The potentiometer is first calibrated by positioning the wiper (arrow) at the spot on the R 1 wire that corresponds to the voltage of a standard cell so that R 2 R 1 = cell voltage V S Constant resistance potentiometer In this circuit, the ends of a uniform resistance wire R 1 are connected to a regulated DC supply V S for use as a voltage divider. The arrow head represents the moving wiper. R 1 is the resistance of the entire resistance wire. The instrument used for comparison must be sensitive, but need not be particularly well-calibrated or accurate so long as its deflection from zero position can be easily detected.ДЄ potentiometer being calibrated and then measuring an unknown voltage.

By comparing the potential at points along the wire with an unknown potential, the magnitude of the unknown potential can be determined. In use, an adjustable regulated voltage source E, of greater magnitude than the potential to be measured, is connected across the wire so as to pass a steady current through it.Д«etween the end of the wire and any point along it will be a potential proportional to the length of wire to that point. One form of potentiometer is a uniform high-resistance wire attached to an insulating support, marked with a linear measuring scale. The potentiometer is a simple device used to measure the electrical potentials (or compare the e.m.f of a cell). The principle of a potentiometer is that the potential dropped across a segment of a wire of uniform cross-section carrying a constant current is directly proportional to its length. Measurement potentiometers are divided into four main classes listed below.Дial potentiometer, with built-in galvanometer and reference voltage source This null balance measuring method is still important in electrical metrology and standards work and is also used in other areas of electronics. At that point the galvanometer draws no current from the unknown source, and the magnitude of voltage can be calculated from the position of the sliding contact. The deflection of the galvanometer is observed and the sliding tap adjusted until the galvanometer no longer deflects from zero.

The sliding contact or wiper of the potentiometer is adjusted and the galvanometer briefly connected between the sliding contact and the unknown voltage. In this arrangement, a fraction of a known voltage from a resistive slide wire is compared with an unknown voltage by means of a galvanometer. The method was described by Johann Christian Poggendorff around 1841 and became a standard laboratory measuring technique. Since the reference voltage can be produced from an accurately calibrated voltage divider, a potentiometer can provide high precision in measurement. If a sensitive indicating instrument is used, very little current is drawn from the source of the unknown voltage.

JSTOR ( December 2014) ( Learn how and when to remove this template message)ДЄ potentiometer is an instrument for measuring voltage or 'potential difference' by comparison of an unknown voltage with a known reference voltage.

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