Optical Transducer for High-Pressure Measurement
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Solution Overview
Problem
Conventional pressure transducers face challenges in measuring high pressures at high temperatures due to material limitations, such as increased stress and potential for yielding and plastic deformation, which affects repeatability and stability, and the need for novel arrangements to handle harsh environments.
Innovation Solution
A transducer design featuring a tube with reflective surfaces and an optical fiber, forming a Fabry-Perot interferometer sensor, where the pressure-induced changes in the gap between reflective surfaces are measured using light interference, allowing for precise pressure and temperature determination without directly bearing the high pressure, and using materials with similar thermal expansion coefficients to manage thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the diaphragm is increased to handle higher pressures, then the pressure rating is improved, but the stress on the diaphragm increases and yields plastically
Solution Approach 1:
The patent replaces the mechanical diaphragm deflection system with an optical interferometric sensing system. Instead of measuring pressure through mechanical diaphragm deflection, the invention uses optical fibers and reflective surfaces to detect pressure-induced changes in gap dimensions, eliminating the stress concentration and plastic deformation issues inherent in mechanical diaphragm systems
Solution Approach 2:
The patent introduces a tube as an intermediary element that shields the sensitive optical components from direct exposure to high pressure. The tube transmits the pressure environment to the optical sensor indirectly through dimensional changes, protecting the optical components while still enabling pressure measurement
2Length of moving object
If the diameter of the transducer is decreased for compactness, then the device complexity is reduced, but the stress on the diaphragm increases
Solution Approach 1:
The patent replaces the mechanical diaphragm system with an optical interferometric system that is not subject to the same stress constraints. The optical components (fibers, reflective surfaces) can be made in small diameters without experiencing the bending stress concentration that plagues mechanical diaphragms, enabling compact transducer design
3Manufacturing precision
If conventional materials are used at high temperatures, then the manufacturing precision is maintained, but the materials yield and deform plastically
Solution Approach 1:
The patent replaces temperature-sensitive mechanical measurement components with optical sensing elements that are inherently more resistant to thermal effects. The optical fiber and interferometric surfaces can be constructed from materials with matched thermal expansion coefficients, maintaining measurement precision at high temperatures where conventional mechanical transducers would yield
4Measurement precision
If the diaphragm is made compliant for sensitivity, then the measurement precision is improved, but the diaphragm yields under high pressure
Solution Approach 1:
The patent replaces the compliant mechanical diaphragm with an optical interferometric sensing system that achieves measurement precision through optical path length changes rather than mechanical compliance. The optical components can be made rigid yet still detect pressure-induced dimensional changes with high precision, eliminating the yield strength limitation of compliant diaphragms
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 stable measurement of high pressures and temperatures by shielding sensitive components from direct pressure and thermal stress, maintaining precision and repeatability, and allowing for a family of transducers with small diameters to be designed for various pressure ratings.
Implementation Method 1
The two reflective surfaces comprise an interferometric sensor, and the light reflected from these two surfaces may be interrogated to determine the precise gap between the two surfaces at any pressure
Implementation Method 2
A transducer design featuring a tube with reflective surfaces and an optical fiber, forming a Fabry-Perot interferometer sensor
Implementation Method 3
using materials with similar thermal expansion coefficients to manage thermal stress
Data Source
AI summary
Apparatus, methods, and other embodiments associated with measuring environmental parameters are described herein. In one embodiment, a transducer comprises a tube, an elongated member, a first reflective surface, a second reflective surface, and an optical fiber. The tube has a first end and a second end, and the elongated member also has a first end and a second end, with the first end of the elongated member secured to the tube. The second reflective surface is secured to the second end of the elongated member, and the first reflective surface is spaced apart from the second reflective surface and secured to the second end of the tube. The optical fiber is positioned to direct light towards the first and second reflective surfaces and to collect the reflected light from these two surfaces.