Electret Accelerometer Diaphragm Mass and Acoustic Isolation
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Solution Overview
Problem
Electret-based accelerometers are prone to producing noisy signals in acoustically noisy environments and are relatively expensive to produce compared to other sensors.
Innovation Solution
A low-cost electret accelerometer is developed by modifying an electret microphone by altering the weight-to-flexibility ratio of the diaphragm and incorporating acoustic isolation to prevent motion in response to acoustic signals, using a solid casing and adding mass to the diaphragm to detect acceleration, while leveraging the manufacturing efficiencies of electret microphones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electret-based accelerometers are used to detect acceleration, then acceleration measurement capability is provided, but noisy signals are produced in acoustically noisy environments
Solution Approach 1:
The patent extracts the diaphragm from the acoustic environment by sealing it within a closed casing, removing the pathway through which acoustic noise could interfere with the diaphragm's motion and thus eliminating the harmful acoustic interference while preserving acceleration detection capability
Solution Approach 2:
The patent applies preliminary anti-action by adding a mass to the diaphragm before exposure to acoustic environments, which increases the diaphragm's inertia and pre-empts acoustic noise interference by making the diaphragm less responsive to acoustic pressure variations
2Reliability
If traditional electret accelerometer manufacturing is used, then accelerometer functionality is achieved, but high production cost results
Solution Approach 1:
The patent applies universality by designing the accelerometer to use the same electret microphone manufacturing processes and components as existing electret microphones, allowing the same production line to manufacture both products and thereby reducing manufacturing costs while maintaining accelerometer functionality
Solution Approach 2:
The patent merges the accelerometer functionality with the electret microphone structure by integrating the diaphragm, electret, and backplate assembly that is already optimized for microphone manufacturing, combining acceleration sensing with existing proven manufacturing techniques
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 solution results in a low-cost accelerometer with reduced noise and no static response, effectively addressing the noise and cost issues of existing electret accelerometers, and is suitable for various applications including bone-conduction microphones and speech processing systems.
Implementation Method 1
An electret-based accelerometer contains an electret, which is a permanently charged material that is an analogue to a permanent magnet
Implementation Method 2
As the diaphragm moves relative to the rest of the accelerometer, the capacitance of the capacitor changes thereby changing the output voltage of the JFET
Implementation Method 3
altering the weight-to-flexibility ratio of the diaphragm and incorporating acoustic isolation to prevent motion in response to acoustic signals, using a solid casing and adding mass to the diaphragm to detect acceleration
Data Source
AI summary
An electret accelerometer is provided in which a diaphragm, an electret, a back plate and an electronic circuit are placed in a casing and the casing is sealed to isolate the diaphragm from external acoustic signals.