US3639828A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Compensation of parasitic or stray magnetic fields, especially aboard an aircraft
Assignee: Commissariat à l'Énergie Atomique et Aux Énergies Alternatives
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Filing: 1969-10-15
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Granted: 1972-02-01
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Expires: 1989-10-15
Abstract
Abstract A magnetometer head generates a e.m.f. f1 at a frequency phi 1 proportional to (Ho+ Delta H1), value of the total magnetic field intensity at a first point aboard a plane or similar object; a frequency meter derives from frequency f1 a voltage e1 proportional to phi 1; at a second point (located aboard said plane or object), where the magnetic field intensity is (Ho+ Delta H2), a nuclear filter is fed by e.m.f. f1 and delivers an e.m.f. f2 out of phase with f1 by d phi proportional to ( Delta H2- Delta H1); a phase-meter is fed by f1 and f2 and delivers a voltage e2 proportional to d phi ; an amplifier having an adjustable gain amplifies the output of said phase-meter and delivers a voltage e3; a subtraction unit receives voltages e1 and e3 and delivers a voltage e4 proportional to (e1-e3), said voltage e4 being a measure of the external magnetic field Ho to be measured as e1 is proportional to (Ho+ Delta H1) and e3 is proportional (with the same proportionality factor) to Delta H1 if Delta x x( cube root Rho -1) and k2. phi /k1 x/3 WITH Delta H1 parasitic magnetic field in the first point, Delta H2 parasitic magnetic field in the second point, Delta X DISTANCE BETWEEN THE FIRST AND THE SECOND POINT, X DISTANCE OF THE FIRST POINT FROM THE BARYCENTER OF THE PARASITIC MAGNETIC SOURCES, K1 THE PROPORTIONALITY FACTOR BETWEEN F1 AND (Ho+ Delta H1), k2 the proportionality factor between f2 and ( Delta H2- Delta H1), phi (function of x) adjustable gain of said amplifier, Rho RATIO BETWEEN Delta H2 and Delta H1, i.e. Rho Delta H2/ Delta H1 In a modification, at the first point a magnetometerhead, identical to the head located in the first point, is substituted to said filter, and a differential frequency-meter fed by the outputs of both heads is substituted to said phase-meter.
Inventors
- 👤 Antoine Salvi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 05:42
CPC Classifications
H; H01; H01H; H01H51/00; H01H51/02; H01H51/04; H01H51/12; G; G01; G01R; G01R33/00; G01R33/02; G01R33/025; H01H51/01; H01H51/22; H01H51/2272
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
267 words
A method of compensating for perturbing magnetic fields in a carrier vehicle in order to permit the accurate measurement of the intensity of an external magnetic field and its perturbations, comprising the steps of: generating a first voltage proportional, with a first proportionality factor k1, to the intensity of the total magnetic field at a first point, located in the carrier vehicle, at a first distance x from the barycenter of the perturbing magnetic fields; generating a second voltage proportional, with a second proportionality factor k2, to the difference between the intensities of the total magnetic field at said first point and at a second point, located in the carrier vehicle, at a second distance from said barycenter; multiplying said second voltage by a factor phi dependent on said first distance to obtain a third voltage proportional, with said first proportionality factor, to the intensity of the perturbing magnetic field at said first point; subtracting said third voltage from said first voltage to obtain a fourth voltage; and, determining the amplitude of said fourth voltage, which is proportional to the intensity of the external magnetic field to be measured at said first point, rid of the influence of the perturbing magnetic fields; the first distance x, the distance Delta x between said first and second points, the first proportionality factor k1, the second proportionality factor k2, said factor phi , and the ratio Rho between the intensities of the perturbing magnetic fields at said second point and said first point respectively being related by the formulas Delta x x( Rho -1) and k2 . phi /k1 x/3.
Claim 2
Independent Claim
267 words
A method of compensating for perturbing magnetic fields in a carrier vehicle in order to permit the accurate measurement of the intensity of an external magnetic field and its perturbations, comprising the steps of: generating a first voltage proportional, with a first proportionality factor k1, to the intensity of the total magnetic field at a first point, located in the carrier vehicle, at a first distance x from the barycenter of the perturbing magnetic fields; generating a second voltage proportional, with a second proportionality factor k2, to the difference between the intensities of the total magnetic field at said first point and at a second point, located in the carrier vehicle, at a second distance from said barycenter; multiplying said second voltage by a factor phi dependent on said first distance to obtain a third voltage proportional, with said first proportionality factor, to the intensity of the perturbing magnetic field at said first point; subtracting said third voltage from said first voltage to obtain a fourth voltage; and, determining the amplitude of said fourth voltage, which is proportional to the intensity of the external magnetic field to be measured at said first point, rid of the influence of the perturbing magnetic fields; the first distance x, the distance Delta x between said first and second points, the first proportionality factor k1, the second proportionality factor k2, said factor phi , and the ratio Rho between the intensities of the perturbing magnetic fields at said second point and said first point respectively being related by the formulas Delta x x( Rho -1) and k2 . phi /k1 x/3.
