| Remote-field eddy current (RFEC) testing technology is an important nondestructive testing technology. It is widely used in pipeline inspection,but rarely used in flat conductive plates inspection. In this paper, RFEC testing technology is studied for flat conductive plates'inspection.In this paper, the principal of RFEC for conductive plates has been explained. Finite element numerical model of RFEC phenomenon for flat conductive plate is concluded based on Maxwell's equations. The RFEC testing technology is simulated by finite element method software: COMSOL. The four different excitation coils is designed based on finite element model. Comparing the characteristic curves of four excitation coils based on the three features: amplitude inflection point, 90°phase changing, indirect coupling energy through plate twice, only dedicated one can successfully realize RFEC for conductive plate. The excitation current frequency is optimized. The distance between remote-field and excitation coil is nearest with 44Hz. So the 44Hz is the best excitation frequency for the dedicated coil. The materials with different permeability have been researched based the dedicated coil. The RFEC can realize in ferromagnetic materials, not in nonferromagnetic materials. The RFEC is simulated in flat conductive plate with different depth cracks: 8mm, 6mm, 4mm, and 2mm. The defects signal is analyzed. The phase signal has a linear relationship with the defects depth.The RFEC inspecting system is constructed: the lock-in amplifier and data acquisition system. The standard sample with different depth defects: 8mm, 6mm, 4mm, 2mm is inspected. The inspection signal is filtered by adaptive filter. The experimental results show that it is very effective. The phase signal has a linear relationship with the defects depth. The experiments results verify the simulation results. The defect depth detection capabilities of the inspection system are calibrated.
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