Apparatus and method to detect moisture

• US 6,906,530 B2
• Filed: 05/17/2003
• Issued: 06/14/2005
• Est. Priority Date: 05/30/2002
• Status: Active Grant

• Current Assignee: D.J. Geisel Technology, Inc., Donald J. Geisel & Assoc., Inc.
• Original Assignee: D.J. Geisel Technology, Inc., Donald J. Geisel & Assoc., Inc.
• Inventors: Geisel, Donald J.
• Primary Examiner(s): Deb, Anjan K.
• Application Number:
  US10/439,556
• Publication Number:
  US 20030222662A1
• Time in Patent Office: 759 Days
• Field of Search: 324/664, 324/545, 324/551, 324/772, 324/663, 324/683, 324/640, 73/73
• US Class Current: 324/664
• CPC Class Codes: G01N 27/045 Circuits measuring resistance per se G01R27/00, e.g. G01R27/22
• CPC Class Codes: G01N 27/048 for determining moisture content of the material

Abstract

A method and apparatus for detecting moisture. An oscillatory electrical signal S₁ generated by an oscillator is propagated into a body that includes an electrically insulative material. A signal due to S₁ emerges from the body as an oscillatory electrical signal S₂. The signals S₁ and S₂ differ in phase by Δφ, wherein Δφ is indicative of moisture along a path traversed by S₁ within the insulative material, and wherein the conductance σ of the insulative material is also indicative of the moisture along the path traversed by S₁ within the insulative material. S₂ is received at a sensing surface of a sensing part (e.g., probe, sensing antenna, etc.) and then transmitted to a moisture detecting device. The moisture detecting device determines from S₁ and S₂ a measure M of the moisture as a function of Δφ or as a function of σ.

Claims

1. An apparatus for detecting moisture, comprising:

an oscillator for generating a first oscillatory electrical signal S₁;

means for propagating S₁ into a body at an electrical conductor disposed entirely within the body and then along a linear path from the electrical conductor through an electrically insulative material disposed entirely within the body such that a signal due to S₁ emerges from the path and from the body as a second oscillatory electrical signal S₂;

a probe having an electrically conductive sensing surface adapted to be in physical contact with the body and to receive S₂, wherein the electrically insulative material is disposed between the sensing surface and the electrical conductor so as to form a parallel plate capacitor across which S₁ and S₂ differ in phase by Δ

φ

such that Δ

φ

is indicative of moisture along the entire path traversed by S₁ within the electrically insulative material; and

a moisture detecting device adapted to determine Δ

φ

from S₁ and S₂ and a measure M of the moisture based on M being proportional to Δ

φ

.

2. The apparatus of claim 1, wherein the moisture detecting device is further adapted to receive S₁ from the oscillator and S₂ from the probe, and to determine Δ

φ

from S₁ and S₂.

3. The apparatus of claim 1, further comprising means for displaying M.

4. The apparatus of claim 1, further comprising means for determining from the magnitude of S₂ a measure of the degree of physical contact between the sensing surface and the body.

5. The apparatus of claim 4, further comprising means for displaying the measure of the degree of physical contact.

6. The apparatus of claim 1, wherein the probe is capable of being hand held.

7. The apparatus of claim 1, wherein the probe is within a metallic case, and wherein the metallic case does not electrically interfere with S₂.

8. The apparatus of claim 1, wherein S₁ has a frequency falling within a frequency range of 1 Khz to 50 Mhz.

9. The apparatus of claim 1, wherein the insulative material surrounds stator bars of a power generator, and wherein the stator bars comprise the electrical conductor.

10. The apparatus of claim 9, wherein the path traversed by S₁ includes a path segment from a copper center of the stator bars through the total thickness of insulative material to a location on an exterior surface of the body where S₂ emerges from the body.

11. The apparatus of claim 9, wherein the stator bars are ungrounded, and wherein S₁ is adapted to be coupled to any of the ungrounded stator bars by a sufficiently large capacitance between the stator bars and a generator frame ground of the power generator, without a DC ground path existing between a copper center of the stator bars and the generator frame ground.

12. A method for detecting moisture, comprising:

propagating a first oscillatory electrical signal S₁ into a body at an electrical conductor disposed entirely within the body and then along a linear path from the electrical conductor through an electrically insulative material disposed entirely within the body such that a signal due to S₁ emerges from the path and from the body as a second oscillatory electrical signal S₂;

receiving S₂ by an electrically conductive sensing surface of a probe, wherein the sensing surface is in contact with the body, and wherein the electrically insulative material is disposed between the sensing surface and the electrical conductor so as to form a parallel plate capacitor across which S₁ and S₂ differ in phase by Δ

φ

such that Δ

φ

is indicative of moisture along the entire path traversed by S₁ within the electrically insulative material; and

transmitting S₂ from the probe to a moisture detecting device that determines Δ

φ

from S₁ and S₂ and a measure M of the moisture, based on M being proportional to Δ

φ

.

