ARRAYED EDDY CURRENT PROBE SYSTEM

摘要

2128861 9315396 PCTABS00024 Eddy current probes for multi-layered structures include a body of a highly permeability material which is shaped to include a central core and an additional wall. A drive coil is wound around the central core of the body and a plurality of sense coils are located in an array in association with the additional wall. An outer drive coil is wound about the outside of the additional wall. The central drive coil is excited with a first alternating high frequency signal producing eddy currents primarily in the top of the layered structure. These eddy currents are sensed with the sense coil array and analyzed for structural defects in the top surface of the layered structure. Next the central core coil is excited with a second signal of a lower frequency than the first signal. Such signal introduces eddy currents in deeper layers of the structure. Such eddy currents are sensed by the sense coils and the signals so sensed are stored. The outer drive coil is now excited with a low frequency signal and the sense coils operated to detect eddy currents in deeper layers of the structure. The signal from excitation of the outer drive coil is scaled with respect to the signal from the central core coil for separating signal indicative of defects from that indicative of differences in the structure of the underlaying components of the layered structure.