Patent US3649908A successfully refreshed from Google Patents.
US3649908A
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Magnetic field gradiometer utilizing a pair of cores driven by a blocking oscillator
Assignee: United States Department of the Navy
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Filing: 1970-10-12
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Granted: 1972-03-14
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Expires: 1990-10-12
Abstract
Abstract A gradiometer having in one embodiment two ring cores of high magnetic permeability with drive windings thereon and a blocking oscillator supplying unidirectional current to the drive windings to drive the cores around a portion of the hysteresis curve. The blocking oscillator drive circuit is controlled by feedback windings around both cores. A pair of sense windings are wound on each core, and each sense winding carries a signal composed of the induced drive signal and a magnetic field induced signal that varies with the ambient fields. The sense windings are connected to a demodulator circuit so that the induced drive signals cancel out and only the difference in ambient fields between the two ring cores is passed, indicative of the gradient in the DC magnetic field. In an alternative embodiment, ferromagnetic scroll cores replace the ring cores.
Inventors
- 👤 Robert E Brown
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 06:24
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/02; G01R33/04; G01R33/045; G01R33/022
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
109 words
A magnetic field gradiometer comprising: a first and a second ferromagnetic core, each core having wound thereon a drive winding, a feedback winding, and at least one sense winding; blocking oscillator means for producing a sequence of drive signals in said drive windings, said drive signals being transformer coupled to said sense windings and said feedback windings, the latter windings feeding signals back to said blocking oscillator and forming with said drive windings the transformer coupling of said blocking oscillator; and demodulator means coupled to said sense windings for producing an output voltage proportional only to the difference in ambient field strength between said first and said second cores.
Claim 2
Dependent Claim
109 words
A magnetic field gradiometer comprising: a first and a second ferromagnetic core, each core having wound thereon a drive winding, a feedback winding, and at least one sense winding; blocking oscillator means for producing a sequence of drive signals in said drive windings, said drive signals being transformer coupled to said sense windings and said feedback windings, the latter windings feeding signals back to said blocking oscillator and forming with said drive windings the transformer coupling of said blocking oscillator; and demodulator means coupled to said sense windings for producing an output voltage proportional only to the difference in ambient field strength between said first and said second cores.
Claim 3
Dependent Claim
12 words
The gradiometer of claim 1, wherein said ferromagnetic cores are ring cores.
Claim 4
Dependent Claim
56 words
The gradiometer of claim 2, wherein said first and said second ferromagnetic ring cores each have a pair of sense windings wound thereon, said feedback windings being wound around 360* of said ring cores, and each of said sense windings being wound around separate 180* segments of said ring cores, thereby defining a gradiometer sensitive axis.
Claim 5
Dependent Claim
48 words
The gradiometer of claim 3, wherein said demodulator means includes means interconnecting said pairs of sense windings for producing a voltage proportional to the difference in ambient magnetic field strength between said first and said second ring cores, and for producing a voltage proportional to said drive signals.
Claim 6
Dependent Claim
115 words
The gradiometer of claim 4, wherein each pair of sense windings comprises a first sense winding and a second sense winding, and said interconnecting means comprises: a first interconnection between said first sense winding of said first ferromagnetic ring core and said second sense winding of said second ferromagnetic ring core; a second interconnection between said first sense winding of said second ferromagnetic ring core and said second sense winding of said first ferromagnetic ring core; and a third interconnection between the other end of said second sense winding of said first ferromagnetic ring core and the other end of said second sense winding of said second ferromagnetic ring core, thereby forming a common juncture.
Claim 7
Dependent Claim
101 words
The gradiometer of claim 5, wherein said demodulator means includes: a first diode having its cathode connected to the other end of said first sense winding of said first ferromagnetic ring core; a second diode having its cathode connected to the other end of said first sense winding of said second ferromagnetic ring core; a first resistor connected between the anode of said first diode and said common juncture; a second resistor connected between the anode of said second diode and said common juncture; a capacitor connected between the anode of said first diode and the anode of said second diode.
Claim 8
Dependent Claim
146 words
The gradiometer of claim 1, wherein said blocking oscillator means comprises a drive circuit and a feedback circuit, said drive circuit comprising said drive windings connected in series, and a transistor, wherein one end of said drive windings is connected to the collector of said transistor, the other end of said drive windings is connectable to a source of unidirectional potential, and the emitter of said transistor is connectable to said source of unidirectional potential, said feedback circuit comprising said feedback windings connected in series, said transistor, a resistor, and a capacitor, wherein one end of said feedback windings is connected to the base of said transistor, and the other end of said feedback windings is connected to one end of the parallel combination of said resistor and said capacitor, and the other end of said parallel combination is connectable to said source of unidirectional potential.
Claim 9
Dependent Claim
41 words
The gradiometer of claim 1, wherein said ferromagnetic cores comprise scrolls, and wherein said drive windings, said feedback windings, and said sense windings are wound solenoidally thereon, thereby defining a gradiometer sensitive axis along the longitudinal axis of said scroll cores.
Claim 10
Dependent Claim
133 words
The gradiometer of claim 8, wherein the sense winding of said first ferromagnetic scroll core is connected in series to the sense winding of said second ferromagnetic scroll core, thereby forming a common juncture between said sense windings, and said demodulator means comprises: a first diode having its cathode connected to the other end of said sense winding of said first ferromagnetic scroll core; a second diode having its cathode connected to the other end of said sense winding of said second ferromagnetic scroll core; a first resistor connected between the anode of said first diode and said common juncture; a second resistor connected between the anode of said second diode and said common juncture; and a capacitor connected between the anode of said first diode and the anode of said second diode.
References Cited (Backward Citations)
US3448376A
Cited
US3541432A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-03-14 | 1975-09-13 | 1976-03-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-03-14 | 1979-09-13 | 1980-03-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-03-14 | 1983-09-13 | 1984-03-14 | $7700.00 | Window Closed / Lapsed |