Trimming Potentiometers are three-terminal resistors that are used to measure or divide voltages, and to protect or control circuits. Potentiometers are variable resistors that are adjusted with a knob or dial. Rheostats and trimmers are types of potentiometers. With a rheostat, a third “wiper” terminal is shorted to one of two fixed terminals. The wiper terminal has a resistance which varies with its position, and the two fixed terminals are connected by a fixed resistance. Trimmers are factory-set devices that require infrequent adjustments. They feature a slotted, actuator-type style and can be adjusted with a special tool or screwdriver. Other types of Trimming Potentiometers are also available. These include standard potentiometers, mechanical devices in which the output resistance is set by a shaft; and digital potentiometers, which set an output resistance by sending a digital signal through an electrical interface.

Trimming Potentiometers carry specifications for potentiometer category and actuator configuration. Industrial-grade potentiometers are protected by an enclosure, typically one that is rated by the National Electrical Manufacturers Association (NEMA). Typically, industrial-grade products are gear-driven and have connector outputs. These Trimming Potentiometers resist the ingress of dirt and dust, and last longer than unenclosed potentiometers. Discrete-board components, another potentiometer category, are also commonly available. In terms of actuator configuration, choices include single-turn, multi-turn, and slide. With single-turn devices, the shaft rotation is limited to less than or equal to 360 degrees. By contrast, multi-turn Trimming Potentiometers can be rotated multiple times, with as many as 15 or 20 turns from stop to stop. Slide-actuated products require the user to move a handle instead of rotating a knob.