Compact GRIN-Lens Instrument for Temperature-Compensated Pressure
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Solution Overview
Problem
Existing fuel measurement systems in aircraft fail to accurately account for varying fuel pressures due to irregular tank shapes and changing flight conditions, leading to inconsistent fuel level calculations.
Innovation Solution
A system utilizing temperature-compensated Fabry-Perot pressure sensors with a graded-index (GRIN) lens and dual Fabry-Perot interferometers to measure pressure, isolating one interferometer from temperature and the other from pressure, allowing for precise fuel level determination by analyzing resonant frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional pressure sensors are used in irregular fuel tanks, then the device complexity is reduced, but the measurement precision deteriorates due to inaccurate fuel level calculations under varying pressure conditions
Solution Approach 1:
The system divides the measurement function into two separate Fabry-Perot interferometers: one dedicated to pressure measurement and another to temperature measurement. This segmentation allows each sensor to specialize in one parameter, improving measurement precision while maintaining manageable device complexity through functional decomposition
Solution Approach 2:
The patent introduces a GRIN lens as an intermediary optical component to couple light from the optical fiber to the Fabry-Perot interferometers. This intermediary element enables precise optical coupling and signal transmission, improving measurement accuracy without significantly increasing overall system complexity
2Measurement precision
If temperature compensation is added to pressure measurement, then the measurement precision improves, but the device complexity increases due to additional sensors and processing
Solution Approach 1:
The patent merges pressure and temperature measurement capabilities into a single integrated sensor housing, with both Fabry-Perot interferometers sharing common optical components and housing structure. This merging approach improves measurement precision through temperature compensation while reducing device complexity by eliminating separate sensor systems
Solution Approach 2:
The sensor system achieves multi-functionality by incorporating both pressure and temperature measurement capabilities within a single device. The dual interferometer configuration allows the system to simultaneously measure both parameters, with the temperature data used to compensate pressure readings, thereby improving overall measurement precision without requiring separate dedicated sensors
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
Enables accurate and precise measurement of fuel pressure and level in aircraft fuel tanks, compensating for tank irregularities and flight-induced changes, enhancing fuel management accuracy.
Implementation Method 1
The optical plate has nominal thickness L 1 (T 0 ) measured along an axis perpendicular to first and second parallel faces that are partially reflective to light normally incident thereon from within the optical plate. Such configuration forms a first Fabry-Perot interferometer between the first and second parallel faces.
Implementation Method 2
The graded-index (GRIN) lens is axially aligned with and adjacent to the first Fabry-Perot interferometer. The GRIN lens is configured to receive, at a first face of the GRIN lens, a diverging optical beam projected from a face of an optical fiber and to collimate the diverging optical beam
Implementation Method 3
The optical interrogator is optically coupled to the Fabry-Perot pressure sensor via an optical fiber
Data Source
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AI summary
Apparatus and associated methods relate to measuring pressure of an external environment using a graded index (GRIN) lens and first and second Fabry-Perot interferometers, each axially aligned with one another. The GRIN lens collimates a beam diverging from a face of an optical fiber so as to direct the collimated beam to the first and second Fabry-Perot interferometers. The first Fabry-Perot interferometer is pressure isolated from the external environment but not temperature isolated. Therefore, the resonant frequency of the first Fabry-Perot interferometer is indicative of temperature. The second Fabry-Perot interferometer has a cavity that changes dimension in response to changes in pressure and temperature of the external atmosphere. The second Fabry-Perot interferometers has a second resonant frequency that is not integer multiple of the first resonant frequency. Pressure is determined based on the first and second resonant frequencies.