Potentiometer(variable resistor/
rheostat). The potentiometer
is a
resistor where the
resistance can be
changed by the
operator.
The potentiometer is
manufactured in
different shapes and
values.
Most potentiometers are
set by turning a
shaft, a screw or a
slider.
You can get potentiometers where the
resistance changes in a
linear
fashion. Others may have a
logarithmic resistance change.
Though potentiometers may
vary in
shape, the basics are the same;
A resistive
track with
connectors in each end, the third
connector
is a
slide that can be moved to set the
resistance.
The
cheapest type to make is the
carbon track potentiometer.
The track is made of
carbon on a
substrate of
phenol paper.
This
type has a
poor linearity, a poor
resolution and a
short lifetime.
It is not
suited for high
effects but are
easy and
cheap
to
manufacture.
A
variation on the
carbon track is the
conductive polymer
track. Here the track is made from
fine-
granulated carbon
mixed with a
polymer. The
conductive polymer track has
a long
life and a
high resolution but has a low
effect tolerance.
It also has a poor
temperature stability.
Cerement track: this type has a good
effect tolerance, high
resolution, good
temperature stability, and a long lifetime.
The track is made from a mix of
metal and
ceramics, and printed
on a
ceramic surface.
Wire wound track. Here the track is
made from a
wire that
is wound round a cor of
ceramic or a
fibre glass.
This type of potentiometer is used for
high effects, and has a good
temperature stability. It has poor
resolution, but by
coating the
track surface with a
conductive polymer it
can be
increased.
The electronic symbol:
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OR
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V
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