Electronic meter having anti-tampering magnetic shield
First Claim
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1. An electronic meter for measuring electricity and being resistant to tampering by an externally applied magnetic field, said electronic meter comprising:
- a housing comprising a base and a cover connected thereto;
a plurality of electrical current sensors positioned within said housing, each of said electrical current sensors comprising a toroidal coil defining a coil axis aligned transverse to the base, outermost ones of said toroidal coils having respective outermost coil portions positioned in closely spaced relation from an adjacent interior surface of said housing; and
a magnetic shield positioned adjacent each outermost toroidal coil to thereby resist tampering by a magnetic field applied from external to said housing, said magnetic shield having an arcuate cross-sectional shape corresponding to the outermost coil portion and having a predetermined arc length covering only a predetermined portion of the outermost coil portion.
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Abstract
An electronic meter for measuring electricity includes a magnetic shield positioned adjacent each outermost toroidal coil of electrical current sensors to thereby resist tampering by a magnetic field applied from outside the meter housing. The magnetic shield has an arcuate cross-sectional shape corresponding to the outermost coil portion and has a predetermined arc length covering only a predetermined portion of the outermost coil portion. The shield preferably has a semicylindrical cross-section shape thereby covering only half the toroidal coil.
30 Citations
20 Claims
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1. An electronic meter for measuring electricity and being resistant to tampering by an externally applied magnetic field, said electronic meter comprising:
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a housing comprising a base and a cover connected thereto; a plurality of electrical current sensors positioned within said housing, each of said electrical current sensors comprising a toroidal coil defining a coil axis aligned transverse to the base, outermost ones of said toroidal coils having respective outermost coil portions positioned in closely spaced relation from an adjacent interior surface of said housing; and a magnetic shield positioned adjacent each outermost toroidal coil to thereby resist tampering by a magnetic field applied from external to said housing, said magnetic shield having an arcuate cross-sectional shape corresponding to the outermost coil portion and having a predetermined arc length covering only a predetermined portion of the outermost coil portion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An electronic meter for measuring electricity and being resistant to tampering by an externally applied magnetic field, said electronic meter comprising:
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a housing comprising a base and a cover connected thereto; at least three electrical current sensors positioned within said housing arranged in side-by-side relation, each of said electrical current sensors comprising a toroidal coil defining a coil axis aligned transverse to said base, outermost ones of said toroidal coils having respective outermost coil portions positioned in closely spaced relation from an adjacent interior surface of said housing; and a magnetic shield positioned adjacent only each outermost toroidal coil to thereby resist tampering by a magnetic field applied from external to said housing, said magnetic shield having an arcuate cross-sectional shape corresponding to the outermost coil portion and having a predetermined arc length covering only a predetermined portion of the outermost coil portion. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. An electronic meter for measuring electricity and being resistant to tampering by an externally applied magnetic field, said electronic meter comprising:
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a housing comprising a base and a cover connected thereto; a plurality of electrical current sensors positioned within said housing, each of said electrical current sensors comprising a toroidal coil defining a coil axis aligned transverse to said base, outermost ones of said toroidal coils having respective outermost coil portions positioned in closely spaced relation from an adjacent interior surface of said housing; and a magnetic shield positioned adjacent each outermost toroidal coil to thereby resist tampering by a magnetic field applied from external to said housing, said magnetic shield comprising cold-rolled carbon strip steel having a relatively low temper, said magnetic shield having a semicylindrical cross-sectional shape corresponding to the outermost coil portion and having an arc length covering the outermost coil portion in a range of about 150°
to 180°
. - View Dependent Claims (17, 18, 19, 20)
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Specification