Cylindrical capacitive force sensing device and method

• US 20070205776A1
• Filed: 03/01/2006
• Published: 09/06/2007
• Est. Priority Date: 03/01/2006
• Status: Active Grant

• Current Assignee: Ypoint Capital, Inc,
• Original Assignee: Loadstar Sensors Incorporated (Ypoint Capital, Inc,)
• Inventors: Harish, Divyasimha, Dallenbach, William D., Schultz, John, Wong, King
• Granted Patent: US 7,570,065 B2
• Time in Patent Office: Days
• US Class Current: 324/662
• 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

Cylindrical capacitance force sensing device/method is disclosed. In one embodiment, an apparatus includes a capacitor having two parallel conductive surfaces, a cylindrical housing with a cover plate to encompass the capacitor, and a sensor in the cylindrical housing to generate a measurement based on a change in a distance between the two conductive surfaces when the cover plate is deflected by a load applied on the cover plate. In another embodiment, a method may include applying a load on top of a housing which encompasses a capacitive sensor having two parallel conductive surfaces to produce a deflection of a cover plate of the housing, automatically generating a measurement from the capacitive sensor when a distance between the two parallel conductive surfaces is charged due to the deflection of the cover plate, and decreasing an error in the measurement via stabilizing to a mounting surface.

Claims

1. An apparatus, comprising:

a capacitor having an upper conductive surface and a lower conductive surface parallel to the upper conductive surface;

a cylindrical housing with a cover plate to encompass the capacitor; and

a sensor in the cylindrical housing to generate a measurement based on a change in a distance between the upper conductive surface and the lower conductive surface when the cover plate is deflected by a load applied on the cover plate.

2. The apparatus of claim 1 wherein the cylindrical housing encompasses a reference capacitor to compensate an error in the measurement based on an environmental condition.

3. The apparatus of claim 1 further comprising coupling a plurality of support bases to a bottom surface of the cylindrical housing.

4. The apparatus of claim 3 wherein a shape of one end of the plurality of support bases contacting a mounting surface is designed to optimize a contact between the cylindrical housing and the mounting surface when the plurality of support bases are affixed on the mounting surface.

5. The apparatus of claim 4 wherein the shape is at least one of a convex shape and a saw blade shape.

6. The apparatus of claim 3 wherein three support bases are coupled to the cylindrical housing.

9. The apparatus of claim 1 further comprising placing a modular spacer between the cover plate and the upper conductive surface to provide a gap between the upper conductive surface and the lower conductive surface and to buffer an effect of the load on the upper conductive surface.

10. The apparatus of claim 1 further comprising coupling a top nut affixed on a center of the cover plate and a support structure associated with the load fastened to an upper inner chamber of the top nut using an upper fastener, wherein the cover plate, a modular spacer and the upper conductive surface are fastened to a lower inner chamber of the top nut using a lower fastener.

11. The apparatus of claim 1 further comprising a layered printed circuit board associated with the sensor, wherein the layered printed circuit board includes a ground plane layer, a power plane layer, and at least one signaling layer having a circuit which generates the measurement and a USB circuit which provides a hardware interface encased by the ground plane layer and the power plane layer.

12. The apparatus of claim 11 wherein the at least one signaling layer further includes a circuit to wirelessly communicate the measurement with a data processing system.

13. The apparatus of claim 1 wherein the cylindrical housing is made of at least one of a conductive material and a non conductive material to isolate any electronic module in the cylindrical housing from an external electromagnetic noise.

7. The apparatus of claim I further comprising forming a groove on at least one side of the cover plate to substantially confine a deflection of the cover plate in the groove.

8. The apparatus of claim 7 wherein a depth and a width of the groove is mathematically engineered to configure a sensitivity of the deflection of the cover plate.

14. A method, comprising:

applying a load on top of a housing which encompasses a capacitive sensor having two parallel conductive surfaces to produce a deflection of a cover plate of the housing;

automatically generating a measurement from the capacitive sensor when a distance between the two parallel conductive surfaces is changed due to the deflection of the cover plate; and

decreasing an error in the measurement via stabilizing the housing to a mounting surface.

15. The method of claim 14 further comprising changing a thickness of a modular spacer placed between the cover plate of the housing and an upper conductive surface of the two parallel conductive surfaces to set up the distance between the two parallel conductive plates.

16. The method of claim 15 further comprising forming a groove on any side of the cover plate to confine the deflection of the cover plate due to the load in the groove, wherein a depth and a width of the groove is mathematically calibrated to configure a rate of the deflection.

17. The method of claim 14 further comprising masking at least one signaling layer of a layered printed circuit board associated with the capacitive sensor between a power plane layer and a ground plane layer to reduce an external electromagnetic noise.

18. The method of claim 17 further comprising the at least one signaling layer to include a circuit to communicate an alarm signal when the load exceeds a threshold value.

19. The method of claim 17 further comprising varying a size of a cylindrical object protruding from a bottom surface of a top nut coupled to a cover plate to configure a deflection rate of the cover plate.

20. The method of claim 14 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 14.