How to directly detect a proximity switch using a multimeter?
Proximity switches can be divided into two-wire and three-wire types. The following is an explanation of each type separately.
First, let's talk about the three-wire proximity switch, which is more commonly used. Its output can be divided into two types: NPN and PNP. A three-wire proximity switch requires an additional power source to operate. Therefore, before measurement, it is necessary to power it on first. Generally, the brown wire is connected to 12-24VDC, the blue wire is connected to 0V, and the black wire is the signal output.
After we connect the wires and power it on, place an object in front of the proximity switch and try to get it as close as possible. If the proximity switch detects the object, its output indicator light will turn on. There is a prerequisite for this, that is, you need to know what the proximity switch is designed to detect. If you don't know, you can try several different objects, such as metal, magnets, etc. If you have tried all these and the indicator light doesn't turn on, then you can use a multimeter for measurement. It doesn't matter what type of proximity switch it is. Just measure the voltage between the signal wire and either 24V or 0V to check if there is any voltage. If there is no voltage, it means that the proximity switch is faulty. If the indicator light is on, it means the switch is in good condition and there is no need for measurement.
Secondly, for the two-wire proximity switch, it does not require an additional power source, but there are also two ways of connection. The measurement method is basically the same as that of the three-wire proximity switch. The two wires are generally brown and blue in color.
The first way of connection is to connect the blue wire to 0V and the brown wire to the signal. Again, bring an object close to the proximity switch. If the proximity switch is in good condition, the indicator light will turn on. If it doesn't, you can use a multimeter to measure. Check if there is any voltage between the signal wire and 24V. If there is no voltage, it means the switch is faulty. The other way of connection and measurement is exactly the opposite.
