Potentiometer: What is it and how does it work?

What is a potentiometer?

A potentiometer is an electrical resistor with a variable resistance value and usually manually adjustable. The linear potentiometers use three terminals and are usually used in circuits of low current. For circuits of heavy current the reostates are used. In many electrical devices the potentiometers are what set the output level. For example, in a loudspeaker the potentiometer adjusts the volume. On a television or a computer monitor it can be used to control the brightness.

The value of a potentiometer is expressed in ohms (symbol Ω) as the resistors, and the value of the potentiometer is always the maximum resistance it can have. The minimum is logically zero. For example, a 10KΩ potentiometer can have a variable resistor with values ​​between 0Ω and 10,000Ω.

The simplest potentiometer is a mechanically variable resistance. The first potentiometers and simpler are the rheostats.

Construction of a potentiometer

There are two types of construction of a potentiometer

Printed:

Made with a carbon or cermet track on a hard support such as bakelised paper (cardboard prespan), fiberglass, bakelite, etc. The track has two contacts at its ends and a cursor connected to a skate that slides along the resistive track.

Windings:

It consists of a toroidal winding of a resistive wire (for example, constantan) with a cursor that moves a skate on it.

Types of potentiometers

We can classify the potentiometers in two ways

Command potentiometers.

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.

Swivels

They are controlled by turning their axis, they are the most used because they are long-lasting and use little space.

Slides

The cursor path is straight, they are used in graphic equalizers.

Adjustment potentiometers

They control the tension by presetting it, normally in the factory. The user does not usually have to touch up, so they are not usually accessible from the outside. There are both encapsulated in plastic and without capsule, and are usually distinguished potentiometers vertical adjustment, whose axis of rotation is vertical, and potentiometers horizontal adjustment, with the axis of rotation parallel to the printed circuit.

According to the law of variation of resistance

Linear variation

The resistance is directly proportional to the angle of rotation.

Logarithmic

These are normally used for audio because of their asymmetrical way of behaving in front of the variation of their axis, at the beginning we will suffer a very slight increase in resistance, until reaching a point where the increase will be much greater. They are often used for example for the volume of a radio.

Sinewales

The resistance is proportional to the sine of the angle of rotation. Two sinusoidal sinusoidal potentiometers rotated 90 ° provide the sine and cosine of the angle of rotation. They may have limit stops or not.

There are also digital potentiometers. They are used to replace the mechanics simulating their operation and avoiding the mechanical problems of the latter. It is formed by an integrated circuit that simulates the behavior of its analog equivalent. They have a resistive divider (voltage divider) with n + 1 resistors.

By WebEditor

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