The most commonly used proximity switches are three-wire proximity switches, two-wire and three-wire, four-wire, five-wire, and the most commonly used three-wire system. The three-wire is divided into NPN type and PNP type. The three-wire system means that the proximity switch has three wires, and the colors are respectively, brown represents + (positive pole), blue represents (negative pole), and black represents (output).

The following is a brief introduction to how to wire the proximity switch three-wire system:
1) The proximity switch has the difference between two-wire and three-wire. The three-wire proximity switch is divided into NPN type and PNP type, and their wiring is different.
2) The wiring of the two-wire proximity switch is relatively simple. The proximity switch can be connected to the power supply in series with the load.
3) Wiring of the three-wire proximity switch: the red (brown) wire is connected to the positive terminal of the power supply; the blue wire is connected to the 0V terminal of the power supply; the yellow (black) wire is the signal and should be connected to the load. The other end of the load is connected like this: for NPN proximity switches, it should be connected to the positive end of the power supply; for PNP proximity switches, it should be connected to the 0V end of the power supply.
4) The load of the proximity switch can be a signal lamp, a relay coil or a digital input module of a programmable controller PLC.
5) Special attention should be paid to the type selection of the three-wire proximity switch connected to the PLC digital input module. PLC digital input modules can generally be divided into two categories: the common input terminal of the first type is the negative pole of the power supply, and the current flows out of the input module.