Displacement sensing system

• US 20040124981A1
• Filed: 04/23/2003
• Published: 07/01/2004
• Est. Priority Date: 04/18/2000
• Status: Active Grant

• Current Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc), Rubicon Holding B.V.
• Original Assignee: Rubicon Holding B.V.
• Inventors: Zhevelev, Boris, Moldavsky, Mark
• Granted Patent: US 6,933,846 B2
• Time in Patent Office: Days
• US Class Current: 340/568.8
• CPC Class Codes: G01D 5/2033 controlling the saturation of a magnetic circuit by means of a movable element, e.g. a magnet
• CPC Class Codes: G01D 5/243 influencing the phase or frequency of ac
• CPC Class Codes: G01V 3/08 operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices with electromagnetic waves G01V3/12
• CPC Class Codes: G08C 19/16 in which transmission is by pulses

Abstract

A displacement sensing system including an oscillator circuit having a characteristic frequency which varies as a function of a magnetic field in the vicinity thereof, an element whose position relative to the oscillator circuit is varied by a displacement, the element being operative to vary the magnetic field in the vicinity of the oscillator circuit as a function of the displacement and circuitry for sensing a change of frequency of the oscillator circuit over time (delta f/delta t) and for providing an output indication when the change in frequency of the oscillator circuit over time exceeds a threshold.

Claims

1. A displacement sensing system comprising:

an oscillator circuit having a characteristic frequency which varies as a function of a magnetic field in the vicinity thereof;

an element whose position relative to said oscillator circuit is varied by a displacement to be sensed, said element being operative to vary the magnetic field in the vicinity of said oscillator circuit as a function of said displacement; and

circuitry for sensing a change of frequency of said oscillator circuit over time (Δ

f/Δ

t) and for providing an output indication when the change in frequency of said oscillator circuit over time exceeds a threshold.

3. A displacement sensing system according to claim 1 or claim 2 and wherein said threshold is variable.

4. A displacement sensing system according to any of the preceding claims and wherein said threshold varies as a function of a currently perceived threat.

5. A displacement sensing system according to claim 4 and wherein said currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

6. A displacement sensing system according to any of the preceding claims and wherein said oscillator circuit and said circuitry for sensing a change of frequency are operated in accordance with a duty cycle.

7. A displacement sensing system according to claim 6 and wherein said duty cycle is variable.

8. A displacement sensing system according to claim 7 and wherein said duty cycle is adaptive.

9. A displacement sensing system according to claim 7 and wherein said duty cycle varies as a function of a currently perceived threat.

10. A displacement sensing system according to claim 9 and wherein said currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

11. A displacement sensing system according to any of the preceding claims and wherein said threshold varies in accordance with long time scale changes in said characteristic frequency.

12. A displacement sensing system according to any of the preceding claims and wherein said threshold -comprises first and second frequency thresholds, respectively above and below said characteristic frequency and which are normally generally equally separated therefrom in the frequency domain.

13. A displacement sensing system according to any of the preceding claims and also comprising wireless communication circuitry operative to transmit said output indication to a remote receiving location.

14. A displacement sensing system according to claim 13 and wherein said wireless communication circuitry is operative to transmit said output indication for at least a predetermined time following sensing of said change in frequency.

15. A displacement sensing system according to any of the preceding claims and also comprising a locator operative for sensing the location of at least one of said oscillator, said element and said circuitry for sensing.

16. A displacement sensing system according to any of the preceding claims and wherein said element is a magnet.

17. A displacement sensing system according to claim 16 and wherein said element is an electromagnet.

18. A displacement sensing system according to claim 16 and wherein said element is a permanent magnet.

19. A displacement sensing system according to any of the preceding claims and wherein said circuitry for sensing a change of frequency comprises a microprocessor which receives an output of said oscillator circuit as a clock input.

20. A displacement sensing system according to any of the preceding claims and wherein said circuitry for sensing a change of frequency is operative to count oscillator pulses over variable time periods which represent variable sensitivity thresholds.

144. Apparatus according to any of the preceding claims and wherein said displacement is a vibrational displacement.

145. Apparatus according to any of the preceding claims and wherein said oscillator circuit and said element are physically attached to each other.

146. Apparatus according to any of the preceding claims and wherein said oscillator circuit and said element are not physically attached to each other.