Claim 3
Dependent Claim
105 words
A method according to claim 1 including the additional step of generating, in order to compensate for the proportion of the perturbing magnetic fields engendered by eddy currents in the carrier vehicle, a corrective magnetic field adjacent said second point and proportional to said proportion of the perturbing magnetic fields engendered by eddy currEnts in the carrier vehicle, the amplitude of said corrective magnetic field being set so as to cause the barycenter of the proportion of the perturbing magnetic fields engendered by said eddy currents to coincide with the barycenter of the perturbing magnetic fields caused by the ferromagnetic mass of the carrier vehicle.
Claim 4
Dependent Claim
94 words
A method according to claim 1 wherein the steps of determining the ratio Rho include: disposing two coils at said first and second points; energizing each coil from a variable source of current; causing the carrier vehicle to describe predetermined motions in predetermined directions; measuring the magnetic field at the first point and the magnetic field gradient between the first and second points; and, adjusting the amplitudes of each of the variable currents applied to said coils until, simultaneously, said magnetic field remains constant and said magnetic field gradient remains null during said motions.
Claim 5
Dependent Claim
304 words
Apparatus for compensating for perturbing magnetic fields in a carrier vehicle in order to permit the accurate measurement of the intensity of an external magnetic field and its perturbations, comprising, in combination: a first magnetometer head located at a first point in said carrier vehicle, substantially on the longitudinal axis thereof, at a first distance from the barycenter of the perturbing magnetic fields and capable of generating, on its output, an e.m.f. having a frequency proportional to the intensity of the total magnetic field at said first point; a frequency-meter connected to the output of said first magnetometer head to receive said e.m.f. therefrom and generate a first voltage proportional to said frequency, and, hence, to said total magnetic field intensity; a second magnetometer head located at a second point in said carrier vehicle, substantially on the longitudinal axis thereof, at a second distance from said barycenter and forming with said first head a magnetic gradient-meter capable of delivering a second voltage proportional to the difference between the intensities of the total magnetic field at said second and first point; a variable-gain amplifier the input of which is connected to the output of said gradient-meter to receive said second voltage and generate a third voltage, the gain of said variable-gain amplifier being adjusted in a predetermined manner; a subtraction unit having two inputs connected respectively to the output of said frequency-meter to receive said first voltage therefrom and to the output of said amplifier to receive said third voltage therefrom, and an output delivering a fourth voltage proportional to the difference between said first voltage applied to its first input and said third voltage applied to its second input; and, means for measuring said fourth voltage which is proportional to the intensity of the external magnetic field to be measured at said first point.
Claim 6
Dependent Claim
304 words
Apparatus for compensating for perturbing magnetic fields in a carrier vehicle in order to permit the accurate measurement of the intensity of an external magnetic field and its perturbations, comprising, in combination: a first magnetometer head located at a first point in said carrier vehicle, substantially on the longitudinal axis thereof, at a first distance from the barycenter of the perturbing magnetic fields and capable of generating, on its output, an e.m.f. having a frequency proportional to the intensity of the total magnetic field at said first point; a frequency-meter connected to the output of said first magnetometer head to receive said e.m.f. therefrom and generate a first voltage proportional to said frequency, and, hence, to said total magnetic field intensity; a second magnetometer head located at a second point in said carrier vehicle, substantially on the longitudinal axis thereof, at a second distance from said barycenter and forming with said first head a magnetic gradient-meter capable of delivering a second voltage proportional to the difference between the intensities of the total magnetic field at said second and first point; a variable-gain amplifier the input of which is connected to the output of said gradient-meter to receive said second voltage and generate a third voltage, the gain of said variable-gain amplifier being adjusted in a predetermined manner; a subtraction unit having two inputs connected respectively to the output of said frequency-meter to receive said first voltage therefrom and to the output of said amplifier to receive said third voltage therefrom, and an output delivering a fourth voltage proportional to the difference between said first voltage applied to its first input and said third voltage applied to its second input; and, means for measuring said fourth voltage which is proportional to the intensity of the external magnetic field to be measured at said first point.
