Patent ID: 11688617

Abstract:
Provided is an electrostatic capacitance sensor which can remove an influence of a noise occurring from a static eliminator or a driving source and accurately perform measurement even on electrostatic capacitance detected by a thin-type detection unit which can be passed to a finger surface of a wafer transfer robot. The present invention is provided with an AC supply source which supplies an AC voltage to a detection unit, a parasitic capacitance compensation circuit, an operational amplifier, a differential amplifier, a phase detection means, and a low pass filter. An operational amplification output terminal is connected to an inversion input terminal of the differential amplifier through a first band pass filter, the AC supply source is connected to a non-inversion input terminal of the differential amplifier through a second band pass filter, an output terminal of the differential amplifier is connected to an input terminal of the phase detection means, and the phase detection means takes, as a reference signal, an AC signal output from the AC supply source.