13. The method of claim 12, further comprising displaying M.

14. The method of claim 12, further comprising generating S₁ by an oscillator that is coupled to the moisture detecting device.

15. The method of claim 12, further determining from the magnitude of S₂ a measure of the degree of physical contact between the sensing surface and the body.

16. The method of claim 15, further comprising displaying the measure of the degree of physical contact.

17. The method of claim 12, wherein the probe is capable of being a hand held.

18. The method of claim 12, wherein the probe is within a metallic case, and wherein the metallic case does not electrically interfere with S₂.

19. The method of claim 12, wherein S₁ has a frequency falling within a frequency range of 1 Khz to 50 Mhz.

20. The method of claim 12, wherein the insulative material surrounds stator bars of a power generator, and wherein the stator bars comprise the electrical conductor.

21. The method of claim 20, wherein the path traversed by S₁ includes a path segment from a copper center of the stator bars through the total thickness of insulative material to a location on an exterior surface of the body where S₂ emerges from the body.

22. The method of claim 20, wherein the stator bars are ungrounded, and wherein S₁ is coupled to any of the ungrounded stator bars by a sufficiently large capacitance between the stator bars and a generator frame ground of the power generator, without a DC ground path existing between a copper center of the stator bars and the generator frame ground.

23. An apparatus for detecting moisture, comprising:

an oscillator for generating a first oscillatory electrical signal S₁;

means for propagating S₁ into a body such at an electrical conductor disposed entirely within the body and then along a linear path from the electrical conductor through an electrically insulative material disposed entirely within the body such that a signal due to S₁ emerges from the path and from the body as a second oscillatory electrical signal S₂;

a sensing part having an electrically conductive sensing surface adapted to be in physical contact with the body and to receive S₂, wherein the electrically insulative material is disposed between the sensing surface and the electrical conductor so as to form a parallel plate capacitor that is in electrical parallel with an electrically resistive path characterized by a conductance σ

, and wherein σ

is indicative of moisture along the entire path traversed by S₁ within the electrically insulative material; and

a moisture detecting device adapted to determine from S₁ and S₂ a function of σ

, wherein said function of σ

is a measure M of the moisture.

24. The apparatus of claim 23, wherein the moisture detecting device is further adapted to receive S₁ from the oscillator and S₂ from the sensing surface.

25. The apparatus of claim 23, further comprising means for displaying M.

26. The apparatus of claim 23, further comprising means for determining from the capacitive component of S₂ a measure of the degree of physical contact between the sensing surface and the body.

27. The apparatus of claim 26, further comprising means for displaying the measure of the degree of physical contact.

28. The apparatus of claim 23, further comprising transmitting means for transmitting to a compute element a signal comprising M.

29. The apparatus of claim 28, wherein the compute element is comprised by a computer system that is remote to an enclosure that encloses the oscillator and the moisture detecting device.

30. The apparatus of claim 28, wherein the compute element includes means for calculating from M the moisture, through deployment of an algorithm that utilizes a correlation between M and the moisture.

31. The apparatus of claim 23, wherein the insulative material surrounds stator bars of a power generator, and wherein the insulative material is disposed between the sensing surface and the stator bars so as to form a parallel plate capacitor.

32. The apparatus of claim 31, wherein the path traversed by S₁ includes a path segment from a copper center of the stator bars through the total thickness of insulative material to a location on an exterior surface of the body where S₂ emerges from the body.

33. The apparatus of claim 31, wherein the stator bars are ungrounded, and wherein S₁ is adapted to be coupled to any of the ungrounded stator bars by a sufficiently large capacitance between the stator bars and a generator frame ground of the power generator, without a DC ground path existing between a copper center of the stator bars and the generator frame ground.

