JPS6439503A - Electrostatic capacity type displacement detecting sensor - Google Patents

Abstract

PURPOSE:To enable detection stable over a long period of time even in adverse environment by using a metal, etc., which have an immobile or blind zone regardless of impressed voltages in a region where a hydrogen ion concn. is nearly neutral to form electrodes which constitute a sensor. CONSTITUTION:This electrostatic capacity type displacement detecting sensor 21 is constituted by housing a stationary plate 1 and a moving plate 2 into a case 11, forming the signal transmission electrode 3 and the signal reception electrode 4 to the stationary plate 1, and forming the coupling electrode 5 and the earth electrode 6 to the moving plate 2. The voltage signal corresponding to the voltage signal of the electrode 3 is induced via the electrode 5 to the electrode 4 when the AC voltages of different phases are impressed to the respective electrodes 3. The signal corresponding to the moving quantity of the spindle 14 is outputted when the moving plate 2 is displaced relative to the stationary plate 1 by the lifting of a spindle 14. The immobile region is obtd. over a wide range of the impressed voltages regardless of the hydrogen ion concn. by forming the electrodes 3, 4, 5, 6 of tantalum and, therefore, the stable detection is possible without inducing corrosion.