Claim 7
Dependent Claim
127 words
Apparatus according to claim 4 wherein said second magnetometer head comprises: a nuclear filter located at said second point, said nuclear filter having its input connected to the output of said first magnetometer head so as to receive therefrom said e.m.f. constituting a first e.m.f. and to deliver, on its output, a second e.m.f. exhibiting with respect to said first e.m.f. a phase-difference proportional to the difference between the intensities of the total magnetic field at said second point and said first point; and, a phase-meter having two inputs connected respectively to the output of said first magnetometer head to receive said first e.m.f. therefrom and to the output of said nuclear filter to receive said second e.m.f. therefrom, and an output which delivers said second voltage.
Claim 8
Dependent Claim
123 words
Apparatus according to claim 5 including, for the purpose of compensating for the perturbing magnetic fields set up by the eddy currents engendered by the carrier vehicle, at least one coil disposed adjacent said second point and a source of electric current of Adjustable amplitude connected for energizing said coil, the current passing through said coil being such that the coil generates, adjacent said second point, a corrective magnetic field in phase opposition with the perturbing magnetic fields set up by said eddy currents, at an intensity such that it causes the barycenter of said perturbing magnetic fields set up by said eddy currents to coincide with the barycenter of the perturbing magnetic fields caused by the ferromagnetic mass of the carrier vehicle.
Claim 9
Dependent Claim
21 words
Apparatus according to claim 6 wherein said source is formed by at least one generating coil mounted within the carrier vehicle.
Claim 10
Dependent Claim
18 words
Apparatus according to claim 7 wherein said source is formed by three generating coils having mutually perpendicular axes.
Claim 11
Dependent Claim
86 words
Apparatus according to claim 4 wherein said second magnetometer head is capable, like said first head, of generating on its output a second e.m.f. at a frequency proportional to the intensity of the magnetic field at said second point; and, including a differential frequency-meter having two inputs connected respectively to the output of said first magnetometer head to receive said first e.m.f. therefrom and to the output of said second magnetometer head to receive said second e.m.f. therefrom, and an output which delivers said second voltage.
Claim 12
Dependent Claim
123 words
Apparatus according to claim 9 including for the purpose of compensating for the perturbing magnetic fields set up by the eddy currents engendered by the carrier vehicle, at least one coil disposed adjacent said second point and a source of electric current of adjustable amplitude connected for energizing said coil, the current passing through said coil being such that the coil generates, adjacent said second point, a corrective magnetic field in phase opposition with the perturbing magnetic fields set up by said eddy currents, at an intensity such that it causes the barycenter of said perturbing magnetic fields set up by said eddy currents to coincide with the barycenter of the perturbing magnetic fields caused by the ferromagnetic mass of the carrier vehicle.
Claim 13
Dependent Claim
21 words
Apparatus according to claim 10 wherein said source is formed by at least one generating coil mounted within the carrier vehicle.
Claim 14
Dependent Claim
18 words
Apparatus according to claim 11 wherein said source is formed by three generating coils having mutually perpendicular axes.
Claim 15
Dependent Claim
123 words
Apparatus according to claim 4 including for the purpose of compensating for the perturbing magnetic fields set up by the eddy currents energized by the carrier vehicle, at least one coil disposed adjacent said second point and a source of electric current of adjustable amplitude connected for energizing said coil, the current passing through said coil being such that the coil generates, adjacent said second point, a corrective magnetic field in phase opposition with the perturbing magnetic fields set up by said eddy currents, at an intensity such that it causes the barycenter of said perturbing magnetic fields set up by said eddy currents to coincide with the barycenter of the perturbing magnetic fields caused by the ferromagnetic mass of the carrier vehicle.
Claim 16
Dependent Claim
21 words
Apparatus according to claim 13 wherein said source is formed by at least one generating coil mounted within the carrier vehicle.
Claim 17
Dependent Claim
18 words
Apparatus according to claim 14 wherein said source is formed by three generating coils having mutually perpendicular axes.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-01-31 | 1975-08-02 | 1976-02-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-01-31 | 1979-08-02 | 1980-02-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-01-31 | 1983-08-02 | 1984-02-01 | $7700.00 | Window Closed / Lapsed |