More about Potentiometers

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A potentiometer can refer to two types of devices: an instrument used to measure electromotive force, or an electronic component with an adjustable resistance. In the latter case, a potentiometer is generally a resistor with a sliding contact that is mounted on a rotating shaft. This device serves as a voltage divider that allows the user to alter the level of resistance offered to the current flowing through it, which means that the output voltage can be modified to anywhere between the maximum level of incoming current and zero volts.

In a typical potentiometer used for low-power applications, a shaft-mounted wiper contact slides across a resistive fixture. The placement of the wiper contact on the resistive element determines the level of output voltage, which is sent through a fixed contact. Another fixed contact provides the input voltage. The resistive part of a potentiometer can be made from graphite or a similar semi-conductor material. Regular applications for these devices are in audio devices, where they control volume levels, or in other low power electronic devices that require level adjustments. Certain potentiometers may also include an “off” position, and therefore act as an on/off switch as well as means to adjust volume or voltage output levels.

As measurement devices, potentiometers are designed in four categories: constant resistance, constant current, thermocouple and microvolt potentiometers. These instruments are used to measure voltage levels in low power circuits. Essentially, a potentiometer uses a known resistance and a sliding contact to determine the voltage of the circuit. A metering device is attached to one end of the circuit, which registers when the sliding contact has reached a level that does not allow current to pass through it (at zero volts). The user then determines the position of the contact, and uses it to calculate the voltage of the circuit.