Variable Resistors
Variable Resistors
Variable Resistors
Potentiometer symbol
IEC standard
Rheostat symbol
IEC standard
Rheostat
Digital Potentiometer
Potentiometer
• The potentiometer is the most common
variable resistor. It functions as a
potential divider and is used to generate
a voltage signal depending on the
position of the potentiometer.
• This signal can be used for a very wide
variety of applications including:
Amplifier gain control(audio volume),
measurement of distance or angles,
tuning of circuits and much more.
• These potentiometers mounted on the
circuit board, can be easily adjusted
using fingers.
Rheostat
• Rheostats are very similar in construction to
potentiometers, but are not used as a potential
divider, but as a variable resistance.
• They use only 2 terminals instead of the 3
terminals potentiometers use. One connection is
made at one end of the resistive element, the
other at the wiper of the variable resistor.
• In the past rheostats were used as power control
devices in series with the load, such as a light
bulb. Nowadays rheostats are not used as power
control anymore as this is an inefficient method.
For power control, rheostats are replaced by
more efficient switching electronics.
Digital Potentiometer
• A digital variable resistor is a type of variable resistor
where the change of resistance is not performed by
mechanical movement but by electronic signals. They
can change resistance in discrete steps and are often
controlled by digital protocols
Trimmer or Preset Resistor
• Presets are just like small version of a
variable resistor. They can be placed easily
on a PCB and can also be adjustable when
needed. The value of the resistance is
normally adjusted with the help of a screw-
driver.
• They are frequently used in applications
that have adjustable frequency tone of the
alarm or adjustable sensitivity circuits.
• These are the cheapest among the devices
that are mentioned above and these are
also highly specific presets that have multi-
turn options.