Wireless vibrating strain gauge for smart civil structures

• US 20060254365A1
• Filed: 05/10/2006
• Published: 11/16/2006
• Est. Priority Date: 05/10/2005
• Status: Active Grant

• Current Assignee: MicroStrain, Inc. (Spectris PLC)
• Original Assignee: MicroStrain, Inc. (Spectris PLC)
• Inventors: Hamel, Michael John
• Granted Patent: US 7,591,187 B2
• Time in Patent Office: Days
• US Class Current: 73/778
• CPC Class Codes: G01B 17/04 for measuring the deformation in a solid, e.g. by vibrating string

Abstract

A gauge includes a wire, a housing, a coil, a processor, and a power supply. The wire is mounted in the housing to vibrate at a natural frequency. The coil is magnetically coupled to the wire. The processor is connected to provide a digital signal to the coil and the processor is further connected to detect when the wire is vibrating. An embodiment provides an efficient technique to excite the wire into vibration. Another embodiment enables long term operation from a small battery. Another embodiment enables wireless communications to be used, eliminating the need for cable runs.

Claims

1. A gauge, comprising a wire, a coil, a processor, and a power supply, wherein said wire is mounted to vibrate at a natural frequency, wherein said coil is magnetically coupled to said wire, wherein said processor is connected to provide a train of pulses to said coil, wherein said processor is further connected to receive a signal between pulses of said train of pulses indicating that said wire is vibrating.

2. A gauge, as recited to claim 1, wherein said processor includes an input connected to receive a signal from said coil.

3. A gauge, as recited to claim 1, further comprising a second coil magnetically coupled to said wire, wherein said processor is connected to receive a signal from said second coil.

4. A gauge, as recited to claim 1, wherein said coil is part of a circuit, wherein said circuit includes a variable reactance for adjusting resonance of said circuit and for providing said circuit at resonance at any frequency within a range of frequencies to provide efficient electromagnetic radiation from said coil to said wire.

5. A gauge, as recited to claim 1, wherein said circuit includes a variable capacitance.

6. A gauge, as recited to claim 1, wherein said wire and said coil are mounted in a housing.

7. A gauge, as recited to claim 6, wherein said processor and said power supply are mounted in said housing.

8. A gauge, as recited to claim 1, further comprising a temperature sensor, wherein said temperature sensor is positioned to provide a temperature of said wire, wherein said temperature sensor is connected to said processor.

9. A gauge, as recited to claim 1, further comprising a switch connected to said power supply and to said coil to provide current to said coil when said switch is closed, wherein timing of closing and opening said switch is controlled by said processor.

10. A gauge, as recited to claim 1, wherein said connection for detecting when said wire is vibrating includes a signal conditioning circuit.

11. A gauge, as recited to claim 9, wherein said signal conditioning circuit includes a capacitor and an amplifier.

12. A gauge, as recited to claim 1, further comprising a transmitter linked to receive data from said processor.

13. A gauge, as recited to claim 11, wherein said transmitter is part of a transceiver.

14. A gauge, as recited to claim 12, wherein operation of said transceiver is programmable.

15. A gauge, as recited to claim 1, further comprising a transient voltage suppressor circuit.

16. A gauge, as recited to claim 1, further comprising an electronic switch, a temperature sensor, and a wireless transceiver, wherein said processor, said power supply, said electronic switch, said temperature sensor, and said wireless transceiver are mounted within said housing.

17. A gauge, as recited to claim 1, further comprising a temperature sensor, wherein said coil and said temperature sensor are mounted in said housing, further comprising a second housing, wherein said processor, said power supply, and said wireless transceiver are mounted in said second housing.

18. A gauge, as recited to claim 1, further comprising a temperature sensor and a switch, wherein said coil, said processor, said switch, and said temperature sensor are mounted in said housing, further comprising a second housing, wherein said wireless transceiver is mounted in said second housing.

19. A gauge, as recited to claim 17, wherein said power supply is mounted in said second housing.

20. A gauge, as recited to claim 1, further comprising a temperature sensor and a switch, wherein said coil, said processor, said switch, and said temperature sensor are mounted in said housing.

21. A gauge, as recited to claim 19, further comprising a cable and a reader, said cable for hard wired connection to said reader.

22. A gauge, as recited to claim 20, wherein said reader includes said power supply.

24. A gauge, as recited to claim 22, further comprising a wired connection for providing power and for communicating data.

25. A gauge, as recited to claim 22, further comprising a transmitter and a power supply.

26. A gauge, as recited to claim 22, wherein said processor is connected to provide a train of pulses to said coil, wherein said processor is further connected to receive a signal between pulses of said train of pulses indicating that said wire is vibrating.

23. A gauge, comprising a housing, said housing including wire, a coil, and a processor, wherein said wire is mounted to vibrate at a natural frequency, wherein said coil is magnetically coupled to said wire, wherein said processor is connected to provide an excitation to said coil, wherein said processor is further connected to receive a signal indicating that said wire is vibrating.

27. A gauge for measuring a property of a structure, comprising a wire, a coil, a switch, a processor, and a power supply, wherein said wire is mounted to vibrate at a natural frequency, wherein said switch is connected to said power supply and to said coil to provide current to said coil when said switch is closed, wherein a control terminal of said switch is connected to said processor, wherein said coil is magnetically coupled to said wire, wherein timing of closing and opening said switch is controlled by a signal from said processor to provide a train of pulses to said coil, said train of pulses having a pulse frequency, wherein said coil emits a train of magnetic pulses at said pulse frequency for stimulating said wire to vibrate.

