Detection and evaluation of subsurface defects using pulse eddy current differential probe

Detection capability of pulsed eddy current testing device is described and illustrated with an example of an artificial subsurface defect in an electrically conductive steel plate. The investigated eddy current probe is of a differential type, consisting of one excitation and two sensing coils with a ferrite magnetic circuit. The numerical solution is carried out in the COMSOL Multiphysics using Magnetic field and Electrical circuit modules. The results are verified by performing laboratory experiment. Effect of the depth of subsurface defect on output differential signal is then analyzed and discussed.