Importance

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Abstract

An electromagnetic-field-focusing remote-field eddy-current probe for inspecting anomalies in a conducting plate. The probe is designed to have the electromagnetic energy released from an excitation coil penetrate through the plate twice, so that the signals received by one or more receiver units (pickup coils, magneto-resistors or SQUIDs) have passed twice through the plate wall; from one side of the plate at the excitation coil to the other side, then back to the original side at the receiver units. The probe detects flaws, with good and substantially equal sensitivity, irrespective of their depth in the plate. It can detect, from one side of a plate, flaws located on the other side of the plate, which is useful for inspecting the bottom plate of a huge tank which is sitting on the ground. The thickness of inspected plates can go up to one inch for aluminum plates and to 3/8' for ferromagnetic plates. The probe generates a periodic magnetic field. The excitation coil and an auxiliary device direct the electromagnetic field into the plate being inspected. In one embodiment, the auxiliary device is a coil driven by a signal having a phase and amplitude relationship to the excitation coil's signal. The excitation and the receiver units are covered by one or more shields made of highly conducting materials, or of highly conducting materials laminated with alternating layers of ferromagnetic materials.

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First Claim