Eddy current measuring circuit - has memory which stores instantaneous impedance measurements for subsequent correction factor

摘要

A clock pulse generator coupled to a multiplexer, produces one or more DC voltages to control a v.c.i. This oscillator has a variable amplitude sine wave output which is fed to a number of eddy current probe coils for workpiece testing. Currents are induced in pick-up coils and fed to multiplier circuits, which are also supplied with constant amplitude sine and cosine outputs from the oscillator, to generate real and imaginary current components. The instantaneous measured impedances are stored in a memory circuit to provide a correction factor for subsequent measuarements.