Displacement sensor, also known as linear sensor, is a linear device belonging to metal induction. The function of the sensor is to convert various measured physical quantities into electricity. According to the different forms of the measured variable, the displacement sensor can be divided into two types: the analog type and the digital type. The former can also be divided into two types: the physical type and the structure type. Commonly used displacement sensors are mostly analog structures, including potentiometer type displacement sensors, inductive displacement sensors, self-aligning machine, capacitive displacement sensors, eddy current displacement sensors, and Hall-type displacement sensors.