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.
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.
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.