Title: Eddy current discontinuity probe utilizing a permanent magnet bobbin with at least one A.C. energized coil mounted in a groove thereon

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Abstract: Eddy-current inspection for cracks, flaws, etc, in rails, rods, etc. is conventional. For ferromagnetic material structures, it is found to be advantageous to magnetically saturate the material during inspection. The inventive eddy current probe facilitates the inspection of ferromagnetic tubing by saturating the tubing from within and only in the region of the test coils. Inspection may therefore be carried out on tubing which is installed in systems such as steam generators. The probe includes a bobbin on which test coils are wound. The bobbin may consist of a permanent magnet having a field of sufficient stength to provide the necessary magnetic saturation, or the field may be supplemented by driving a direct current through one or more of the coils. In a third embodiment, the bobbin may be made from high .mu. material and the entire saturating field is provided by driving a direct current either through the test coils or through additional dc bias coils located on the bobbin.


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