Compact Laser Trace-Gas Sensor Spectral Fitting for High Dynamic Range
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Solution Overview
Problem
Existing trace gas sensors face limitations in achieving a high dynamic range of sensitivity for accurately detecting and quantifying gases like methane and sulfur dioxide, particularly in environments with noise and non-uniformities, which affect the accuracy and precision of concentration measurements.
Innovation Solution
The system employs spectral fitting of direct and harmonic detection absorption spectroscopy, using a laser-based gas sensor to scan absorption features, fit a polynomial to the scan edges, derive a baseline signal, and apply a spectral model to solve for mole fraction, incorporating lock-in amplifiers and lookup tables to enhance sensitivity and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional absorption spectroscopy is used for gas detection, then the sensor can detect gas concentrations, but the dynamic range of sensitivity is limited and cannot accurately measure concentrations over multiple orders of magnitude
Solution Approach 1:
The patent segments the absorption spectrum into multiple regions (line center, line wings, and continuum regions) and applies different analysis methods to each segment. The line center region provides high sensitivity for low concentrations, while the line wings and continuum regions enable measurement of higher concentrations, collectively achieving a dynamic range spanning multiple orders of magnitude.
Solution Approach 2:
The patent extends the measurement from traditional single-point absorption measurements to multi-dimensional spectral analysis by utilizing both frequency-domain information (different spectral regions) and amplitude-domain information (absorption magnitudes). This dimensional expansion enables simultaneous measurement across a wide concentration range.
2Object-affected harmful factors
If the sensor operates in noisy environments with non-uniformities, then it can function in harsh conditions, but the accuracy and precision of concentration measurements deteriorates
Solution Approach 1:
The patent extracts and separately analyzes different spectral components (line center, line wings, continuum) to isolate the absorption signal from background noise and non-uniformities. By extracting the relevant absorption features from the complex spectrum and analyzing them independently, the method maintains measurement precision even in noisy environments.
Solution Approach 2:
The patent employs iterative optimization where the measured spectrum is compared against a spectral model, and the model parameters are adjusted to minimize residuals. This feedback loop continuously refines the concentration measurement, compensating for noise and non-uniformities in the measured signal.
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 significantly improves the dynamic range of sensitivity, enabling accurate gas concentration measurements over multiple orders of magnitude, even in harsh environments with noise and non-uniformities, by normalizing signals and modeling absorption profiles effectively.
Implementation Method 1
spectral fitting of direct and harmonic detection absorption spectroscopy, using a laser-based gas sensor to scan absorption features
Implementation Method 2
apply a spectral model to solve for mole fraction, incorporating lock-in amplifiers and lookup tables to enhance sensitivity and reduce noise
Data Source
AI summary
Systems, devices, and methods for scanning a laser into wings of an absorption feature; fitting a polynomial to the edges of the scan; dividing a transmitted signal by a fit-derived baseline to compute a transmission of the light; fitting a spectral model with the transmitted signal; and solving for a mole fraction.