Capacitive Sensor Array Differential Measurement for Precision Positioning
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Solution Overview
Problem
Conventional capacitive sensor systems face challenges with low resolution and accuracy due to variations in physical properties like temperature changes, requiring additional hardware for current compensation which increases costs and slows down scanning.
Innovation Solution
The system employs differential capacitance measurements between adjacent or distant rows and columns to determine object location, eliminating the need for current compensation circuitry and enhancing resolution by focusing on capacitance differences rather than absolute values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current compensation is used to center the measurement window and avoid low resolution, then measurement precision is improved, but device complexity increases due to extra hardware requirements
Solution Approach 1:
The patent extracts and eliminates the current compensation circuitry from the measurement system. By using differential capacitance measurements between adjacent rows or columns, the system removes the need for complex current source hardware that was previously required to center the measurement window and compensate for baseline capacitance variations.
Solution Approach 2:
The differential measurement approach enables the system to self-center the measurement window automatically. By measuring the difference in capacitance between adjacent elements, the system inherently centers measurements around zero differential capacitance, eliminating the need for external current compensation circuits to perform this function.
2Measurement precision
If current compensation is implemented to improve measurement accuracy, then measurement precision is improved, but productivity decreases due to additional operations and settling times
Solution Approach 1:
The patent removes the current compensation operations from the measurement process. By directly measuring differential capacitance between adjacent rows or columns, the system eliminates the additional settling times and operations required for current source compensation, thereby increasing scanning speed and productivity.
3Loss of information
If absolute capacitance values are measured, then the full capacitance range is captured, but measurement precision decreases due to low resolution in the measurement range
Solution Approach 1:
The patent changes the measurement parameter from absolute capacitance values to differential capacitance values. By measuring the difference in capacitance between adjacent rows or columns, the system transforms the measurement range to be centered around zero, which maximizes the resolution and precision of the measurement system while still capturing the full range of capacitance variations.
4Area of stationary object
If sequential scanning of rows and columns is performed, then complete array coverage is achieved, but measurement precision decreases due to susceptibility to physical property variations
Solution Approach 1:
The patent segments the measurement approach by comparing adjacent rows or columns rather than measuring each intersection independently. This segmentation allows differential measurements that are immune to common-mode variations affecting the entire array, such as temperature changes or dielectric variations, thereby improving position accuracy while maintaining complete array coverage.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in more precise and frequent scans, reducing measurement requirements and eliminating the necessity for current compensation, leading to improved accuracy and faster scanning capabilities.
Implementation Method 1
The current, based on the change of the capacitance at the intersection of a row and a column of the array, which varies depending on the presence or absence of a touch
Data Source
AI summary
A system and method for determining position information. The method includes selecting a column, a first row, and a second row of a capacitive sensor array. The first row and second row intersect with the column of the capacitive sensor array. The method further includes measuring a differential capacitance between the first row and the second row and utilizing the differential capacitance in determining a location of an object proximate to the capacitive sensor array.