Touch Sensor Switching Between Capacitance and Impedance Sensing
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Solution Overview
Problem
Capacitance touch sensors face challenges in accurately detecting user touch and sensing parameters like humidity, temperature, pressure, or displacement due to variations in impedance and capacitance, which affect the reliability of input signals for electronic devices.
Innovation Solution
A multi-function sensing apparatus comprising a capacitance touch sensor arrangement with variable capacitance, a variable impedance sensor, and a switch that configures output impedance based on detected parameters, allowing for precise detection of user touch and environmental changes by switching between configurations to prioritize either capacitance or impedance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitance touch sensor is used to detect user touch, then touch detection capability is provided, but variations in impedance and capacitance reduce measurement precision
Solution Approach 1:
The patent implements dynamic switching between capacitance sensing mode and impedance sensing mode based on the detected parameter type. The system adapts its measurement approach in real-time, selecting the appropriate sensing method to maintain precision across different parameter types. This dynamic configuration resolves the contradiction by ensuring that measurements are always taken using the optimal method for the current sensing objective.
Solution Approach 2:
The patent changes the electrical parameters being measured by switching between capacitance (C) and impedance (Z) measurements. By adjusting which parameter is actively sensed based on the input signal characteristics, the system maintains high measurement precision for both touch detection and environmental parameter sensing, overcoming the limitation of fixed sensing mode.
2Adaptability or versatility
If a single sensor configuration is used, then device complexity is reduced, but the ability to detect multiple parameters accurately is limited
Solution Approach 1:
The patent makes a single sensor arrangement multi-functional by enabling it to operate in different sensing modes (capacitance mode and impedance mode) depending on the parameter being detected. This universal approach allows one sensor to accurately detect multiple parameters including touch, humidity, temperature, pressure, and displacement without requiring separate dedicated sensors for each function, thus maintaining low device complexity while achieving high adaptability.
3Measurement precision
If capacitance variations are used for touch detection, then touch sensitivity is improved, but environmental parameter sensing becomes less reliable
Solution Approach 1:
The system dynamically selects the sensing mode based on the parameter detection requirement. When touch detection is needed, capacitance sensing is activated for high precision. When environmental parameters like humidity or temperature are being sensed, the system switches to impedance sensing for improved reliability. This dynamic adaptation resolves the contradiction by ensuring each sensing task uses the optimal method.
Solution Approach 2:
The patent introduces a switching mechanism that acts as an intermediary between the sensor and the measurement circuitry. This switch routes the sensor output through different measurement paths (capacitance measurement or impedance measurement) based on the detection task, allowing the system to leverage the strengths of each measurement method for their respective optimal applications.
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 and reliability of detecting user touch and environmental parameters by optimizing output impedance configurations, reducing dependency on parameter presence or location, and enabling efficient detection of multiple parameters simultaneously.
Implementation Method 1
a capacitance touch sensor arrangement (20) configured to have a variable capacitance (22) that varies when a conductive object (2) approaches
Implementation Method 2
a variable impedance sensor (30) configured to have a variable impedance (32) that varies with a sensed parameter p
Data Source
Figure 1~4
Figure 5~8B
Figure 9~11
AI summary
An apparatus comprising: a capacitance touch sensor arrangement configured to have a variable capacitance that varies when a conductive object approaches; and at least one variable impedance sensor configured to have a variable impedance that varies with a sensed parameter; an output node; and at least one switch configured to provide, in a first configuration, an output impedance at the output node that depends upon the variable capacitance and configured to provide, in a second configuration, an output impedance at the output node that depends upon the variable impedance.