2. A displacement sensing system according to claim I and wherein said circuitry for sensing a change of frequency over time provides at least first and second different output indications when said change in frequency of said oscillator circuit over time exceeds respective at least first and second different thresholds.

21. A displacement sensing system comprising:

an oscillator circuit having a characteristic frequency which varies as a function of a magnetic field in the vicinity thereof;

an element whose position relative to said oscillator circuit is varied by a displacement to be sensed, said element being operative to vary the magnetic field in the vicinity of said oscillator circuit as a function of said displacement; and

circuitry for sensing a time duration over which a change of frequency of at least a given amount takes place and for providing an output indication when said time duration exceeds a threshold.

22. A displacement sensing system according to claim 21 and wherein said circuitry for sensing a time duration provides at least first and second different output indications when said time duration exceeds respective at least first and second different thresholds.

23. A displacement sensing system according to claim 21 or claim 22 and wherein said threshold is variable.

24. A displacement sensing system according to any of the preceding claims 21-23 and wherein said threshold varies as a function of a currently perceived threat.

25. A displacement sensing system according to claim 24 and wherein said currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

26. A displacement sensing system according to any of the preceding claims 21-25 and wherein said oscillator circuit and said circuitry for sensing a time duration are operated in accordance with a duty cycle.

27. A displacement sensing system according to claim 26 and wherein said duty cycle is variable.

28. A displacement sensing system according to claim 27 and wherein said duty cycle is adaptive.

29. A displacement sensing system according to claim 27 and wherein said duty cycle varies as a function of a currently perceived threat.

30. A displacement sensing system according to claim 29 and wherein said currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

31. A displacement sensing system according to any of the preceding claims 21-30 and wherein said given amount remains generally constant notwithstanding long time scale changes in said characteristic frequency.

32. A displacement sensing system according to any of the preceding claims 21-31 and also comprising wireless communication circuitry operative to transmit said output indication to a remote receiving location.

33. A displacement sensing system according to claim 32 and wherein said wireless communication circuitry is operative to transmit said output indication for at least a predetermined time following sensing of said change in frequency.

34. A displacement sensing system according to any of the preceding claims 21-33 and also comprising a locator operative for sensing the location of at least one of said oscillator, said element and said circuitry for sensing.

35. A displacement sensing system according to any of the preceding claims 21-34 and wherein said element is a magnet.

36. A displacement sensing system according to claim 35 and wherein said element is an electromagnet.

37. A displacement sensing system according to claim 35 and wherein said element is a permanent magnet.

38. A displacement sensing system according to any of the preceding claims 21-37 and wherein said circuitry for sensing a time duration comprises a microprocessor which receives an output of said oscillator circuit as a clock input.

39. A displacement sensing system according to any of the preceding claims 21-38 and wherein said circuitry for sensing a time duration is operative to count oscillator pulses over variable time periods which represent variable sensitivity thresholds.

40. A displacement sensing system according to any of the preceding claims 21-39 and wherein said circuitry for sensing a time duration comprises a microprocessor which provides said output indication.

41. A displacement sensing system comprising:

an oscillator circuit having a characteristic frequency which varies as a function of a magnetic field in the vicinity thereof,

an element whose position relative to said oscillator circuit is varied by a displacement to be sensed, said element being operative to vary the magnetic field in the vicinity of said oscillator circuit as a function of said displacement;

circuitry for sensing a change of frequency of said oscillator circuit over time (Δ

f/Δ

t) and for providing an output indication when the change in frequency of said oscillator circuit over time exceeds a frequency threshold; and

circuitry for sensing a time duration over which a change of frequency of at least a given amount takes place and. for providing an output indication when said time duration exceeds a time threshold.

42. A displacement sensing system according to claim 41 and wherein said circuitry for sensing a change of frequency over time provides at least first and second different output indications when said change in frequency of said oscillator circuit over time exceeds respective at least first and second different thresholds.

43. A displacement sensing system according to claim 41 or claim 42 and wherein said frequency threshold is variable.

44. A displacement sensing system according to claim 43 and wherein said frequency threshold varies as a function of a currently perceived threat.

45. A displacement sensing system according to claim 44 and wherein said currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

46. A displacement sensing system according to any of the preceding claims 41-45 and wherein said frequency threshold varies in accordance with long time scale changes in said characteristic frequency.

