JPS57165740A - Compensation circuit of displacement detection device - Google Patents

Abstract

PURPOSE:To conduct highly precise detection of displacement without causing any measurement error, by compensating the change in displacement detection characteristics by such a closed-loop control of an excitation voltage that makes the voltage equal to a reference voltage prescribed beforehand. CONSTITUTION:A fixed voltage Vc is generated based on the outputs V1 and V2 of a rectifier circuit 13 irrespective of a displacement x of a core of a differential transformer 12 by a differential voltage absolute value circuit 16, a broken-line approximation circuit 17 and a buffer amplifier 18, and a primary excitation voltage of the transformer 12 is subjected to a closed- loop control so that the voltage Vc be equal to a reference voltage Vf1 by a voltage comparison circuit 19 and a driving circuit 11. Then, by using an average voltage Vm from the circuit 16 which changes little to the displacement x, an excitation voltage Vp of the primary coil 12a of the transformer 12 is controlled to maintain the voltage Vm at a fixed level, and thus the characteristics of the displacement x and a difference voltage Vd are made unchanged even when an excitation frequency, a voltage and a temperature are changed.