I am looking for a way to control a valve using a liner motor. The valve will set a level in a tank. I was thinking of using two Potentiometers. One for tank level and one for valve position. Then some how be able to read the voltage diffrence to turn on relays. > would turn on a relay until voltage was same on both Potentiometers and < for the other. I need a very fine level control for this project. My motor is 12 vdc. I sure someone out there can help. Thanks