Bobbin-Type Solid-State Hall Sensor Array With High Spatial Resolution for Cracks Inspection in Small-Bore Piping Systems

Bobbin coil and bobbin-type Hall sensor arrays are proposed as an alternative for crack inspection inside a small-bore piping system. The cracks can be imaged at high speed without using a scanner since the electromagnetic ( EM) field is distorted by the cracks. An array of 32 x 32 Hall sensors with 0.78 mm spatial resolution was set in a cylinder with diameter of 15 mm and length of 24.96 mm. A bobbin coil operating at 5 kHz of alternating current was positioned inside of a piping system and the sensor array outside the cylinder. Distorted EM fields around outside diameter stress corrosion cracking was imaged at 1 frame/s.