Microelectro-mechanical high resolution current sensing apparatus

• US 6,504,356 B2
• Filed: 09/18/2001
• Issued: 01/07/2003
• Est. Priority Date: 09/28/1999
• Status: Expired due to Term

• Current Assignee: Rockwell Automation Technologies Incorporated (Rockwell Automation, Inc.)
• Original Assignee: Rockwell Automation Technologies Incorporated (Rockwell Automation, Inc.)
• Inventors: Sullivan, Gerard J., Yao, Jun Jason, Anderson, Robert J.
• Primary Examiner(s): Nguyen, Vinh P.
• Application Number:
  US09/955,493
• Publication Number:
  US 20020021119A1
• Time in Patent Office: 476 Days
• Field of Search: 324/99.R, 324/106, 324/244, 324/259, 324/260, 324/658, 324/684, 340/664
• US Class Current: 324/99.00R
• CPC Class Codes: G01R 15/185 with compensation or feedback windings or interacting coils, e.g. 0-flux sensors using galvano-magnetic field sensors G01R15/20; conversion of DC into AC using transductors G01R19/20
• CPC Class Codes: G01R 17/08 in which a force or torque representing the measured value is balanced by a force or torque representing the reference value
• CPC Class Codes: G01R 19/20 using transductors , i.e. a magnetic core transducer the saturation of which is cyclically reversed by an AC source on the secondary side
• CPC Class Codes: G01R 33/0286 comprising microelectromechanical systems [MEMS] MEMS devices in general B81B

Abstract

A current sensor includes a deflectable member disposed in a magnetic field. Nulling or compensating members may be mechanically coupled to the deflectable member. Feedback or readout devices coupled to the structure provide signals indicative of deflection of the deflectable member under the influence of applied current and the magnetic field. Nulling current applied to the nulling members tends to oppose deflection of the deflectable member. The nulling current may be modulated to drive the feedback signal to a desired level and is used as a basis for calculating the current to be measured. The current may be measured directly upon calibration of feedback devices coupled to the deflectable member or to the nulling members. Arrays of sensors may be coupled to common busses for applying measured and nulling currents to sensors of the arrays and for detecting feedback signals.

Claims

1. A current sensor comprising:

a magnetic field source for generating a magnetic field;

a current sensing system having a sensing element, the sensing element disposed in the magnetic field, configured to receive a current to be sensed, and being deflectable under the influence of the magnetic field and the current; and

a feedback element coupled to the current sensing system and configured to produce a signal representative of deflection of the sensing element.

2. The current sensor of claim 1, wherein the feedback element includes a capacitive sensor.

3. The current sensor of claim 1, wherein the magnetic field source includes a permanent magnet.

4. The current sensor of claim 1, wherein the sensing system further includes at least one micromachined compensation element disposed generally parallel to the sensing element, the compensation element being coupled to the sensing element and configured to resist deflection of the sensing element.

5. The current sensor of claim 4, wherein the feedback element includes a capacitor coupled to the compensation member, the capacitor being configured to provide output signals representative of deflection of the sensing element.

6. A current sensor comprising:

a magnetic base for producing a magnetic field;

a micromachined current sensing system disposed within the magnetic field and configured to receive a current to be measured and to deflect a sensing member under the influence of the current and the magnetic field; and

a readout device coupled to the sensing system for determining deflection of the sensing member.

7. The current sensor of claim 6, wherein the magnetic base includes a permanent magnet.

8. The current sensor of claim 6, wherein the sensing member includes first and second ends and conductive regions at each of the first and second ends for transmitting current to be measured to and from the sensing member.

9. The current sensor of claim 6, wherein the sensing system further includes at least one micromachined compensation member disposed generally parallel to the sensing member, the compensation member being coupled to the sensing member and configured to resist deflection of the sensing member.

10. The current sensor of claim 9, wherein the readout device includes at least one capacitor coupled to the compensation member, the capacitor being configured to provide output signals representative of deflection of the sensing member.

11. The current sensor of claim 9, including first and second compensation members disposed on first and second sides of the sensing members.

12. The current sensor of claim 11, wherein the readout device includes first and second capacitors coupled to the first and second compensation members, respectively, the capacitors being configured to provide output signals representative of deflection of the sensing member.

13. The current sensor of claim 6, wherein the readout device includes at least one capacitor coupled to the sensing system for providing output signals representative of deflection of the sensing system.

14. A current sensor comprising:

a substrate including a magnetic field source;

a device layer disposed over the substrate and forming a deflectable current sensing structure, a readout device, the device layer including at least a conductive layer forming conductive paths on the sensing structure and conductive regions on the readout device; and

a support layer disposed between the device layer and the substrate, the support layer bounding a cavity between the device layer and the substrate to support the sensing structure and the readout device while allowing deflection of the sensing structure under the influence of a measured current and a magnetic field from the field source.

15. The current sensor of claim 14, wherein the substrate includes a permanent magnet.

16. The current sensor of claim 14, wherein the device layer includes a structural layer disposed adjacent to the conductive layer.

17. The current sensor of claim 16, wherein the structural layer consists essentially of silicon or polysilicon.

18. The current sensor of claim 14, wherein the cavity is contiguous with gaps formed between portions of the device layer, the gaps being configured to vary in width during deflection of the sensing structure.

19. The current sensor of claim 14, wherein the readout device includes a capacitor coupled to the sensing structure, the capacitor being configured to provide output signals representative of deflection of the sensing structure.

20. The current sensor of claim 14, wherein the sensing structure includes a compensation structure coupled to the sensing structure, the compensation structure configured to resist deflection of the sensing member.