What is a potentiometer?

Variable resistors, as the name implies, have a terminal resistance that can be varied by turning a dial, knob, screw, or whatever seems appropriate for the application. They can have two or three terminals, but most have three terminals. If the two- or three-terminal device is used as a variable resistor, it is usually referred to as a rheostat. If the three-terminal device is used for controlling potential levels, it is then commonly called a potentiometer. Even though a three-terminal device can be used as a rheostat or a potentiometer (depending on how it is connected), it is typically called a potentiometer when listed in trade magazines or requested for a particular application.

(a) potentiometer symbol; (b) and (c) rheostat connections; (d) rheostat symbol

How to wire a potentiometer in the circuit?

Terminal a: This is the output of the pot, which means it should be wired to the circuit’s input.

Terminal b: This the input of the potentiometer, meaning the output line from the circuit should connect to it.

Terminal c: Connect it to the ground.

How to measure a potentiometer in the circuit?

1. The resistance between the outside terminals a and c is always fixed at the full rated value of the potentiometer, regardless of the position of the wiper arm b.
2. The resistance between the wiper arm and either outside terminal can be varied from a minimum of 0 Ω to a maximum value equal to the full rated value of the potentiometer.

Measurement: (a) between outside terminals; (b) between wiper arm and each outside terminal.

Tags: Inquiry/Analysis, Integrate Learning, Depth of knowledge