Dual Optical Path Spectrometer for Wide Range Gas Concentration
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Solution Overview
Problem
Optical absorption spectrometers, such as CIPS and NDIR devices, face limitations in measuring a wide range of gas concentrations due to inherent sensitivity issues and radiation absorption problems, making it difficult to accurately measure both low and high concentrations simultaneously.
Innovation Solution
The implementation of a dual optical path system within the spectrometer, where one path is longer and the other shorter, allows for high sensitivity at low concentrations while accommodating high concentrations by reducing the number of gas molecules along the shorter path, combined with a processing circuit that generates normalized and average signals to enhance measurement accuracy across a broader concentration range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long optical path is used to increase sensitivity for low concentration measurements, then measurement sensitivity is improved, but the device cannot accurately measure high concentrations due to radiation saturation
Solution Approach 1:
The optical path is segmented into multiple paths of different lengths (first optical path and second optical path). The first optical path has length L1 suitable for measuring low concentrations with high sensitivity, while the second optical path has length L2 suitable for measuring high concentrations. This segmentation allows the device to handle both low and high concentration ranges accurately.
Solution Approach 2:
The invention transitions from a single optical path to multiple optical paths with different lengths. By adding the dimension of path length variation, the system can selectively use appropriate path lengths for different concentration ranges, thereby expanding the overall measurement range while maintaining high sensitivity for low concentrations.
2Device complexity
If a single optical path length is used, then the device structure is simple, but it cannot accurately measure both low and high concentrations simultaneously
Solution Approach 1:
The single optical path is divided into multiple segments (first optical path of length L1 and second optical path of length L2). Each segment serves a specific concentration range, allowing the device to maintain structural simplicity while achieving versatile measurement capabilities across different concentration levels.
Solution Approach 2:
The optical system is designed to perform multiple functions using different optical paths. The same basic optical components (radiation source, detector, filter) are used across multiple paths with different lengths, making the system universal for measuring both low and high concentrations without requiring entirely separate measurement systems.
3Measurement precision
If the optical path length is increased to detect low gas concentrations, then detection sensitivity is improved, but radiation is completely absorbed at high concentrations making measurement impossible
Solution Approach 1:
The optical path is segmented into a first path (length L1) for low concentration detection where high sensitivity is needed, and a second path (length L2) for high concentration measurement where complete absorption would occur. This segmentation prevents radiation saturation by selecting the appropriate path length for the given concentration level.
Solution Approach 2:
Different regions of the optical system use different path lengths optimized for local conditions. The first optical path uses length L1 optimized for low concentration regions, while the second optical path uses length L2 optimized for high concentration regions. This local optimization ensures accurate measurement across the entire concentration range.
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 approach enables accurate measurement of gas concentrations across a wide range, reducing the impact of radiation intensity variations and absorption issues, allowing for reliable detection from low to high concentrations.
Implementation Method 1
optical absorption spectrometer for determining the concentration of a substance within a sample... based on the measurement of the absorption of incident radiation by the gas molecules
Implementation Method 2
The cIPF is formed from a modified interference polarisation filter (IPF) which uses the phenomenon of birefringence in certain crystals to obtain a transmission spectrum which is characterised by a quasi-periodic sequence of spectral passbands
Data Source
AI summary
An optical absorption spectrometer is provided for determining the concentration of a substance within a sample. The optical absorption spectrometer comprises a first radiation source for supplying radiation to the sample to be measured; at least one cavity for containing the sample during measurement; and a detector assembly for detecting radiation transmitted along first and second optical paths through the sample, the length of the first optical path being greater than that of the second optical path.