Types and Characteristics
Classification by resistive element material
Wire-wound potentiometer: Offers high precision, good stability, low temperature coefficient, reliable contact, high temperature tolerance, and strong power-handling capability. Drawbacks include a limited resistance range, poor high-frequency performance, lower resolution, susceptibility to wire breakage at high resistances, larger size, and higher cost. This type is commonly used in electronic instruments and test equipment. The resistive element is formed by winding resistance wire on an insulating substrate. The wire material is chosen based on the potentiometer structure, available space for the winding, desired resistance value, and temperature coefficient. Thinner wire yields higher resistance and resolution within a given space, but excessive thinness increases the risk of breakage and reduces sensor lifetime.
Carbon film potentiometer
Carbon film potentiometers have a wide resistance range, relatively good resolution, simple manufacturing, and low cost. Their disadvantages include high wiper noise and poor moisture resistance. They are suitable as function potentiometers and are widely used in consumer electronic products. Printing processes enable automated production of carbon film tracks.
Organic solid potentiometer
Solid organic potentiometers provide a wide resistance range, high resolution, good heat resistance, strong overload capacity, good wear resistance, and high reliability. However, they have poorer resistance to humidity and heat and higher wiper noise. They are typically manufactured as small trimmers for fine adjustments in circuits.
Metal-glaze (metal film with enamel) potentiometer
Metal-glaze potentiometers combine many advantages of solid organic types with a relatively small resistance temperature coefficient, similar to wire-wound types. They tend to have higher dynamic contact resistance and higher equivalent noise resistance, so they are often used for semi-fixed resistance adjustments. Development has improved their temperature, humidity, and shock resistance, allowing reliable operation in harsher environments.
Conductive plastic potentiometer
Conductive plastic potentiometers offer a wide resistance range, high linear accuracy, strong resolution, and exceptionally long wear life. Although their temperature coefficient and contact resistance are relatively large, they are suitable for use in analog and servo systems in automatic control instruments.
Digital potentiometer
Digital potentiometers are implemented with integrated circuit technology. A resistor string is integrated on a chip and MOSFETs control the taps. They can be used in analog circuits for impedance matching and amplifier gain control, avoiding manual adjustment and enabling automated gain control, voltage variation compensation, and impedance matching.
Multiturn precision adjustable potentiometer
In industrial control and instrumentation circuits that require high adjustment precision, multiturn adjustable potentiometers are used. They provide a large adjustment range and high accuracy.
Functions of Potentiometers
Potentiometers serve several primary functions in circuits:
- As a voltage divider:
A potentiometer is a continuously adjustable resistor. When the knob or slider is moved, the wiper slides along the resistive element. The output voltage at the potentiometer output is determined by the applied voltage and the wiper position or rotation angle.
- As a variable resistor (rheostat):
When used as a variable resistor, the potentiometer should be connected as a two-terminal device. Within its travel range, a smooth, continuously varying resistance value is obtained.
- As a current controller:
When a potentiometer is used to control current, one of the chosen current output terminals must be the wiper terminal.
