User Manual

Television
Potentiometers were formerly used to control picture brightness, contrast, and color response. A
potentiometer was often used to adjust "vertical hold", which affected the synchronization between
the receiver's internal sweep circuit (sometimes a multivibrator) and the received picture signal,
along with other things such as audio-video carrier offset, tuning frequency (for push-button sets)
and so on.
Motion control
Potentiometers can be used as position feedback devices in order to create "closed loop" control,
such as in a servomechanism. This method of motion control used in the DC Motor is the simplest
method of measuring the angle or speed.
Transducers
Potentiometers are also very widely used as a part of displacement transducers because of the
simplicity of construction and because they can give a 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
A potentiometer with a resistive load, showing equivalent fixed resistors for clarity.
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 R
L
can be calculated by:
If R
L
is large compared to the other resistances (like the input to an operational amplifier), the
output voltage can be approximated by the simpler equation: