Mass sensor and mass sensing method

• US 6,457,361 B1
• Filed: 08/31/1999
• Issued: 10/01/2002
• Est. Priority Date: 09/04/1998
• Status: Expired due to Fees

• Current Assignee: NGK Insulators Limited
• Original Assignee: NGK Insulators Limited
• Inventors: Takeuchi, Yukihisa, Ohnishi, Takao, Kimura, Koji
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US09/387,012
• Time in Patent Office: 1,127 Days
• Field of Search: 73/240.6, 73/32.A, 73/544.1, 73/645.3, 735/80, 735/142.9, 737/02, 737/04, 435/287.2
• US Class Current: 73/580
• CPC Class Codes: G01G 3/13 having piezoelectric or piezoresistive properties

Abstract

A mass sensor including: a connecting plate having one or more slit(s) and/or opening portion(s) formed therein and/or having a thin-walled portion and a thick-walled portion formed therein; a diaphragm joined with the connecting plate at respective side surfaces; a piezoelectric element; a sensing plate with the piezoelectric element being provided at least at one part on at least one surface of the sensing plate, which has its side surface joined with a side surface of the connecting plate in the direction perpendicular to the joining direction of the diaphragm and the connecting plate; and a sensor substrate with which at least a part of side surfaces of the connecting plate as well as the sensing plate are joined, and the diaphragm, the connecting plate, the sensing plate, and the piezoelectric element form a resonating portion. The mass sensor can conveniently be used for determining the mass of a substance to be sensed by measuring changes in resonant frequencies caused by changes in the mass of the diaphragm on which a catching substance for catching a substance to be sensed by reacting only with the object of sensing is applied.

Claims

1. A mass sensor comprising:

a connecting plate having at least one of a slit, an opening portion, and a thin-walled portion and a thick-walled portion formed therein;

a diaphragm joined with the connecting plate at respective side surfaces thereof;

a sensing plate with a piezoelectric element being provided at least at one part on at least one surface of the sensing plate, which has its side surface joined with a side surface of said connecting plate in a direction perpendicular to the joining direction of said diaphragm and said connecting plate; and

a sensor substrate with which at least a part of side surfaces of said connecting plate as well as said sensing plate are joined,

wherein said diaphragm, said connecting plate, said sensing plate, and said piezoelectric element form a resonating portion.

11. The mass sensor according to claim 1, wherein said connecting plate is formed by joining one thin plate and another plate or post-like spring plate having at least one of a slit and an opening portion formed therethrough.

16. The mass sensor according to claim 1, wherein said diaphragm, said connecting plate, said sensing plate, and said sensor substrate are integrally formed.

21. The mass sensor according to claim 11, wherein a portion of said connecting plate, said diaphragm, and said sensing plate are integrally formed from a thin vibrating plate, and another plate- or post-like spring plate forming said connecting plate is integrally formed from an intermediate plate, and said connecting plate is integrally formed by laminating said intermediate plate and said thin vibrating plate, and said sensor substrate is integrally formed by laminating said vibrating plate, said intermediate plate, and a base plate.

26. The mass sensor according to claim 1, wherein the thickness of the thin-walled portion of said connecting plate is thicker than the thickness of one of said diaphragm and said sensing plate.

31. The mass sensor according to claim 26, wherein the thickness of the thin-walled portion of said connecting plate is thicker than the thickness of said sensing plate and of said piezoelectric element.

36. The mass sensor according to claim 1, further comprising at least one recessed portion or through hole, and said resonating portion is formed on each inner circumferential surface of at least one recessed portion or through hole formed through said sensor substrate.

41. The mass sensor according to claim 1, wherein a catching substance reacting with and catching only a substance to be sensed is applied on said diaphragm, the resonant frequencies of said resonating portion are measured by said piezoelectric element in the state where said substance to be sensed has not been caught by said catching substance, and in the state after said substance to be sensed has been caught by said catching substance, and the mass of said substance to be sensed having been caught is measured from a change in the measured resonant frequencies.

46. The mass sensor according to claim 41, wherein said mass sensor has at least a plurality of said diaphragms, and said catching substance is not applied to at least one of said diaphragms.

51. The mass sensor according to claim 41, wherein said mass sensor comprises at least a plurality of diaphragms, and different types of catching substances are applied to each of said diaphragms.

56. The mass sensor according to claim 1, further comprising a plurality of said connecting plates, a plurality of said diaphragms, a plurality of said sensing plates and a plurality of said piezoelectric elements forming a plurality of resonating portions, wherein said resonating portions are provided at least at two or more places on said sensor substrate so as to increase the dynamic range by integrating signals derived from said respective resonating portions.

61. The mass sensor according to claim 1, wherein said piezoelectric element is divided into two, and one is used for driving and the other is used for sensing.

66. The mass sensor according to claim 1, wherein two piezoelectric elements are provided at said resonating portion, and one of said piezoelectric elements is used for driving and the other of said piezoelectric elements is used for sensing.

71. The mass sensor according to claim 1, wherein a piezoelectric element for sensing is provided on a surface of said connecting plate.

76. The mass sensor according to claim 1, wherein a position sensor consisting of a pair of electrodes is provided on a middle position between said diaphragm and said piezoelectric element on said sensor substrate.

81. The mass sensor according to claim 1, wherein said piezoelectric element, and electrode leads respectively connected to the electrode of said piezoelectric element are coated with a resin or glass insulation coating layer.

86. The mass sensor according to claim 81, wherein said resin is fluorocarbon resin or silicone resin.

91. The mass sensor according to claim 81, wherein a shield layer consisting of a conductive member is formed on at least a part of the surface of said insulation layer.

96. The mass sensor according to claim 1, wherein said sensor substrate, said diaphragm, said connecting plate, and said sensing plate are fabricated using completely stabilized zirconia or partially stabilized zirconia.

101. The mass sensor according to claim 1, wherein a piezoelectric film of said piezoelectric element is a material consisting mainly of lead zirconate, lead titanate, or lead magnesium niobate.

2. A mass sensor comprising:

a connecting plate having at least one of a slit, an opening portion, and a thin-walled portion and a thick-walled portion formed therein;

a diaphragm joined with said connecting plate at respective side surfaces thereof;

two sensing plates with a piezoelectric element being provided at least at one part on at least one surface of at least one of said sensing plates, each of which has its side surface joined with a side surface of said connecting plate so as to sandwich the connecting plate in a direction perpendicular to the joining direction of said diaphragm and said connecting plate; and

a sensor substrate with which at least a part of side surfaces of said connecting plate as well as said sensing plates are joined;

wherein said diaphragm, said connecting plate, said sensing plates, and said piezoelectric element form a resonating portion.

3. The mass sensor according to claim 2, wherein at least one slit is formed through at least one of said sensing plates in the direction perpendicular to the joining direction of said sensing plates and said connecting plate.

4. The mass sensor according to claim 2, wherein two piezoelectric elements respectively are provided on the surfaces of said two sensing plates facing the same direction, and the direction of polarization of a piezoelectric film of each of said piezoelectric elements is opposite.

12. The mass sensor according to claim 2, wherein said connecting plate is formed by joining one thin plate and another plate or post-like spring plate having at least one of a slit and an opening portion formed therethrough.

17. The mass sensor according to claim 2, wherein said diaphragm, said connecting plate, said sensing plates, and said sensor substrate are integrally formed.

22. The mass sensor according to claim 12, wherein a portion of said connecting plate, said diaphragm, and said sensing plates are integrally formed from a thin vibrating plate, and another plate- or post-like spring plate forming said connecting plate is integrally formed from an intermediate plate, and said connecting plate is integrally formed by laminating said intermediate plate and said thin vibrating plate, and said sensor substrate is integrally formed by laminating said vibrating plate, said intermediate plate, and a base plate.

