Multiprobe inspection for enhancing sizing ability in eddy current nondestructive testing

This paper proposes a unique idea for enhancing sizing ability in eddy current nondestructive testing. A detected crack is inspected using several probes driven at the same exciting frequency but producing different eddy current distributions. Two probes are utilized for the purpose in the paper. The crack signals obtained with the two probes are linearly superposed and a unique value of the ratio of superposition is extracted from the mixed signals. Numerical investigations and experimental verification reveal that the value provides clear indications of the crack's depth. In addition, the depth of a notch five times as deep as the standard depth of penetration was well evaluated using the method.