Experimental methods for eddy current probe design and testing

This chapter examines the influence of eddy current (EC) probe parameters on the performance of the complete nondestructive evaluation (NDE) system and describes experimental methods for measuring these parameters. Topics considered include the theory of EC probe operation, the influence of probe geometry on flaw and liftoff signals, probe field measurements, and field transformations. Direct measurements of the probe field is an essential step in comparing an actual probe with its design properties. It is necessary to be able to measure the probe field in air very close to the probe. The following probe parameters are examined: the ratio of probe field intensity to input current, for sensitivity, and the distribution (or shape) of the flaw interrogating field generated by the probe for control of flaw response, liftoff response and spatial resolution (e.g. separation of closely spaced flaws and discrimination against edges and corners)