Linear Potentiometer VS Logarithmic potentiometer

Potentiometers varies potential difference between it’s terminals.It’s a very common and useful device used to vary voltage, current as well as gain in a circuit. Depending upon the physical size and form factor there are various types of Potentiometers.In this post we will differentiate potentiometers (in short POT) on the basics of Output Response with respect to angular displacement of the knob.

Basic Construction of Potentiometer:

There is a strip of resistive elements , and an wiper moves along with the strip of resistive material creating a good electrical contact. As the wiper moves effective resistance varies with the length from one terminal. Here is image explaining the internal construction of the potentiometer.

internal construction of a potentiometer
internal construction of a potentiometer

Depending upon the the output response Potentiometers are of two types

1. Linear response Potentiometers

2. Logarithmic response Potentiometers

Linear Response Potentiometers: Output response of this type of potentiometer is linear with the angular displacement of the knob.The strip of resistive element inside has uniform cross section.These type of POT’s are used for adjusting the centering of the display on an analog cathode-ray oscilloscope. Precision potentiometers have an accurate relationship between resistance and slider position.

Logarithmic response Potentiometers: 

A Logarithmic response Potentiometers is a potentiometer that has a bias built into the resistive element. Basically this means the center position of the potentiometer is not one half of the total value of the potentiometer.

Logarithmic potentiometer
Logarithmic potentiometer response vs linear

The resistive element is designed to follow a logarithmic taper. The strip is made from such material whose resistivity varies from one end to another. Common log pots are not exactly logarithmic in response.It uses two region of different resistance to approximate the effect.

Logarithmic taper potentiometers are often used in connection with audio amplifiers, as human perception of audio volume is logarithmic.


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