Exponential potentiometer, logarithmic potentiometer, linear potentiometer2021

Potentiometers can be divided into linear potentiometers, exponential potentiometers and logarithmic potentiometers according to the changing law of resistance value. For the definitions and changing laws of these three potentiometers, please see the following sharing.After understanding clearly, we will not choose the wrong potentiometer when choosing the potentiometer.

When we get an adjustable resistor or potentiometer, we often see a mark such as B20K, A100K, and C50K. This mark refers to the resistance and linearity of the potentiometer. A, B, C refer to the different linearity of the potentiometer. The so-called resistance linearity of the potentiometer refers to the relationship between the rotation angle (or stroke) of the potentiometer and the output voltage when used as a voltage divider. The resistance of the potentiometer varies with the angle of rotation of the sliding contact point. This relationship can be in any functional form in theory, but the resistance of common potentiometers has linear changes [B type] and exponential changes. Type [A type], logarithmic change type [C type].

B-type linear potentiometer: the conductive material on the resistor body is evenly distributed, the resistance value per unit length is approximately equal, and the resistance value changes in a linear relationship with the rotation angle of the potentiometer, which is mostly used for voltage division; the resistance value is uniform according to the rotation angle Change, suitable for adjustment of partial pressure, monotony, etc. This is the most commonly used linear potentiometer.

Type A exponential potentiometer, exponential (reversal logarithmic) potentiometer, when it starts to rotate, the resistance changes greatly. When the angle of rotation is closer to one end of the maximum resistance value, the resistance value changes smaller. Exponential (inverted logarithmic) potentiometers, whose resistance changes exponentially according to the angle of rotation, are commonly used in volume control circuits such as volume controllers in radios, tape recorders, and televisions. Because the human hearing has an exponential relationship to the strength of the sound, if the modulation volume changes with the resistance exponential, the sound heard by the human ear will feel stable and comfortable. So this kind of potentiometer is suitable for tone control circuit of audio circuit.

C-type logarithmic potentiometer, when the logarithmic potentiometer starts to rotate, the resistance value changes smaller, and when the rotation angle is closer to the end of the maximum resistance value, the resistance value changes larger. The resistance value changes according to the logarithmic relationship according to the rotation angle. This type of potentiometer is mostly used in meters and is also suitable for tone control circuits. The conductive material on the resistor body of this potentiometer is unevenly distributed. The change is large; when the rotation angle increases, the resistance value changes less. The change in resistance is logarithmic in relation to the rotation angle of the potentiometer, which is mostly used for volume control. Because the human ear’s perception of volume is roughly linearly related to the logarithm of the sound power, that is, when the sound increases from small, the human ear feels very sensitive, but after a certain value, even if the sound power has a large increase, the human ear feels very sensitive. The ears feel little change. It can be seen that the resistance change rule of the logarithmic potentiometer is more in line with the characteristics of human hearing. Therefore, the logarithmic potentiometer should be used in the volume control circuit of radios and televisions.