KEYWORDS: Laser induced breakdown spectroscopy, Chemical elements, Denoising, Quantitative analysis, Wavelets, LabVIEW, Analytical research, Databases, Signal detection, Signal to noise ratio
In order to simplify the data processing process of laser induced breakdown spectroscopy (LIBS)spectral detection system. In this paper, a LIBS automatic spectral detection system based on LabVIEW is designed and applied to the quantitative analysis of Cr element in aqueous solution. The LIBS automatic spectral detection system includes four parts: wavelet noise reduction, spectral peak detection, spectral line recognition and quantitative analysis. The collected spectral data are filtered and denoised by LabVIEW combined with MATLAB, and the spectral line recognition and peak detection are realized by second derivative and threshold method. The qualitative and quantitative analysis of metal elements in the mixed solution was realized by gelatin solidification method combined with LIBS automatic spectrum detection system. The detection results showed that the mixed solution contained Fe, Cu and Cr three kinds of metal elements. The Cr calibration curve R2 was 0.962, and the relative error was 1.92027%. The research shows that the system is simple and fast, and can be widely used in LIBS spectral detection and analysis of various samples.
As the most important greenhouse gas, CO2 has caused a lot of climate change problems. Therefore, the measurement of CO2 is of great significance. Based on the tunable diode laser absorption spectroscopy (TDLAS), the effect of temperature on the absorption spectrum of CO2 was studied. A DFB laser with the center wavelength of 1430 nm was selected. The absorption line of CO2 near 1432 nm at different temperatures (293-373 K, interval 10K) was measured by wavelength modulation spectroscopy (WMS). By comparing S-G filtering method, FFT filtering method and P-F filtering method, the spectral data was preprocessed, and the optimal preprocessing method was determined. The measurement error caused by noise was reduced effectively, the second harmonic signal of CO2 at different temperatures was obtained, and the influence of temperature on the absorption spectrum of CO2 was analyzed. The goodness of fit of temperature and signal strength under different orders was evaluated. Finally, the second-order polynomial fitting was chosen as the optimal model of CO2. The experimental results complement and improve the existing database to ensure the accuracy of CO2 inversion, which has an important reference significance for the measurement of CO2 in practical applications.
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