Testing substrate using eddy-current sensor arrays

摘要

An eddy current test circuit for measuring cracks, fatigue or stress in a specimen comprises a meandering primary winding having concentric circular substantially closed winding segments for imposing a spatially periodic magnetic field in the radial direction of at least two spatial wavelengths in a test substrate. At least one sensing element for sensing the response of the test substrate to the imposed magnetic field is included concentric with the winding segments.