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Potentiometers can be divided into exponential potentiometers, logarithmic potentiometers and linear potentiometers according to the linear change rule of resistance value. The so-called resistance linearity of the potentiometer refers to the rotation angle (or stroke) of the potentiometer Relation with output voltage when used as voltage divider. The relationship between the resistance value of the potentiometer and the rotation angle of the contact point of the slider can be any functional form in theory. The resistance change characteristic of the potentiometer refers to the relationship between the resistance of the potentiometer and the length of the moving contact or the rotation angle of the rotating shaft, that is, the resistance output function characteristic. There are three common types: 1) Characteristic of resistance change of exponential potentiometer The resistance change of the exponential potentiometer has an exponential relationship with the change of the position of the moving contact. Due to the uneven distribution of conductive substances on the resistor body, the resistance value of the exponential potentiometer changes slowly when the potentiometer starts to rotate, and changes rapidly when the rotation angle reaches the second half of the stroke. The exponential potentiometer is applicable to the volume adjustment circuit, because the human ear is the most sensitive to the hearing of the loudness of the sound. When the volume reaches a certain level, the human ear's hearing gradually becomes dull. Therefore, the volume adjustment generally adopts the exponential potentiometer to make the sound change appear stable and comfortable. 2) Characteristics of resistance change of logarithmic potentiometer The resistance change of logarithmic potentiometer is logarithmic with the change of moving contact position. Due to the uneven distribution of conductive substances on the resistor body, the resistance value of the logarithmic potentiometer changes rapidly when the potentiometer starts to rotate, and changes slowly when the rotation angle reaches the second half of the stroke. Logarithmic potentiometer is applicable to electronic circuits that are contrary to the requirements of exponential potentiometer, such as contrast control circuit and tone control circuit of TV. 3) Characteristics of resistance change of linear potentiometer The resistance change of linear potentiometer is linear with the change of moving contact position. The conductive substances on the resistance body of the linear potentiometer are evenly distributed, and the resistance values per unit length are roughly equal. It is suitable for occasions requiring uniform adjustment (such as voltage divider).