JPS5450357A - Edge detector - Google Patents

Abstract

PURPOSE: To improve the detecting accuracy by compensating the detecting error coming from the perpendicular displacement to the moving direction of a conductive body in response to the detected outputs of two sensors which are operative to detect the end faces of the conductive body in accordance with the variation in the mutual inductance.

CONSTITUTION: If a conductor 1 sich as a steel plate being produced comes close to sensors 2 and 3 which are equipped with an oscillatory circuit such as a coil 6 or a variable capacitor C, there is generated a discrepancy in the resonant frequency through the reference frequency oscillator 7 by the mutual inductance due to the eddy current which is generated in the ends of the conductor 1. The capacity of the capacitor C is so adjusted that a discrepancy is generated in the resonant frequency in accordance with the vertical displacement of the conductor 1, and the DC voltage which is produced by detecting the discrepancy of the resonant frequency of the sensor 2 is applied to an A/D converter 12 so that the detected output of the discrepancy in the resonant frequency corresponding to the horizontal and vertical displacements Δx and Δy of the conductor 1 by the sensor 3 for controlling a gain control circuit 13 is compensated. As a result, the displacement of the conductor 1 can be detected highly accurately in a non-contact manner without any influence upon oscillations or the like

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