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US 5,942,893 AGranted
Shielded eddy current sensor for enhanced sensitivity
AssigneeGeneral Dynamics Advanced Technology Systems, Inc.
InventorGregory Weston Terpay
Life of this patent
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AssigneeGeneral Dynamics Advanced Technology Systems, Inc.
InventorGregory Weston Terpay
Estimating the term…
An eddy current sensor comprises a generally E-shaped core having three parallel legs joined together by a bridge. Current carrying coils are mounted on each of the outer legs and a signal coil is mounted on the central leg. Identical a.c. currents are caused to flow through the two outer coils for generating two magnetic fields which combine to form a sensing magnetic field extending outwardly from the ends of the legs for sensing purposes but which cancel one another within the central leg. The sensor is disposed within an E-shaped, hollow shield of an eddy current producing, electrically conductive material. The sensor fits within the shield as fingers in a glove with the parallel legs of the sensor magnetically separated from one another by walls of the shield. Only the ends of the sensor legs are exposed through apertures through the shield for emergence of the various magnetic fields. The shield cancels unwanted fringing fields and better guides the magnetic fields in desired directions.
An eddy current sensor comprising first and second electrical coils each for generating respective first and second magnetic fields in response to the flow of electrical currents through said coils, and a third electrical coil for generating a signal voltage in response to a variable magnetic field intersecting said third coil, said coils being arranged relative to one another whereby said first and second fields combine to form a third magnetic field having a first portion forming a sensing field extending from an end of the sensor and having a second portion intersecting said third coil, whereby, upon disturbance of said sensing field by an electrically conductive object therewithin, said disturbance is detected by said third coil, the sensor including an eddy current suppressing frame on which all of said coils are mounted for defining paths through said frame for said magnetic fields, and further including a shielding member of electrically conductive material substantially fully enclosing and magnetically isolating said frame and said coils from one another along paths other than through said frame with the exception of said end of said sensor exposed through said shielding member for directing said coil generated magnetic fields towards said sensor end for amplifying said sensing field.
A method of operating an eddy current sensor comprising first, second and third electrical coils mounted in spaced apart relation on a support member, the method comprising the steps of flowing variable amplitude currents through said first and second coils for generating first and second variable amplitude magnetic fields which combine to form a variable amplitude sensing magnetic field having two portions, a first of which extends away from one end of said sensor and the second of which intersects said third coil, and disposing the sensor in an eddy current generating housing, of electrically conductive material substantially fully enclosing all but said one end of the sensor which is exposed through an opening in said housing for directing said coil generated fields towards said sensor end for increasing the strength of said sensing magnetic field.
A housing for an eddy current sensor of generally E-shape including three generally parallel legs end-connected to a common bridge, one of said legs being disposed between the other two of said legs each of which mounts thereon a magnetic field generating first electrical coil, and a magnetic field sensing second electrical coil mounted on said one leg, the housing comprising a hollow shell of electrically conductive material for generating magnetic-field inducing eddy currents in response to variable amplitude magnetic fields, said shell including walls defining an E-shaped interior space including three generally parallel first spaces end-connected to a common transversely extending second space, each of said spaces being substantially completely enclosed by said shell except for openings through said shell at ends of said first spaces oppositely disposed to said second space, said space ends being each shaped in conformity with respective end surfaces of the three parallel legs of a said E-shaped sensor disposed within said shell with the parallel legs of the sensor disposed within respective parallel first spaces of said shell, each of said sensor legs being substantially fully enclosed and magnetically separated from the other sensor legs by walls of said shell except for said end surfaces of said legs exposed through said shell openings for allowing interaction of magnetic fields generated by said first coils with said enclosing shell walls for directing said magnetic fields through said shell openings.
Dependencies are inferred from the claim text.