Capacitive Measurement Device with Electrode Switching for Ghost Measurement Reduction
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Solution Overview
Problem
Existing capacitive touch-sensitive and contactless human-machine interfaces face challenges with large leakage capacitances and interconnection issues, leading to reduced sensitivity and ghost measurements, especially when detecting multiple objects or large surfaces.
Innovation Solution
A capacitive measurement device with a single detection surface featuring a matrix of capacitive measurement electrodes and electrode switching means, where electrodes can be connected to either measurement means or a guard potential, utilizing planar manufacturing techniques like thin-layer deposition and transistors to minimize interconnection problems and stray capacitances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of measurement electrodes are integrated on a detection surface, then the detection capability and resolution are improved, but the interconnection problems and stray capacitances increase
Solution Approach 1:
The patent divides the detection surface into multiple detection regions, each with its own subset of measurement electrodes. This segmentation allows independent measurement of capacitance values in different regions, reducing the complexity of interconnections while maintaining high detection capability across the entire surface.
Solution Approach 2:
The patent introduces a switching device as an intermediary component that selectively connects measurement electrodes to measurement circuits. This switching mechanism enables multiple electrodes to share common measurement resources, reducing the number of direct interconnections needed while maintaining the ability to measure capacitance of individual electrodes or groups of electrodes.
2Ease of manufacture
If traditional row-column electrode structures are used, then the manufacturing process is simplified, but ghost measurements occur when detecting multiple objects
Solution Approach 1:
The patent segments the electrode array into multiple independent detection regions, where each region can independently detect objects within its boundaries. This segmentation prevents ghost measurements by ensuring that capacitance changes in one region do not interfere with detection in other regions, while still allowing simplified manufacturing through standard electrode fabrication techniques.
3Measurement precision
If self-capacitance measurement technique is used, then ghost measurements are eliminated, but the surface area required for electrical connections increases
Solution Approach 1:
The patent combines the advantages of self-capacitance measurement with shared measurement resources by implementing multiple detection regions that can use common measurement circuits through switching devices. This merging approach eliminates ghost measurements while reducing the total surface area required for connections compared to fully independent self-capacitance measurements.
Solution Approach 2:
The patent makes measurement circuits universal by enabling them to serve multiple detection regions through switching devices. A single measurement circuit can sequentially or selectively measure capacitance in multiple regions, reducing the total number of measurement circuits needed and thereby reducing the surface area required for electrical connections.
4Adaptability or versatility
If mutual capacitance technique is used, then contactless detection is enabled, but large leakage capacitances reduce sensitivity
Solution Approach 1:
The patent segments the detection surface into multiple regions with dedicated measurement electrodes, allowing contactless detection in each region while using switching devices to selectively activate only the necessary electrodes. This segmentation reduces the total leakage capacitance affecting the measurement at any given time, thereby improving sensitivity while maintaining contactless detection capability.
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
Enables efficient detection of multiple objects without ghost measurements and reduces the surface area required for electrical connections, enhancing sensitivity and scalability of capacitive interfaces.
Implementation Method 1
measure the variation of the capacitances appearing between the electrodes and the object to be detected
Implementation Method 2
the coupling capacitances existing between these rows and columns. When a finger is very close to the active surface, the coupling capacitances close to the finger are altered
Data Source
AI summary
The present invention relates to a capacitive-measurement device for touch-sensitive and/or contactless interfaces, including at least one capacitive-measurement electrode (1) and electrode-switching means (2) capable of electrically connecting said at least one electrode (1), either to capacitive-measurement means or to a guard potential (11), said at least one capacitive-measurement electrode (1) and said electrode-switching means (2) being provided on a single detection surface (7) according to a technique for manufacturing planar electronic components. The invention also relates to an apparatus implementing the device.