The equivalent circuit model of pulsed eddy current testing (PECT) has simple mathematics but its applications are limited to qualitative analysis such as principle illustration and signal interpretation. In this paper, the parameters of equivalent circuit model are estimated using system identification method and quantitative relationships are found between some of the parameters and the size of the defect. The equivalent circuit equations were solved from the perspective of system analysis to yield the system transfer function. An m-sequence of 10 order was selected to excite the system and the probe current was used as the output. A set of experiment input-output data for system identification were obtained by performing experiments on two aluminium alloy 6061 slabs, one of which was machined with five slots of different widths, and the other one was machined with five depth-varied slots. The equivalent circuit parameters were finally estimated based on the identified transfer function parameters. It is found that the values of resistance and self-inductance of the secondary windings decrease greatly and monotonically with the increase of the slot width or depth. The self-inductance is more sensitive to the slot size variation than the resistance. Both of them have the potential to serve as the signal feature for defect evaluation in PECT applications.

脉冲涡流检测（PECT）的等效电路模型数学简单，但其应用仅限于定性分析，如原理图解和信号解释。本文采用系统辨识方法估计等效电路模型的参数，并找出其中一些参数与缺陷大小之间的定量关系。从系统分析的角度求解等效电路方程，得到系统传递函数。一米选择 10 阶的序列来激励系统，并使用探针电流作为输出。通过对两块6061铝合金板进行实验，得到一组用于系统辨识的实验输入输出数据，其中一块加工了五个不同宽度的槽，另一块加工了五个不同深度的槽。最后根据确定的传递函数参数估计等效电路参数。发现次级绕组的电阻值和自感值随着槽宽或槽深的增加而大幅度单调下降。自感对槽尺寸变化比电阻更敏感。它们都有可能作为 PECT 应用中缺陷评估的信号特征。