Solid state watt-hour meter using GMR sensor

• US 6,026,355 A
• Filed: 06/23/1998
• Issued: 02/15/2000
• Est. Priority Date: 09/18/1996
• Status: Expired due to Fees

• Current Assignee: Itron, Inc.
• Original Assignee: Itron, Inc.
• Inventors: Capriotti, Roberto, Conley, Jerry J., Rahman, Mizanur, Mortensen, Gary B.
• Primary Examiner(s): Hoff, Marc S.
• Assistant Examiner(s): Bui, Bryan
• Application Number:
  US09/103,230
• Time in Patent Office: 602 Days
• Field of Search: 702/189, 702/60, 702/61, 702/64, 364/528.3, 364/528.21, 324/103 R, 324/116, 324/142, 324/178-179, 324/144
• US Class Current: 702/189
• CPC Class Codes: G01R 21/133 by using digital technique

Abstract

A power consumption meter is disclosed for measuring the power consumed by a load on a power conductor, wherein the electronics of the power consumption meter are isolated from lightning and power transients. The meter has a first GMR sensor that is disposed proximate the power conductor and is magnetically coupled to the power conductor. The first GMR sensor detects magnetic flux in the power conductor and produces a first output responsive to the detected magnetic flux that is representative of the current flowing through the power conductor. A second GMR sensor is disposed proximate the power conductor and is magnetically coupled to the power conductor. The second GMR sensor detects magnetic flux in the power conductor and produces a second output responsive to the detected magnetic flux that is representative of the voltage on the power conductor. A processor is operably communicatively coupled to the first and second GMR sensors and is responsive to the first output and the second output for producing a third output that is representative of the energy consumption of the load on the power conductor. In an embodiment, a third GMR sensor provides feedback for auto-scaling of the first GMR sensor.

Claims

1. A power consumption meter for measuring the power consumed by a load on a power conductor, the meter comprising:

first GMR sensor means, the first GMR sensor means being disposed proximate the power conductor and being magnetically coupled to the power conductor, the first GMR sensor means for detecting magnetic flux in the power conductor and producing a first output responsive to the detected magnetic flux that is representative of the current flowing through the power conductor;

second GMR sensor means, the second GMR sensor being disposed proximate the power conductor and being magnetically coupled to the power conductor, the second GMR sensor for detecting magnetic flux in the power conductor and producing a second output responsive to the detected magnetic flux that is representative of the voltage on the power conductor; and

processor means being operably communicatively coupled to the first and second GMR sensor means and being responsive to the first output and the second output for producing a third output that is representative of the energy consumption of the load on the power conductor.

2. The power consumption meter of claim 1 wherein the first and second GMR sensor means are substantially electrically and physically isolated from the power conductor.

3. The power consumption meter of claim 1 wherein the first GMR sensor means has a characteristic sensor operating curve, the first GMR sensor means being selectively adjustable to operate in a substantially linear portion of the operating curve at conditions of low power consumption.

4. The power consumption meter of claim 1 wherein the first GMR sensor means comprises at least two first GMR sensors and wherein the second GMR sensor means comprises at least two second GMR sensors.

5. The power consumption meter of claim 1, wherein the second output is representative of the rectified voltage on the power conductor.

6. The power consumption meter of claim 1, further comprising a translator and data storage device, the translator and data storage device receiving the third output for translating the third output to a format suitable for presentation on a visual display.

7. The power consumption meter of claim 1, further comprising a translator and data storage device, wherein the translator and data storage device stores the third output for transfer to a central site.

8. The power consumption meter of claim 7, wherein the transfer is effected by communicatively coupling the translator and data storage device to transmission means, the transmission means being communicatively coupled to the central site.

9. The power consumption meter of claim 8, wherein the transmission means are selected from a group consisting of;

a radio frequency transmitter;

a radio frequency transceiver;

a wire direct line interface;

a fiberoptic cable interface; and

a telephonic interface.

