In this paper, we present an eddy current transducer with rotating permanent magnets for the inspection of planar conducting plates. The transducer consists of a rotating head with permanent magnets, which is used to generate variable magnetic fields and thus induce eddy currents in the tested material. Two Hall sensors connected in a differential manner are used to detect a nonuniform distribution of eddy currents induced in a specimen containing a defect. To prove the usability of the transducer, a number of experiments were conducted on thick aluminum samples containing notches at different depths. Selected results of the achieved measurements are presented.

This paper presents a new method for nondestructive testing—a pulsed multifrequency excitation and spectrogram eddy current testing (PMFES-ECT), which is an extension of the multifrequency excitation and spectrogram eddy current testing. The new method uses excitation in the form of pulses repeated at a specified time, containing several periods of a waveform consisting of the sum of sinusoids with a selected frequency, amplitude and phase. This solution allows the maintenance of the advantages of multifrequency excitation and, at the same time, generates high energy pulses similar to those used in pulse eddy current testing (PECT). The effectiveness of the new method was confirmed by numerical simulations and the measurement of thin Inconel plates, consisting of notches manufactured by the electric-discharge method.

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