How to build reliable capacitive sensors for an industrial environment

Capacitive technologies play an increasingly important role in the fields of industrial and automotive sensors. The noncontact working principle, on the one hand, is the main advantage of this technology, on the other hand the sensor is thus sensitive to electromagnetic disturbances. This paper describes methods how to successfully develop capacitive sensors which can reliably be operated in harsh industrial and automotive environments. A carrier frequency system combined with a ratiometric evaluation algorithm and a frequency hopping strategy can guarantee safe operation of capacitive sensors.