10. A power consumption meter for measuring the power consumed by a load on a power conductor, the meter comprising:

first GMR sensor means, the first GMR sensor means having an input for receiving a selectively variable drive current and being magnetically coupled to the power conductor means for detecting magnetic flux in the power conductor, the first GMR sensor having a magnetic flux detection sensitivity adjustment being adjustable proportionate to the drive current, the first GMR sensor adapted to produce a first output responsive to the detected magnetic flux that is representative of the load current in the power conductor;

a peak detector, the peak detector responsive to the first output in producing a second output representative of the peak load current in the power conductor;

a second GMR sensor, the second GMR sensor responsive to the first output, the second GMR sensor magnetically coupled to the power conductor and adapted to detect magnetic flux in the power conductor, the second GMR sensor adapted to produce a third output responsive to the detected magnetic flux that is representative of the load voltage on the power conductor; and

power evaluation means being operably communicatively coupled to the second GMR sensor and the peak detector, the power evaluation means for evaluating the average power consumption of the load on the power conductor in response to the second and third outputs.

11. The power consumption meter of claim 10, the meter having sensitivity adjustment means coupled to at least the first GMR sensor means for providing accurate power consumption readings particularly during conditions of low power consumption.

12. The power consumption meter of claim 10 wherein the first and second GMR sensor means are substantially electrically and physically isolated from the power conductor.

13. The power consumption meter of claim 10 wherein the first GMR sensor means has a characteristic sensor operating curve, the first GMR sensor means being selectively adjustable to operate in a substantially linear portion of the operating curve at conditions of low power consumption.

14. The power consumption meter of claim 13, further comprising an auto scaler circuit operably coupled to the first GMR sensor means to selectively control the magnitude of the drive current.

15. The power consumption meter of claim 14, wherein the auto scaler circuit comprises third GMR sensor means, the third GMR sensor means being magnetically coupled to the power conductor for detecting magnetic flux in the power conductor, the third GMR sensor means producing a fourth output responsive to the detected magnetic flux that is representative of the load current in the power conductor.

16. The power consumption meter of claim 15, wherein the auto scaler circuit further comprises a processor being operably communicatively coupled to the first GMR sensor means and to the third GMR sensor means, the processor controlling the magnitude of the drive current in response to the magnitude of the fourth output.

17. The power consumption meter of claim 16, wherein the magnitude of the drive current is controlled by the auto scaler circuit to be inversely proportional to the magnitude of the load current.

18. The power consumption meter of claim 10, wherein the power evaluation means comprises a processor for calculating the average power consumed by the load on the power conductor.

19. The power consumption meter of claim 10, wherein the power evaluation means comprises a multiplier and a processor, the multiplier and processor means being operably communicatively coupled to the peak power detector and second GMR sensor means, the multiplier being responsive to the second and third outputs in producing an output representative of the power consumed by the load on the power conductor.

20. The power consumption meter of claim 19, wherein the processor is adapted to calculate the average power consumed using the output representative of the peak power.

21. The power consumption meter of claim 20, wherein the power evaluation means comprises a track and hold circuit being operably communicatively coupled to the peak power detector and second GMR sensor means, the track and hold circuit being responsive to the second and third outputs for producing a continuous output representative of the peak power in the power conductor, the processor responsive to the second output and the pulses in evaluating average power consumed by the load on the power conductor.

22. The power consumption meter of claim 10, wherein the power evaluation means comprises a track and hold circuit and a processor being operably communicatively coupled to the peak power detector and second GMR sensor means, the track and hold circuit responsive to the second and third outputs in producing a continuous output representative of the peak power in the power conductor, the processor responsive to the second output and the pulses in evaluating average power consumed by the load on the power conductor, the processor controlling the magnitude of the drive current in response to the magnitude of the fourth output.

23. The power consumption meter of claim 22, wherein the processor uses a scaling factor in evaluating average power consumed by the load on the power conductor.

24. The power consumption meter of claim 10, wherein the power evaluation means is coupled to a display for displaying the average power consumed.

25. The power consumption meter of claim 10, wherein the power evaluation means is coupled to transmission means for transferring the evaluated average power consumption to a remote site.

26. The power consumption meter of claim 25 further including a translator and data storage device, wherein the transfer is effected by communicatively coupling the power evaluation means and the translator and data storage device to transmission means, the transmission means being communicatively coupled to the central site.

27. The power consumption meter of claim 26, wherein the transmission means are selected from a group consisting of;

a radio frequency transmitter;

a radio frequency transceiver;

a wire direct line interface;

a fiberoptic cable interface; and

a telephonic interface.