27. The mass sensor according to claim 2, wherein the thickness of the thin-walled portion of said connecting plate is thicker than the thickness of one of said diaphragm and said sensing plates.

32. The mass sensor according to claim 27, wherein the thickness of the thin-walled portion of said connecting plate is thicker than the thickness of said sensing plates and of said piezoelectric element.

37. The mass sensor according to claim 2, further comprising at least one recessed portion or through hole, and said resonating portion is formed on each inner circumferential surface of at least one recessed portion or through hole formed through said sensor substrate.

42. The mass sensor according to claim 2, wherein a catching substance reacting with and catching only a substance to be sensed is applied on said diaphragm, the resonant frequencies of said-resonating portion are measured by said piezoelectric element in the state where said substance to be sensed has not been caught by said catching substance, and in the state after said substance to be sensed has been caught by said catching substance, and the mass of said substance to be sensed having been caught is measured from a change in the measured resonant frequencies.

47. The mass sensor according to claim 42, wherein said mass sensor has at least a plurality of said diaphragms, and said catching substance is not applied to at least one of said diaphragms.

52. The mass sensor according to claim 42, wherein said mass sensor comprises at least a plurality of diaphragms, and different types of catching substances are applied to each of said diaphragms.

57. The mass sensor according to claim 2, further comprising a plurality of said connecting plates, a plurality of said diaphragms, a plurality of said sensing plates and a plurality of said piezoelectric elements forming a plurality of resonating portions, wherein said resonating portions are provided at least at two or more places on said sensor substrate so as to increase the dynamic range by integrating signals derived from said respective resonating portions.

62. The mass sensor according to claim 2, wherein said piezoelectric element is divided into two, and one is used for driving and the other is used for sensing.

67. The mass sensor according to claim 2, wherein two piezoelectric elements are provided at said resonating portion, and one of said piezoelectric elements is used for driving and the other of said piezoelectric elements is used for sensing.

72. The mass sensor according to claim 2, wherein a piezoelectric element for sensing is provided on a surface of said connecting plate.

77. The mass sensor according to claim 2, wherein a position sensor consisting of a pair of electrodes is provided on a middle position between said diaphragm and said piezoelectric element on said sensor substrate.

82. The mass sensor according to claim 2, wherein said piezoelectric element, and electrode leads respectively connected to the electrode of said piezoelectric element are coated with a resin or glass insulation coating layer.

87. The mass sensor according to claim 82, wherein said resin is fluorocarbon resin or silicone resin.

92. The mass sensor according to claim 82, wherein a shield layer consisting of a conductive member is formed on at least a part of the surface of said insulation layer.

97. The mass sensor according to claim 2, wherein said sensor substrate, said diaphragm, said connecting plate, and said sensing plates are fabricated using completely stabilized zirconia or partially stabilized zirconia.

102. The mass sensor according to claim 2, wherein a piezoelectric film of said piezoelectric element is a material consisting mainly of lead zirconate, lead titanate, or lead magnesium niobate.

5. A mass sensor comprising:

a sensor substrate;

two connecting plates each having at least one of a slit, an opening portion, and a thin-walled portion and a thick-walled portion formed therein;

a diaphragm joined with said connecting plates at respective side surfaces thereof, and being sandwiched by said connecting plates such that said connecting plates and said diaphragm bridge a gap between side surfaces of a recessed portion provided in said sensor substrate; and

a sensing plate with a piezoelectric element being provided at least at one part on at least one surface of said sensing plate, which bridges a gap between a lower side surface of the recessed portion and a side surface of said respective connecting plate in a direction perpendicular to the joining direction of said connecting plate and said diaphragm,

wherein said diaphragm, said connecting plate, said sensing plate, and said piezoelectric element form a resonating portion.

13. The mass sensor according to claim 5, wherein said connecting plates are formed by joining one thin plate and another plate or post-like spring plate having at least one of a slit and an opening portion formed therethrough.

