Touch-Gated Capacitive Displacement Sensing for Accurate Press Detection
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Solution Overview
Problem
Capacitive sensing techniques face challenges in accurately determining displacement due to interference from surrounding objects, making it difficult to distinguish actual displacement from changes caused by other factors such as a user's hand or the device's position.
Innovation Solution
A sensing apparatus that combines displacement sensing and touch sensing using capacitive techniques, where the processing circuitry uses the output from the touch sensor to establish a baseline for the displacement sensor, allowing a displacement to be detected only when an object is touching the displacement element, thereby reducing interference and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If capacitive sensing techniques are used to measure displacement, then touch-sensitive input functionality is achieved, but surrounding objects interfere with capacitance measurements making it difficult to determine actual displacement
Solution Approach 1:
The sensing system is divided into two separate sensor types: a capacitive touch sensor for detecting touch input and a displacement sensor (using different measurement principles) for measuring physical displacement. This segmentation allows each sensor to perform its specialized function without interference from surrounding objects affecting the other's measurements.
Solution Approach 2:
A processor acts as an intermediary that receives signals from both the capacitive touch sensor and the displacement sensor. It correlates the touch detection signal with the displacement measurement signal to determine when a press action has occurred, filtering out false readings caused by surrounding objects.
2Device complexity
If capacitive sensing is used for both touch and displacement sensing, then consistent sensing technology is adopted, but it is difficult to distinguish actual displacement from changes caused by surrounding objects
Solution Approach 1:
The system uses two different sensing technologies: capacitive sensing for touch detection and a separate displacement sensing mechanism (such as optical or mechanical) for measuring physical displacement. This segmentation allows accurate displacement measurement independent of surrounding objects while maintaining capacitive sensing for touch functionality.
Solution Approach 2:
The processor continuously monitors both capacitive touch signals and displacement sensor signals, using feedback from the touch sensor to validate displacement measurements. Only displacement changes that coincide with validated touch events are registered as actual press actions.
3Speed
If baseline displacement sensor output signal is determined continuously, then displacement detection is responsive, but false displacement detection occurs when objects are not touching the displacement element
Solution Approach 1:
The system first detects a touch event using the capacitive touch sensor before validating any displacement measurement. This preliminary touch detection acts as a gatekeeper, ensuring that only displacement measurements occurring during confirmed touch events are processed, preventing false detections when no object is touching the displacement element.
Solution Approach 2:
The processor uses feedback from the capacitive touch sensor to validate displacement measurements in real-time. The touch sensor provides continuous feedback about object presence, which is correlated with displacement sensor output to confirm whether a measured displacement represents a genuine press action or spurious movement.
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 enhances the precision and responsiveness of displacement detection, reducing sluggish responses and improving user experience by accurately determining when a displacement occurs and when it ceases, aligning with the intended action.
Implementation Method 1
measure a change in capacitive coupling between them
Implementation Method 2
capacitive sensing techniques
Data Source
AI summary
A sensing apparatus comprising: a displacement sensor comprising capacitance measurement circuitry configured to provide a displacement sensor output signal indicative of a separation between a frame element and a displacement element movably mounted with respect to the frame element; a touch sensor comprising measurement circuitry configured to provide a touch sensor output signal indicative of when an object is determined to be touching the displacement element; and a processing element configured to output a displacement detection signal to indicate there is determined to be a displacement of the displacement element relative to the frame element in response to determining the touch sensor output signal indicates an object is touching the displacement element and a difference between the displacement sensor output signal and a baseline displacement sensor output signal exceeds a threshold value, wherein the baseline displacement sensor output signal is determined from the displacement sensor output signal in a time period determined from when the touch sensor output signal initially indicates the object is touching the displacement element.