Differential eddy current testing sensor composed of double gradient winding coils for crack detection

In this paper the eddy current testing (ECT) sensor composed of double gradient winding coils is researched to detect crack in conductive materials. The gradient winding coil has a high resolution of crack position which can reduce probability of crack undetected and advance test efficiency compared with the round coil. The novel differential configuration makes a multi-functional ECT sensor which can evaluate the characteristics of crack including position and size according to two coils´ inductance variations. The data reconstruction algorithms of crack position and width are established by curve fitting method based on the least square principle, and correspondingly estimation errors are both studied. Conclusion and further work are derived on the basis of the findings.