Experimental Methods for Eddy Current Probe Design and Testing

Abstract

The purpose of this paper is to briefly review the influence of EC probe parameters on the performance of the complete NDE system and to describe experimental methods for measuring these parameters. Combined theory and experiment is required to quantify probe response to design optimum probes for specific applications, to verify the reproducibility of probe performance during manufacture, and to verify the stability and precision of probe calibration. For these purposes it is necessary to consider, at least, the following probe parameters (1) input impedance, for design of adjacent circuitry; (2) self-resonant frequency, for upper frequency limits of operation; (3) the ratio of probe field intensity to input current, for sensitivity; and (4) the distribution (or shape) of the flaw interrogating field generated by the probe — for control of flaw response, liftoff response and spatial resolution (i.e., separation of closely spaced flaws and discrimination against edges and corners).