What is a potentiometer?
A potentiometer is an electrical resistor with variable resistance value and generally manually adjustable. The potentiometers use three terminals and are usually used in low current circuits, for higher current circuits the rheostats are used. In many electrical devices, potentiometers are what set the output level. For example, on a speaker the potentiometer adjusts the volume; on a television or computer monitor, it can be used to control brightness.
The value of a potentiometer is expressed in ohms (symbol Ω) as the resistances, and the value of the potentiometer is always the maximum resistance that it can have. The minimum is logically zero. For example, a 10KΩ potentiometer can have a variable resistance with values between 0Ω and 10,000Ω.
The simplest potentiometer is a mechanically variable resistance. The first and simplest potentiometers are rheostats.
Construction of a potentiometer
There are two types of construction of a potentiometer
Made with a carbon or cermet track on hard support such as bakelite paper (pre span cardboard), fibreglass, bakelite, etc. The track has two separate contacts at its ends and a cursor connected to a skate that slides along the resistive track.
It consists of a toroidal winding of resistive wire (for example, constantán) with a cursor that moves a skate on it.
Types of potentiometers
We can classify potentiometers in two ways
according to your application
They are suitable for use as a voltage control element in electronic devices. The user operates on them to vary the normal operating parameters. For example, the volume of an audio device.
Within the command, we can find.
They are controlled by rotating their axis, they are the most used because they are long-lasting and use little space.
The cursor path is straight, they are used in graphic equalizers.
They control the tension by presetting it, usually at the factory. The user does not usually have to touch up, so they are not usually accessible from the outside. They exist both encapsulated in plastic and without capsule, and potentiometers with vertical adjustment, whose axis of rotation is vertical, and potentiometers with horizontal adjustment, with the axis of rotation parallel to the printed circuit board, are usually distinguished.
According to the law of variation of resistance
The resistance is directly proportional to the turning angle. linear potentiometer
These are normally used for audio due to their asymmetric way of behaving when faced with the variation of their axis. At first we will experience a very slight increase in resistance until we reach a point where the increase will be much greater. They are usually used for example for the volume of a radio.
The resistance is proportional to the sine of the angle of rotation. Two integral and 90 ° rotated sinusoidal potentiometers provide the sine and cosine of the rotation angle. They may have limit stops or not.
There are also digital potentiometers. They are used to replace mechanics by simulating their operation and avoiding mechanical problems of the latter. It is made up of an integrated circuit that simulates the behavior of its analog equivalent. They have a resistive divider (voltage divider) with n + 1 resistances.
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