47. A displacement sensing system according to any of claims 41-46 and wherein said frequency threshold comprises first and second frequency thresholds, respectively above and below said characteristic frequency and which are normally generally equally separated therefrom in the frequency domain.

48. A displacement sensing system according to claim 41 and wherein said time threshold is variable.

49. A displacement sensing system according to claim 48 and wherein said time threshold varies as a function of a currently perceived threat.

50. A displacement sensing system according to claim 49 and wherein said, currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

51. A displacement sensing system according to any of the preceding claims 41-50 and wherein said oscillator circuit and said circuitry for sensing a time duration are operated in accordance with a duty cycle.

52. A displacement sensing system according to claim 51 and wherein said duty cycle is variable.

53. A displacement sensing system according to claim 51 and wherein said duty cycle is adaptive.

54. A displacement sensing system according to claim 52 and wherein said duty cycle varies as a function of a currently perceived threat.

55. A displacement sensing system according to claim 54 and wherein said currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

56. A displacement sensing system according to any of the preceding claims 41-55 and wherein said given amount remains generally constant notwithstanding long time scale changes in said characteristic frequency.

57. A displacement sensing system according to claim 41 and wherein said circuitry for sensing a time duration provides at least first and second different output indications when said time duration exceeds respective at least first and second different thresholds.

58. A displacement sensing system according to any of the preceding claims 41-57 and also comprising wireless communication circuitry operative to transmit said output indication to a remote receiving location.

59. A displacement sensing system according to claim 58 and wherein said wireless communication circuitry is operative to transmit said output indication for at least a predetermined time following sensing of said change in frequency.

60. A displacement sensing system according to any of the preceding claims 41-59 and also comprising a locator operative for sensing the location of at least one of said oscillator, said element and said circuitry for sensing.

61. A displacement sensing system according to any of the preceding claims 41-59 and wherein said element is a magnet.

62. A displacement sensing system according to claim 61 and wherein said element is an electromagnet.

63. A displacement sensing system according to claim 61 and wherein said element is a permanent magnet.

64. A displacement sensing system according to any of the preceding claims 41-63 and wherein said circuitry for sensing a time duration and said circuitry for sensing a change of frequency comprises a microprocessor which receives an output of said oscillator circuit as a clock input.

65. A displacement sensing system according to any of the preceding claims 41-63 and wherein said circuitry for sensing a time duration is operative to count oscillator pulses over variable time periods which represent variable sensitivity thresholds.

66. A protected object comprising:

an object having associated therewith a displacement sensing system including;

an oscillator circuit having a characteristic frequency which varies as a function of a magnetic field in the vicinity thereof;

an element whose position relative to said oscillator circuit is varied by a displacement to be sensed, said element being operative to vary the magnetic field in the vicinity of said oscillator circuit as a function of said displacement; and

circuitry for sensing a change of frequency of said oscillator circuit over time (Δ

f/Δ

t) and for providing an output indication when the change in frequency of said oscillator circuit over time exceeds a threshold, wherein

one but not both of said oscillator circuit and said element is fixedly mounted onto said object.

67. A protected object according to claim 66 and wherein said oscillator circuit is fixedly mounted onto said object.

68. A protected object according to claim 66 and wherein said element is fixedly mounted onto said object.

69. A protected object according to claim 66 and wherein said threshold is variable.

70. A protected object according to claim 67 and wherein said threshold varies as a function of a currently perceived threat.

71. A protected object according to claim 68 and wherein said currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

72. A protected object according to any of the preceding claims 66-71 and wherein said oscillator circuit and said circuitry for sensing a change of frequency are operated in accordance with a duty cycle.

73. A protected object according to claim 72 and wherein said duty cycle is variable.

74. A protected object according to claim 73 and wherein said duty cycle is adaptive.

75. A protected object according to claim 73 and wherein said duty cycle varies as a function of a currently perceived threat.

76. A protected object according to claim 75 and wherein said currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

77. A protected object according to any of the preceding claims 66-76 and wherein said threshold varies in accordance with long time scale changes in said characteristic frequency.

78. A protected object according to any of claims 66-77 and wherein said threshold comprises first and second frequency thresholds, respectively above and below said characteristic frequency and which are normally generally equally separated therefrom in the frequency domain.

