How to do the direct detection of the proximity switch with a multimeter
Proximity switches are divided into two-wire and three-wire. Let's explain separately below.
The first is the three-wire, and the three-wire proximity switch is more widely used. The output is divided into NPN and PNP. The three-wire proximity switch needs an additional power supply to work, so it must be powered on before measurement. Generally, the brown connection is connected to 12-24VDC, the blue connection is connected to 0V, and the black connection is the signal output. We connect the wires and turn on the power, put something in front of the proximity switch, as close as possible, if the proximity switch detects an object, its output indicator will light up. The premise of this is that you need to know what the proximity switch detects. If you don’t know, you can try a few more objects, such as metals, magnets, etc. If you've tried all of these and the light doesn't come on, it's time to measure with a multimeter. It doesn't matter what type of proximity switch it is, just measure the voltage between the signal line and 24V or 0V to see if there is any voltage. If there is no voltage, the proximity switch is bad. If the indicator light is on, it is good, no need to measure.
The second is two-wire. The two-wire proximity switch does not require an additional power supply, but it is also divided into two connection methods. The measurement method is basically the same as that of the third line. 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 be on. If it is not on, you can use a multimeter to measure it. Check whether there is voltage between the signal line and the 24V voltage. Nothing is bad. Another connection and measurement is just the opposite.
