Study on flux-differential type eddy-current testing technique by planar coils

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We proposed a new planar type eddy-current probe that detects induced voltage as sensing signal. We researched the detection characteristics and application of this ECT probe as one of the advanced non-destructive inspection. The achievements of the research project are follows ;1.Fabrication of meander/mesh planar probeWe developed the planar ECT probe as most excellent ECT structure where a meander type coil, and a mesh coil are used as exciting, and sensing coils respectively. The probe is flexible in structure and can be scanned close to the surface of object. Particularly, it is easy to fabricate it by etching techniques.2.Characteristics of the planar ECT probeRegarding the advanced ECT techniques, the detection of shape, size, and direction of crack or defect is needed actually. We confirmed experimentally that the ECT probe has the sensitivity enough to detect the 60%, 10mm outside crack with 1.0mm copper plate. The 2-D imaging pattern of the sensing signal enables us to give the information of size, shape, and direction of crack. And we measured the detecting characteristics by using Inconel 600 plate which is pipe-material at atomic power plant.3.Inspection printed wiring by using ECT approachWe discussed the possibility of using ways of this probe to inspect disconnections in printed wirings. To induce eddy currents on printed wiring, the meander exciting coil of the ECT probe has the suitable structure. Experimentally, we confirmed that we can detect the signal of disconnection. But to check the defect on the complicated wiring pattern, we also need the comparison techniques as teaching signal at the normal wiring board.