Gas concentration measurement method based on WMS main peak spectrum fitting

A fast and accurate gas concentration measurement method by fitting the main peak of the absorption spectrum harmonic signal is proposed for the first time to significantly improve the speed and accuracy of gas concentration measurement by laser wavelength modulation spectroscopy (WMS). In the proposed method, only the main peak of the absorption spectrum harmonic signal is scanned to obtain the peak value of the harmonic signal (WMS-2f/1f). This can greatly improve the scan speed due to the reduction of absorption spectrum scan range. Higher accuracy measurement can be achieved via fitting the main peak of the absorption spectrum harmonic signal (WMS-2f/1f) by a polynomial. The methods for choosing a suitable polynomial's degree and the influence of fitting data length on measurement result are discussed in this paper. The experimental results of carbon dioxide concentration measurement under different conditions validate the effectiveness of the proposed method.