Ceramic Fabry-Perot Pressure Sensor for High-Temperature Vacuum
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Solution Overview
Problem
Existing high vacuum pressure sensors, particularly those made of silicon, face limitations in measuring pressures below 10^-1 mbar due to surface reactions with water vapor and chemical aggression, leading to reduced sensitivity and durability, especially at high temperatures.
Innovation Solution
The development of an optical diaphragm gauge using mostly ceramic materials with an integrated optical fiber and a Fabry-Perot interferometer for pressure measurement, which reduces temperature expansion distortions and mechanical stress, and employs a ceramic adhesive and glass paste for high-temperature stability and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon-based capacitive pressure sensors are used, then manufacturing cost is reduced and mass production is enabled, but measurement precision deteriorates at pressures below 10^-1 mbar due to surface reactions with water vapor and chemical aggression
Solution Approach 1:
The patent changes the material parameter from silicon to ceramic materials (such as alumina), which fundamentally alters the surface chemistry and eliminates the harmful surface reactions that occur with silicon at low pressures. This material substitution resolves the contradiction by providing both manufacturing feasibility and high measurement precision in vacuum conditions.
Solution Approach 2:
The patent employs composite material structures combining ceramic housing bodies with ceramic membranes, creating a corrosion-resistant system that maintains measurement precision in aggressive environments. The composite construction provides both structural integrity and chemical resistance, solving the contradiction between manufacturability and precision.
2Reliability
If protective coatings are deposited on silicon sensor surfaces, then resistance against chemically aggressive environments is improved, but device complexity increases and manufacturing cost increases
Solution Approach 1:
Instead of adding protective coatings to silicon surfaces, the patent fundamentally changes the base material to ceramic, which inherently provides chemical resistance. This eliminates the need for additional protective layers, reducing device complexity while maintaining reliability in chemically aggressive environments.
3Measurement precision
If ceramic materials are used for vacuum measuring cells, then measurement precision is improved through corrosion resistance, but device complexity increases due to specialized sealing and bonding requirements
Solution Approach 1:
The patent changes the material parameter to ceramic, which provides inherent corrosion resistance and enables high-temperature operation. By selecting appropriate ceramic materials and bonding techniques, the system achieves measurement precision without excessive complexity in sealing and bonding.
4Measurement precision
If thin ceramic membranes are used for high vacuum measurement, then measurement precision is improved, but mechanical strength deteriorates making the membranes more fragile
Solution Approach 1:
The patent optimizes the thickness parameter of the ceramic membrane to achieve the desired measurement precision while maintaining adequate mechanical strength. By carefully selecting the thickness range and material composition, the system resolves the contradiction between precision and strength.
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 provides a high-accuracy, stable, and economically viable fiber optic membrane pressure measuring cell capable of measuring high pressures at elevated temperatures with improved linearity, repeatability, and relative resolution, while minimizing the impact of environmental disturbances.
Implementation Method 1
The pressure depending deflection of the diaphragm is measured by an optical system in the sensor and the measured signal is then transported by means of an optical fiber to the optical signal conditioner unit
Implementation Method 2
an optical fiber is arranged within the hole of said first housing body and tightly fixed within said hole with fiber sealing means for feeding in and out light onto the surface of the membrane
Implementation Method 3
at least in the central region of the membrane and in opposite of the hole the surface of the membrane is formed as a first optically reflective area
Implementation Method 4
pressures or pressure differences can be measured by applying pressure to a thin membrane and measuring its deflection
Data Source
AI summary
A pressure measuring cell has a first housing body and a membrane arranged proximate the housing body, both of ceramic. The membrane has a peripheral edge joined to the first housing body to create a reference pressure chamber. A second housing body made of ceramic material is opposite the membrane and is joined to the peripheral edge of the membrane, the second housing body together with the membrane forming a measurement pressure chamber. The second housing body has a port for connecting the pressure measuring cell to a medium to be measured. The first housing body, the second housing body and the membrane are tightly connected along the peripheral edge of the membrane in a central area of the first housing body a hole is formed, reaching through the first housing body and at least in the central region of the membrane and opposite the hole a surface of the membrane is formed as a first optically reflective area. An optical fiber is arranged and tightly fixed within the hole for feeding light onto the surface of the membrane. The end of the fiber reaches at least the surface of the first housing body and is formed as a second reflective optical area linking the surface so that between the fiber end and the reflection area an optical cavity is present which forms a measuring section for determining the level of deflection of the membrane and which is part of a Fabry-Perot Interferometer.