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capacitive sensor

Capacitive sensors are based on the conversion of their capacitance into another physical quantity or the time constant and frequency changederived from it. A simple principle of a capacitive sensor is based on the change of the dielectric.

The construction of a dielectric sensor is very simple. It consists of two conductive tracks placed side by side on a printed circuit board to form a capacitance. The medium between the two conductive tracks has a dielectric constant that is close to "1". If another material is immersed in the electric field of the capacitor, then its capacitance changes.

In order to achieve a sufficiently large change in capacitance, the classical capacitive sensors need a corresponding stroke that causes the change in capacitance. To enable sensors with small changes in capacitance, such as those found in keyboards of mobile devices, to be used as well, a method has been developed that meets these requirements in the form of the Capacity to Digital Converter( CDC) conversion process. The CDC method works like a sigma-delta converter and detects an unknown capacitance instead of an unknown voltage.

Capacitive high-performance sensor for fingerprints, Photo: Siemens

Capacitive high-performance sensor for fingerprints, Photo: Siemens

Capacitive sensors are easy and inexpensive to manufacture and have low power consumption, but they are temperature-dependent and have little aging stability. Inautomotive technology, dielectric sensors are used as fill level sensors and as anti- trap protection for power windows, and also in non-contact switches, keyboards and mobile devices.

Englisch: capacitive sensor
Updated at: 22.02.2019
#Words: 236
Links: conversion, constant, frequency (f), sensor, dielectric
Translations: DE

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