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概要

The magnetic field sensors based on the tunnel magneto-resistive effect (TMR) present enhanced characteristics such as the high sensitivity and a good linearity. They can distinguish the two orientations along a single direction of measurement and don’t need a DC field to set the working point. In this article we shall use TMRs to measure the small magnetic field in the context of an eddy current inspection of a planar aluminum material. The magnetic field disturbance due to the presence of a flaw is measured in two different directions, one parallel to the material surface and the other perpendicular to the surface. The measurements are performed in a rectangular zone, around a machined defect, and two data maps are obtained depicting two components of the perturbation field. Both maps are then subject to an inversion process, with regularization, in order to obtain the eddy current density. Both eddy current maps describe the same current, and must be fused to increase the accuracy of the current map. On the map the zones without any significant currents represent the defects with null conductivity.

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