Capacitive Pressure Sensor with Distributed Filter for High Temperature
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Solution Overview
Problem
Existing pressure sensors, such as capacitive microphones, require internal or local electronics that degrade in high temperature environments, leading to measurement errors due to parasitic capacitance and signal noise.
Innovation Solution
A pressure sensor design featuring an acousto-mechanical diaphragm with an electrically conductive element and a distributed element filter spaced by an air gap, which changes capacitance and resonant frequency in response to pressure changes, allowing for electronic signal processing without internal electronics, and capable of operating at temperatures above 600 degrees Celsius.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If internal or local electronics are used in capacitive-based microphones, then signal to noise ratio is improved, but reliability deteriorates in high temperature environments
Solution Approach 1:
The patent removes all internal and local electronic components from the microphone assembly. The capacitive element is isolated with no surrounding electronics, eliminating the source of thermal degradation while maintaining measurement capability through pure capacitive coupling to external electronics located away from the high temperature environment.
Solution Approach 2:
A buffer amplifier is positioned remotely from the capacitive element, connected through wiring that acts as an intermediary transmission medium. This allows the sensitive capacitive measurement to be isolated from electronic processing components, enabling high temperature operation at the sensing element while electronic processing occurs in a cooler environment.
2Measurement precision
If internal or local electronics are placed close to the microphone, then signal to noise ratio is improved, but device complexity increases
Solution Approach 1:
The buffer amplifier and other electronic components are extracted from the immediate microphone assembly and placed in a separate location. This reduces the complexity of the high temperature sensor package to essentially just the capacitive element and its mechanical support structure.
Solution Approach 2:
The system is divided into distinct segments: the simple capacitive sensing element operating in the high temperature environment, and the electronic processing components operating in a separate, cooler environment. This segmentation allows each part to be optimized for its specific operating conditions.
3Measurement precision
If wiring is added for signal feeding and powering, then signal to noise ratio is improved, but device complexity increases
Solution Approach 1:
The patent employs capacitive coupling through electric field interaction rather than direct electrical wiring connections for signal transmission. The capacitive element couples signals to external circuitry through displacement current in the electric field, eliminating the need for direct wire connections to the high temperature sensing element.
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 solution enables accurate measurement of dynamic and static pressures in high temperature environments without the need for internal electronics, reducing signal noise and extending sensor lifespan.
Implementation Method 1
a distributed element filter configured to capacitively couple the input terminal to the output terminal
Implementation Method 2
The air gap changes in response to a deflection of the acousto-mechanical diaphragm caused by a change in pressure on the acousto-mechanical diaphragm
Implementation Method 3
a distributed element filter spaced from the electrically conductive element by an air gap. The air gap changes in response to a deflection of the acousto-mechanical diaphragm
Data Source
AI summary
A pressure sensor includes an input terminal configured to receive an electrical input signal and an output terminal configured to provide an electrical output signal in response to the electrical input signal. The pressure sensor also includes an acousto-mechanical diaphragm and an electrically conductive element formed on the acousto-mechanical diaphragm. The pressure sensor further includes a distributed element filter configured to capacitively couple the input terminal to the output terminal. The distributed element filter is spaced from the electrically conductive element by an air gap. The air gap changes in response to a deflection of the acousto-mechanical diaphragm caused by a change in pressure on the acousto-mechanical diaphragm.