SIGNAL SIMULATOR FOR THE CALIBRATION OF EDDY-CURRENT PROBES

This paper describes a signal simulator which is designed to calibrate eddy current probes. By using simultaneously an excitation coil and a n electrically conducting plane, the simulator can emulate signals whi ch correspond to spot welds with different flaws. The presence of a co nducting plane allows a wide variation of the amplitude and phase of t he excitation coil voltage during the calibration of a probe. A mathem atical model for the simulator is derived and used to study the variat ion of the impedance change upon the parameters of the probe. Numerica l computation shows that the impedance change depends in an important way on the frequency of the excitation coil current.