Capacitive device and method with an enhanced measurement error correction capability

• US 20080190210A1
• Filed: 02/12/2007
• Published: 08/14/2008
• Est. Priority Date: 02/12/2007
• Status: Active Grant

• Current Assignee: Ypoint Capital, Inc,
• Original Assignee: Loadstar Sensors Incorporated (Ypoint Capital, Inc,)
• Inventors: Harish, Divyasimha, Schultz, John, Lim, Jonathan T., Wong, King
• Granted Patent: US 7,743,667 B2
• Time in Patent Office: Days
• US Class Current: 73/780
• CPC Class Codes: G01L 1/142 using capacitors

Abstract

A capacitive device and method with an enhanced measurement error correction capability is disclosed. In one embodiment, an apparatus includes a sensor capacitor based on one or more pairs of parallel conductor surfaces, a housing to encompass the sensor capacitor, a digitizer module in the housing to generate a digital measurement based on a change in a capacitance of the sensor capacitor when a contact zone of the housing is deflected by a force applied on the contact zone. The apparatus also includes a compensation module of the digitizer module to apply another digital measurement of one or more distortion factors to the digital measurement to minimize an effect of the one or more distortion factors to the apparatus. In addition, the apparatus includes a communication module to communicate an analog signal and/or a digital signal through a wired channel and/or a wireless channel.

Claims

1. An apparatus, comprising:

a sensor capacitor based on at least one pair of parallel conductor surfaces;

a housing to encompass the sensor capacitor;

a digitizer module in the housing to generate a digital measurement based on a change in a capacitance of the sensor capacitor when a contact zone of the housing is deflected by a force applied on the contact zone;

a compensation module of the digitizer module to apply another digital measurement of at least one distortion factor to the digital measurement to minimize an effect of the at least one distortion factor to the apparatus; and

a communication module to communicate at least one of an analog signal and a digital signal through at least one of a wired channel and a wireless channel, wherein the at least one of the analog signal and the digital signal to include at least the change in the capacitance.

2. The apparatus of claim 1, further comprising a reference capacitor having an upper reference surface and a lower reference surface in the housing to compensate an error in the digital measurement based on at least one environmental condition.

3. The apparatus of claim 1, wherein the change in the capacitance of the sensor capacitor is based on a displacement of a distance between an upper sensor surface of the sensor capacitor and a lower sensor surface parallel to the upper sensor surface.

4. The apparatus of claim 1, wherein the change in the capacitance of the sensor capacitor is based on a displacement of an overlap area between an inner conductive area and an outer conductive area parallel to the inner conductive area.

5. The apparatus of claim 1, wherein the change in the capacitance of the sensor capacitor is based on both a displacement of a distance between an upper sensor surface of the sensor capacitor and a lower sensor surface parallel to the upper sensor surface and a displacement of an overlap area between an inner conductive area and an outer conductive area parallel to the inner conductive area.

6. The apparatus of claim 1, further comprising a processor module having a central procession unit (CPU) to execute a set of instructions associated with at least the digitizer module, the compensation module, and the communication module.

7. The apparatus of claim 1, further comprising a wireless communication module of the communication module to wirelessly communicate with an external device based on at least one of a wireless universal serial bus (USB), a Wi-Fi, a Bluetooth, and a Zigbee.

8. The apparatus of claim 1, further comprising a wired communication module of the communication module to communicate with an external device, wherein the at least one of the analog signal and the digital signal to include at least one of a universal serial bus (USB) signal, a voltage signal, a frequency signal, and a current signal.

9. The apparatus of claim 1, further comprising a tilt adaptor surface surrounding the lower sensor surface to minimize the another digital measurement of the at least one distortion factor associated with a tilting effect of the force applied on the contact zone.

10. The apparatus of claim 1, wherein the housing is composed of a low creep material which includes at least one of a 17-4 PH stainless steel, a 15-5 PH stainless steel, and a maraging stainless steel, and wherein at least one printed circuit board in the housing is composed of a plurality of materials including at least one of a flame resistant 4 (FR4), a ceramic, and a glass.

11. The apparatus of claim 1, further comprising a sensor module in the housing to measure a plurality of environmental conditions of the apparatus, wherein the plurality of environmental conditions to include at least one of a temperature, a pressure, a radiation, a humidity, a vibration, and a motion.

12. The apparatus of claim 11, wherein the another digital measurement of the at least one distortion factor is based on at least one of the plurality of environmental conditions.

13. The apparatus of claim 1, further comprising an alarm module associated with the sensor capacitor to generate a sensory data when a parameter of the digital measurement exceeds a threshold value.

14. The apparatus of claim 1, further comprising a capacitance-to-frequency converter module to generate a frequency value based on the change in the capacitance of the sensor capacitor, wherein the frequency value is processed by the digitizer module.

15. The apparatus of claim 1, further comprising a groove surrounding the contact zone to perform at least one of substantially confining a deflection of the contact zone in the groove and adjusting a degree of the deflection of the contact zone.

16. The apparatus of claim 1, further comprising at least one of an upper mounting structure and a lower mounting structure to fasten the housing to an external structure, wherein the at least one of the upper mounting structure and the lower mounting structure to include at least a threaded stud.

17. An apparatus, comprising:

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

a housing having a top plate to encompass the sensor capacitor;

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

at least one guard ring surrounding all sides of the lower sensor surface except a side of the lower sensor surface facing the upper sensor surface to minimize a stray capacitance through equalizing a potential of the lower sensor surface and a potential of the at least one guard ring.

18. A method, comprising:

producing a deflection in a contact zone of a top plate of a housing which encompasses a sensor capacitor having two parallel conductive surfaces when a load is applied on the contact zone;

generating a capacitance data from the sensor capacitor based on a displacement of the two parallel conductive surfaces of the sensor capacitor due to the deflection in the contact zone;

processing a frequency data associated with the capacitance data using a timer module; and

minimizing an effect of an input capacitance intrinsic to an operational amplifier coupled to the timer module by driving a power supply of the operational amplifier such that a potential of the input capacitance is substantially equivalent to a potential of a driving plate of the two parallel conductive surfaces of the sensor capacitor.

19. The method of claim 18, further comprising compensating an error of the capacitance data due to an effect of a plurality of environmental conditions to the housing and to at least one printed circuit board in the housing using a reference capacitor having two parallel conductive surfaces, wherein the plurality of environmental conditions to include at least one of a temperature, a humidity, a pressure and a radiation.

20. The method of claim 19, further comprising bonding a lower one of the at least one printed circuit board (PCB) to a bottom plate of the housing using a thermal bonding adhesive fill such that a distortion of the printed circuit board (PCB) due to the plurality of environmental conditions is minimized.

21. The method of claim 19, further comprising fastening the at least one printed circuit board (PCB) to an inner surface of the housing with a connector made of a same material as the housing such that a change in a displacement of a distance between the two parallel conductive surfaces of the sensor capacitor due to the temperature is equivalent to a displacement of a distance between to two parallel conductive surfaces of the reference capacitor.

22. The method of claim 18 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 18.