Tuning fork magnetometer
View Patent ↗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.
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,
wherein said magnets have anti-parallel magnetic moments, said tines are elongated in a particular direction, and said anti-parallel magnetic moments are oriented essentially along said direction.
2. The apparatus of claim 1 , wherein said magnets comprise permanent magnets.
3. The apparatus of claim 1 , wherein said magnets comprise electromagnets.
4. 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.
5. 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.
6. The apparatus of claim 1 , further including a vacuum enclosure, said apparatus being disposed within said enclosure.
7. The apparatus of claim 1 , wherein said tuning fork comprises a piezoelectric material.
8. 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.
9. 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, Wherein said magnets have anti-parallel magnetic moments, said lines are elongated in a particular direction, and said anti-parallel magnetic moments are oriented essentially along said direction,
causing the apparatus to oscillate at or near its resonant frequency, and
detecting magnetic-field-induced changes in a parameter of the oscillation.
10. The method of claim 9 , wherein the detecting step includes sensing changes in the frequency, phase or amplitude of the oscillation.