ELECTROSTATIC CAPACITY DISPLACEMENT METER

PROBLEM TO BE SOLVED: To provide a stable electrostatic capacity displacement meter capable of performing a precise measurement without being influenced by a beat frequency changing following a temperature change or the like. SOLUTION: In this electrostatic capacitance displacement meter, a capacitance voltage converting circuit having an arithmetic amplifier 4 connected to a measuring electrode 1 is used. The displacement meter comprises a guard ring 7 surrounding the arithmetic amplifier 4 and a reference capacitor 5 in a floating structure; an oscillator 8 for driving the circuit, and a power source 10 for supplying an insulating power 9 to the arithmetic amplifier 4. The output of the arithmetic amplifier 4 is detected via an insulating amplifier 11 and a band pass filter 12 by a phase detector 13 by a reference signal 16 from the transmitter 8, and outputted from a low pass filter 14. The transmitting frequency fo of the transmitter 8 is synchronized with the transmitting frequency fd of the power source 10 by a synchronizing circuit 17 to fix the beat frequency generated, whereby a noise to be included in the band fc of the band pass filter 12 is prevented. COPYRIGHT: (C)2005,JPO&NCIPI