Capacitive Touchscreen Water Detection via Dual-Mode Sensing
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Solution Overview
Problem
Capacitive touchscreen panels face challenges in accurately distinguishing between user touches and water presence, as both can alter capacitance readings, leading to false detections and reduced reliability in multi-touch scenarios.
Innovation Solution
A method involving mutual and self-capacitance touch detection, using fixed and randomized node selection windows to determine touch status, which compares touch strengths across different node configurations to differentiate between intended touches and water presence, employing a touch status truth table for accurate classification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive sensing is used to detect user touches, then touch detection capability is improved, but water presence causes false detections reducing reliability
Solution Approach 1:
The patent segments the detection process into three distinct phases: mutual capacitance detection, self-capacitance detection, and touch status determination. Each phase uses different node selection strategies (fixed windows for mutual, randomized windows for self-capacitance reference nodes) to gather different types of capacitance data that, when combined, enable reliable differentiation between touches and water presence
Solution Approach 2:
The patent changes the detection parameters dynamically by switching between mutual capacitance mode and self-capacitance mode with different node selection windows. The reference node selection window uses randomized node selection while the peak node selection window uses fixed node selection, and these parameter changes enable the system to distinguish between water and touches based on their different capacitance signatures
2Measurement precision
If randomized node selection is used for water detection, then water detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent makes the capacitive sensing panel universal by enabling it to perform multiple functions: mutual capacitance touch detection, self-capacitance touch detection, and water detection. The same hardware infrastructure (conductive features, controller) is used for all three functions by changing the operational mode and node selection strategy, avoiding the need for separate dedicated water detection hardware
Solution Approach 2:
The patent introduces dynamics into the node selection process by using randomized node selection for the reference window in self-capacitance mode. This dynamic approach allows the system to adapt to different detection scenarios and improves water detection accuracy by varying which nodes are used as references, rather than using a fixed static selection
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
Enhances the accuracy of touch detection by effectively differentiating between user inputs and water, improving the reliability of multi-touch recognition while maintaining high resolution and rejecting unwanted water interference.
Implementation Method 1
The capacitive sensing panel may evaluate changes in capacitance at each capacitive node to detect a user touch or hover
Data Source
AI summary
A system and method for multi-touch integrity sensing for a multi-touch capacitive touch screen determines a distinction between wanted touches, such as via a finger or stylus, and unwanted touches such as via foreign matter, errors, and the like. Mutual capacitance and self-capacitance sensing data is collected and processed to identify reference strengths and detection thresholds. If differences between mutual/self-capacitance strength and the corresponding reference strengths exceed the corresponding detection thresholds, then the touch is classified as an unwanted (for example, water) touch.