28. The power consumption meter of claim 10, wherein the power evaluation means are coupled to a transmission line for transferring the evaluated average power consumption to a remote central site.

29. A power consumption meter for measuring the power consumed by a load on a power conductor, comprising:

a first GMR sensor being magnetically coupled to the power conductor for detecting magnetic flux in the power conductor the detected magnetic flux being related to a load current in the power conductor; and

a second GMR sensor being magnetically coupled to the power conductor for detecting magnetic flux in the power conductor the detected magnetic flux being related to a load voltage on the power conductor.

30. The power consumption meter of claim 29 further including an auto scaler circuit for selectively scaling a sensitivity of the first GMR sensor.

31. The power consumption meter of claim 30 wherein the auto scaler circuit includes a third GMR sensor, the third GMR sensor being magnetically coupled to the power conductor for detecting magnetic flux in the power conductor, the third GMR sensor adapted to produce an output responsive to the detected magnetic flux that is representative of the load current in the power conductor.

32. The power consumption meter of claim 31, wherein the auto scaler circuit further comprises a processor, the processor controlling the magnitude of a first GMR sensor drive current in response to the magnitude of the third GMR sensor.

33. The power consumption meter of claim 32, wherein the magnitude of the drive current is controlled by the auto scaler circuit to be inversely proportional to the magnitude of the load current.

34. The power consumption meter of claim 29 further including power evaluation means, the power evaluation means having a processor for calculating an average power consumed by the load on the power conductor.

35. The power consumption meter of claim 34, wherein the power evaluation means comprises a multiplier and a processor, the multiplier producing an output representative of a peak power consumed by the load on the power conductor, the processor adapted to calculate the average power consumed using the output representative of the peak power.

36. The power consumption meter of claim 35, wherein the power evaluation means comprises a track and hold circuit and a processor, the track and hold circuit producing a series of connected pulses, the pulses representative of the peak voltage in the power conductor.

37. The power consumption meter of claim 29 further including power evaluation means, the power evaluation means having a track and hold circuit and a processor, the track and hold circuit producing a continuous output representative of a peak power in the power conductor, the processor evaluating average power consumed by the load on the power conductor, the processor adapted to control the magnitude of a first GMR sensor drive current.

38. The power consumption meter of claim 37, wherein the processor uses a scaling factor in evaluating average power consumed by the load on the power conductor.

39. The power consumption meter of claim 29, wherein the power evaluation means is coupled to a display for displaying the average power consumed.

40. The power consumption meter of claim 29 further including power evaluation means being communicatively coupled to the first and second GMR sensor means for evaluating average power consumed by the load on the power conductor, the power evaluation means being coupled to transmission means for transferring the evaluated average power consumption to a remote site.

41. The power consumption meter of claim 40, wherein the transmission means are selected from a group consisting of;

a radio frequency transmitter;

a radio frequency transceiver;

a wire direct line interface;

a fiberoptic cable interface; and

a telephonic interface.

42. The power consumption meter of claim 29, the meter having sensitivity adjustment means for providing accurate power consumption readings particularly during conditions of low power consumption.

43. The power consumption meter of claim 29 wherein the first and second GMR sensor means are substantially electrically and physically isolated form the power conductor.

44. The power consumption meter of claim 29 wherein the first GMR sensor means has a characteristic sensor operating curve, the GMR sensor means being selectively adjustable to operate in a substantially linear portion of the operating curve at conditions of low power consumption.

45. A current sensor for use in a watt-hour meter, comprising:

a GMR sensor for sensing a flux generated in a conductor by current flowing in the conductor, the GMR sensor sensitivity being increased by sensing a Barkhausen effect, the Barkhausen effect being produced by a magnetic field affecting the GMR sensor; and

a feedback circuit operably coupled to the GMR sensor for providing a flux that is additive to the flux generated in the conductor under a condition of relatively low current flow in the conductor and for providing a flux that is subtractive to the flux generated in the conductor under a condition of relatively high current flow in the conductor.

46. The current sensor of claim 45 providing current sensing for both alternating current and direct current application.

47. The current sensor of claim 45 wherein the feedback circuit includes a solenoid coil, the solenoid coil being wound around the GMR sensor.