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SPEED-UP NDT BASED ON GMR ARRAY UNIFORM EDDY CURRENT PROBE

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

SPEED-UP NDT BASED ON GMR ARRAY UNIFORM EDDY CURRENT PROBE , Proc IMEKO World Congress, Busan, Korea, South, Vol. I, pp. 1 - 5, September, 2012.

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Abstract
The usage of eddy current probes including single magnetic field sensor represents a common solution for defect detection in conductive specimens but it is a time consuming procedure when large surface specimens are tested. In order to speed-up the nondestructive testing procedure, eddy current probes including a single excitation coil and an array of detection coils represent one of the solutions to reduce the NDT times but mainly detects the surface defects, but deep defects require different sensing elements such as GMR. In this work an optimized uniform eddy current probe architecture including two planar excitation coils, a rectangular magnetic field biasing coil and a GMR magnetometer sensor array is presented. An ac current is applied to the planar spiral rectangular coil of the probe, while a set of GMR magnetometer sensors detects the induced magnetic field in the specimens under test. The rectangular coil provides the dc uniform magnetic field assuring appropriate biasing of the GMR magnetometers of the probe, setting-up the functioning point on the linear region and at the same branch of GMR static characteristics. Elements of automated measurement system for NDT including a validation procedure based on 2D template matching algorithm and corresponding experimental results are included in the paper.