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Characteristics of Rotating Potentiometers and Guidelines for Selection and Use of Potentiometers
Date:2018-11-22 Views:39
I. The Concept of Rotating Potentiometer

rotary encoder potentiometer is composed of a resistor and a rotating or sliding system. It has three lead-out terminals and resistance value can be adjusted according to certain changing rules. When a voltage is applied between the two fixed contacts of the resistor, the position of the contacts on the resistor is changed by rotating or sliding system, and a voltage related to the position of the moving contacts can be obtained between the moving contacts and the fixed contacts. It is mostly used as a voltage divider, when the rotary potentiometer is a four-terminal element. Rotating potentiometer is a kind of adjustable electronic component, which is generally used to adjust the volume switch of speaker and the power of laser head.

II. Main Characteristics of rotary encoder potentiometer and Guidelines for Selection and Use of Rotating Potentiometers

Parameters and characteristics. The main characteristics of rotary potentiometer are output function characteristics, coincidence, resolution and sliding noise. The nominal resistance, allowable deviation, rated power and resistance temperature coefficient of the rotary potentiometer are the same as those of the resistor. The indexes of rotary potentiometer include wear resistance life and starting moment.

Output function characteristics. The functional relationship between the voltage ratio of the precision rotary potentiometer (the ratio of output voltage to input voltage) and the stroke ratio (the ratio of stroke to total stroke of the brush on the resistor) is also known as the law of resistance variation. There are three commonly used functional relationships: linear, exponential and logarithmic. In addition, there are sine and cosine forms suitable for special purposes.

Conformity. The deviation degree between the actual output function characteristics and the theoretical value of the rotary potentiometer is expressed by the percentage of the absolute difference between the actual output and the theoretical output. For linear rotary potentiometers, the consistency is expressed by linearity, and the allowable deviation range is called linear accuracy.

Resolution. precision rotary potentiometer's finest adjusting ability to output voltage or resistance represents the output change caused by the smallest movement of brush. It has an important influence on the adjustment accuracy of instrument or control system.

Sliding noise. The irregular parasitic potential caused by the brush moving on the resistor (assuming there is no thermal noise and current noise). The sliding noise of non-wire-wound rotary potentiometer is expressed by dynamic noise or smoothness, and the sliding noise of wire-wound rotary potentiometer is expressed by equivalent noise resistance.

III. The Main Role of Rotating Potentiometer in Circuit

1. Used as voltage divider.
precision rotary potentiometer is a continuously adjustable resistor. When the rotating handle or sliding handle of the rotating potentiometer is adjusted, the moving contact slides on the resistor. At this time, the output voltage of the rotary potentiometer, which is related to the applied voltage of the rotary potentiometer and the angle or stroke of the movable arm, can be obtained at the output end of the rotary potentiometer.

2. Used as rheostat.
When a rotary encoder potentiometer is used as a rheostat, it should be connected to two end devices, so that a smooth and continuous variation of resistance can be obtained within the range of the travel of the rotary potentiometer.

3. Used as current controller
When a rotary potentiometer is used as a current controller, one of the selected current output terminals must be the sliding contact lead-out.