MICRO-ELECTROMECHANICAL SYSTEM (MEMS) BASED CURRENT AND MAGNETIC FIELD SENSOR USING TUNNELING CURRENT SENSING

• US 20070181963A1
• Filed: 04/18/2007
• Published: 08/09/2007
• Est. Priority Date: 06/07/2004
• Status: Active Grant

• Current Assignee: ABB SPA (ABB Limited)
• Original Assignee: General Electric Company
• Inventors: Chandrasekaran, Shankar, Berkcan, Ertugrul, Aimi, Marco, Kapusta, Christopher, Claydon, Glenn
• Granted Patent: US 7,741,832 B2
• Time in Patent Office: Days
• US Class Current: 257/415
• CPC Class Codes: G01R 15/148 involving the measuring of a magnetic field or electric field G01R15/18, G01R15/20, G01R15/24, G01R15/26 take precedence
• CPC Class Codes: G01R 15/207 Constructional details independent of the type of device used
• CPC Class Codes: G01R 33/0283 in which a current or voltage is generated due to relative movement of conductor and magnetic field
• CPC Class Codes: G01R 33/0286 comprising microelectromechanical systems [MEMS] MEMS devices in general B81B
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence

Abstract

A micro-electro-mechanical system (MEMS) current sensor for sensing a magnetic field produced by an electrical current flowing in a conductor includes a first fixed element and a moving element. The moving element is spaced away from the first fixed element and is movable relative to the fixed element responsive to a magnetic field produced by an electrical current flowing in a conductor for providing a mechanical indication of a strength of the magnetic field. The sensor also includes a tunneling current generator for generating a tunneling current between the first fixed element and the moving element and a tunneling current monitor for monitoring a change in the tunneling current responsive to the mechanical indication to provide an indication of a value of the electrical current in the conductor.

Claims

1. A micro-electro-mechanical system (MEMS) current sensor for sensing a magnetic field produced by an electrical current flowing in a conductor comprising:

a first fixed element;

a moving element spaced away from the first fixed element and movable relative to the fixed element responsive to a magnetic field produced by an electrical current flowing in a conductor for providing a mechanical indication of a strength of the magnetic field;

a tunneling current generator for generating a tunneling current between the first fixed element and the moving element; and

a tunneling current monitor for monitoring a change in the tunneling current responsive to the mechanical indication to provide an indication of a value of the electrical current in the conductor.

2. The sensor of claim 1, wherein the tunneling current generator comprises:

a first tunneling electrode disposed on a first portion of one of the first fixed element and the moving element; and

a first tunneling current element disposed on a second portion of an opposite one of the first fixed element and the moving element proximate the first tunneling electrode.

3. The sensor of claim 2, wherein the first tunneling current element comprises a tunneling tip.

4. The sensor of claim 2, wherein the first tunneling electrode is disposed on the moving element and the first tunneling current element is disposed on the first fixed element.

5. The sensor of claim 2, further comprising:

a second tunneling electrode disposed on a third portion of one of the first fixed element and the moving element; and

a second tunneling current element disposed on a fourth portion of an opposite one of the first fixed element and the moving element proximate the second tunneling electrode, wherein the second tunneling electrode and the second tunneling current element are configured in a counterbalancing relationship with respect to the first tunneling electrode and the first tunneling current element.

6. The sensor of claim 2, further comprising a second fixed element spaced away from a side of the moving element opposite from the first fixed element.

7. The sensor of claim 6, further comprising:

a second tunneling electrode disposed on a third portion of one of the second fixed element and the moving element; and

a second tunneling current element disposed on a fourth portion of an opposite one of the second fixed element and the moving element proximate the second tunneling electrode, wherein the second tunneling electrode and the second tunneling current element are configured in a counterbalancing relationship with respect to the first tunneling electrode and the first tunneling current element.

8. The sensor of claim 1, further comprising a positioner in communication with the tunneling current monitor for positioning the moving element responsive to the change in the tunneling current to maintain a desired value of the tunneling current.

9. The sensor of claim 8, wherein the positioner comprises a positioning electrode disposed on the first fixed element.

10. The sensor of claim 8, wherein the positioner is configured for generating a force acting on the moving element to position the moving element to maintain the desired value of the tunneling current.

11. The sensor of claim 10, wherein the force generated by the positioner comprises at least one of an electrostatic force and a magnetic force.

12. The sensor of claim 1, wherein the movable element comprises at least one of a beam, a cantilever, a deflectable membrane, a diaphragm and a flexure member.

13. The sensor of claim 1, wherein the beam is configured for at least one of flexion and rotation about a point between a first end and a second end of the beam.

14. The sensor of claim 13, wherein the tunneling current generator comprises:

a first electrode disposed on the beam proximate the first end of the beam facing the first fixed element; and

a first tunneling tip disposed opposite the first electrode on the fixed element.

15. The sensor of claim 14, further comprising:

a second electrode disposed on the beam proximate the second end of the beam and facing the fixed element; and

a second tunneling tip disposed opposite the second electrode on the fixed element.

16. The sensor of claim 14, further comprising a second fixed element spaced away from a side of the beam opposite from the first fixed element.

17. The sensor of claim 16, further comprising:

a second electrode disposed on the beam proximate the first end of the beam and facing the second fixed element; and

a second tunneling tip disposed opposite the second electrode on the second fixed element.

18. The sensor of claim 16, further comprising:

a second electrode disposed on the beam proximate the second end of the beam and facing the second fixed element; and

a second tunneling tip disposed opposite the second electrode on the second fixed element.

19. A micro-electro-mechanical system (MEMS) current sensor for sensing a magnetic field produced by an electrical current flowing in a conductor comprising:

a MEMS-based magnetic field sensing component having a magneto-MEMS component for sensing a magnetic field produced by an electrical current flowing in a conductor; and

a tunneling current circuit associated with the magneto-MEMS component for providing an indication of the electrical current flowing in the conductor based on the sensed magnetic field.

20. The MEMS current sensor of claim 19, wherein the magneto-MEMS component comprises a fixed element and a moving element spaced away from the fixed element and movable relative to the fixed element responsive to a magnetic field produced by an electrical current flowing in a conductor, wherein the magnetic field is sensed based at least in part upon a change in a tunneling current defined between the fixed element and the moving element.

21. The MEMS current sensor of claim 20, further comprising a magnetic-to-mechanical converter coupled to the moving element such that the magnetic-to-mechanical converter exerts a force on the moving element to generate a measurable displacement of the moving element when exposed to said magnetic field.

22. The MEMS current sensor of claim 21, wherein the tunneling current circuit comprises a tunneling current generator for generating a tunneling current between the fixed element and the moving element.

23. The MEMS current sensor of claim 22, wherein the tunneling circuit comprises a tunneling current monitor for monitoring the change in the tunneling current responsive to the measurable displacement of the moving element to provide an indication of the electrical current in the conductor.

24. A method for sensing a magnetic field produced by an electrical current flowing in a conductor using a micro-electro-mechanical system (MEMS) current sensor comprising:

generating a tunneling current between a fixed element and a moving element of a MEMS current sensor, wherein the moving element is movable relative to the fixed element responsive to a magnetic field produced by an electrical current flowing in a conductor; and

identifying a change in the tunneling current responsive to movement of the moving element away from a position relative to the fixed element; and

providing an indication of the strength of the magnetic field responsive to the change in the tunneling current.

25. The method of claim 24, further comprising generating a force for acting on the moving element to return the moving element to the position.

26. The method of claim 25, wherein the indication is based on an amount of the force sufficient to return the moving element to the position.