Vibration Sensor Air Venting Channels Squeeze Film Damping
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Solution Overview
Problem
Squeeze film damping effects in vibration sensors with narrow air gaps lead to increased noise levels and reduced usable bandwidth, as the viscous damping caused by air in these gaps is excessive.
Innovation Solution
Incorporating air venting channels in the capacitor electrodes to balance air pressure and reduce squeeze film damping, allowing air to escape when the gap decreases and enter when it increases, thereby reducing viscous damping between the electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a narrow air gap is used between capacitor electrodes to increase sensitivity, then measurement precision is improved, but squeeze film damping increases causing higher noise levels and reduced bandwidth
Solution Approach 1:
The capacitor electrode is segmented into multiple sections by introducing air venting channels that divide the electrode surface. These channels create localized capacitor regions while allowing air pressure equalization, thus reducing squeeze film damping effects while maintaining overall capacitance for sensitive detection
Solution Approach 2:
Air venting channels act as intermediary pathways that mediate between the capacitor electrodes, allowing controlled air flow to balance pressure differences during electrode movement. This intermediary mechanism reduces the harmful squeeze film damping while preserving the narrow air gap configuration for high sensitivity
2Measurement precision
If a narrow air gap is used between capacitor electrodes, then sensitivity is improved, but noise level increases due to excessive viscous damping
Solution Approach 1:
The electrode surface is segmented by air venting channels into multiple smaller capacitor regions. This segmentation allows the narrow air gap to be maintained for sensitivity while the channels prevent excessive air pressure buildup that would cause viscous damping and noise
Solution Approach 2:
Air venting channels extract excess air pressure from the narrow air gap region during electrode movement. By removing the problematic pressurized air that causes viscous damping, the channels enable the system to maintain narrow gaps for sensitivity without suffering from noise-generating damping effects
3Object-affected harmful factors
If air venting channels are added to capacitor electrodes, then squeeze film damping is reduced, but device complexity increases
Solution Approach 1:
The air venting channels are merged with the capacitor electrode structure itself, combining the electrode function with the air venting function in a single integrated component. This merging approach reduces device complexity by eliminating separate air venting mechanisms while still achieving squeeze film damping reduction
Solution Approach 2:
The capacitor electrode is designed with multi-functionality, serving both as the capacitive sensing element and as the air venting structure. The channels that define capacitor regions also serve as air pressure equalization pathways, reducing squeeze film damping without requiring additional dedicated components
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
The vibration sensor achieves a low noise level and high sensitivity with a large moveable mass and thin air gap, making it suitable for applications like voice recognition in noisy environments, while being reflowable for manufacturing convenience.
Implementation Method 1
squeeze film damping effects between the first and second capacitor electrodes are reduced
Implementation Method 2
the one or more air venting channels should prevent that air becomes pressurised in the air gap when the air gap is decreased, and that air can be guided to the air gap when the air gap is increased
Implementation Method 3
the read-out arrangement comprises a capacitor formed by a first capacitor electrode and a second capacitor electrode separated by an air gap
Data Source
AI summary
The present invention relates to a vibration sensor comprising a carrier substrate comprising a first surface and a second surface, a suspension member and a moveable mass secured thereto, wherein the moveable mass and/or at least part of the suspension member is/are adapted to vibrate when the vibration sensor is exposed to external vibrations, a read-out arrangement for detecting vibrations of the moveable mass and/or at least part of the suspension member, and a signal processor for at least processing an electric signal from the read-out arrangement, wherein the read-out arrangement comprises a capacitor formed by a first capacitor electrode and a second capacitor electrode separated by an air gap, and wherein the first capacitor electrode and/or the second capacitor electrode comprises one or more air venting channels in order to reduce squeeze film damping effects between the first and second capacitor electrodes. The present invention further relates to a hearing device comprising such a vibration sensor and use of the vibration sensor for voice recognition in a hearing device.