CIRCUMFERENTIALLY DIFFERENTIATING MULTIPLE COIL EDDY CURRENT PROBE

摘要

An eddy current probe for nondestructive testing of pipes (30) has an a.c. supply and a signal measuring unit, and is especially sensitive to localized defects. A coil carrier fits inside a probe housing (32) capable of moving freely inside the pipe. The coil carrier has several pairs of coils, each of which is symmetrical in a plane normal to the axis of the housing. The coil carrier may have one pair of identical coils with each coil wound on a D-shaped core. In the case of more than one pair of coils the cores are identical and they are symmetrical relative to the centre of the carrier. The probe is pulled along the pipe by a cable (38).