i have resistor based sensor, when i test it using arduino connect to PC using serial monitor without sharing ground to other circuit it has a nice value between 300-650 in adc range and the error/ accuracy reading just have about 5 value (ex: 607-612) if there is no condition change in the sensor.
But the problem comes when i sharing the ground to the other circuit. The accuracy is messed up bigger than 60 adc value (570-660) with the same condition without sharing ground.
My circuit is powered by PSU 24V and 24V driver to produce input signal for electric pressure regulator. The arduino ground is sharing because to control the input of the 24V driver. Here my circuit in the attachment.
So there is two ground from PC (i need it to use serial monitor) and the PSU 24V
How to eliminate the noise? Is there any way to control the 24v driver and read the sensor at the same time without sharing ground? Maybe using two controller with master/slave? Or there is any advice?