POTENTIOMETER3

"2. A somewhat archaic measurement system, based on a resistor with a continuously variable tap, that can be used to measure the electromotive force of electrochemical cells that can be easily polarized by current. It uses a comparison technique to compare a ""standard"" voltage source to the unknown, under conditions of practically zero current. It is seldom used today because high input resistance voltmeters and electrometers are readily available. "