A potentiometer is a resistance element with three output terminals and a resistance value that can be adjusted according to a certain variation pattern. Potentiometers are usually composed of resistors and movable electric brushes. When the electric brush moves along the resistor, it obtains a resistance value or voltage at the output end that is proportional to the displacement. Potentiometers can be used as both three terminal and two terminal components. The latter can be regarded as a variable resistor, which is called a potentiometer because its function in the circuit is to obtain an output voltage that is proportional to the input voltage (applied voltage).