28. A gauge, as recited to claim 27, wherein said processor is further connected to receive a signal between pulses of said train of pulses indicating that said wire is vibrating.

29. A gauge, as recited to claim 28, wherein said wire and said coil are mounted in a housing.

30. A gauge, as recited to claim 29, wherein said processor and said power supply are mounted in said housing.

31. A gauge, as recited to claim 30, further comprising a transmitter mounted in said housing, wherein power for operating said transmitter is derived from said power supply, further wherein said transmitter is connected to transmit data derived from said received signal.

32. A gauge, as recited to claim 29, wherein said power supply is external to said housing, further comprising a wired connection for providing power from said power supply.

33. A method of making a measurement, comprising:

a. providing a wire, a coil, a processor, and a power supply, wherein said wire is mounted to vibrate at a natural frequency and wherein said coil is magnetically coupled to said wire;

b. providing a train of pulses to said coil, wherein said train of pulses is derived from said power supply under control of said processor; and

c. receiving a signal between pulses of said train of pulses, wherein said signal is derived from vibration of said wire.

34. A method, as recited to claim 33, further comprising determining that said wire is vibrating from presence of said signal above a predetermined threshold.

35. A method, as recited to claim 34, further comprising determining a parameter characteristic of frequency of vibration of said wire.

36. A method of making a measurement, comprising:

a. providing a housing, said housing including a wire, a coil, and a processor, wherein said wire is mounted in said housing to vibrate at a natural frequency and wherein said coil is magnetically coupled to said wire;

b. providing an excitation signal derived from said processor to said coil; and

c. receiving a signal derived from vibration of said wire.

37. A method, as recited to claim 36, further comprising determining that said wire is vibrating from presence of said signal above a threshold.

38. A method, as recited to claim 37, further comprising determining a parameter characteristic of frequency of vibration of said wire.

39. method of making a measurement, comprising:

a. providing a wire, a coil, a processor, a switch, and a power supply, wherein said wire is mounted to vibrate at a natural frequency, wherein said coil is magnetically coupled to said wire, wherein said switch includes a control terminal, wherein said control terminal is connected to said processor, wherein said switch is connected to said power supply and to said coil to provide current to said coil when said switch is closed; and

b. providing a first signal from said processor to said control terminal to repeatedly close and to open said switch to provide a train of current pulses from said power supply to said coil, wherein said first signal has a first pulse frequency, wherein said train of current pulses has said first pulse frequency, and wherein said coil emits a train of magnetic pulses at said first pulse frequency for stimulating said wire to vibrate.

40. A method, as recited to claim 39, further comprising receiving an analog signal between pulses of said train of current pulses, wherein said analog signal is derived from vibration of said wire.

41. A method, as recited to claim 40, further comprising determining that said wire is vibrating from presence of said analog signal above a predetermined threshold.

42. A method, as recited to claim 41, further comprising determining a parameter characteristic of frequency of vibration of said wire.

43. A method, as recited to claim 39, further comprising providing at least one housing, wherein said wire, said coil, said processor, and said power supply are mounted in said at least one housing.

44. A method, as recited to claim 43, wherein said wire, said coil, said processor, and said power supply are mounted in one housing.

45. A method, as recited to claim 39, further comprising measuring a temperature related to temperature of said wire.

46. A method, as recited to claim 39, further comprising providing a switch connected to said power supply and to said coil to provide current to said coil when said switch is closed, wherein said switch is controlled by said signal from said processor.

47. A method, as recited to claim 39, further comprising providing a signal conditioning circuit for detecting when said wire is vibrating.

48. A method, as recited to claim 47, wherein said signal conditioning circuit includes a capacitor and an amplifier.

49. A method, as recited to claim 39, further comprising providing a transmitter linked to receive data derived from vibration of said wire.

50. A method, as recited to claim 49, wherein said transmitter is part of a transceiver.

51. A method, as recited to claim 50, wherein power provided to said transceiver is under control of said processor.

52. A method, as recited to claim 39, further comprising providing a transient voltage suppressor circuit.

53. A method as recited in claim 39, further comprising measuring current in said coil at two times between said current pulses in said coil.

54. A method as recited in claim 53, wherein said two times are set to provide approximately a maximum difference if said wire is vibrating.

55. A method as recited in claim 54, further comprising repeatedly measuring current in said coil, further comprising averaging differences of said repeated two measurements.

56. A method as recited in claim 39, further comprising providing a second signal from said processor if said wire is not found to be vibrating as a result of said first signal, wherein said second digital signal is provided with a second pulse frequency that is different from said first pulse frequency of said first signal.

57. A method as recited in claim 39, further comprising repeatedly providing signals having different pulse frequencies until detecting wire vibration.

58. A method as recited in claim 57, further comprising storing and transmitting pulse frequency wire vibration is detected.

59. A method as recited in claim 58, further comprising storing and transmitting a temperature.

60. A method as recited in claim 39, further comprising providing said processor in sleep mode.

61. A method as recited in claim 39, further comprising providing a signal derived from said processor, wherein said signal is in a pulse frequency range based on a previous measurement as corrected for a measured temperature.

62. A method as recited in claim 39, further comprising performing a calculation in said processor and transmitting a calculated result to provide at least one from the group including strain, pressure, inclination, temperature, displacement, and level.