Method for sensing electrical current

• US 6,411,214 B1
• Filed: 09/29/2000
• Issued: 06/25/2002
• 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., Anderson, Robert J., Yao, Jun Jason
• Primary Examiner(s): Wu, Daniel J.
• Application Number:
  US09/675,861
• Time in Patent Office: 634 Days
• Field of Search: 340/664, 340/660, 340/657, 340/686.1, 324/207.13, 324/658, 324/684
• US Class Current: 340/664
• 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 33/0286 comprising microelectromechanical systems [MEMS] MEMS devices in general B81B

Abstract

A method is provided for sensing and measuring an electrical current. The current to be measured is applied to a deflectable member in a sensing module in the presence of a magnetic field. Deflection of the member is detected as an indication of the current. A nulling current may be applied to one or more additional deflectable members mechanically linked to the deflectable member. Feedback or readout signals indicative of deflection of the members are monitored. The nulling current is modulated to drive the feedback signals to a desired level. The nulling current value is converted to a value representative of the current to be measured.

Claims

1. A method for sensing electrical current, the method comprising the acts of:

applying a current to a deflectable sensing element, the deflectable sensing element positioned in a magnetic field; and

sensing deflection of the deflectable sensing element and producing a readout signal representative thereof.

2. The method of claim 1, wherein the deflectable sensing element includes first and second ends and is mechanically supported at both the first and second ends.

3. The method of claim 1, wherein the deflection of the sensing element is sensed via a capacitive readout device coupled to the sensing element.

4. The method of claim 1, comprising the further step of applying a compensation current to at least one deflectable compensation element coupled to the sensing element in the presence of the magnetic field, the compensation current tending to prevent deflection of the sensing element.

5. The method of claims 4, comprising the further step of adjusting the compensation current to produce a feedback signal of a desired level.

6. The method of claim 5, wherein the feedback signal is produced by a capacitive element having an electrode at a common electrical potential with the compensation element.

7. A system for sensing electrical current, the system comprising:

means for applying a current to a deflectable sensing element, the deflectable sensing element positioned in a magnetic field; and

means for sensing deflection of the deflectable sensing element and producing a readout signal representative thereof.

8. The system of claim 7, wherein the deflectable sensing element includes first and second ends and is mechanically supported at both the first and second ends.

9. The system of claim 7, wherein the deflection of the sensing element is sensed via readout means coupled to the sensing element.

10. The system of claim 7, comprising the further step of applying a compensation current to at least one deflectable compensation element coupled to the sensing element in the presence of the magnetic field, the compensation current tending to prevent deflection of the sensing element.

11. The system of claim 10, comprising the further step of adjusting the compensation current to produce a feedback signal of a desired level.

12. The system of claim 11, wherein the feedback signal is produced by a capacitive element having an electrode at a common electrical potential with the compensation element.

13. An electrical current sensing device comprising:

a magnetic field;

a deflectable sensing element disposed in the magnetic field; and

a deflectable nulling element coupled to the deflectable sensing element;

wherein a current to be measured to applied to the deflectable sensing element and a nulling current is applied to the nulling element, and the nulling current is modulated to control deflection of the deflectable sensing element.

14. The electrical current sensing device of claim 13, comprising a feedback element configured to generate a feedback signal representative of deflection of the sensing element.

15. The electrical current sensing device of claim 14, wherein the feedback element includes at least one capacitive element coupled to the deflectable nulling element.

16. The electrical current sensing device of claim 15, wherein an electrode of the at least one capacitive element is configured to receive an electrical potential equal to that of the deflectable nulling element.

17. The electrical current sensing device of claim 13, wherein the nulling current is applied at a level convertible to a value representative of the current to be measured.

18. The electrical current sensing device of claim 13, wherein the nulling current is applied to a pair of nulling elements coupled to the deflectable sensing element.

19. A method for sensing an electrical current, the method comprising the steps of:

applying a current to be measured to first input and output terminals of a sensing array in a stationary magnetic field;

applying a nulling current to second input and output terminals of the sensing array; and

detecting feedback signals from a plurality of feedback devices coupled to the sensing array.

20. The method of claim 19, wherein the sensing array comprises a plurality of sensing modules having deflectable sensing members and deflectable nulling members, and wherein the deflectable nulling members are coupled to the deflectable sensing member and to the plurality of feedback devices for detecting deflection of the sensing and nulling members.

21. The method of claim 20, wherein the second input and output terminals are coupled to the nulling members of the sensing modules.

22. The method of claim 19, wherein the nulling current is modulated to drive the feedback signals to a desired level.

23. The method of claim 19, wherein a value representative of the nulling current is converted to a value representative of the current to be measured.

24. The method of claim 19, wherein the feedback signals of the plurality of sensing modules of the sensing array are detected via common busses coupled to each module.

25. The method of claim 19, comprising the step of applying a uniform magnetic field extending at least over a region occupied by the sensing array.

26. A system for measuring electrical current, the system comprising:

means for applying a current to be measured to a first deflectable member in a first polarity in the presence of a magnetic field;

means for applying a compensating current to a second deflectable member in a second polarity opposite to the first polarity in the presence of the magnetic field, the second deflectable member being mechanically linked to the first deflectable member;

means for detecting deflection of the first and second deflectable members;

means for determining the current to be measured based upon the detected deflection and the compensating current.

27. The system of claim 26, wherein the compensating current is applied to a pair of second deflectable members both linked to the first deflectable member.

28. The system of claim 26, wherein the compensating current is modulated to drive the deflection to a desire level.

29. The system of claim 26, wherein the deflection is detected via a feedback device coupled to the second deflectable member.

30. The system of claim 29, wherein the feedback device includes a capacitor.

31. The system of claim 30, wherein one electrode of the capacitor is placed at a common electrical potential as the second deflectable member.

32. A tangible medium for measuring an electrical current comprising:

a routine for applying a first current to first input and output terminals of a sensing array disposed in a magnetic field;

a routine for applying a second current to second input and output terminals of the sensing array; and

a routine for detecting feedback signals from a plurality of feedback devices, the plurality of feedback devices adapted to detect deflection in the sensing array.

33. The tangible medium as in claim 32, wherein the second current is a nulling current.

34. The tangible medium as in claim 32, comprising a routine for modulating the second current to drive the feedback signals to a desired level.

35. The tangible medium as in claim 32, comprising a routine for calculating a value representative of the current to be sensed by converting a value representative of the second current.

36. The tangible medium as in claim 32, comprising a routine for detecting feedback signals of a plurality of modules of the sensing array via a plurality of terminals coupled to each one of the plurality of modules.

37. The tangible medium as in claim 32, comprising a routine for applying a uniform magnetic field extending at least over a region occupied by the sensing array.