US4517515A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetometer with a solid-state magnetic-field sensing means
Assignee: United States Department of the Navy
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Filing: 1981-06-03
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Granted: 1985-05-14
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Expires: 2001-06-03
Abstract
Abstract A magnetic-field detection device useful as a sensitive magnetometer. The device employs a solid-state field-sensing element which experiences a change in permeability when it is exposed to a magnetic field. The change in permeability results in a change in skin depth and therefore in resistance offered by the element to passage of a high-frequency alternating current. The element is used as one arm of a balanced bridge circuit to which an A.C. voltage is applied. Upon exposure to a magnetic field, the bridge is rebalanced to a null, the amount of current flow or rebalancing being measures of the magnetic field strength.
Inventors
- 👤 Karl Reinitz
- 👤 Lynn Hart
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 22:50
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/02; Y; Y10; Y10S; Y10S505/00; Y10S505/825; Y10S505/842; Y10S505/843; Y10S505/845
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
132 words
Apparatus for detecting a magnetic field comprising: magnetic sensing means consisting of a solid-state material having the property that its magnetic permeability is a function of the strength of any magnetic field which penetrates the material, and its skin depth and therefore its resistance are functions of its permeability, said solid-state material having a maximum permeability of about 750,000 and a steep hysteresis loop; signal-producing means, connected to said magnetic field sensing means, said signal-producing means comprising a multivibrator oscillator wherein said magnetic-field sensing means and a capacitor forms an RC-time-constant circuit of said oscillator, whereby a change in resistance of the sensing means changes the frequency of oscillation of said oscillator; and indicator means, connected to said signal-producing means, for providing an indication of the existence of an output signal therefrom.
Claim 2
Dependent Claim
132 words
Apparatus for detecting a magnetic field comprising: magnetic sensing means consisting of a solid-state material having the property that its magnetic permeability is a function of the strength of any magnetic field which penetrates the material, and its skin depth and therefore its resistance are functions of its permeability, said solid-state material having a maximum permeability of about 750,000 and a steep hysteresis loop; signal-producing means, connected to said magnetic field sensing means, said signal-producing means comprising a multivibrator oscillator wherein said magnetic-field sensing means and a capacitor forms an RC-time-constant circuit of said oscillator, whereby a change in resistance of the sensing means changes the frequency of oscillation of said oscillator; and indicator means, connected to said signal-producing means, for providing an indication of the existence of an output signal therefrom.
Claim 3
Dependent Claim
11 words
Apparatus as in claim 1, wherein: said solid-state material is Metglas.
Claim 4
Dependent Claim
32 words
Apparatus as in claim 1, wherein: said sensing means is formed in the shape of a rod approximately 0.002" by 0.002" in width and thickness and approximately 2" to 4" in length.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-05-13 | 1988-11-12 | 1989-05-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-05-13 | 1992-11-12 | 1993-05-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-05-13 | 1996-11-12 | 1997-05-14 | $7700.00 | Window Closed / Lapsed |