General Information
A potentiometer is an adjustable voltage divider, usually a resistor with a movable tap contact. Potentiometers are used when it is necessary to smoothly change the voltage supplied to a consumer (load).
Operating Principle of a Potentiometer
A potentiometer is a device for smoothly dividing a given voltage into smaller values. It has three connection points. The middle point is variable (marked with an arrow) and makes contact with the winding of a fixed elongated resistor. The voltage between the adjustable point and either of the remaining ends of the resistor is determined by the resistance between them. If only two points are connected, the device functions as a variable resistor, or rheostat.
Types of Potentiometers
By voltage division characteristic, potentiometers can be linear, logarithmic, or inverse-logarithmic (also referred to as exponential or antilogarithmic). The logarithmic response is achieved by altering the shape of the resistive element — its width changes along its length. Therefore, potentiometers are often classified as linearly tapered or logarithmically tapered.
A trimmer or preset resistor is a type of potentiometer intended for single-time or infrequent adjustment. It is smaller in size and used on electronic circuit boards only for calibration purposes.
By control mechanism, potentiometers can be rotary or slider (sliding) types. Rotary potentiometers may be single-turn or multi-turn for high precision adjustments. Some come with a built-in switch — in the Soviet era, such designs were common in portable receivers. There are also automatic potentiometers adjusted by control systems, optical potentiometers (frequently used in DJ equipment), motorized potentiometers (in Pro Tools consoles), touch-sensitive sliders (elongated touchpads working in a single axis), and resistive touchscreens.
By construction, there are dual potentiometers — used in stereo equipment. Discrete potentiometers, used in professional audio equipment, consist of a set of fixed resistors switched by mechanical contacts. They produce less noise compared to standard variable resistors and have a much longer service life. Electronic potentiometers, or “digital resistors,” are integrated circuits that change their resistance according to numerical values received from a controller via a data bus.
Applications of Potentiometers
Potentiometers are used to adjust the brightness of lamps (dimmers), LEDs, audio levels (simple selectors or equalizers), the rotation speed of fans, and low-power electric motors. In professional audio equipment, linear potentiometers are referred to as faders.
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