Automatically balanced sensing device and method for multiple capacitive sensors

• US 8,816,704 B1
• Filed: 10/21/2011
• Issued: 08/26/2014
• Est. Priority Date: 04/01/2005
• Status: Expired due to Fees

• Current Assignee: Monterey Research, LLC (Vector Capital Corporation)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Seguine, Dennis
• Primary Examiner(s): NATALINI, JEFF WILLIAM
• Application Number:
  US13/278,478
• Time in Patent Office: 1,040 Days
• Field of Search: 324/679
• US Class Current: 324/679
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G01R 35/00 Testing or calibrating of apparatus covered by the other groups of this subclass
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing

Abstract

A method includes generating a correction value for a capacitive sensor based on a difference between a capacitance of the capacitive sensor and a capacitance of at least one other capacitive sensor when an input to the capacitive sensor and the at least one other capacitive sensor is absent. The method further includes generating a compensated capacitance value for the capacitive sensor based on applying the correction value to a difference between the capacitance of the capacitive sensor when the input is absent and another capacitance of the capacitive sensor.

Claims

1. A method comprising:

generating a correction value for a capacitive sensor based on a difference between a capacitance of the capacitive sensor and a capacitance of at least one other capacitive sensor when an input to the capacitive sensor and the at least one other capacitive sensor is absent; and

calculating a compensated capacitance value for the capacitive sensor based on applying the correction value to a difference between the capacitance of the capacitive sensor when the input is absent and another capacitance of the measured from the capacitive sensor.

2. The method of claim 1, wherein the generating of the correction value includes determining the difference in capacitance between the capacitive sensor and the at least one other capacitive sensor when the input to the capacitive sensor is absent.

3. The method of claim 1, wherein the generating of the compensated capacitance value includes determining the difference between the capacitance of the capacitive sensor when the input is absent and the other capacitance measured from the capacitive sensor.

4. The method of claim 1, wherein the capacitance of the capacitive sensor when the input is absent is a first baseline capacitance value and the capacitance of the at least one other capacitive sensor when the input is absent is a second baseline capacitance value.

5. The method of claim 4, wherein the generating of the correction value for the capacitive sensor includes using an average baseline capacitance value of the first baseline capacitance value and the second baseline capacitance value.

6. The method of claim 4, wherein the generating of the correction value for the capacitive sensor includes determining a maximum baseline capacitance value from a set of baseline capacitance values including both the first baseline capacitance value and the second baseline capacitance value.

7. The method of claim 6, wherein the generating of the correction value for the capacitive sensor further includes dividing the determined maximum baseline capacitance value by the first baseline capacitance value of the capacitive sensor.

8. The method of claim 4, wherein the other capacitance of the capacitive sensor includes a run-time capacitance value, and the generating of the compensated capacitance value comprises:

determining the difference through subtracting the run-time capacitance value from the baseline capacitance value, and multiplying the difference by the generated correction value.

9. The method of claim 8, further comprising comparing the compensated capacitance value to a predetermined threshold value to determine if the input to the capacitive sensor is present.

10. The method of claim 9, further comprising calculating, using the compensated capacitance value, a centroid value that reflects that the input to the capacitive sensor is present.

11. The method of claim 10, further comprising determining a position of a switch by comparing the calculated centroid value to a predetermined position value.