Although it is also a switch, the measurement of this proximity switch is somewhat special. If we measure it directly, we will definitely not be able to measure anything, because this proximity switch requires power supply during normal operation, just like an electrical appliance, which needs to be connected to a power source. Most of them are DC 24V, which is a three-wire wiring method.

After supplying power to the proximity switch, we also need to understand its internal wiring method. Let's take the three-wire proximity switch as an example. Friends who know some circuit knowledge can easily see that the on-off of the proximity switch is related to a transistor. When an object is sensed in the main circuit of the proximity switch, the on-off change inside the circuit will occur, which will form a closed circuit at both ends of the load in the figure below, That is, a 24V power supply is added to both sides of the load, which is actually the working principle of the proximity switch.