Piezoelectric sensor

• US 6,526,834 B1
• Filed: 08/23/2000
• Issued: 03/04/2003
• Est. Priority Date: 08/23/2000
• Status: Expired due to Term

• Current Assignee: Measurement Specialties Incorporated (TE Connectivity Limited)
• Original Assignee: Measurement Specialties Incorporated (TE Connectivity Limited)
• Inventors: Kohler, David, Swan, Jeffrey D.
• Primary Examiner(s): NOORI, MAX H
• Application Number:
  US09/645,007
• Time in Patent Office: 923 Days
• Field of Search: 737/74, 737/75, 737/76, 737/77, 737/96, 738/626.8
• US Class Current: 73/777
• CPC Class Codes: G01G 19/024 using electrical weight-sensitive devices
• CPC Class Codes: G01G 3/13 having piezoelectric or piezoresistive properties
• CPC Class Codes: G08G 1/02 using treadles built into the road pads or other sensitive devices responsive to passage of vehicles E01F11/00

Abstract

A sensor having an inner conductor, a piezoelectric layer, and an outer conductor. The piezoelectric layer formed from a piezoelectric strip wrapped around the inner conductor and having adjacent turns wherein substantially each turn overlaps substantially fifty percent of an adjacent turn. The piezoelectric layer has a substantially uniform thickness. The outer conductor substantially surrounds the piezoelectric layer.

Claims

1. A piezoelectric pressure/load sensor comprising:

an inner conductor;

a piezoelectric layer formed from a piezoelectric strip wrapped around the inner conductor having adjacent turns wherein substantially each turn overlaps substantially fifty percent of an adjacent turn and wherein the piezoelectric layer has a substantially uniform thickness; and

an outer conductor substantially surrounding the piezoelectric layer wherein the sensor includes an inner conductor and an outer conductor and an intervening piezoelectric layer having a substantially uniform thickness.

2. The sensor of claim 1 wherein the piezoelectric strip is formed from PVDF.

3. The sensor of claim 2 wherein the piezoelectric strip is uniaxially oriented.

4. The sensor of claim 2 wherein the piezoelectric strip is biaxially oriented.

5. The sensor of claim 2 wherein the piezoelectric strip is unmetalized.

6. The sensor of claim 2 wherein the piezoelectric strip is metalized on one side only.

7. The sensor of claim 2 wherein the inner conductor is stranded.

8. The sensor of claim 2 wherein the inner conductor is round.

9. The sensor of claim 2 wherein the inner conductor is flat.

10. The sensor of claim 7 wherein inner conductor is formed from copper.

11. The sensor of claim 10 wherein the inner conductor is plated.

12. The sensor of claim 2 wherein the outer conductor is formed from a stranded wire braid.

13. The sensor of claim 2 wherein the outer conductor is formed from a malleable tube.

14. The sensor of claim 13 wherein the outer conductor further comprises a conductive tape.

15. The sensor of claim 13 wherein the outer conductor further comprises a conductive polymer.

16. The sensor of claim 2 further comprising an outer jacket.

17. The sensor of claim 16 wherein the outer jacket is formed from a polymer.

18. The sensor of claim 2 wherein the piezoelectric layer is formed from a single layer of piezoelectric material.

19. A piezoelectric pressure/load sensor comprising:

an inner conductor;

a piezoelectric layer formed from first and second overlapping portions of a piezoelectric strip, the first portion wrapped around the inner conductor and the second portion wrapped around the first portion and wherein the piezoelectric layer has a substantially uniform thickness; and

an outer conductor substantially surrounding the piezoelectric layer wherein the sensor includes an inner conductor and an outer conductor and an intervening piezoelectric layer having a substantially uniform thickness.

20. The sensor of claim 19 wherein the first portion and the second portion are wrapped in the same direction.

21. The sensor of claim 19 wherein the first portion and the second portion are wrapped in the opposite directions.

22. The sensor of claims 20 or 21 wherein the first portion is formed from a first piezoelectric strip and the second portion is formed from a separate second piezoelectric strip.

23. The sensor of claim 22 wherein the piezoelectric strip is formed from PVDF.

24. The sensor of claim 23 wherein the piezoelectric strip is uniaxially oriented.

25. The sensor of claim 23 wherein the piezoelectric strip is biaxially oriented.

26. The sensor of claim 23 wherein the piezoelectric strip is unmetalized.

27. The sensor of claim 23 wherein the piezoelectric strip is metalized on one side only.

28. The sensor of claim 23 wherein the inner conductor is stranded.

29. The sensor of claim 23 wherein the inner conductor is round.

30. The sensor of claim 23 wherein the inner conductor is flat.

31. The sensor of claim 28 wherein inner conductor is formed from copper.

32. The sensor of claim 31 wherein the inner conductor is plated.

33. The sensor of claim 23 wherein the outer conductor is formed from a stranded wire braid.

34. The sensor of claim 23 wherein the outer conductor is formed from a malleable tube.

35. The sensor of claim 23 wherein the outer conductor further comprises a conductive tape.

36. The sensor of claim 23 wherein the outer conductor further comprises a conductive polymer.

37. The sensor of claim 23 further comprising an outer jacket.

38. The sensor of claim 37 wherein the outer jacket is formed from a polymer.

39. The sensor of claim 38 wherein the piezoelectric layer is formed from only the first portion and the second portion.

40. A piezoelectric pressure/load sensor comprising:

an inner conductor;

a piezoelectric layer formed from first and second overlapping portions of a piezoelectric strip, the first portion wrapped around the inner conductor and having adjacent turns wherein substantially each turn overlaps substantially fifty percent of an adjacent turn and the second portion wrapped around the first portion and having adjacent turns wherein substantially each turn overlaps substantially fifty percent of an adjacent turn and wherein the piezoelectric layer has a substantially uniform thickness; and

an outer conductor substantially surrounding the piezoelectric layer wherein the sensor includes an inner conductor and an outer conductor and an intervening piezoelectric layer having a substantially uniform thickness.

41. The sensor of claim 40 wherein the first portion and the second portion are wrapped in the same direction.

42. The sensor of claim 40 wherein the first portion and the second portion are wrapped in the opposite directions.

43. The sensor of claim 41 or 42 wherein the piezoelectric strip is formed from PVDF.

44. The sensor of claim 43 wherein the piezoelectric strip is uniaxially oriented.

45. The sensor of claim 43 wherein the piezoelectric strip is biaxially oriented.

46. The sensor of claim 43 wherein the piezoelectric strip is unmetalized.

47. The sensor of claim 43 wherein the piezoelectric strip is metalized on one side only.

48. The sensor of claim 43 wherein the inner conductor is stranded.

49. The sensor of claim 43 wherein the inner conductor is round.

50. The sensor of claim 43 wherein the inner conductor is flat.

51. The sensor of claim 48 wherein inner conductor is formed from copper.

52. The sensor of claim 51 wherein the inner conductor is plated.

53. The sensor of claim 43 wherein the outer conductor is formed from a stranded wire braid.

54. The sensor of claim 43 wherein the outer conductor is formed from a malleable tube.

55. The sensor of claim 43 wherein the outer conductor further comprises a conductive tape.

56. The sensor of claim 43 wherein the outer conductor further