Design of eddy current testing probe for surface defect evaluation

Early detection of defects in metallic components used in infrastructure is crucial to ensure theirsafety and reliability.This paper presents adevelopmentof a small eddy current testing (ECT) probe for evaluation of sub-millimetresurface defects.The ECT probe is developed in a planar differential using sensitive anisotropy magnetoresistance sensors, andthe signal amplification is achieved by a home-made instrumentation amplifier. The developed ECT probe is evaluatedby performing phase sensitive measurement of the magnetic responses of sub-millimetresurface slitsat the excitation field of 200 Hz and 10 kHz.Compared to the real component of the magnetic response, the imaginarycomponent can be used to identify the existence and position of the slits based on the signal intensity change caused by the induced eddy current.The spatial distribution of the magnetic response measured by the ECT probe can be used to estimate the dimension of the slit. It is expectedthat the developed ECT probe can be utilisedfor assessment of sub-millimetresurface defect