Tuning fork magnetometer

• US 20070296410A1
• Filed: 06/26/2006
• Published: 12/27/2007
• Est. Priority Date: 06/26/2006
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Inventors: Blumberg, Girsh Elias, Dennis, Brian Scott
• Granted Patent: US 7,830,142 B2
• Time in Patent Office: Days
• US Class Current: 324/244
• CPC Class Codes: G01R 33/02 Measuring direction or magnitude of magnetic fields or magnetic flux G01R33/20 takes precedence
• CPC Class Codes: G01R 33/028 Electrodynamic magnetometers

Abstract

Apparatus comprises a tuning fork having first and second tines, a first magnet disposed on the first tine, and a second magnet disposed on the second tine. In one embodiment the magnets comprise permanent magnets; in another they comprise electromagnets. In a preferred embodiment the magnets have magnetic moments oriented essentially parallel to the axis of the tines and anti-parallel to one another. In operation, the apparatus is made to oscillate at or near its resonant frequency, and in the presence of a magnetic field a parameter of the oscillation (e.g., its frequency, phase or amplitude) is altered in a fashion that allows the magnitude or direction of the magnetic field to be determined. In a preferred embodiment, the tuning fork is disposed within a vacuum enclosure, which increases the Q of the apparatus.

Claims

1. Apparatus comprising:

a tuning fork having first and second tines,

a first magnet disposed on said first tine, and

a second magnet disposed on said second tine.

2. The apparatus of claim 1, wherein said magnets comprise permanent magnets.

3. The apparatus of claim 1, wherein said magnets comprise electromagnets.

4. The apparatus of claim 1, wherein said tines are elongated in a particular direction and said magnets have anti-parallel magnetic moments that are oriented essentially along said direction.

5. The apparatus of claim 1, wherein said tines are elongated in a particular direction and said magnets have anti-parallel magnetic moments that are oriented essentially perpendicular to said direction.

6. Apparatus comprising at least two apparatuses accordingly to claim 1, the tuning fork of one of said apparatuses being oriented so that a line through the tips of its tines is essentially perpendicular to the corresponding line of the tuning fork of another of said apparatuses.

7. The apparatus of claim 1, further including

a drive circuit for causing said apparatus to oscillate at or near its resonant frequency;

and

a detection system of sensing changes in a parameter of said oscillation induced by the presence of a magnetic field.

8. The apparatus of claim 1, further including a vacuum enclosure, said apparatus being disposed within said enclosure.

9. The apparatus of claim 1, wherein said tuning fork comprises a piezoelectric material.

10. A magnetometer comprising:

a vacuum enclosure,

apparatus having a resonant frequency, said apparatus being disposed within said enclosure and including

a piezoelectric tuning fork having first and second tines, each of said tines having a surface on a free end thereof,

a first permanent magnet disposed on said free end surface of said first tine,

a second permanent magnet disposed on said free end surface of said second tine;

said tines being elongated in a particular direction and said magnets having anti-parallel magnetic moments that are oriented essentially along said direction,

a drive circuit for causing said apparatus to oscillate at or near said resonant frequency,

a detection system of sensing magnetic-field-induced changes in the frequency, amplitude or phase of said oscillation caused by the presence of a magnetic field having at least a component oriented parallel to the imaginary line joining the ends of said tines.

11. A method comprising the steps of:

locating apparatus in a magnetic field, the apparatus including a tuning fork having first and second tines, a first magnet disposed on the first tine, and a second magnet disposed on the second tine,

causing the apparatus to oscillate at or near its resonant frequency, and

detecting magnetic-field-induced changes in a parameter of the oscillation.

12. The method of claim 11, wherein the detecting step includes sensing changes in the frequency, phase or amplitude of the oscillation.