PULSED EDDY CURRENT SENSOR FOR PRECISION LIFT-OFF MEASUREMENT

摘要

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