Apparatus for detecting an external magnetic field
First Claim
1. An apparatus for detecting an external magnetic field, comprising:
- a magnetic sensor comprising an elongated member of an electrically conductive material and a thin magnetic film disposed thereabout and formed of an uniaxial magnetic anisotropic material having a magnetic hard axis disposed essentially parallel to the axis of said elongated member and a magnetic easy axis disposed about the circumference of said elongated member, and a detection coil wound about said elongated member, said magnetic sensor producing parametric oscillations and having first and second oscillation states of respectively opposite phase and a non-oscillation state, in accordance with selective magnetization of said thin film in corresponding ones of first and second oscillation domains and a non-oscillation domain,first means for producing an alternating magnetic field along said easy axis of an intensity to establish magnetization of said thin film in an oscillation domain, said first means includes further means for producing a magnetic field along said hard axis for establishing magnetization of said thin film in a desired one of said first and second oscillation states,second means for producing an external magnetic field, andthird means for moving said second means relatively to said sensor to provide adjacent positions thereof wherein the external magnetic field of said second means is coupled in the direction of said hard axis of said sensor and produces magnetization of said thin film in a different one of said domains, and a displaced position wherein the external magnetic field of said second means is not coupled to said sensor and said thin film thereof is magnetized in said given domain, whereby said magnetic sensor changes its state from that corresponding to magnetization of said thin film in said given domain to a state corresponding to magnetization of said thin film in said different domain,said second means produces an external magnetic field of an intensity and polarity such that in said adjacent position thereof to said sensor, said external magnetic field switches the magnetization of said thin film to the other of said first and second oscillation domains, whereby said sensor changes from said one to said other of said first and second oscillation states of respectively opposite phases when said magnetization switches from said one to said other of said oscillation domains,said detecting coil producing an oscillating voltage output in accordance with said sensor being in either of said first and second oscillating states and producing a zero voltage output when the sensor switches from one to the other of said first and second oscillation states of respectively opposite phase, andmeans receiving the output of said detecting coil and responding to the zero voltage output of said detecting coil when the oscillation state of said sensor changes from one to the other of said first and second oscillation states of respectively opposite phase to provide an indication of the detection by said sensor of an external magnetic field.
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Abstract
Apparatus for detecting an external magnetic field comprises a magnetic sensor which produces para-magnetic oscillations and includes an elongated member of an electrically conductive material and a thin magnetic film disposed thereabout. Alternative embodiments of the invention are presented in each of which the detection of an external magnetic field by the sensor results in a change in the oscillating state. In a first embodiment, the sensor is maintained normally in an oscillating state of a given domain and thus a given phase; when the sensor is subjected to an external magnetic field of appropriate intensity and polarity, the magnetization of the sensor shifts from the first domain to the second domain and accordingly there is produced a change or reversal in phase of the oscillatory output derived from the sensor. In that change of phase, the sensor output passes through a zero voltage value which is detected for providing an indication of the sensing of the external magnetic field. In an alternative embodiment, the exciting magnetic field normally maintains the state of magnetization in a first domain producing a non-oscillating state of the sensor; an external magnetic field has the effect of switching the magnetization to an oscillation domain; the sensor accordingly switches from a non-oscillating state to an oscillating state in response to sensing the external magnetic field.
16 Citations
4 Claims
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1. An apparatus for detecting an external magnetic field, comprising:
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a magnetic sensor comprising an elongated member of an electrically conductive material and a thin magnetic film disposed thereabout and formed of an uniaxial magnetic anisotropic material having a magnetic hard axis disposed essentially parallel to the axis of said elongated member and a magnetic easy axis disposed about the circumference of said elongated member, and a detection coil wound about said elongated member, said magnetic sensor producing parametric oscillations and having first and second oscillation states of respectively opposite phase and a non-oscillation state, in accordance with selective magnetization of said thin film in corresponding ones of first and second oscillation domains and a non-oscillation domain, first means for producing an alternating magnetic field along said easy axis of an intensity to establish magnetization of said thin film in an oscillation domain, said first means includes further means for producing a magnetic field along said hard axis for establishing magnetization of said thin film in a desired one of said first and second oscillation states, second means for producing an external magnetic field, and third means for moving said second means relatively to said sensor to provide adjacent positions thereof wherein the external magnetic field of said second means is coupled in the direction of said hard axis of said sensor and produces magnetization of said thin film in a different one of said domains, and a displaced position wherein the external magnetic field of said second means is not coupled to said sensor and said thin film thereof is magnetized in said given domain, whereby said magnetic sensor changes its state from that corresponding to magnetization of said thin film in said given domain to a state corresponding to magnetization of said thin film in said different domain, said second means produces an external magnetic field of an intensity and polarity such that in said adjacent position thereof to said sensor, said external magnetic field switches the magnetization of said thin film to the other of said first and second oscillation domains, whereby said sensor changes from said one to said other of said first and second oscillation states of respectively opposite phases when said magnetization switches from said one to said other of said oscillation domains, said detecting coil producing an oscillating voltage output in accordance with said sensor being in either of said first and second oscillating states and producing a zero voltage output when the sensor switches from one to the other of said first and second oscillation states of respectively opposite phase, and means receiving the output of said detecting coil and responding to the zero voltage output of said detecting coil when the oscillation state of said sensor changes from one to the other of said first and second oscillation states of respectively opposite phase to provide an indication of the detection by said sensor of an external magnetic field. - View Dependent Claims (2, 3)
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4. An apparatus for detecting an external magnetic field, comprising:
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a magnetic sensor comprising an elongated member of an electrically conductive material and a thin magnetic film disposed thereabout and formed of an uniaxial magnetic anisotropic material having a magnetic hard axis disposed essentially parallel to the axis of said elongated member and a magnetic easy axis disposed about the circumference of said elongated member, and a detection coil wound about said elongated member, said magnetic sensor producing parametric oscillations and having oscillation states including first and second oscillation states of respectively opposite phase and a non-oscillation state, in accordance with selective magnetization of said thin film in corresponding ones of first and second oscillation domains and a non-oscillation domain, first means for establishing an alternating magnetic field along said easy axis of an intensity to produce an oscillation state of said sensor and including means for magnetizing said thin film along said hard axis thereof to produce a given one of said first and second oscillation states, second means for producing an external magnetic field, third means for moving said second means relatively to said sensor to provide adjacent and displaced positions of said second means and said sensor, the external magnetic field of said second means being of an intensity and a polarity such that when said second means is moved from said displaced to said adjacent positions thereof, the external magnetic field of said second means is coupled in the direction of the hard axis of said sensor and switches the magnetization of said thin film from said given one of said first and second domains to the other thereof, and when said second means is moved relatively to said sensor from said adjacent to said displaced positions thereof, the magnetic field of said second means is not coupled to said sensor and the magnetization of said thin film switches to said given one of said first and second oscillation domains, whereby the magnetic sensor switches from said first to said second oscillation state in response to said third means moving said second means relatively to said sensor from said displaced to said adjacent positions thereof, and switches from said second to said first oscillation state in response to said third means moving said second means relatively to said sensor from said adjacent to said displaced position thereof, said detecting coil producing a voltage output in accordance with the first and second oscillation states of said sensor and producing no voltage output at each switching of the oscillation state of said sensor, and means receiving the output of said detecting coil and responsive to each change from a voltage output to no voltage output thereof to produce a pulse output for indicating the detection by the sensor of an external magnetic field.
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Specification