79. A protected object according to claim 66 and wherein said circuitry for sensing a change of frequency over time provides at least first and second different output indications when said change in frequency of said oscillator circuit over time exceeds respective at least first and second different thresholds.

80. A protected object according to any of the preceding claims 66-79 and also comprising wireless communication circuitry operative to transmit said output indication to a remote receiving location.

81. A protected object according to claim 80 and wherein said wireless communication circuitry is operative to transmit said output indication for at least a predetermined time following sensing of said change in frequency.

82. A protected object according to any of the preceding claims 66-81 and wherein said element is a magnet.

83. A protected object according to claim 82 and wherein said element is an electromagnet.

84. A protected object according to claim 82 and wherein said element is a permanent magnet.

85. A protected object according to any of the preceding claims 66-84 and wherein said circuitry for sensing a change of frequency comprises a microprocessor which receives an output of said oscillator circuit as a clock input.

86. A protected object according to any of the preceding claims 66-85 and wherein said circuitry for sensing a change of frequency is operative to count oscillator pulses over variable time periods which represent variable sensitivity thresholds.

87. A protected object according to any of the preceding claims 66-86 and wherein said circuitry for sensing a change of frequency comprises a microprocessor which provides said output indication.

88. A protected object comprising:

an object having associated therewith a displacement sensing system including;

an oscillator circuit having a characteristic frequency which varies as a function of a magnetic field in the vicinity thereof;

an element whose position relative to said oscillator circuit is varied by a displacement to be sensed, said element being operative to vary the magnetic field in the vicinity of said oscillator circuit as a function of said displacement; and

circuitry for sensing a time duration over which a change of frequency of at least a given amount takes place and for providing an output indication when said time duration exceeds a threshold, wherein

one but not both of said oscillator circuit and said element is fixedly mounted onto said object.

89. A displacement sensing system according to claim 88 and wherein said circuitry for sensing a time duration provides at least first and second different output indications when said time duration exceeds respective at least first and second different thresholds.

90. A protected object according to claim 88 and wherein said oscillator circuit is fixedly mounted onto said object.

91. A protected object according to claim 88 and wherein said element is fixedly mounted onto said object.

92. A protected object according to claim 88 and wherein said threshold is variable.

93. A protected object according to claim 92 and wherein said threshold varies as a function of a currently perceived threat.

94. A protected object according to claim 93 and wherein said currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

95. A protected object according to any of the preceding claims 88-94 and wherein said oscillator circuit and said circuitry for sensing a time duration are operated in accordance with a duty cycle.

96. A protected object according to claim 95 and wherein said duty cycle is variable.

97. A protected object according to claim 95 and wherein said duty cycle is adaptive.

98. A protected object according to claim 96 and wherein said duty cycle varies as a function of a currently perceived threat.

99. A protected object according to claim 98 and wherein said currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

100. A protected object according to any of the preceding claims 88-99 and wherein said given amount remains generally constant notwithstanding long time scale changes in said characteristic frequency.

101. A protected object according to claim 88 and wherein said circuitry for sensing a time duration provides at least first and second different output indications when said time duration exceeds respective at least first and second different thresholds.

102. A protected object according to any of the preceding claims 88-101 and also comprising wireless communication circuitry operative to transmit said output indication to a remote receiving location.

103. A protected object according to any of the preceding claims 88-102 and wherein said wireless communication circuitry is operative to transmit said output indication for at least a predetermined time following sensing of said change in frequency.

104. A protected object according to any of the preceding claims 88-103 and wherein said element is a magnet.

105. A protected object according to claim 104 and wherein said element is an electromagnet.

106. A protected object according to claim 104 and wherein said element is a permanent magnet.

107. A protected object according to any of the preceding claims 88-106 and wherein said circuitry for sensing a change of frequency comprises a microprocessor which receives an output of said oscillator circuit as a clock input.

108. A protected object according to any of the preceding claims 88-107 and wherein said circuitry for sensing a change of frequency is operative to count oscillator pulses over variable time periods which represent variable sensitivity thresholds.

139. A protected object according to any of claims 66-138 and wherein said protected object is an art object.

140. A protected object according to claim 139 and wherein said art object is a painting and wherein one but not both of said oscillator circuit and said element is fixedly mounted onto a frame of said painting.

141. A protected object according to claim 139 and wherein said art object is a painting and wherein one but not both of said oscillator circuit and said element is fixedly mounted onto a canvas of said painting.

