Potentiometer

Article By:

Harris, Forest K. Electrical Measurements Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland.

Dziuba, Ronald F. Electrical Measurements Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland

Kibble, Bryan P. Formerly, Division of Electrical Science, National Physical Laboratory, Teddington, Middlesex, United Kingdom.

Last reviewed:January 2020

DOI:https://doi.org/10.1036/1097-8542.540400

An instrument that precisely measures an electromotive force (emf) by balancing it against a known potential drop established by a three-terminal resistive divider (Fig. 1), across which a known voltage exists. A divider can adjust and control the voltage applied to some device or part of a circuit, for example, a volume control. The ratio of output to input voltage is equal to that of the tapped to total divider resistance when the current required by the controlled device is negligible. Potentiometers as voltage-measuring instruments have largely been replaced by the ratio instrument known as a digital voltmeter. The Weston standard cells which supplied a known standard voltage have also been superseded by solid-state voltage reference devices which are usually incorporated in the digital voltmeter.

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