Dual-Path Gas Sensor Resolving Interference With Water Vapor
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Solution Overview
Problem
Existing gas sensors face challenges in measuring gas concentrations accurately when interference gases, such as water vapor, have absorption wavelengths near those of the target gas, leading to interference and reduced measurement precision.
Innovation Solution
A gas sensor design incorporating two infrared light paths with different optical path lengths and sensitivity characteristics, where one path's sensitivity peak wavelength overlaps with the absorption wavelength of water vapor, allowing for optimized detection and reduction of interference effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single light source and photodetector are used for gas concentration measurement, then the device complexity is reduced, but measurement precision deteriorates when interference gases are present
Solution Approach 1:
The patent divides the measurement system into two separate optical paths: a first optical path for measuring the target gas and a second optical path for measuring the interference gas. Each path has its own light source and photodetector, allowing independent measurement and compensation of interference effects, thus resolving the contradiction between device complexity and measurement precision.
Solution Approach 2:
The patent introduces a second optical path as an intermediary measurement system that specifically targets the interference gas. By measuring the interference gas concentration separately and using this information to compensate the target gas measurement, the system achieves high precision without excessive complexity.
2Measurement precision
If the optical path length is increased to improve signal strength, then measurement precision improves, but the device size increases
Solution Approach 1:
The patent uses multiple optical paths with different lengths instead of extending a single optical path. The first optical path has length L1 and the second has length L2, allowing the system to optimize signal strength for each measurement target independently without increasing the overall device volume proportionally.
Solution Approach 2:
The patent applies different optical path lengths to different measurement functions: the first optical path uses length L1 optimized for target gas detection, while the second optical path uses length L2 optimized for interference gas detection. This localized optimization allows precise measurement without requiring uniformly long optical paths throughout the device.
3Measurement precision
If the optical path length is increased to improve detection sensitivity, then measurement precision improves, but loss of energy increases
Solution Approach 1:
The patent applies partial action by using two optical paths with different lengths rather than one excessively long path. The first optical path uses length L1 sufficient for target gas detection, and the second uses length L2 sufficient for interference gas detection, avoiding the excessive energy loss that would result from using a single very long optical path for both measurements.
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 high-accuracy gas concentration measurement even in the presence of interference gases by optimizing signal-to-noise ratio and reducing the impact of water vapor, thereby improving measurement precision and reliability.
Implementation Method 1
the first light receiving part and the second light receiving part have different sensitivity peak wavelengths; a sensitivity peak wavelength of the second light receiving part overlaps with an absorption wavelength of water vapor
Implementation Method 2
the absorption wavelength of the gas to be measured (methane gas) and that of water vapor occurs
Data Source
AI summary
A gas sensor comprises first and second light emitting parts, first and second light receiving parts, and first and second optical path regions, wherein the optical path regions have a common region, a first light receiving part has a larger rate of change of an output signal with respect to a first gas than a second light receiving part, the second light receiving part has a larger rate of change of an output signal with respect to an second gas than the first light receiving part, the first light receiving part has a sensitivity peak wavelength closer to a first wavelength in an absorption wavelength band of the first gas than the second light receiving part, and the second light receiving part has a sensitivity peak wavelength closer to a second wavelength in an absorption wavelength band of the second gas than the first light receiving part.