142. A protected object according to any of the preceding claims 66-141 and also comprising wireless communication circuitry operative to transmit said output indication to a remote receiving location.

143. A protected object according to claim 142 and wherein said wireless communication circuitry is operative to transmit said output indication for at least a predetermined time following sensing of said change in frequency.

109. A protected object comprising:

an object having associated therewith a displacement sensing system including;

an oscillator circuit having a characteristic frequency which varies as a function of a magnetic field in the vicinity thereof;

an element whose position relative to said oscillator circuit is varied by a displacement to be sensed, said element being operative to vary the magnetic field in the vicinity of said oscillator circuit as a function of said displacement;

circuitry for sensing a change of frequency of said oscillator circuit over time (Δ

f/Δ

t) and for providing an output indication when the change in frequency of said oscillator circuit over time exceeds a frequency threshold; and

circuitry for sensing a time duration over which a change of frequency of at least a given amount takes place and for providing an output indication when said time duration exceeds a time threshold, wherein

one but not both of said oscillator circuit and said element is fixedly mounted onto said object.

110. A protected object according to claim 109 and wherein said oscillator circuit is fixedly mounted onto said object.

111. A protected object according to claim 109 and wherein said element is fixedly mounted onto said object.

112. A protected object according to claim 109 and wherein said frequency threshold is variable.

113. A protected object according to claim 112 and wherein said frequency threshold varies as a function of a currently perceived threat.

114. A protected object according to claim 113 and wherein said currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

115. A protected object according to any of the preceding claims 109-114 and wherein said oscillator circuit and said circuitry for sensing a change of frequency are operated in accordance with a duty cycle.

116. A protected object according to claim 115 and wherein said duty cycle is variable.

117. A protected object according to claim 116 and wherein said duty cycle is adaptive.

118. A protected object according to claim 117 and wherein said duty cycle varies as a function of a currently perceived threat.

119. A protected object according to claim 118 and wherein said currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

120. A protected object according to any of the preceding claims 109-119 and wherein said frequency threshold varies in accordance with long time scale changes in said characteristic frequency.

121. A protected object according to any of claims 109-120 and wherein said frequency threshold comprises first and second frequency thresholds, respectively above and below said characteristic frequency and which are normally generally equally separated therefrom in the frequency domain.

122. A protected object according to claim 109 and wherein said circuitry for sensing a change of frequency over time provides at least first and second different output indications when said change in frequency of said oscillator circuit over time exceeds respective at least first and second different thresholds.

123. A protected object according to claim 109 and wherein said time threshold is variable.

124. A protected object according to claim 123 and wherein said time threshold varies as a function of a currently perceived threat.

125. A protected object according to claim 124 and wherein said currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

126. A protected object according to any of the preceding claims 109-125 and wherein said oscillator circuit and said circuitry for sensing a time duration are operated in accordance with a duty cycle.

127. A protected object according to claim 126 and wherein said duty cycle is variable.

128. A protected object according to claim 126 and wherein said duty cycle is adaptive.

129. A protected object according to claim 127 and wherein said duty cycle varies as a function of a currently perceived threat.

130. A protected object according to claim 129 and wherein said currently perceived threat is determined by a pattern of past outputs of said circuitry for sensing a change of frequency.

131. A protected object according to any of the preceding claims 109-130 and wherein said given amount remains generally constant notwithstanding long time scale changes in said characteristic frequency.

132. A protected object according to claim 109 and wherein said circuitry for sensing a time duration provides at least first and second different output indications when said time duration exceeds respective at least first and second different thresholds.

133. A protected object according to any of the preceding claims 109-132 and wherein said element is a magnet.

134. A protected object according to claim 133 and wherein said element is an electromagnet.

135. A protected object according to claim 133 and wherein said element is a permanent magnet.

136. A protected object according to any of the preceding claims 109-135 and wherein said circuitry for sensing a change of frequency is a microprocessor which receives an output of said oscillator circuit as a clock input.

137. A protected object according to any of the preceding claims 109-136 and wherein said circuitry for sensing a change of frequency is operative to count oscillator pulses over variable time periods which represent variable sensitivity thresholds.

138. A protected object according to any of the preceding claims 109-137 and wherein said circuitry for sensing a change of frequency comprises a microprocessor which provides said output indication.