18. The mass sensor according to claim 5, wherein said diaphragm, said connecting plates, said sensing plate, and said sensor substrate are integrally formed.

23. The mass sensor according to claim 13, wherein a portion of said connecting plates, said diaphragm, and said sensing plate are integrally formed from a thin vibrating plate, and another plate- or post-like spring plate forming said connecting plates is integrally formed from an intermediate plate, and said connecting plates are integrally formed by laminating said intermediate plate and said thin vibrating plate, and said sensor substrate is integrally formed by laminating said vibrating plate, said intermediate plate, and a base plate.

28. The mass sensor according to claim 5, wherein the thickness of the thin-walled portion of said connecting plates is thicker than the thickness of one of said diaphragm and said sensing plate.

33. The mass sensor according to claim 28, wherein the thickness of the thin-walled portion of said connecting plates is thicker than the thickness of said sensing plate and of said piezoelectric element.

38. The mass sensor according to claim 5, further comprising at least one recessed portion or through hole, and said resonating portion is formed on each inner circumferential surface of at least one recessed portion or through hole formed through said sensor substrate.

43. The mass sensor according to claim 5, wherein a catching substance reacting with and catching only a substance to be sensed is applied on said diaphragm, the resonant frequencies of said resonating portion are measured by said piezoelectric element in the state where said substance to be sensed has not been caught by said catching substance, and in the state after said substance to be sensed has been caught by said catching substance, and the mass of said substance to be sensed having been caught is measured from a change in the measured resonant frequencies.

48. The mass sensor according to claim 43, wherein said mass sensor has at least a plurality of said diaphragms, and said catching substance is not applied to at least one of said diaphragms.

53. The mass sensor according to claim 43, wherein said mass sensor comprises at least a plurality of diaphragms, and different types of catching substances are applied to each of said diaphragms.

58. The mass sensor according to claim 5, further comprising a plurality of said connecting plates, a plurality of said diaphragms, a plurality of said sensing plates and a plurality of said piezoelectric elements forming a plurality of resonating portions, wherein said resonating portions are provided at least at two or more places on said sensor substrate so as to increase the dynamic range by integrating signals derived from said respective resonating portions.

63. The mass sensor according to claim 5, wherein said piezoelectric element is divided into two, and one is used for driving and the other is used for sensing.

68. The mass sensor according to claim 5, wherein two piezoelectric elements are provided at said resonating portion, and one of said piezoelectric elements is used for driving and the other of said piezoelectric elements is used for sensing.

73. The mass sensor according to claim 5, wherein a piezoelectric element for sensing is provided on a surface of at least one of said connecting plates.

78. The mass sensor according to claim 5, wherein a position sensor consisting of a pair of electrodes is provided on a middle position between said diaphragm and said piezoelectric element on said sensor substrate.

83. The mass sensor according to claim 5, wherein said piezoelectric element, and electrode leads respectively connected to the electrode of said piezoelectric element are coated with a resin or glass insulation coating layer.

88. The mass sensor according to claim 83, wherein said resin is fluorocarbon resin or silicone resin.

93. The mass sensor according to claim 83, wherein a shield layer consisting of a conductive member is formed on at least a part of the surface of said insulation layer.

98. The mass sensor according to claim 5, wherein said sensor substrate, said diaphragm, said connecting plates, and said sensing plate are fabricated using completely stabilized zirconia or partially stabilized zirconia.

103. The mass sensor according to claim 5, wherein a piezoelectric film of said piezoelectric element is a material consisting mainly of lead zirconate, lead titanate, or lead magnesium niobate.

