# Glossary Definition for Potentiometer

## Glossary Term: Potentiometer

Definition

A potentiometer (also pot or electronic pot) is a variable resistor in which a wiper sweeps from one end of the resistive element to the other, resulting in resistance that is proportional to the wiper’s position.

## How does a potentiometer work?

A potentiometer has three terminals, shown in green, red, and blue in the diagram. The red is the wiper that can be adjusted to vary the resistance between it and the other two terminals. By increasing the resistance between the green and the red, the resistance is decreased between the red and the blue. The resistance between the green and blue terminals remains constant.

The potentiometer symbol is a resistor symbol with an arrow representing the variable wiper.

## What is the difference between A and B potentiometers?

The relationship between the wiper position and the resistance is referred to as the “taper,” which can either be linear or logarithmic. In a linear taper, the resistance is proportional to the distance between the wiper and the terminal. In a logarithmic taper, either the size or material of the resistive element is not uniform from one end to the other in order to create a resistance that varies as a logarithmic function instead of a linear one.

A letter code may be given by the manufacturer to distinguish between linear and logarithmic taper. Manufacturers in the U.S. and Asia will usually mark potentiometers as type A for logarithmic and type B for linear. Manufacturers in Europe often do the reverse, with A being linear and B logarithmic.

## What kind of potentiometer do I need?

When using a mechanical pot, the wiper position is adjusted manually. In many cases, it is advantageous to use a digital pot, where the wiper position is digitally controlled in order to provide a resolution that is fully specified and repeatable. For more on mechanical and digital pots, see App Note 3484: Upgrading from Mechanical Potentiometers to Digital Pots.

Potentiometers vary by taper, end-to-end resistance, and size. Digital potentiometers also vary by number of steps, type of control interface, and whether the wiper memory is volatile or non-volatile. For more on how to choose a potentiometer for a specific application, see App Note 4101: Differentiating Digital Potentiometer Features.