Displacement sensor is to measure the position of the object of high precision automation measuring tool. Displacement is also known as linear sensor, displacement sensor and the position of an object in motion in the process of moving about the amount of displacement measurement method involves the range is quite broad. In the conversion process, there are many physical quantities are often need to transform as the displacement, then the displacement transform into electricity. So the displacement sensor is a kind of important basic sensor. In the process of production, displacement measurement generally divided into two physical dimensions and mechanical displacement measurement. Mechanical displacement including linear displacement and angular displacement. According to the measured variable transformation, different kind of displacement sensor can be divided into analog and digital two kinds. Potentiometer type displacement sensor, it through the potentiometer elements will be converted to mechanical displacement and a linear or arbitrary function relationship of the resistance or voltage output. Ordinary linear potentiometer and circular potentiometer can be used as a linear displacement and angular displacement sensors, respectively. However, it is designed for measuring the displacement of potentiometer, requires changes in displacement and has a certain relationship between the resistance.

In some applications, the potentiometer displacement sensor of the moving brush connected to the object under test. Potentiometer mobile end resistance change with the displacement of the object. Resistance variation reflects the value of displacement, increase or decrease of resistance indicates the direction of the displacement. Usually on the potentiometer is connected to the power supply voltage, resistance to change is converted to a voltage output. Wire wound resistor due to its brush while moving resistance to turn resistance change for ladder, its output characteristic also stepped in. If this kind of displacement sensor is used as the feedback element displacement in the servo system, big step voltage will cause the system oscillations. So in the potential of making should try to reduce the resistance of each turn. Potentiometer displacement sensor of another major drawback is easy to wear and tear. Its advantages are: simple structure, the output signal is big, easy to use, low price.