Coil return energy measurement magnetic field sensor and method thereof
First Claim
1. A magnetic field sensor for detecting the presence of a magnetic field exceeding a predetermined threshold strength, comprising:
- a core member formed of a material selected to be magnetically saturated in the presence of a magnetic field exceeding the threshold strength;
a coil which forms plural turns on said core member, said coil having a quality factor (Q), representative of a ratio of energy returned from said coil to energy put into said coil, that depends upon whether said core member is magnetically saturated;
a coil energizing circuit which energizes said coil by applying an amount of DC current to said coil;
an energy measurement circuit which measures a quantity of energy returned by said coil after said coil has been energized by said coil energizing circuit; and
an evaluation circuit which determines whether said core member is in the presence of a magnetic field exceeding said threshold strength based upon the quantity of energy returned by said coil.
1 Assignment
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Accused Products
Abstract
A magnetic field sensor comprises a substantially planar core member having flux concentrating fins, and relatively narrow segments that interconnect the fins so that an external magnetic field becomes concentrated within the segments. A quality factor (Q) of a single coil which is wrapped around the segments is monitored to measure or detect the presence of an external magnetic field. To measure an external field, a current is passed through the coil to charge the coil with a known quantity of energy. A circuit of the sensor then measures the quantity of energy returned by the coil to measure the Q of the coil, and to thereby measure the external magnetic field. The magnetic sensor is suitable for pacemaker applications as a substitute for reed switches.
107 Citations
23 Claims
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1. A magnetic field sensor for detecting the presence of a magnetic field exceeding a predetermined threshold strength, comprising:
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a core member formed of a material selected to be magnetically saturated in the presence of a magnetic field exceeding the threshold strength; a coil which forms plural turns on said core member, said coil having a quality factor (Q), representative of a ratio of energy returned from said coil to energy put into said coil, that depends upon whether said core member is magnetically saturated; a coil energizing circuit which energizes said coil by applying an amount of DC current to said coil; an energy measurement circuit which measures a quantity of energy returned by said coil after said coil has been energized by said coil energizing circuit; and an evaluation circuit which determines whether said core member is in the presence of a magnetic field exceeding said threshold strength based upon the quantity of energy returned by said coil. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for detecting the presence of a magnetic field exceeding a predetermined threshold strength, comprising the steps of:
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(a) positioning a core member, formed of a material selected to be magnetically saturated in the presence of a magnetic field exceeding the threshold strength, so that said external magnetic field passes through said core member; (b) applying an amount of DC current to a coil which forms a conductive path around at least a portion of said core member, said coil having a quality factor (Q), representative of a ratio of energy returned from said coil to energy put into said coil, that depends upon whether said core member is magnetically saturated; (c) measuring a quantity of energy returned by said coil after said current has been applied to said coil in step (b); and (d) utilizing said quantity of energy returned to determine whether said external magnetic field that passes through said core member exceeds said threshold strength. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A magnetic field sensor for detecting the presence of a magnetic field exceeding a predetermined threshold strength, comprising:
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a core member formed of a material selected to be magnetically saturated in the presence of a magnetic field exceeding the threshold strength; a coil which forms plural turns on said core member, said coil having a quality factor (Q), representative of a ratio of energy returned from said coil to energy put into said coil, that depends upon whether said core member is magnetically saturated; a coil energizing circuit which energizes said coil by applying a predetermined quantity of energy to said coil; an energy measurement circuit which measures a quantity of energy returned by said coil after said coil has been energized by said coil energizing circuit; and an evaluation circuit which determines whether said core member is in the presence of a magnetic field exceeding said threshold strength based upon the quantity of energy returned by said coil as compared to the predetermined quantity of energy applied to said coil.
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18. A magnetic field sensor for detecting the presence of a magnetic field exceeding a predetermined threshold strength, comprising:
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a core member formed of a material selected to be magnetically saturated in the presence of a magnetic field exceeding the threshold strength; a coil which forms plural turns on said core member, said coil having a quality factor (Q), representative of a ratio of energy returned from said coil to energy put into said coil, that depends upon whether said core member is magnetically saturated; a coil energizing circuit which energizes said coil by applying an amount of current to said coil; an energy measurement circuit which measures a quantity of energy returned by said coil after said coil has been energized by said coil energizing circuit; and an evaluation circuit which determines whether said core member is in the presence of a magnetic field exceeding said threshold strength based upon the quantity of energy returned by said coil; wherein said measurement circuit comprises a capacitor which charges in response to a current produced by said coil once said coil has been energized, a voltage across said capacitor indicating said quantity of energy returned by said coil. - View Dependent Claims (19)
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20. A magnetic field sensor for detecting the presence of a magnetic field exceeding a predetermined threshold strength, comprising:
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a core member formed of a material selected to be magnetically saturated in the presence of a magnetic field exceeding the threshold strength; a coil which forms plural turns on said core member, said coil having a quality factor (Q), representative of a ratio of energy returned from said coil to energy put into said coil, that depends upon whether said core member is magnetically saturated; a coil energizing circuit which energizes said coil by applying an amount of current to said coil; an energy measurement circuit which measures a quantity of energy returned by said coil after said coil has been energized by said coil energizing circuit; and an evaluation circuit which determines whether said core member is in the presence of a magnetic field exceeding said threshold strength based upon the quantity of energy returned by said coil; wherein said measurement circuit comprises a capacitor connected in series with said coil.
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21. A magnetic field sensor for detecting the presence of a magnetic field exceeding a predetermined threshold strength, comprising:
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a core member formed of a material selected to be magnetically saturated in the presence of a magnetic field exceeding the threshold strength; a coil which forms plural turns on said core member, said coil having a quality factor (Q), representative of a ratio of energy returned from said coil to energy put into said coil, that depends upon whether said core member is magnetically saturated; a coil energizing circuit which energizes said coil by applying a single pulse to said coil; an energy measurement circuit which measures a quantity of energy returned by said coil after said coil has been energized by said coil energizing circuit; and an evaluation circuit which determines whether said core member is in the presence of a magnetic field exceeding said threshold strength based upon the quantity of energy returned by said coil in response to said single pulse.
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22. A method for detecting the presence of a magnetic field exceeding a predetermined threshold strength, comprising the steps of:
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(a) positioning a core member, formed of a material selected to be magnetically saturated in the presence of a magnetic field exceeding the threshold strength, so that said external magnetic field passes through said core member; (b) applying a current for a period of time to a coil, the coil forming a conductive path around at least a portion of the core member, said coil having a quality factor (Q), representative of a ratio of energy returned from said coil to energy put into said coil, that depends upon whether said core member is magnetically saturated; (c) at the end of the period of time, halting the application of the current to the coil; (d) measuring a quantity of energy returned by the coil after the period of time; and (e) utilizing said quantity of energy returned to determine whether said external magnetic field that passes through said core member exceeds said threshold strength.
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23. A magnetic field sensor for detecting the presence of a magnetic field exceeding a predetermined threshold strength, comprising:
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a core member formed of a material selected to be magnetically saturated in the presence of a magnetic field exceeding the threshold strength; a coil which forms plural turns on said core member, said coil having a quality factor (Q), representative of a ratio of energy returned from said coil to energy put into said coil, that depends upon whether said core member is magnetically saturated; a coil energizing circuit which energizes said coil by applying an amount of DC current to said coil; an energy measurement circuit which measures a quantity of energy returned by said coil after said coil has been energized by said coil energizing circuit; and an evaluation circuit which determines the external magnetic field strength based upon the quantity of energy returned by said coil.
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Specification