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GMR Based Eddy Current Sensing Probe for Weld Zone Testing

Postolache, O. ; Ramos, H. ; Ribeiro, A. L. ; Alegria, F.

GMR Based Eddy Current Sensing Probe for Weld Zone Testing, Proc IEEE Sensors, Chrischurch, New Zealand, Vol. 1, pp. 73 - 78, October, 2009.

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Abstract
The detection of flaws in the weld zone of conductive
plates is an important issue and, in this field, different solutions
using eddy current probes are mentioned in the literature.
However, when eddy current pancake probes are used, it is
difficult to detect the flaws or the welding non-uniformities due
to the lift-off effects. Thus, in the present work we present a
novel uniform eddy current probe architecture based on a
tangential excitation coil with a rectangular geometry and highly
sensitive giant magnetoresistances (GMR). The induced
magnetic field is measured using a GMR sensor fixed on the axis
midpoint inside the coil. The sensor sensitive axis is
perpendicular to the excitation coil axis in order to measure only
the induced magnetic fields caused by the presence of flaws. We
developed an automatic testing system to characterize the sensor
and to perform tests on aluminum plate specimens with flaws
included in the weld zone.