6. A mass sensor comprising:

a sensor substrate having a pair of recessed portions facing each other, each of said portions defined by a bottom surface and two side surfaces;

two connecting plates having at least one of a slit, an opening portion, and a thin-walled portion and a thick-walled portion formed therein;

a diaphragm joined with said connecting plates at respective side surfaces thereof, and being sandwiched by said connecting plates such that said connecting plates and said diaphragm bridge a gap between said bottom surfaces of said recessed portions; and

four sensing plates with a piezoelectric element being provided at least at one part on at least one surface of two of said sensing plates which face each other with one of said connecting plates therebetween, said two of said sensing plates bridging a gap between side surfaces of one recessed portion and side surfaces of said connecting plate in a direction perpendicular to the joining direction of said connecting plate and said diaphragm;

wherein said diaphragm, said connecting plates, said sensing plates, and said piezoelectric elements form a resonating portion.

7. The mass sensor according to claim 6, wherein at least one slit is formed in one of said sensing plates that does not carry said piezoelectric element, in a direction perpendicular to the joining direction of said sensing plate and said connecting plate.

8. The mass sensor according to claim 6, wherein two piezoelectric elements are respectively provided on the surfaces of the two sensing plates facing each other via said connecting plate, and the direction of polarization of a piezoelectric film of each of said piezoelectric elements is opposite.

14. The mass sensor according to claim 6, wherein said connecting plates are formed by joining one thin plate and another plate or post-like spring plate having at least one of a slit and an opening portion formed therethrough.

19. The mass sensor according to claim 6, wherein said diaphragm, said connecting plates, said sensing plates, and said sensor substrate are integrally formed.

24. The mass sensor according to claim 14, wherein a portion of said connecting plates, said diaphragm, and said sensing plates are integrally formed from a thin vibrating plate, and another plate- or post-like spring plate forming said connecting plates is integrally formed from an intermediate plate, and said connecting plates are integrally formed by laminating said intermediate plate and said thin vibrating plate, and said sensor substrate is integrally formed by laminating said vibrating plate, said intermediate plate, and a base plate.

29. The mass sensor according to claim 6, wherein the thickness of the thin-walled portion of said connecting plates is thicker than the thickness of one of said diaphragm and said sensing plates.

34. The mass sensor according to claim 29, wherein the thickness of the thin-walled portion of said connecting plates is thicker than the thickness of said sensing plates and of said piezoelectric element.

39. The mass sensor according to claim 6, further comprising at least one recessed portion or through hole, and said resonating portion is formed on each inner circumferential surface of at least one recessed portion or through hole formed through said sensors substrate.

44. The mass sensor according to claim 6, wherein a catching substance reacting with and catching only a substance to be sensed is applied on said diaphragm, the resonant frequencies of said resonating portion are measured by said piezoelectric element in the state where said substance to be sensed has not been caught by said catching substance, and in the state after said substance to be sensed has been caught by said catching substance, and the mass of said substance to be sensed having been caught is measured from a change in the measured resonant frequencies.

49. The mass sensor according to claim 44, wherein said mass sensor has at least a plurality of said diaphragms, and said catching substance is not applied to at least one of said diaphragms.

54. The mass sensor according to claim 44, wherein said mass sensor comprises at least a plurality of diaphragms, and different types of catching substances are applied to each of said diaphragms.

59. The mass sensor according to claim 6, further comprising a plurality of said connecting plates, a plurality of said diaphragms, a plurality of said sensing plates and a plurality of said piezoelectric elements forming a plurality of resonating portions, wherein said resonating portions are provided at least at two or more places on said sensor substrate so as to increase the dynamic range by integrating signals derived from said respective resonating portions.

64. The mass sensor according to claim 6, wherein at least one of said piezoelectric elements is divided into two, and one is used for driving and the other is used for sensing.

69. The mass sensor according to claim 6, wherein two piezoelectric elements are provided at said resonating portion, and one of said piezoelectric elements is used for driving and the other of said piezoelectric elements is used for sensing.

74. The mass sensor according to claim 6, wherein a piezoelectric element for sensing is provided on a surface of at least one of said connecting plates.

79. The mass sensor according to claim 6, wherein a position sensor consisting of a pair of electrodes is provided on a middle position between said diaphragm and said piezoelectric element on said sensor substrate.

