Contactless proximity sensor with multilevel response

摘要

A signal detector of a contactless proximity sensor feeds three voltage comparators with reference inputs connected to points of different threshold potentials. When the incoming signal exceeds only the lowest threshold, a light-emitting diode is flashed at a low frequency; when the intermediate threshold is surpassed, the diode flashes at a higher frequency, whereas its light emission is continuous in the presence of a signal level above the highest threshold. Only in the last two instances will a load-control circuit be switched.