Potentiometer resistance linear relationship

When we select the potentiometer, we will ask to choose the resistance and linearity of the potentiometer. Some customers and friends are not very clear about the concept of linearity. This article will tell you about the relationship between the resistance of the potentiometer and the changes that have occurred to help you Understand this concept.

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 value of the potentiometer varies with the rotation angle of the contact point of the sliding piece. This relationship can be in any functional form in theory. The resistance of common potentiometers has logarithmic change type [C type], linear change type [B type], and exponential change type [A type]. Soundwell will give you a detailed analysis of the linear changes in the resistance of these three potentiometers. The details are as follows:

Type C is a logarithmic type. When the logarithmic potentiometer starts to rotate, the resistance value changes smaller, and the closer the rotation angle is to the end of the maximum resistance value, the greater the resistance value changes. 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 distribution of conductive materials on the resistor body of this potentiometer is uneven. The change is great; 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.

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

Type A is an exponential, exponential (inverted logarithmic) potentiometer. When it starts to turn, 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.