84. The mass sensor according to claim 6, wherein said piezoelectric element, and electrode leads respectively connected to the electrode of said piezoelectric element are coated with a resin or glass insulation coating layer.

89. The mass sensor according to claim 84, wherein said resin is fluorocarbon resin or silicone resin.

94. The mass sensor according to claim 84, wherein a shield layer consisting of a conductive member is formed on at least a part of the surface of said insulation layer.

99. The mass sensor according to claim 6, wherein said sensor substrate, said diaphragm, said connecting plates, and said sensing plates are fabricated using completely stabilized zirconia or partially stabilized zirconia.

104. The mass sensor according to claim 6, wherein a piezoelectric film of said piezoelectric element is a material consisting mainly of lead zirconate, lead titanate, or lead magnesium niobate.

9. A mass sensor comprising:

a sensor substrate;

a first connecting plate and a second connecting plate having at least one of a slit, an opening portion, and a thin-walled portion and a thick-walled portion formed therein; and

a first diaphragm joined with said first connecting plate at respective side surfaces thereof, and a second diaphragm joined with said second connecting plate at respective side surfaces thereof, between which connecting plates a first sensing plate is bridged;

wherein side surfaces of a second sensing plate, said first sensing plate, and said first connecting plate are joined to each other so that said first connecting plate is sandwiched by said second sensing plate and said first sensing plate, and a third sensing plate and said first sensing plate are joined with the second connecting plate so as to sandwich the second connecting plate at respective side surfaces thereof;

a piezoelectric element is provided at least on a part of at least one surface of said second sensing plate and said third sensing plate respectively; and

bottom side surfaces of a recessed portion provided in said sensor substrate are joined with side surfaces of said first connecting plate and said second connecting plate, such that the side surfaces are opposed to joint side surfaces of the first diaphragm and the first connecting plate, and the second diaphragm and the second connecting plate, and said second sensing plate and said third sensing plate join with at least side surfaces of the recessed portion.

10. The mass sensor according to claim 9, wherein at least one slit is formed in said first sensing plate in a direction perpendicular to the bridging direction of said first sensing plate.

15. The mass sensor according to claim 9, wherein said connecting plates are formed by joining one thin plate and another plate or post-like spring plate having at least one of a slit and an opening portion formed therethrough.

20. The mass sensor according to claim 9, wherein said diaphragms, said connecting plates, said sensing plates, and said sensor substrate are integrally formed.

25. The mass sensor according to claim 15, wherein a portion of said connecting plates, said diaphragms, and said sensing plates are integrally formed from a thin vibrating plate, and another plate- or post-like spring plate forming said connecting plates is integrally formed from an intermediate plate, and said connecting plates are integrally formed by laminating said intermediate plate and said vibrating plate, and said sensor substrate is integrally formed by laminating said vibrating plate, said intermediate plate, and a base plate.

30. The mass sensor according to claim 9, wherein the thickness of the thin-walled portion of said connecting plates is thicker than the thickness of one of said diaphragms and said sensing plates.

35. The mass sensor according to claim 30, wherein the thickness of the thin-walled portion of said connecting plates is thicker than the thickness of said sensing plates and of said piezoelectric element.

40. The mass sensor according to claim 9, further comprising at least one recessed portion or through hole, and said resonating portion is formed on each inner circumferential surface of at least one recessed portion or through hole formed through said sensor substrate.

45. The mass sensor according to claim 9, wherein a catching substance reacting with and catching only a substance to be sensed is applied on at least one of said diaphragms, the resonant frequencies of said resonating portion are measured by said piezoelectric element in the state where said substance to be sensed has not been caught by said catching substance, and in the state after said substance to be sensed has been caught by said catching substance, and the mass of said substance to be sensed having been caught is measured from a change in the measured resonant frequencies.

50. The mass sensor according to claim 45, wherein said mass sensor has at least a plurality of said diaphragms, and said catching substance is not applied to at least one of said diaphragms.

