Importance

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Abstract

Eddy current test apparatus of the type that generates eddy currents in an object and that senses flaws or defects by sensing changes in the induced eddy current. Two differential encircling coils surround a moving workpiece moving relative to said coils. One of the two test coils has an enclosed tubular pathway forming a loop adjacent to the coil. A steel ball is placed in the enclosed tubular pathway and is air driven through the pathway so that it continuously revolves in close proximity to the coil. The steel ball disrupts the magnetic field flux generated by the test coil in the workpiece. This disruption modifies the eddy current in the workpiece which in turn induces a well defined output signal in the test coil. In an alternate and preferred embodiment, two ferrite object are rotated near the two encircling coils to disrupt the eddy currents produced by both coils. The ferrite objects are radially offset so that they do not disrupt the magnetic field near a flaw at the same time.

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First Claim