PULSED EDDY CURRENT SENSOR FOR PRECISION LIFT-OFF MEASUREMENT

摘要

There is described a pulsed eddy current sensor for measurement of a lift-off distance over a surface of a metallic substrate (a metallic surface). The pulsed eddy current sensor comprises: a primary excitation coil to which are applied voltage pulses for generating primary magnetic fields, wherein an interaction of the primary magnetic fields with the metallic substrate produces secondary magnetic fields; and secondary pick-up probes, each of the secondary pick-up probes located at a different vertical distance from the metallic surface, the secondary pick-up probes used for measuring the primary and secondary magnetic fields and for producing a differential signal that is representative of the lift-off distance.