Capacitive Pressure Sensor Linearization via Impedance Matching
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Solution Overview
Problem
Existing pressure sensors for touch input devices require correction for each application to accurately detect pressure magnitude due to varying distances between the pressure electrode and the reference potential layer, complicating uniform pressure detection.
Innovation Solution
A pressure sensor design incorporating a drive unit and a sensing unit with first and second impedances, both being pure capacitors, which allows for linear detection of pressure magnitude by measuring capacitance changes between the electrode and the reference potential layer, independent of the operating frequency of the drive signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the distance between the pressure electrode and the reference potential layer is changed for each application, then the pressure sensor can be adapted to different applications, but the pressure detection requires correction for each application which increases device complexity
Solution Approach 1:
The patent introduces a capacitor as an intermediary component between the pressure electrode and the reference potential layer. This capacitor mediates the electrical connection and allows the system to achieve linear pressure detection without requiring application-specific correction circuits, thus maintaining versatility while reducing complexity
Solution Approach 2:
The patent changes the electrical parameters by introducing capacitive coupling and using a capacitor with specific characteristics (capacitance value, dielectric material) to transform the non-linear capacitance change into a linear output signal, eliminating the need for correction circuits across different applications
2Measurement precision
If the distance between the pressure electrode and the reference potential layer is changed, then different pressure ranges can be detected, but the output signal becomes non-linear which reduces measurement precision
Solution Approach 1:
The capacitor acts as an intermediary that linearizes the relationship between pressure and output signal. By placing the capacitor in the electrical path, it transforms the non-linear capacitance variation into a linear voltage or current output, improving measurement precision while simplifying signal processing
Solution Approach 2:
The patent utilizes the capacitive reactance parameter and its relationship with frequency and capacitance value to achieve linearization. By carefully selecting the capacitor parameters (capacitance, dielectric material), the system transforms the non-linear physical quantity change into a linear electrical signal
3Measurement precision
If a correction circuit is added for each application, then uniform pressure detection can be achieved, but the manufacturing cost increases
Solution Approach 1:
The patent creates a universal pressure detection structure where a single capacitor component serves multiple functions: it couples the pressure electrode electrically, linearizes the output signal, and eliminates the need for application-specific correction circuits. This universal design reduces manufacturing complexity and cost while maintaining uniform pressure detection across different applications
Solution Approach 2:
The capacitor as an intermediary component provides a universal solution that works across different applications without requiring custom correction circuits for each case, thereby reducing manufacturing costs while achieving uniform pressure detection
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 accurate and uniform pressure detection without the need for application-specific corrections, as the output signal changes linearly with distance changes, simplifying signal processing and reducing manufacturing costs by eliminating the dependency on operating frequency.
Implementation Method 1
The first impedance and the second impedance are pure capacitors. The first impedance is provided between the drive unit and the electrode, and the second impedance between the sensing unit and the electrode.
Implementation Method 2
a reception signal including information on a capacitance which is between the electrode and a reference potential layer, wherein the reference potential layer is spaced from the electrode at a predetermined distance which is changed depending on the application of pressure to a touch surface, and the capacitance is changed according to a distance change between the electrode and the reference potential layer
Data Source
Figure 1~3
Figure 4~6
Figure 7a~7c
AI summary
A pressure sensor may be provided that includes: an electrode; a drive unit which applies a drive signal to the electrode; a sensing unit which receives, through the electrode, a reception signal including information on a capacitance which is between the electrode and a reference potential layer and is changed according to a relative distance between the electrode and the reference potential layer spaced from the electrode; and a first impedance between the drive unit and the electrode, and a second impedance between the sensing unit and the electrode.