Gas Concentration Measurement Using Phase-Corrected Wavelength Modulation
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Solution Overview
Problem
Current methods for measuring gas concentration in gas mixtures are computationally complex and prone to errors.
Innovation Solution
A method involving wavelength modulation spectroscopy, where a light beam is modulated in a ramp and/or step shape, and periodically, with a derivative signal determined through Fourier transformation, followed by phase correction using a correction function to minimize measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current methods for measuring gas concentration are used, then gas concentration can be determined, but the measurement process becomes computationally complex and error-prone
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing reference absorption spectra and phase correction functions in a database before actual measurements. During measurement, the system retrieves these pre-computed references and compares them with actual signals, avoiding complex real-time calculations. This resolves the contradiction by maintaining high measurement precision while significantly reducing computational complexity during operation.
Solution Approach 2:
The patent implements feedback through an iterative phase correction process. The system determines initial phase values from the derivative signal, uses these to calculate correction functions, applies the corrections to improve the signal, and recalculates phases to verify improvement. This feedback loop continues until convergence, ensuring high measurement accuracy while using efficient algorithms that reduce computational burden compared to non-iterative approaches.
2Measurement precision
If complex signal processing transformations are applied to improve measurement accuracy, then gas concentration determination becomes more precise, but computational time and complexity increase
Solution Approach 1:
The patent performs computationally intensive operations in advance by pre-calculating phase correction functions and storing reference spectra. During actual measurement, only lightweight retrieval and comparison operations are needed, reducing real-time processing time while maintaining high precision through the use of pre-computed accurate references.
Solution Approach 2:
The patent uses periodic wavelength modulation of the laser at a fixed frequency to generate derivative signals at specific harmonics (e.g., 2f, 3f). This periodic action converts complex spectral information into time-domain signals at known frequencies, enabling efficient Fourier transformation and phase extraction. The periodic modulation rhythm structures the measurement process, allowing systematic extraction of gas concentration information with reduced computational requirements compared to continuous spectral analysis.
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
Facilitates accurate and efficient gas concentration measurement by optimizing signal processing and reducing errors, enabling reliable determination of gas concentrations in gas mixtures.
Implementation Method 1
In TDLS (Tunable Diode Laser Spectroscopy), the wavelength of a laser is varied so that absorption lines of a gas or a gas mixture are scanned or detected
Implementation Method 2
Each gas in this respect absorbs light of one or more specific wavelengths or of a specific wavelength range, i.e. each gas or gas mixture has a different absorption line
Implementation Method 3
the transmitted light of the laser is modulated in its wavelength and is detected by a detector after a passing through of the gas to be measured. The amount of light absorbed by a gas mixture in a specific wavelength range can be taken from a detector signal
Implementation Method 4
a derivative signal is determined based on the detector signal by performing a transformation of the detector signal into the frequency range, in particular by a Fourier transformation of the detector signal
Data Source
AI summary
The invention relates to a method for measuring a concentration of a gas in a gas mixture, said method comprising that: a light beam modulated in a ramp shape and/or in a step shape in its wavelength and additionally periodically modulated, in particular in its wavelength, is transmitted from a light source, in particular a laser, into a measurement zone; the modulated light beam passes through a gas mixture in the measurement zone and is detected as reception light by a detector, wherein the reception light is converted by the detector into a detector signal; a derivative signal is determined based on the detector signal by performing a transformation of the detector signal into the frequency range, in particular by a Fourier transform of the detector signal, wherein an evaluation of the detector signal transformed into the frequency range is performed, in particular only, for an n-fold of the frequency of the modulated light beam in order to obtain the derivative signal; and at least two measurement values of a phase of the derivative signal are determined and a correction function is calculated based on the determined measurement values of the phase of the derivative signal in order to correct the derivative signal with the correction function.