Method for sensing electrical current

• US 6,188,322 B1
• Filed: 09/28/1999
• Issued: 02/13/2001
• Est. Priority Date: 09/28/1999
• Status: Expired due to Term

• Current Assignee: Allen-Bradley Company LLC (Rockwell Automation, Inc.)
• Original Assignee: Rockwell Technologies, LLC
• Inventors: Sullivan, Gerard J., Anderson, Robert J., Yao, Jun Jason
• Primary Examiner(s): Wu, Daniel J.
• Application Number:
  US09/406,364
• Time in Patent Office: 504 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 steps of:

applying a current to be measured to a deflectable sensing element in the presence of a magnetic field to urge the element towards a deflected position; and

sensing deflection of the 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 claim 4, comprising the further step of adjusting the compensation current to produce a feedback signal of a desired level.

6. The method of claim 4, wherein the feedback signal is produced by a capacitive element having an electrode at a common electrical potential with the compensation element.

7. A method for sensing electrical current comprising the steps of:

providing a magnetic field;

applying an electrical current to be sensed to a deflectable sensing element in the magnetic field;

applying a nulling current to a deflectable nulling element coupled to the sensing element; and

modulating the nulling current to control deflection of the sensing element.

8. The method of claim 7, wherein the step of modulating the nulling current includes detecting a feedback signal representative of deflection of the sensing element.

9. The method of claim 8, wherein the feedback signal is generated by at least one capacitive element coupled to the nulling element.

10. The method of claim 9, including the step of placing an electrode of the at least one capacitive element at an electrical potential equal to that of the nulling element.

11. The method of claim 7, comprising the further step of converting a value representative of the nulling current to a value representative of the current to be sensed.

12. The method of claim 7, wherein the nulling current is applied to a pair of nulling elements coupled to the sensing element.

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

applying a current to be sensed in the presence of a stationary magnetic field across input and output terminals of a sensing array, the sensing array including a plurality of sensing modules having deflectable sensing members, deflectable nulling members coupled to the sensing members, and feedback devices for detecting deflection of the sensing and nulling members, the first input and output busses being coupled to the sensing elements;

applying a nulling current to second input and output busses of the sensing array, the second input and output busses being coupled to the nulling members of the sensing modules; and

detecting feedback signals from the feedback devices.

14. The method of claim 13, wherein the nulling current is modulated to drive the feedback signals to a desired level.

15. The method of claim 14, wherein a value representative of the nulling current is converted to a value representative of the current to be sensed.

16. The method of claim 13, wherein the feedback signals of all modules of the array are detected via common busses coupled to each module.

17. The method of claim 13, comprising the step of applying a uniform magnetic field extending at least over a region occupied by the array.

18. A method for measuring electrical current, the method comprising the steps of:

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

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;

detecting deflection of the first and second deflectable members;

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

19. The method of claim 18, wherein the compensating current is applied to a pair of second deflectable members both linked to the first deflectable member.

20. The method of claim 18, wherein the compensating current is modulated to drive the deflection to a desire level.

21. The method of claim 18, wherein the deflection is detected via a feedback device coupled to the second deflectable member.

22. The method of claim 21, wherein the feedback device includes a capacitor.

23. The method of claim 22, wherein one electrode of the capacitor is placed at a common electrical potential as the second deflectable member.