Eddy current sensor with a novel probe for crack position detection

An eddy current testing probe is researched to detect crack. The probe is composed of double uneven step distributing planar coils. When a crack in test metallic surface is in measurable range beneath probe, its position can be detected directly and quickly in non-scanning detection mode. This static crack detection can reduce measurement work and advance test efficiency greatly compared with the traditional dynamic crack detection by scanning. Experimental results show that the difference inductance of two probe coils is approximately linear with crack position in measurable range. By doing curve fitting for the dependence of difference inductance on crack position based on the least squares principle, an expression of crack position estimation is finally deduced and its estimating error is studied.