Fiber Optic Pressure Sensor Temperature Compensation
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Solution Overview
Problem
Existing pressure sensors using fiber Bragg gratings (FBGs) face challenges in high temperature and high pressure environments, as they respond not only to pressure but also to temperature variations, 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 a diaphragm with a first FBG sensor attached to the deflection region and a second FBG sensor in thermal equilibrium but not subject to deflection, both coupled to an optical source, allowing for wavelength interrogation to distinguish between pressure and temperature effects, enabling accurate measurements by converting reflected or transmitted wavelengths into pressure and temperature readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single FBG sensor is used on the diaphragm surface, then pressure measurement capability is provided, but temperature variations cause measurement errors and require separate temperature sensors for compensation
Solution Approach 1:
The single FBG sensor is segmented into two functional regions: an active sensing region that responds to both pressure and temperature, and an inactive reference region that responds only to temperature. This segmentation allows the sensor to simultaneously measure pressure while compensating for temperature effects, eliminating the need for separate temperature sensors and reducing system complexity.
Solution Approach 2:
The FBG sensor is designed to perform multiple functions: the active region provides both pressure sensing and temperature compensation, while the inactive region provides temperature reference. This multi-functionality allows a single sensor component to replace what would traditionally require separate pressure and temperature sensors, reducing device complexity while maintaining measurement precision.
2Measurement precision
If the FBG is placed in a region of maximum deflection for optimal pressure sensitivity, then pressure response is maximized, but temperature compensation becomes difficult
Solution Approach 1:
The diaphragm surface is segmented into two distinct regions: an active region at the location of maximum deflection where the FBG provides pressure-sensitive measurements, and an inactive reference region where a second FBG provides temperature-only measurements. This spatial segmentation allows optimal pressure sensitivity in the active region while enabling reliable temperature compensation through the inactive region.
3Measurement precision
If separate temperature sensors are used for compensation, then temperature effects can be compensated, but the device complexity and calibration requirements increase
Solution Approach 1:
The temperature compensation function is merged with the pressure sensing function by integrating both active and inactive FBG regions into a single sensor component. This merging eliminates the need for separate temperature sensors and their associated wiring and calibration systems, reducing device complexity while maintaining temperature compensation accuracy through the wavelength ratio measurement method.
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 effectively isolates temperature effects from pressure measurements, providing reliable and accurate pressure sensing in high temperature and high pressure environments without the need for separate temperature sensors, enhancing measurement precision and simplifying calibration processes.
Implementation Method 1
fiber optic Bragg gratings (FBG), for displacement measurement where the FBG has response coefficients such that the FBG is responsive not only to pressure but also to temperature
Implementation Method 2
the diaphragm having an optical fiber with a first FBG mechanically coupled to a deflecting part of the diaphragm, the FBG oriented to couple to mechanical strain of the diaphragm
Implementation Method 3
the diaphragm having a second region with a second FBG which is coupled to the temperature of the first FBG, but not to mechanical strain in the diaphragm
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.