Gap-change sensing through capacitive techniques

• US 7,451,659 B2
• Filed: 09/28/2005
• Issued: 11/18/2008
• Est. Priority Date: 09/29/2004
• Status: Active Grant

• Current Assignee: Ypoint Capital, Inc,
• Original Assignee: Loadstar Sensors Incorporated (Ypoint Capital, Inc,)
• Inventors: Harish, Divyasimha, Dallenbach, William D.
• Primary Examiner(s): Lefkowitz; Edward
• Assistant Examiner(s): Kirkland, III; Freddie
• Application Number:
  US11/237,060
• Publication Number:
  US 20060065973A1
• Time in Patent Office: 1,147 Days
• Field of Search: 737/18, 737/77, 737/80, 738/626.25, 738/626.26
• US Class Current: 73/780
• CPC Class Codes: G01B 7/22 using change in capacitance
• CPC Class Codes: G01G 23/3735 using a digital network
• CPC Class Codes: G01G 7/06 by electrostatic action
• CPC Class Codes: G01L 1/142 using capacitors

Abstract

A gap-change sensing through capacitive techniques is disclosed. In one embodiment, an apparatus includes a first conductive surface and a second conductive surface substantially parallel to the first conductive surface, and a sensor to generate a measurement based on a change in a distance between the first conductive surface and the second conductive surface. The change in the distance may be caused by a deflection of the first conductive surface with respect to the second conductive surface, and the deflection may be a compressive force and/or an expansive force. The sensor may apply an algorithm that converts a change in capacitance to at least one of a change in voltage and/or a change in frequency to generate the measurement. The change in the distance may be caused by a load applied to the surface above the first conductive surface with respect to the second conductive surface.

Claims

1. An apparatus, comprising:

a first conductive surface and a second conductive surface substantially parallel to the first conductive surface;

a sensor to generate a measurement based on a change in a distance between the first conductive surface and the second conductive surface; and

a reference capacitor having a shielding spacer between the reference capacitor and a bottom of the apparatus to minimize an effect of a stray capacitance affecting the measurement to enable the sensor to adjust the measurement based on at least one environmental condition.

2. The apparatus of claim 1 wherein the change in the distance is caused by a deflection of the first conductive surface with respect to the second conductive surface;

and wherein the deflection is at least one of a compressive force and an expansive force.

3. The apparatus of claim 1 wherein the change in the distance is caused by a change in thickness of at least one spacer between the first conductive surface and the second conductive surface.

4. The apparatus of claim 1 wherein the sensor applies an algorithm that converts a change in capacitance to at least one of a change in voltage and a change in frequency to generate the measurement.

5. The apparatus of claim 4 wherein the measurement is of a force applied to a surface above the first conductive surface with respect to the second conductive surface.

6. The apparatus of claim 5 wherein the change in the distance is caused by a load applied to the surface above the first conductive surface with respect to the second conductive surface.

7. The apparatus of claim 6 wherein the first conductive surface and the second conductive surface form a sensor capacitor, and wherein a change in capacitance of the sensor capacitor is inversely proportional to the change in the distance between the first conductive surface and the second conductive surface.

8. The apparatus of claim 1 wherein the at least one environmental condition is humidity in a gap between the first conductive surface and the second conductive surface, a temperature of the apparatus, and an air pressure of an environment surrounding the apparatus, and wherein a height of the shielding spacer is at least ten times larger than a plate spacer between plates of the reference capacitor and between plates of the sensor capacitor.

9. The apparatus of claim 1 wherein the first conductive surface and the second conductive surface are fabricated in a geometric shape, comprising at least one of a rectangular shape, an oval shape, and a shape having sides that are not all the same length.

10. An apparatus of claim 1 wherein the first conductive surface and the second conductive surface are painted on a plurality of nonconductive printed circuit boards forming the apparatus.

11. An apparatus, comprising:

a reference capacitor whose capacitance changes based on an environmental condition surrounding the apparatus;

a sensor capacitor whose capacitance changes based on a deflection of at least one plate forming the sensor capacitor and the environmental condition;

a circuit to generate a measurement after removing an effect of the environmental condition from a capacitance of the sensor capacitor; and

a housing that encompasses the reference capacitor, the sensor capacitor, and the circuit, and wherein the at least one plate experiencing the deflection is integrated in the housing, wherein the housing is formed by a plurality of metal plates that are each laser etched and bonded together to create the housing.

12. The apparatus of claim 11 wherein the housing is formed by a single metal block that is milled to form the housing.

13. The apparatus of claim 11 wherein the deflection of the at least one plate forming the sensor capacitor is caused by a load applied to the housing;

and wherein the measurement is of a force applied to the housing.

