Automatic environmental compensation of capacitance based proximity sensors
First Claim
1. A method of operating a capacitive sensor assembly comprising at least one capacitive sensor element and a capacitance-to-digital converter (CDC) that supplies output codes corresponding to sensor element capacitance, comprising acts of:
- a. determining an ambient value of the CDC output codes;
b. modifying at least one threshold value in response to changes in said ambient value; and
c. detecting proximity of a ground mass to the sensor element and preventing the modification of threshold values while said proximity is detected.
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Accused Products
Abstract
Improved capacitive sensor operation is achieved with improved discrimination between environmental drift and apparent drift attributable to human proximity to the sensor. A proximity algorithm detects conditions interpreted as indicating a user is close to, but not touching, a sensor. When such proximity is detected, ambient value calibration is halted, thereby avoiding treating the human'"'"'s proximity as environmental drift requiring compensation and preventing miscalculation of calibration. The proximity algorithm employs two moving-average filters (implemented in hardware or software) to monitor the CDC output values over time and to make appropriate adjustments to a signal representing the ambient, while distinguishing environmental drift from proximity-induced pseudo-drift. Accurate ambient values allow for improved proximity detection by providing this environmentally compensated average value to an adaptive threshold algorithm which features a fast attack, slow decay peak detection to automatically track and compensate for different response characteristics (typically finger sizes).
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Citations
28 Claims
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1. A method of operating a capacitive sensor assembly comprising at least one capacitive sensor element and a capacitance-to-digital converter (CDC) that supplies output codes corresponding to sensor element capacitance, comprising acts of:
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a. determining an ambient value of the CDC output codes;
b. modifying at least one threshold value in response to changes in said ambient value; and
c. detecting proximity of a ground mass to the sensor element and preventing the modification of threshold values while said proximity is detected. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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- 9. A method of operating a capacitive sensor assembly comprising at least one capacitive sensor element and a capacitance-to-digital converter (CDC) that supplies output codes corresponding to sensor element capacitance, comprising using a proximity algorithm to detect conditions which are interpreted as indicating a user is close to, but not touching, a sensor element and then halting ambient value calibration while said condition or conditions persist.
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12. A method of operating a capacitive sensor assembly having at least one capacitive sensor element and a capacitance-to-digital converter (CDC) that supplies output codes corresponding to sensor element capacitance, comprising:
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a. performing an ambient value calibration of the CDC output;
b. using a proximity algorithm, processing the CDC output to detect a condition or conditions interpreted as indicating a user is close to, but not touching, a sensor element; and
c. halting ambient value calibration of the CDC output when the proximity algorithm indicates said condition or conditions persist;
d. the proximity algorithm employing first and second moving average filters to monitor the CDC output values over time and to detect said condition or conditions. - View Dependent Claims (13)
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14. A method of operating a capacitive sensor assembly having at least one capacitive sensor element and a capacitance-to-digital converter (CDC) that supplies output codes corresponding to sensor element capacitance, comprising:
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a. using a multi-step proximity algorithm, detecting from output of the CDC a condition or conditions indicative of a user being close to, but not touching, a sensor element; and
b. halting ambient value calibration of the sensor assembly while said condition or conditions persist;
wherein the proximity algorithm employs at least a first step and a second step and said first step and said second step apply different criteria directly or indirectly to the CDC output, to distinguish environmental drift from proximity induced pseudo-drift. - View Dependent Claims (15)
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16. A calibration assembly for use with a capacitive sensor assembly having at least one capacitive sensor element and a capacitance-to-digital converter (CDC) that supplies output codes corresponding to sensor element capacitance, comprising a processor executing one or more sequences of program instructions to:
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a. determine an ambient value of the CDC output codes;
b. modify at least one threshold value in response to changes in said ambient value; and
c. detect proximity of a ground mass to the sensor element and prevent the modification of threshold values while said proximity is detected. - View Dependent Claims (17, 18, 19, 28)
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- 20. A calibration assembly for use with a capacitive sensor assembly having at least one capacitive sensor element and a capacitance-to-digital converter (CDC) that supplies output codes corresponding to sensor element capacitance, comprising a processor executing instructions to perform a proximity algorithm to detect conditions which are interpreted as indicating a user is close to, but not touching, a sensor element and then halting ambient value calibration while said condition or conditions persist.
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23. A calibration assembly for a capacitive sensor assembly having at least one capacitive sensor element and a capacitance-to-digital converter (CDC) that supplies output codes corresponding to sensor element capacitance, comprising a processor executing instructions to:
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a. perform an ambient value calibration of the CDC output;
b. use a proximity algorithm to processing the CDC output to detect a condition or conditions indicating a user is close to, but not touching, a sensor element; and
c. halt ambient value calibration of the CDC output when the proximity algorithm indicates said condition or conditions persist;
d. the proximity algorithm employing first and second moving average filters to monitor the CDC output values over time and to detect said condition or conditions. - View Dependent Claims (24)
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25. A calibration assembly for a capacitive sensor assembly having at least one capacitive sensor element and a capacitance-to-digital converter (CDC) that supplies output codes corresponding to sensor element capacitance, comprising a processor adapted to:
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a. use a multi-step proximity algorithm to detect from output of the CDC a condition or conditions indicative of a user being close to, but not touching, a sensor element; and
b. halt ambient value calibration of the sensor assembly while said condition or conditions persist;
wherein the proximity algorithm employs at least a first step and a second step and said first step and said second step apply different criteria directly or indirectly to the CDC output, to distinguish environmental drift from proximity-induced pseudo-drift. - View Dependent Claims (26, 27)
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Specification