Capacitive Sensor Auxiliary Electrode Asymmetry
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Solution Overview
Problem
Current capacitive physical quantity sensors, such as acceleration sensors, face limitations in detection sensitivity, which hinders their ability to accurately measure physical quantities like acceleration and angular velocity.
Innovation Solution
The capacitive physical quantity sensor design incorporates a movable electrode, a fixed electrode, and an auxiliary electrode on a substrate, where the auxiliary electrode varies its facing area differently based on the displacement direction of the movable electrode, allowing for improved sensitivity by detecting capacitance changes between these electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional capacitive sensor structure with only fixed and movable electrodes is used, then the device complexity is low, but the detection sensitivity is insufficient
Solution Approach 1:
The sensor electrode system is segmented into three distinct electrodes: a fixed electrode, a movable electrode, and an auxiliary electrode. This segmentation allows the auxiliary electrode to specifically detect capacitance changes related to displacement direction, thereby improving detection sensitivity without requiring complex restructuring of the entire sensor system.
Solution Approach 2:
The auxiliary electrode acts as an intermediary element that mediates the detection of displacement direction. By measuring capacitance changes between the movable electrode and the auxiliary electrode, the system can determine displacement direction, which enhances the overall measurement capability without directly complicating the primary sensing mechanism.
2Measurement precision
If the auxiliary electrode is designed to detect both displacement magnitude and direction, then the measurement precision is improved, but the difficulty of detecting and measuring increases
Solution Approach 1:
The measurement function is segmented across two electrode pairs: the fixed-movable electrode pair measures displacement magnitude, while the auxiliary-movable electrode pair measures displacement direction. This functional segmentation simplifies the measurement task for each electrode pair while achieving comprehensive measurement precision.
Solution Approach 2:
The auxiliary electrode is positioned to create a specific geometric relationship with the movable electrode, where the facing area varies with displacement direction. This partial action approach allows the auxiliary electrode to specifically detect directional information without requiring full 360-degree measurement capability, reducing measurement complexity.
3Measurement precision
If the facing area of the auxiliary electrode varies differently based on displacement direction, then the detection sensitivity is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The auxiliary electrode is designed with an asymmetric configuration relative to the movable electrode, such that the facing area between them varies differently depending on the displacement direction. This asymmetric design inherently provides directional sensitivity while maintaining manufacturability through standard photolithography and etching processes.
Solution Approach 2:
The facing area parameter of the auxiliary electrode is designed to change in response to movable electrode displacement. By optimizing the initial geometric parameters (width, length, spacing) of the auxiliary electrode, the system achieves high detection sensitivity while keeping manufacturing tolerances within standard fabrication capabilities.
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 configuration enhances the detection sensitivity of physical quantities by differentiating displacement directions and reducing noise, enabling more precise measurements of acceleration and angular velocity.
Implementation Method 1
an interval between the movable electrode and the fixed electrode changes. For that reason, the acceleration is detected on the basis of the capacitance between the movable electrode and the fixed electrode
Implementation Method 2
The auxiliary electrode is different in a variation of a facing area with the movable electrode in a case where the movable electrode is displaced in one direction of the predetermined direction from a case where the movable electrode is displaced in a direction opposite to the one direction. The capacitive physical quantity sensor detects the physical quantity on the basis of a capacitance corresponding to the interval between the movable electrode and the fixed electrode, and a capacitance corresponding to the facing area of the movable electrode and the auxiliary electrode
Data Source
AI summary
A capacitive physical quantity sensor includes a first substrate, a movable electrode, a fixed electrode, and a second substrate. An auxiliary electrode is disposed on a portion of the second substrate to face the movable electrode and the auxiliary electrode has a facing area that faces the movable electrode. The facing area in a case where the movable electrode is displaced in one direction is different from the facing area in a case where the movable electrode is displaced in an opposite direction opposite to the one direction. The physical quantity is detected based on a capacitance, which is generated corresponding to the interval between the fixed electrode and the movable electrode, and a capacitance, which is generated corresponding to an interval between the facing area of the movable electrode and the auxiliary electrode.