EDDY CURRENT SURFACE PROBE

摘要

TITLE EDDY CURRENT SURFACE PROBE INVENTORS Hugh W. Ghent Valentino S. Cecco The eddy current probe consists of two coils mounted coaxially with each coil capable of separate axial adjustment. The coils are connected to the adjacent arms of an AC bridge circuit which can be balanced at the desired test frequency. The voltage output from the AC bridge due to lift-off or defects is the difference between the voltage change of each coil. The coils are adjusted axially to provide a voltage output due to lift-off which is in the order of 90.degree. with regard to the voltage output due to shallow defects making the latter simple to detect. A thin conducting shim may be positioned between one of the coils and the test surface in order to further rotate the lift-off signal of that coil.