Inversion of Transient Eddy-Current Signals for the Determination of Conducting Plate Parameters

In traditional eddy-current NDE, an electromagnetic field is excited by a coil driven with a time-harmonic current. Information about the test piece is found from the effect of induced current on the coil impedance. Additional information may be obtained by using a number of different frequencies. In contrast, transient eddy-currents are excited by means of a pulsed coil current and perturbations of the magnetic field due to the test piece are monitored by observing the variation of the induced emf across the coil with time. Alternatively, the field perturbations may be detected by sensing the magnetic field using a Hall device