Inductive proximity sensors are widely used in industrial automation, robotics, machinery manufacturing and other fields. For example, in the automatic production line, sensors can be used to detect the position, existence and motion state of the workpiece, so as to realize the automation and intelligence of the production process. In addition, it can also be used to detect the speed of sprocket teeth in textile, chemical fiber, machine tool, machinery, metallurgy, locomotive and automobile industries, the speed and distance of chain conveyor belt, and the control of automobile protection system.