Asymmetric Cap Layer Acceleration Sensor Zero Point Drift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acceleration sensors face challenges in maintaining low production costs while minimizing initial and over-time zero point drifts, especially in poor installation environments, due to complex design and production requirements for matching the center of the cavity and rotation center, and the reduction of facing area for sensing electrodes.
Innovation Solution
The acceleration sensor features a proof mass inside a cavity surrounded by a support substrate and cap layer, where the cap layer has different weights per unit area on both sides of the rotation axis, allowing for rotation and differential detection to minimize zero point drifts without requiring complex production processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the center of the cavity and rotation center are matched using complex design and production processes, then zero point drift is reduced, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent intentionally creates an asymmetric configuration by deliberately mismatching the cavity center and rotation center. The offset distance is specifically designed to generate a compensating moment that counteracts the unwanted moment from asymmetric electrode arrangement, thereby reducing zero point drift without requiring complex matching processes
Solution Approach 2:
The patent changes the geometric parameters of the proof mass (area, shape, or position) to adjust the moment of inertia and center of gravity position. By optimizing these parameters, the rotation center is positioned at a specific offset from the cavity center, creating a compensating moment that reduces zero point drift while maintaining simple manufacturing processes
2Measurement precision
If sensing electrodes are arranged symmetrically to cancel capacitance changes from distortion, then measurement precision improves, but the facing area between electrodes and proof mass is reduced
Solution Approach 1:
The patent deliberately arranges sensing electrodes asymmetrically with different distances from the rotation center. This asymmetric arrangement increases the facing area between electrodes and proof mass, improving capacitance change magnitude. The compensating moment mechanism offsets the unwanted effects of this asymmetric arrangement, maintaining measurement precision while enhancing signal strength
Solution Approach 2:
The patent applies different properties to different regions of the sensing system. The sensing electrodes are positioned with different areas and distances from the rotation center, creating localized variations in capacitance. This allows optimization of capacitance change magnitude in specific regions while the overall compensating moment mechanism maintains measurement accuracy
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 effectively inhibits zero point drifts caused by environmental and over-time changes, maintaining reliability and low production costs by equalizing capacitance changes through differential detection.
Implementation Method 1
when acceleration is applied in the third direction to the proof mass, the proof mass rotates around the first direction or the second direction. That is, since the rotation center of the proof mass is away from center of gravity part of the proof mass, moment arises in the rotation center in proportion to acceleration applied in the third direction
Implementation Method 2
a sensing electrode that forms capacitance with the proof mass
Data Source
AI summary
Provided is a highly reliable acceleration sensor that keeps production costs low and has low zero point drift initially and over time even when used in a poor installation environment. In this acceleration sensor, a weight that rotates when acceleration is applied in the z-direction is disposed in a cavity surrounded by a support substrate and a cap layer. The cap layer is formed such that both sides thereof across the axis of rotation of the weight have different masses per unit area.