Automobile speed sensors mostly use Hall type structure. Hall speed sensor is a kind of magnetoelectric sensor based on Hall effect. It has the characteristics of high sensitivity to magnetic field, stable output signal, high frequency response, strong ability to resist electromagnetic interference, simple structure and easy to use. It is mainly composed of permanent magnets (usually 4 or 8 pairs) with a specific pair of poles, Hall elements, rotating mechanisms and input/output plug-ins. Its working principle is that when the rotating mechanism of the sensor rotates under the action of external drive, it will drive the permanent magnet to rotate, and the magnetic field passing through the Hall element will produce periodic changes, resulting in the change of the output voltage of the Hall element. Through subsequent circuit processing, stable pulse voltage signal is formed as the output signal of the speed sensor.