Basics Capacitive Sensors
Basic Knowledge of Capacitive Sensors
Capacitive sensors detect metallic and non-metallic, solid and fluid materials. The principle of function of capacitive sensors is based on the capacity change at the active area of the sensor when a target with corresponding dielectric characteristics approaches. This active surface is created by two electrodes. The shape of the electrode is adaptable to the type of the sensor. If a target approaches the active area of the sensor, a change in capacity in the electric field occurs. Capacitive sensors can work according to two different principles:
Principle 1 uses the oscillation shot break or the damping that is created by the target in the electric field. The target takes energy out of the electric field. The height of energy extraction depends on the permittivity of the target's material. The higher the permittivity, the more energy is taken from the electric field. The electronics inside the sensor is recognising this change and is switching as soon as a certain value is reached.
Principle 2 is based on the unleashing of oscillation at a RC-oscillator when the target approaches. The oscillator creates a high-frequency oscillation. When an object is entering into the electric field, the permittivity is changing and therefore, the whole oscillation characteristics of the oscillator. The electronics inside the sensor is evaluating the oscillation and switches on the sensor if a certain value is exceeded.
Capacitive proximity switches of Pulsotronic are available as N or P switching and as normally open or normally closed versions. The sensitivity settings for different materials and environmental conditions is realised via a potentiometer. The available switching distance depends on the material and shape of the object.