A novel biaxial probe implementing multifrequency excitation and SVM processing for NDT

The paper proposes a hand held eddy current based measurement instrument for the detection of thin defect on conductive planar specimens. The measurement instrument adopts a Giant Magneto Resistance based probe to detect the eddy current reaction field from the specimen and a suitable positioning system to measure the sensor position in the specimen plane. Two main novelties are proposed respect to previous realizations by the same authors: the improvement of the probe through the use of a bi-axial magnetic field sensor and the implementation of a suitable multi-frequency excitation strategy; the realization of a new processing section, based on an optimized SVM regressor, for the reliable estimation of the position and the geometrical characteristics of the thin defect. Results obtained on both simulated environments and real specimens showed the goodness of the proposal and the ability in the geometrical characterization of the thin defect.