An Improved WMS-2f/1f Spectral Fitting Method Using Orthogonal Test in Initial Parameters Selection

Area of Science:

• Spectroscopy
• Gas Sensing
• Physical Chemistry

Background:

• Wavelength modulation spectroscopy (WMS) is a sensitive technique for gas analysis.
• The WMS-2f/1f method offers improved signal-to-noise ratio for spectral measurements.
• Accurate initial parameter selection is crucial for efficient spectral fitting.

Purpose of the Study:

• To develop an improved WMS-2f/1f spectral fitting method.
• To enhance the efficiency and accuracy of spectral fitting using orthogonal test for initial parameter selection.
• To experimentally validate the proposed method for temperature measurement of H2O in air.

Main Methods:

• Implementation of an improved WMS-2f/1f spectral fitting method.
• Utilizing orthogonal test for optimizing initial spectral fitting parameters.
• Experimental validation using a gas cell with diluted H2O in air at 1 atm, 291K, and 0.7% concentration.
• Targeting a transition center wavelength near 1344 nm.

Main Results:

• Significant reduction in sum-square-error (SSE) between calculated and measured WMS-2f/1f spectra with optimized parameters.
• Faster convergence of the fitting routine compared to conventional methods.
• Accurate temperature measurements of water vapor, showing good agreement with true values.

Conclusions:

• The proposed WMS-2f/1f spectral fitting method with orthogonal test-based initial parameter optimization improves fitting efficiency and accuracy.
• This method provides a reliable approach for precise gas temperature measurements.
• The technique is validated for determining the temperature of diluted H2O in air.