14. The apparatus of claim 13 further comprising a shielding spacer between the reference capacitor and a bottom of the housing to minimize an effect of a stray capacitance affecting the measurement, wherein a height of the shielding spacer is at least ten times larger than a plate spacer between plates of the reference capacitor and between plates of the sensor capacitor.

15. The apparatus of claim 11 wherein an area of each plate forming the reference capacitor is at least ten times larger than an area of each plate forming the sensor capacitor to reduce the amount of amplification required in generating the measurement.

16. The apparatus of claim 11 wherein the circuit includes a wireless transmitter and a wireless receiver and wherein the apparatus communicates through a network with a data processing system that analyzes data generated by various operation of the apparatus.

17. A method, comprising:

automatically generating a measurement based on a change in a distance between a first conductive surface and a second conductive surface forming a variable capacitor;

communicating the measurement to a data processing system associated with the variable capacitor; and

adjusting the measurement based on at least one environmental condition by analyzing data of a reference capacitor having a shielding spacer between the reference capacitor and a bottom of a housing to minimize an effect of a stray capacitance affecting the measurement.

18. The method of claim 17 wherein the change in the distance is caused by a deflection of the first conductive surface with respect to the second conductive surface, wherein the deflection is at least one of a compressive force and an expansive force, and, wherein a height of the shielding spacer is larger than a plate spacer between plates of the reference capacitor and between plates of the variable capacitor.

19. The method of claim 17 wherein the change in the distance is caused by a change in thickness of at least one spacer between the first conductive surface and the second conductive surface.

20. The method of claim 17 further comprising applying an algorithm that converts a change in capacitance to at least one of a change in voltage and a change in frequency to generate the measurement, and wherein the measurement is of a force applied to a surface above the first conductive surface with respect to the second conductive surface.

21. The method of claim 20 wherein the change in the distance is caused by a load applied to the surface above the first conductive surface with respect to the second conductive surface.

22. The method of claim 21 wherein a change in capacitance of the variable capacitor is inversely proportional to the change in the distance between the first conductive surface and the second conductive surface.

23. The method of claim 17 wherein the at least one environmental condition is humidity in a gap between the first conductive surface and the second conductive surface, a temperature of the variable capacitor, and an air pressure of an environment surrounding the variable capacitor.

24. The method of claim 23 further comprising fabricating the variable capacitor and the reference capacitor in a geometric shape, comprising at least one of a rectangular shape, an oval shape, and a shape having sides that are not all the same length.

25. An method of claim 17 further comprising painting the first conductive surface and the second conductive surface on a plurality of nonconductive printed circuit boards.

26. A method of claim 17 in a form of a machine-readable medium embodying a set of instructions that, when executed by a machine, cause the machine to perform a method comprising

automatically generating a measurement based on a change in a distance between a first conductive surface and a second conductive surface forming a variable capacitor;

communicating the measurement to a data processing system associated with the variable capacitor; and

adjusting the measurement based on at least one environmental condition by analyzing data of a reference capacitor having a shielding spacer between the reference capacitor and a bottom of a housing to minimize an effect of a stray capacitance affecting the measurement.

27. An apparatus, comprising:

a reference capacitor whose capacitance changes based on an environmental condition surrounding the apparatus;

a sensor capacitor whose capacitance changes based on a deflection of at least one plate forming the sensor capacitor and the environmental condition;

a circuit to generate a measurement after removing an effect of the environmental condition from a capacitance of the sensor capacitor; and

a shielding spacer between the reference capacitor and a bottom of the housing to minimize an effect of a stray capacitance affecting the measurement, wherein a height of the shielding spacer is at least ten times larger than a plate spacer between plates of the reference capacitor and between plates of the sensor capacitor.

28. The apparatus of claim 27 further comprising a housing that encompasses the reference capacitor, the sensor capacitor, and the circuit, and wherein the at least one plate experiencing the deflection is integrated in the housing.

29. The apparatus of claim 28 wherein the housing is formed by a plurality of metal plates that are each laser etched and bonded together to create the housing.

30. The apparatus of claim 28 wherein the housing is formed by a single metal block that is milled to form the housing.

31. The apparatus of claim 28 wherein the deflection of the at least one plate forming the sensor capacitor is caused by a load applied to the housing;

and wherein the measurement is of a force applied to the housing.

32. The apparatus of claim 28 wherein an area of each plate forming the reference capacitor is at least ten times larger than an area of each plate forming the sensor capacitor to reduce the amount of amplification required in generating the measurement.

33. The apparatus of claim 28 wherein the circuit includes a wireless transmitter and a wireless receiver and wherein the apparatus communicates through a network with a data processing system that analyzes data generated by various operation of the apparatus.