Introduction to Measuring Proximity Switches with a Multimeter
A proximity switch can be measured with a multimeter. The measurement method is also very simple; you can just treat it as an ordinary switch.
Now, let's get to know what a proximity switch actually is.
As the name suggests, a proximity switch is a switch that only functions when an object gets "close" to it. It should be classified as a type of position switch. The biggest difference between a proximity switch and the commonly - seen limit switch is that a proximity switch can measure the position of an object without physical contact.
In short, the essence of a proximity switch is still a switch, but its working principle is different. Currently, the common proximity switches on the market can be roughly divided into the following categories:
Photoelectric proximity switch: It works based on the reflection of light. When an obstacle blocks the emitted light, the device generates an on - or - off signal.
Hall - effect proximity switch: You may not be very familiar with the term "Hall". In fact, Hall refers to a type of circuit form. It is sensitive to magnetic substances. When a magnetic object is detected, the internal circuit of the switch changes, and then through a conversion circuit, it outputs a corresponding on - or - off signal.
Capacitive proximity switch: When it comes to capacitive proximity switches, you need to understand the concept of dielectric constant. When an object passes between the two plates of a capacitor, the dielectric constant changes, generating a signal, which is then converted and output through a circuit.
How to measure a proximity switch with a multimeter?
Although it is also a switch, measuring a proximity switch is a bit special. If we directly measure it, we definitely won't get any useful results. This is because a proximity switch needs to be powered during normal operation. It's like an electrical appliance and needs to be connected to a power supply, and most of them use a 24V DC power supply. After powering the proximity switch, we also need to understand its internal wiring method. Let's take the three - wire proximity switch as an example. For those who know some circuit knowledge, it's not difficult to see that the on - off state of the proximity switch is related to a transistor. When the main circuit of the proximity switch senses an object, there will be an on - off change in the internal circuit. This will form a closed loop across the load in the following figure, which means that the 24V power supply is applied across the load. This is actually the working principle of the proximity switch.
