Capacitive Sensors
The active element in a capacitive proximity sensor consists of a sensor electrode and shielding. Together, these two electrodes form the capacitor.
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On the approach of a sensing flag (metallic or non-metallic object), a change in capacity takes place in the electrical field of this capacitor, i.e. the capacitor of the RC oscillation circuit is arranged in such a way that its capacity increases when an object approaches.
The oscillator is set in such a way that it only becomes capable of oscillation through this increase in capacity. The start in oscillation when an object approaches is detected by the signal analyser and output via the signal amplifier.
Reduction Factor R
As with the inductive proximity sensors, the reduction factor depends on the material. It describes the factor by which the sensing range S is reduced by a certain material, with reference to the nominal sensing range Sn, which results from the use of an earthed ST37 metal plate as sensing flag.
The most important reduction factors for capacitive proximity sensors are:
