Design of coil size and selection of excitation frequency are essential for eddy current testing.The standard penetration depth equation as the standard for eddy current testing does not take into account the effect of coil size.Aiming at this problem

a finite element simulation model for transmission eddy current detection is established.The influence of different excitation frequency and different size probe on penetration depth of transmission eddy current is studied.The validity of simulation analysis is proved by experiments. Simulation and experimental results show that:When the excitation frequency is high

the transmission eddy current can detect the depth of the defect is greater than the standard penetration depth

and the higher excitation frequency can guarantee better detection effect; higher excitation frequency can ensure better detecting effect

and it is less affected by coil size.