Dual FBG Diaphragm Sensor for Temperature-Compensated Pressure Measurement
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Solution Overview
Problem
Existing pressure sensors using fiber Bragg gratings (FBGs) face challenges in high temperature and high pressure environments due to temperature-induced responses, requiring separate temperature sensors for compensation, which complicates measurements in applications like supersonic jet exhaust gas and oil and gas exploration.
Innovation Solution
A temperature-compensated pressure sensor design featuring two FBGs on a diaphragm, one responsive to pressure-induced strain and the other to temperature, with distinct wavelength ranges to allow for simultaneous measurement and compensation, using a wavelength interrogator to differentiate between pressure and temperature effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single FBG is used on the diaphragm surface, then pressure measurement is achieved, but temperature variations cause measurement errors
Solution Approach 1:
The single FBG sensor is segmented into two functionally distinct FBGs: one positioned in the deflection region to sense pressure-induced strain, and another in the non-deflection region to sense only temperature. This segmentation allows separate measurement of pressure and temperature effects, enabling temperature compensation to eliminate measurement errors caused by temperature variations.
Solution Approach 2:
The second FBG acts as an intermediary temperature sensor that measures temperature effects independently. By using this intermediary sensor, the system can isolate and compensate for temperature interference without directly measuring it with the primary pressure-sensing FBG, thereby improving pressure measurement accuracy in varying temperature conditions.
2Measurement precision
If separate temperature sensors are added for compensation, then temperature effects can be compensated, but device complexity increases
Solution Approach 1:
The temperature sensing function is merged with the existing FBG sensor system by adding a second FBG on the same diaphragm surface. Both pressure and temperature sensing are achieved using the same FBG technology platform, eliminating the need for separate temperature sensor integration and reducing overall device complexity compared to using different sensor types.
Solution Approach 2:
The FBG sensor system is made universal by enabling it to perform both pressure measurement and temperature compensation functions. The two FBGs work together as a multi-functional sensing system, where the same type of sensor (FBG) serves dual purposes, simplifying the device architecture compared to using specialized separate sensors for each function.
3Measurement precision
If FBGs are placed in regions of minimal deflection for temperature sensing, then temperature measurement is achieved, but strain coupling must be minimized
Solution Approach 1:
Different regions of the diaphragm are assigned different functional qualities: the deflection region contains the pressure-sensing FBG that responds to strain, while the non-deflection region contains the temperature-sensing FBG that is isolated from strain. This local differentiation ensures that each FBG measures only its intended parameter without interference from the other, achieving accurate temperature measurement free from strain coupling.
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 design enables accurate pressure measurement in high temperature and high pressure environments by isolating temperature effects from pressure measurements, improving precision and simplifying calibration in harsh conditions.
Implementation Method 1
the two FBGs transmitting or reflecting narrowband optical energy, and a wavelength interrogator for determination of pressure and temperature based on the reflected or transmitted wavelengths of the FBG
Implementation Method 2
fiber optic Bragg gratings, also known as fiber Bragg gratings (FBG)
Data Source
AI summary
A temperature correcting pressure gauge which has a diaphragm having at least one surface coupled to a source of pressure to be measured, the diaphragm first surface having a first FBG from a first optical fiber attached in an appropriately sensitive region of the diaphragm, a FBG from a second optical fiber attached to the opposite surface from the first FBG, the first and second FBGs reflecting or transmitting optical energy of decreasing or increasing wavelength, respectively, in response to an applied pressure. The first and second FBGs have nominal operating wavelength ranges that are adjacent to each other but are exclusive ranges and the FBGs also have closely matched pressure coefficients and temperature coefficients.