In many automatic detection systems, it is necessary to convert the measured physical quantity (such as pressure, flow, acceleration, etc.) into displacement first, and then convert the displacement into an electrical signal output. Therefore, displacement sensor is one of the most important basic sensors. According to the different forms of transformation of the measured variable, displacement sensors can be divided into analog and digital types. The analog type can be divided into characteristic type (such as self-generating type) and structural type. Commonly used displacement sensors are mostly analog, including resistive displacement sensors, capacitive displacement sensors, inductive displacement sensors, etc. An important advantage of digital displacement sensors is that it is easy to send signals directly into computer systems. This type of sensor has developed rapidly and is increasingly widely used. There are mainly three types: gratings, magnetic gratings and capacitive gratings. Classification of displacement sensors: