**3.1 Common non-contact sensor technologies and real-world applications**

There have been some common non-contact sensor technology developments in recent years, through a series of innovations, research and development.

#### *3.1.1 Capacitive sensor technology*

These non-contact sensor varieties track changes in capacitance to gather important details about the movement or location of a specific target. A capacitor can store energy in an electric field between two plates known as electrodes. This technology

targets the other capacitor plate; the capacitance sensor is the first. The amplitude of the AC voltage, when a fixed frequency AC current is delivered, serves as a gauge of the separation between the sensor and target [28].

Position sensing and dynamic and thickness measuring are typical uses for capacitive sensor technology. In addition, on workstations, conveyors and robots, capacitive sensors can be utilised to detect parts and count and monitor liquid levels.

Everyday devices, such as digital audio players, smartphones and tablets, leverage capacitive sensing touchscreen as input devices. These sensors can also replace mechanical buttons [28].

### *3.1.2 Laser displacement sensor technology*

The high accuracy of distance, position and displacement measurements of targets at long ranges are well suited for laser displacement sensors, also known as laser triangulation sensors.

These sensors are utilised for displacement measurement in a wide range of applications and sectors, from automated process control and research and development testing to Original Equipment Manufacturer integration, inventory management and more.

They are designed to measure and check the levels of liquid and bulk materials as well as the position, size, surface profile, vibrations, and sensing of technical items [28].

## *3.1.3 Inductive sensors technology*

Inductive sensors employ magnetic fields produced in the coil to assess a target's motion or location.

When targets are conductive, one kind of inductive sensor technology uses Eddy currents.

This kind of sensor creates an alternating magnetic field by applying an alternating current to a coil.

The field causes currents—Eddy currents—in the target when it gets close to the sensor.

A secondary magnetic field is created by these currents and opposes the sensor's magnetic field.

The interaction can be gauged and utilised to calculate how far away the sensor is from the target.

Due to its resistance to grease, filth, dampness, magnetic interference fields and harsh industrial settings, Eddy current sensors are appropriate for use in places with limited access.

The measurement of internal combustion engine cylinder vibrations or sheet metal thickness in roller gaps is two instances of this technique in action [28].
