How to use a multimeter to directly detect proximity switches
There are two or three wire proximity switches. Let's explain separately below.
Firstly, three wire proximity switches are widely used. The output is divided into two types: NPN and PNP. The three-wire proximity switch requires additional power to operate, so it needs to be powered on before measurement. Generally, the brown wire is connected to 12-24VDC, the blue wire is connected to 0V, and the black wire is the signal output. We connect the wire and power it on. Put something in front of the proximity switch and try to get closer. If the proximity switch detects an object, its output indicator light will light up. There is a premise that you need to know what the proximity switch is detecting. If you don't know, you can try several more objects, such as metals, magnets, etc. If all of these have been tried and the indicator light is not on, then a multimeter can be used to measure. No matter what type of proximity switch it is, just measure the signal line and 24V or 0V voltage to see if there is any voltage. If there is no voltage, it indicates that the proximity switch is faulty. If the indicator light is on, it is good and there is no need to measure.
Secondly, there are two wire proximity switches, which do not require additional power supply, but can also be connected in two ways. The measurement method is basically the same as the three-line method. The colors of the two wires are generally brown and blue. The first connection method is to connect the blue wire to 0V and the brown wire to the signal. Still use an object to approach the proximity switch. If the proximity switch is good, the indicator light will light up. If it is not, you can use a multimeter to measure. Measure for voltage between the signal line and the 24V voltage. Nothing is bad. Another connection method and measurement are exactly the opposite.