55. The mass sensor according to claim 45, wherein said mass sensor comprises at least a plurality of diaphragms, and different types of catching substances are applied to each of said diaphragms.

60. The mass sensor according to claim 9, further comprising a plurality of said connecting plates, a plurality of said diaphragms, a plurality of said sensing plates and a plurality of said piezoelectric elements forming a plurality of resonating portions, wherein said resonating portions are provided at least at two or more places on said sensor substrate so as to increase the dynamic range by integrating signals derived from said respective resonating portions.

65. The mass sensor according to claim 9, wherein said piezoelectric element is divided into two, and one is used for driving and the other is used for sensing.

70. The mass sensor according to claim 9, wherein two piezoelectric elements are provided at said resonating portion, and one of said piezoelectric elements is used for driving and the other of said piezoelectric elements is used for sensing.

75. The mass sensor according to claim 9, wherein a piezoelectric element for sensing is provided on a surface of at least one of said connecting plates.

80. The mass sensor according to claim 9, wherein a position sensor consisting of a pair of electrodes is provided on a middle position between said diaphragms and said piezoelectric element on said sensor substrate.

85. The mass sensor according to claim 9, wherein said piezoelectric element, and electrode leads respectively connected to the electrode of said piezoelectric element are coated with a resin or glass insulation coating layer.

90. The mass sensor according to claim 85, wherein said resin is fluorocarbon resin or silicone resin.

95. The mass sensor according to claim 85, wherein a shield layer consisting of a conductive member is formed on at least a part of the surface of said insulation layer.

100. The mass sensor according to claim 9, wherein said sensor substrate, said diaphragms, said connecting plates, and said sensing plates are fabricated using completely stabilized zirconia or partially stabilized zirconia.

105. The mass sensor according to claim 9, wherein a piezoelectric film of said piezoelectric element is a material consisting mainly of lead zirconate, lead titanate, or lead magnesium niobate.

106. A mass sensing method comprising:

providing a mass sensor comprising;

a sensor substrate, a connecting plate having at least one of a slit, an opening portion, and a thin-walled portion and a thick-walled portion formed in the connecting plate, a diaphragm being joined with the connecting plate at respective side surfaces thereof, at least one sensing plate joined with the connecting plate at respective side surfaces thereof, at least one portion of the side surfaces of said connecting plate and said sensing plate being joined with a portion of side surfaces of the sensor substrate, and a piezoelectric element provided on at least a part of said sensing plate; and

measuring the resonant frequency of said mass sensor by using said piezoelectric element at least based either on ν

mode swing oscillation or ν

z mode swing oscillation, ν

mode swing oscillation involving straight-line like reciprocal oscillation of said diaphragm with a perpendicular axis passing through perpendicularly at the center of joint surfaces of said connecting plate and said sensor substrate being the center, in a direction in parallel with the surface of said diaphragm and perpendicular with said perpendicular axis, and ν

z mode swing oscillation involving swing-like reciprocal oscillation of said diaphragm with said perpendicular axis being the center, in a direction in parallel with the surface of said diaphragm and perpendicular with said perpendicular axis, accompanied by movement in a direction perpendicular with the surface of said diaphragm.

107. A mass sensor comprising:

a sensor substrate;

a connecting plate having a first end joined to said sensor substrate and a second end opposed to said first end along a first direction, said connecting plate having at least one of (i) a slit therethrough, (ii) an opening therethrough, and (iii) a thin-walled portion and a thick-walled portion formed therein;

a diaphragm joined to said second end of said connecting plate;

a sensing plate having a first side joined to a side of said connecting plate and a second side opposed to said first side along a second direction substantially perpendicular to said first direction, said second side being joined to said sensor substrate; and

a piezoelectric element disposed on at least a portion of at least one of opposed main surfaces of said sensing plate;

wherein said connecting plate, said diaphragm, said sensing plate and said piezoelectric element form a resonating portion.