How does a Proximity Sensor Work?

There are different types of presence sensors that vary according to the principle of operation. We will see what are the main types of presence sensors, the operation of proximity sensors and their respective application.

How does a proximity sensor work?

The proximity sensor is a suitable sensor for determining the distance and the presence of an object that is nearby, without having direct contact. Upon detecting any presence, it activates an electrical circuit, which activates a mechanism, be it an audible alarm, opening a door, among others. The operation of a presence sensor can occur in two ways: movement and temperature.

Throughout each year, modern sensors appear for the purpose of use in different industrial areas. To choose the best sensor, it is necessary to analyze the factory environment and which areas the entrepreneur wants to automate, it is also important to select devices that allow obtaining quality and accuracy.

Main types of sensors and their operation

Infrared sensor

This proximity sensor model detects objects by reflecting infrared rays. The sensor launches an invisible light and the moment the material invades its range, it estimates the light particles that were redirected by the object that entered the place, thus, connecting an electrical circuit. By calculating the frequency of the signal reached, it is possible to check its distance from the light portrayed by the object.

The setback with this type of sensor is that its accuracy can be limited by interference with different light sources around it, however, there are prototypes developed to lower this interference of lights, through its own frequency.

Infrared proximity sensor

Acoustic sensor

As the sensor’s name says, it works through sound. The functioning of this sensor is similar to that of the infrared, but, instead of photons, the machine perceives and manifests numerous frequencies of sound waves in the atmosphere. The sensor releases several inaudible waves and identifies the reflection stimulated by the closing of a foreign matter, similar to a scar. Whoever owns a car that has the parking sensor installed, has already used this type of proximity sensor.

Acoustic proximity sensor, used as a parking sensor

Capacitive sensor

Capacitive sensors have a different operating method from the others, since they make use of the capacitor standard, in order to identify the influence of objects on the side. That is, a plate is attached to a radiofrequency oscillator, in order to identify changes in a capacitor produced by the foreign object (second pole) and air (dielectric).

At the moment, when there is a change in the distance between the object and the plate, the capacitance of the arrangement changes, causing the oscillator to send a signal towards the device. The usefulness of this sensor is its variability in relation to the various objects it can see, for example, paper, wood, plastic, glass and even liquids, since all these materials hinder the performance of the scheme of storing electrical energy.

Capacitive proximity sensor, used to detect metallic objects.

Inductive sensor

Inductive proximity sensors use magnetic fields to identify objects. Certain electrical circuit is connected to a coil, which supports interference from the magnetic field. From the moment an object invades the magnetic field, the current in the coil changes and the circuit can be opened or closed, depending on the purpose of the scheme. This proximity sensor seeks to become sensitive to electrically conductive materials, and becomes more seen in factories, in robot controls and mechanical arms in the training procedure.

Inductive proximity sensor.

This video below explains how to perform a load with a 12 V to 24 V DC inductive sensor. Observe the working principle of this sensor to identify nearby metal, see also the wiring diagram.