Microelectromechanical magnetometer

• US 7,253,616 B2
• Filed: 10/13/2005
• Issued: 08/07/2007
• Est. Priority Date: 10/13/2005
• Status: Expired due to Fees

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Simon, Maria E., Bolle, Christian A.
• Primary Examiner(s): DEB, ANJAN K
• Application Number:
  US11/250,123
• Publication Number:
  US 20070085533A1
• Time in Patent Office: 663 Days
• Field of Search: 324/662, 324/259, 324/260, 324/261, 324/257, 324/258, 324/658, 324/244
• US Class Current: 324/244
• CPC Class Codes: G01R 33/0286 comprising microelectromechanical systems [MEMS] MEMS devices in general B81B
• CPC Class Codes: G01R 33/038 using permanent magnets, e.g. balances, torsion devices

Abstract

An apparatus comprising a substrate and a MEM device. The MEM includes a comb capacitor and a magnetic element physically connected to one electrode of the comb capacitor. The magnetic element is capable of moving the one electrode in a manner that alters a capacitance of the comb capacitor. The apparatus also includes at least one spring physically connecting the magnetic element to the substrate.

Claims

1. An apparatus, comprising:

a substrate;

a MEM device including a comb capacitor and a magnetic element physically connected to one electrode of said comb capacitor, said magnetic element capable of moving said one electrode in a manner that alters a capacitance of said comb capacitor; and

at least one spring physically connecting said magnetic element to said substrate, wherein said comb capacitor comprises a fixed electrode having fixed fingers projecting from a fixed surface opposing a surface of the one electrode, said one electrode having fingers that interdigitate with said fixed fingers.

2. The apparatus of claim 1, wherein said magnetic element is configured to rotate, said rotation causing said movement of said one electrode.

3. The apparatus of claim 1, wherein said at least one spring holds said magnetic element such that rotations of said magnetic element are able to vary an amount of inter-digitation of said fixed fingers of said comb capacitor.

4. The apparatus of claim 1, wherein said comb capacitor further comprises a second fixed electrode having second fixed fingers projecting from a second fixed surface that opposes a second surface of said one electrode, said second surface having fingers that interdigitate with said second fixed fingers.

5. The apparatus of claim 1, further comprising a drive circuit configured to apply a voltage across said comb capacitor such that said voltage produces a torque on said at least one spring.

6. The apparatus of claim 1, wherein said MEM device is configured to detect changes in a magnetic field.

7. The apparatus of claim 1, wherein said apparatus is a metal detector.

8. The apparatus of claim 1, wherein said apparatus is a magnetometer.

16. The apparatus of claim 1, wherein there is a constant gap between adjacent interdigitated said fixed fingers of said fixed electrode and said fingers of said one electrode over a range of rotation of said magnetic element.

17. The apparatus of claim 1, wherein said fixed fingers of said fixed electrode and said fingers of said one electrode are both arc-shaped.

18. The apparatus of claim 1, said capacitance is linearly dependent upon an amount of overlap between said interdigitated fingers.

9. A method of use, comprising:

placing an apparatus in a magnetic field, where said apparatus comprises a MEM device having a comb capacitor, a magnetic element physically connected to one electrode of said comb capacitor and at least one spring physically connecting said magnetic element to a substrate of said apparatus, wherein said comb capacitor comprises a fixed electrode having fixed fingers projecting from a fixed surface opposing a surface of the one electrode, said one electrode having fingers that interdigitate with said fixed fingers; and

changing said magnetic field thereby causing said magnetic element to move said one electrode in a manner that alters a capacitance of said comb capacitor.

10. The method of claim 9, wherein said changing magnetic field causes said magnetic element to rotate, said rotation causing said movement of said one electrode.

11. The method of claim 9, wherein a capacitance of said comb capacitor is linearly related to an angle of rotation of said magnetic element.

12. The method of claim 11, wherein said angle of rotation is at least about 1 degree.

13. The method of claim 9, wherein at least one spring physically connecting said magnetic element to a substrate of said MEMS device opposes said movement of said one electrode.

14. The method of claim 9, applying a voltage across said comb capacitor such that said voltage produces a torque on said magnetic element.

15. The method of claim 14, wherein said torque opposes said movement of said one electrode.

19. The method of claim 9, wherein there is a constant gap between adjacent interdigitated said fixed fingers of said fixed electrode and said fingers of said one electrode during a rotation of said magnetic element.