34. An apparatus for detecting moisture, comprising:

an oscillator for generating first oscillatory electrical signal S₁;

means for propagating S₁ into a body such that a signal due to S₁ emerge from the body as a second oscillatory electrical signal S₂, wherein the body includes an electrically insulative material having a conductance σ

, and wherein σ

is indicative of moisture along a path traversed by S₁ within the insulative material;

a sensing part having an electrically conductive sensing surface adapted to be in physical contact with the body and to receive S₂; and

a moisture detecting device adapted to determine from S₁ and S₂ a measure M of the moisture, said measure M being a function of σ

, wherein the moisture detecting device comprises a first synchronous demodulator for determining the in-phase component V_IN of S₂ relative to S₁, wherein M is a function of V_IN, and wherein V_IN increases as σ

increases.

35. The apparatus of claim 34, wherein the apparatus further comprises an electrically insulative enclosure that encloses the oscillator and the moisture detecting device, and wherein the sensing part comprises a probe located external to the enclosure.

36. The apparatus of claim 34, wherein the apparatus further comprises an electrically insulative enclosure that encloses the oscillator and the moisture detecting device, wherein the sensing part comprises a sensing antenna, wherein the sensing antenna includes a transmitting element, a receiving element comprising the sensing surface, and a ground element, wherein the ground element is electrically connected to a ground potential within the enclosure, wherein the transmitting element is adapted to transmit S₁ to the body, wherein the receiving element is adapted to receive S₂ from the body, and wherein the apparatus is essentially capacitatively uncoupled to any electrical potential external to the enclosure.

37. The apparatus of claim 36, wherein the sensing antenna comprises a two-conductor transmission line that includes the grounded conductor interposed between the transmitting element and the receiving element.

38. The apparatus of claim 36, wherein the insulative material surrounds stator bars of a power generator.

39. The apparatus of claim 36, further comprising an electrically insulative handle mechanically connected to the enclosure, wherein the handle can be manipulated by a user of the apparatus to move the sensing surface into physical contact with the body.

40. The apparatus of claim 36, wherein the enclosure and its contents is capable of being hand held.

41. The apparatus of claim 36, further comprising a flexible conductive interface electrically connecting an element to the body, wherein the element is selected from the group consisting of the transmitting element, the receiving element, and the ground element.

42. The apparatus of claim 41, further comprising a constant-force assembly coupled to the flexible conductive interface so as to cause the flexible conductive interface to exert an approximately constant force on the body, wherein the constant-force assembly includes a constant-force spring.

43. The apparatus of claim 36, further comprising an electrically conductive band wrapped around the enclosure, wherein the conductive band includes the transmitting element.

44. The apparatus of claim 43, wherein a person comprises the body, wherein the enclosure and its contents is capable of being held at the band by a hand of a person, and wherein the sensing surface is adapted to be placed by said hand at a surface location on the skin of the person to determine M as a function of the surface location.

45. The apparatus of claim 34, further comprising a second synchronous demodulator for determining from S₁ and S₂ the 90-degree out-of-phase component V₉₀ of S₂ relative to S₁, wherein V₉₀ is a measure of the degree of physical contact between the sensing surface and the body.

46. The apparatus of claim 34, further comprising an internal switch within the first synchronous demodulator for switching S₁ and S₂ between a first switch setting and a second switch setting, wherein the first switch setting enables a determination of V_IN, wherein the second switch setting enables a determination the 90-degree out-of-phase component V₉₀ of S₂ relative to S₁, and wherein V₉₀ is a measure of the degree of physical contact between the sensing surface and the body.

47. A method for detecting moisture, comprising:

propagating a first oscillatory electrical signal S₁ into a body at an electrical conductor disposed entirely within the body and then along a linear path from the electrical conductor through an electrically insulative material disposed entirely within the body such that a signal due to S₁ emerges from the path and from the body as a second oscillatory electrical signal S₂;

receiving S₂ by a sensing surface of a sensing part, wherein the sensing surface is in physical contact with the body, and wherein the electrically insulative material is disposed between the sensing surface and the electrical conductor so as to form a parallel plate capacitor that is in electrical parallel with an electrical resistive path characterized by a conductance σ

, and wherein σ

is indicative of moisture along the entire path traversed by S₁ within the electrically insulative material; and

transmitting S₂ from the sensing surface to a moisture detecting device that determines from S₁ and S₂ a function of σ

, wherein said function of a σ

is a measure M of the moisture.

48. The method of claim 47, further comprising:

generating S₁ by an oscillator; and

transmitting S₁ from the oscillator to the moisture detecting device.

49. The method of claim 47, further comprising displaying M.

50. The method of claim 47, further comprising determining from the capacitive component of S₂ a measure of the degree of physical contact between the sensing surface and the body.

