large output signal. Computation In analog computers, high precision potentiometers are used to scale intermediate results by desired constant factors, or to set initial conditions for a calculation. A motor-driven potentiometer may be used as a function generator, using a non-linear resistance card to supply approximations to trigonometric functions. For example, the shaft rotation might represent an angle, and the voltage division ratio can be made proportional to the cosine of the angle. Theory of operation The potentiometer can be used as a voltage divider to obtain a manually adjustable output voltage at the slider (wiper) from a fixed input voltage applied across the two ends of the potentiometer. This is their most common use. The voltage across can be calculated by: If is large compared to the other resistances (like the input to an operational amplifier), the output voltage can be approximated by the simpler equation: (dividing throughout by and cancelling terms with as denominator) As an example, assume , , , and Since the load resistance is large compared to the other resistances, the output voltage will be approximately: Because of the load resistance, however, it will actually be slightly lower: . One of the advantages of the potential divider compared to a variable resistor in series with the source is that, while variable resistors have a maximum resistance where some current will always flow, dividers are able to vary the output voltage from maximum () to ground (zero volts) as the wiper moves from one end of the potentiometer to the other. There is, however, always a small amount of contact resistance. In addition, the load resistance is often not known and therefore simply placing a variable resistor in series with the load could have a negligible effect or an excessive effect, depending on the load. See also Potentiometric sensor Trimmer References Further reading The Potentiometer Handbook; 1ed; Carl Todd; McGraw-Hill; 300 pages; 1975; . (download) Potentiometer caution (Problems); Alpsalpine talks about some care with pots. (download) Contactless potentiometer; The AS5600 is an easy to program magnetic rotary position sensor with a high-resolution 12-bit analog or PWM output. This contactless system measures the absolute angle of a diametric magnetized on-axis magnet. This AS5600 is designed for contactless potentiometer applications; (AS5600) External links Beginners' Guide to Potentiometers Pictures of measuring potentiometers Electrical calibration equipment including various measurement potentiometers The Secret Life of Pots - Dissecting and repairing potentiometers