Electronic Proximity Sensor Technology Explained

Proximity: Electronic Control Elements

Electronic control elements are components that are not subject to metal wear and exhibit insensitivity to adverse environmental conditions. Their use is primarily justified in installations requiring high security, connection point accuracy, long-term reliability, large switching frequencies, and high operating speeds.

To function, these sensors require a power supply and an amplification device capable of feeding their output to the detector via an electromagnetic circuit. Currently, the most notable types widely used in industry include the following:

Inductive Proximity Sensors

This sensor signals the presence of a metal object close to its sensitive face. It consists of an oscillator, where the sensitive face coils form a particular shape. This configuration creates an alternating magnetic field. When a metal screen enters this field, eddy currents induce an additional load that causes oscillations to dampen. Subsequently, a switching circuit output provides a signal equivalent to a contact closing and opening.

Capacitive Proximity Sensors

Capacitive proximity sensors can be defined as limit switches that operate without metal or friction contacts. They can detect materials without physical contact, including conductive or electrically non-conductive materials that are in solid, liquid, or powder form. Examples include glass, ceramic, wood, oil, water, paper, plastics, and cardboard.

The detector signals when the material is present within a certain distance in front of it.

Ultrasonic Proximity Sensors

This detector operates without mechanical friction or contact, meaning its components do not suffer mechanical wear. This type of detector emits ultrasonic pulses; detecting the echo reflected by the object allows for switching an output signal.

It is important that the sensing object has a minimum size relative to the distance. These sensors can detect objects that are solid, liquid, or powder.

Photoelectric Detectors

A photoelectric detector consists of a light transmitter associated with a photosensitive receptor. Detection occurs when the intensity of the light beam is interrupted or varied. The resulting signal, after amplification, can be utilized by an external receiver or an output element.

The light emission is typically made using light-emitting diodes (LEDs) that emit an invisible beam. This broadcast method guarantees high immunity to stray light and offers a virtually unlimited lifespan.

The operating range must ensure reliable detection of the moving object in extreme cases. Therefore, the distances between the transmitter and receiver must equal the useful range.