51. The method of claim 50, further comprising displaying the measure of the degree of physical contact.

52. The method of claim 47, further comprising transmitting to a compute element a signal comprising M.

53. The method of claim 52, wherein said transmitting is performed by a transmitting device, and wherein the compute element is comprised by a computer system that is remote to an enclosure that encloses the moisture detecting device and the transmitting device.

54. The method of claim 52, wherein the method further comprises calculating from M the moisture using the compute element to perform said calculating, through deployment of an algorithm that utilizes a correlation between M and the moisture.

55. The method of claim 47, wherein the insulative material surrounds stator bars of a power generator, and wherein the insulative material is disposed between the sensing surface and the stator bars so as to form a parallel plate capacitor.

56. The method of claim 55, wherein the path traversed by S₁ includes a path segment from a copper center of the stator bars through the total thickness of insulative material to a location on an exterior surface of the body where S₂ emerges from the body.

57. The method of claim 55, wherein the stator bars are ungrounded, and wherein S₁ is adapted to be coupled to any of the ungrounded stator bars by a sufficiently large capacitance between the stator bars and a generator frame ground of the power generator, without a DC ground path existing between a copper center of the stator bars and the generator frame ground.

58. A method for detecting moisture, comprising;

propagating a first oscillator electrical signal S₁ into a body such that a signal due to S₁ emerges from the body as a second oscillatory electrical signal S₂ wherein the body includes an electrically insulative material having a conductance σ

, and wherein σ

indicative of moisture along a path traversed by S₁ within the insulative material;

receiving S₂ by a sensing surface of a sensing part wherein the sensing surface is in physical contact with the body; and

transmitting from S₂ the sensing surface to a moisture detecting device that determines S₁ and S₂ a measure M of the moisture, said measure M being a function of σ

, wherein the moisture detecting device comprises a first synchronous demodulator, wherein the method further comprises determining by the first synchronous demodulator the in-phase component V_IN of S₂ relative to S₁, wherein M is a function of V_IN, and wherein V_IN increases as σ

increases.

59. The method of claim 58, further comprising providing an electrically insulative enclosure that encloses the oscillator and the moisture detecting device, and wherein the sensing part comprises a probe located external to the enclosure.

60. The method of claim 58, further comprising:

providing an electrically insulative enclosure that encloses the oscillator and the moisture detecting device, wherein the sensing part comprises a sensing antenna, wherein the sensing antenna includes a transmitting element, a receiving element comprising the sensing surface, and a ground element, wherein the ground element is electrically connected to a ground potential within the enclosure, and wherein all electrically conductive surfaces within the enclosure are essentially capacitatively uncoupled to any electrical potential external to the enclosure; and

transmitting S₁ to the body by the transmitting element; and

receiving S₂ from the body by the receiving element.

61. The method of claim 60, wherein the sensing antenna comprises a two-conductor transmission line that includes the grounded conductor interposed between the transmitting element and the receiving element.

62. The method of claim 60, wherein the insulative material surrounds stator bars of a power generator.

63. The method of claim 62, further comprising holding the enclosure and its contents by a hand of a person.

64. The method of claim 60, further comprising moving the sensing surface into physical contact with the body by use of an electrically insulative handle mechanically connected to the enclosure.

65. The method of claim 60, wherein a flexible conductive interface electrically connects an element to the body, wherein the element is selected from the group consisting of the transmitting element, the receiving element, and the ground element.

66. The method of claim 65, wherein a constant-force assembly is coupled to the flexible conductive interface thereby causing the flexible conductive interface to exert an approximately constant force on the body, wherein the constant-force assembly includes a constant-force spring.

67. The method of claim 66, wherein a person comprises the body, and the method further comprises:

holding the enclosure and its contents at the band by a hand of a person; and

placing the sensing surface by the hand at a surface location on the skin of the person to determine M as a function of the surface location.

68. The method of claim 60, further comprising providing an electrically conductive band wrapped around the enclosure, wherein the conductive band includes the transmitting element.

69. The method of claim 58, further comprising using a second synchronous demodulator to determine from S₁ and S₂ the 90-degree out-of-phase component V₉₀ of S₂ relative to S₁, wherein V₉₀ is a measure of the degree of physical contact between the sensing surface and the body.

70. The method of claim 58, further comprising:

providing an internal switch within the first synchronous demodulator; and

switching S₁ and S₂ between a first and second switch setting of the internal switch, respectively, wherein the first switch setting enables a determination of V_IN, wherein the second switch setting enables a determination the 90-degree out-of-phase component V₉₀ of S₂ relative to S₁, and wherein V₉₀ is a measure of the degree of physical contact between the sensing surface and the body.