JPS57158052A - Detection system for fine variation in electrostatic capacity - Google Patents

Abstract

PURPOSE:To detect variation in capacty accurately from a varying resonance frequency by driving a voltage variable capacity element by applying a DC voltage to an electrostatic capacity variation point through a high resistance, and converting it into fine variation in voltage. CONSTITUTION:A DC voltage E1 is applied to an electrostatic capacity variation point P through a high resitance to convert fine electrostatic capacity variation into fine voltage variation DELTAV, which is converted into variation in the electrostatic capacity of a voltage variable capacity element like a varactor diode 9. Then, the variation is converted into variation in the resonance frequency of a resonating circuit 10, and the variation is converted into voltage variation. On disk having variation DELTAC in electrostatic capacity by ruggedness 2, the tip of a conductive head 3 is moved in contact. At the point P, voltage variation DELTAV=DELTAC.E1/(CS+CB) appear according to the variation DELTAC. In this case, CS is the floating capacity of the head 3, and CB is that of the varactor diode. The capacity of the varactor diode 9 varies with the DELTAV and then the resonance point of the resonating circuit 10 varies to vary a peak detection output 23. This system is therefore suitable for the recording and reproduction of a capacity variation equipment.