Area-change sensing through capacitive techniques

• US 20060066319A1
• Filed: 09/28/2005
• Published: 03/30/2006
• 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
• Granted Patent: US 7,187,185 B2
• Time in Patent Office: Days
• US Class Current: 324/662
• CPC Class Codes: G01D 5/2412 by varying overlap
• CPC Class Codes: G01G 7/06 by electrostatic action
• CPC Class Codes: G01L 1/142 using capacitors

Abstract

An area-change sensing through capacitive techniques is disclosed. In one embodiment, a first conductive surface is substantially parallel to a second conductive surface. The first conductive surface may be moveable relative to the second conductive surface in a direction substantially parallel to the second conductive surface. A processing module may detect an overlap area between the first conductive surface and the second conductive surface. In addition, a reference surface may be substantially parallel to the first conductive surface and the second conductive surface. The processing module may be configured to measure a reference capacitance between the reference surface and a selected surface of the first conductive surface and the second conductive surface. The processing module may apply an algorithm that considers the reference capacitance and converts a change in capacitance between the first conductive surface and the second conductive surface to at least one of a voltage response and a frequency response to determine the measurement.

Claims

1. An apparatus comprising:

a first conductive surface substantially parallel to a second conductive surface and moveable relative to the second conductive surface in a direction substantially parallel to the second conductive surface; and

a processing module to detect an overlap area between the first conductive surface and the second conductive surface and to generate a measurement based on a position of the first conductive surface relative to the second conductive surface.

2. The apparatus of claim 1 further comprising a reference surface substantially parallel to the first conductive surface and the second conductive surface, the reference surface coupled to at least one of the first conductive surface and the second conductive surface.

3. The apparatus of claim 2 wherein the processing module is configured to measure a reference capacitance between the reference surface and a selected surface of the first conductive surface and the second conductive surface.

4. The apparatus of claim 3 wherein the processing module applies an algorithm that considers the reference capacitance and converts a change in capacitance between the first conductive surface and the second conductive surface to at least one of a voltage response and a frequency response to determine the measurement.

5. The apparatus of claim 1 wherein a movement is caused by a load applied to a layer adjacent to the first conductive surface.

6. The apparatus of claim 1 wherein the first conductive surface and the second conductive surface form a sensor capacitor, and wherein a capacitance of the sensor capacitor corresponds to the area overlapping the first conductive surface and the second conductive surface.

7. The apparatus of claim 1 further comprising a reference capacitor associated with the apparatus to enable the processing module to adjust the capacitance based on at least one environmental condition.

8. The apparatus of claim 7 wherein the at least one environmental condition is selected from the group comprising a 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.

9. The apparatus of claim 1 wherein the first conductive surface and the second conductive surface are coaxial.

10. The apparatus of claim 9 wherein the first conductive surface and the second conductive surface have a substantially similar cross-sectional shape.

11. The apparatus of claim 10 wherein the substantially similar cross-sectional shape corresponds to a shape selected from the group comprising a circle, a square, an ellipse, a rectangle, a rounded rectangle, a pentagon, a hexagon, and an octagon.

12. The apparatus of claim 1 further comprising at least one spacer to movably separate the first conductive surface from the second conductive surface.

13. An apparatus, comprising:

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

a variable capacitor whose capacitance changes based on the environmental condition and a change in an overlap area of a first conductive plate and a second conductive plate forming the variable capacitor; and

a processing module to generate a measurement after removing an effect of the environmental condition from a capacitance of the variable capacitor.

14. The apparatus of claim 13 further comprising at least one spacer to movably separate the first conductive plate from the second conductive plate, wherein the first conductive plate is substantially parallel to the second conductive plate, and wherein the first conductive plate is moveable relative to the second conductive plate in a direction substantially parallel to the second conductive plate.

15. The apparatus of claim 13 wherein the processing module includes a wireless transmitter to communicate through a network with a data processing system that analyzes data generated by various operations of the processing module.

16. The apparatus of claim 13 further comprising a housing that encompasses the reference capacitor, the variable capacitor, and the processing module, and wherein the first conductive plate is integrated in the housing.

17. The apparatus of claim 16 wherein the housing is formed by a plurality of metal plates that are each laser etched and bonded together to create the housing.

18. The apparatus of claim 16 wherein the housing is formed by a single metal block that is milled to form the housing.

19. The apparatus of claim 16 wherein the change in the overlap area is caused by a load applied to the housing, wherein the measurement is of a force applied to the housing, and wherein the force is at least one of a compressive force and an expansive force.

20. The apparatus of claim 16 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.

21. The apparatus of claim 13 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 to generate the measurement.

22. A method, comprising:

automatically generating a measurement based on a change in an overlap area of a first conductive surface and a second conductive surface of a variable capacitor, the first conductive surface substantially parallel to the second conductive surface, the first conductive surface moveable relative to the second conductive surface in a direction substantially parallel with the second conductive surface; and

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

23. The method of claim 22 further comprising applying an algorithm that converts a change in capacitance to at least one of a voltage response and a frequency response to automatically generate the measurement.

24. The method of claim 22 wherein a capacitance between the first conductive surface and the second conductive surface corresponds to the overlap area of the first conductive surface and the second conductive surface.

25. The method of claim 22 further comprising adjusting the measurement based on at least one environmental condition by analyzing data of a reference capacitor, 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.

26. The method of claim 22 wherein a change in capacitance of the variable capacitor is proportional to the change in the overlap area between the first conductive surface and the second conductive surface when a load is applied to the first conductive surface.

27. The method of claim 26 further comprising fabricating the variable capacitor and the reference capacitor in any geometric shape, including a rectangular shape, an oval shape, and a shape having sides that are not all the same length.

28. The method of claim 22 further comprising wirelessly communicating the measurement through a network with a data processing system that analyzes data generated by various operations of the variable capacitor.

29. The method of claim 22 further comprising forming the first conductive surface and the second conductive surface on a plurality of nonconductive printed circuit boards.

30. The method of claim 22 in a form of a machine-readable medium embodying a set of instructions that, when executed by a machine, cause the machine to perform the method of claim 22.