earth and the VFD earth grounds.
How should the system be properly grounded to earth?
Should the potential difference between the earths be zero?
Does anyone have experience with such system?