基于可调谐多模二极管激光吸收光谱的二氧化碳浓度测量
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摘要
可调谐二极管激光吸收光谱技术(TDLAS)具有高分辨率、高灵敏度和快速测量等特点,是气体探测中的主流技术。使用多模二极管激光器作为光源,将多模二极管激光吸收光谱技术与关联光谱技术相结合有助于提高测试可靠性和稳定性,同时还可有效解决单模二极管激光器长时间工作时中心波长随外界温度或机械特性的变化而发生偏移的问题。以1 570 nm多模二极管激光器为光源,利用多模二极管激光关联光谱和波长调制的气体测量技术(TMDL-COSPEC-WMS),通过计算待测气体和参考池气体之间二次谐波信号峰值高度之间的关系,实现了对二氧化碳浓度的测量。实验中二氧化碳浓度测量范围在0.6%~30%之间,计算结果表明,二氧化碳浓度与真实浓度值之间具有良好的线性关系,其线性度为0.998 7,线性拟合的斜率为1.061±0.016 8。对二氧化碳与氮气混合气体的连续测量结果表明,系统的探测极限达到335ppm·m,对同一样品在20 min内的20次连续测量的标准偏差为0.036 7%,表明了系统良好的稳定性,所有测量结果都显示了系统用于二氧化碳气体监测的有效性。
Tunable diode laser absorption spectroscopy(TDLAS) technology is a kind of fast time response,large-range,continuous on-line monitoring gas detection technique.It is the mainstream technology of gas detectioa In this paper the multimode laser diode was used as light source.Multi-mode laser combined with correlation spectroscopy can improve the test reliability and stability.It can also conquer the problem of the central wavelength change of the single mode diode laser due to thermal or mechanical fluctuations in durable working process.A FP laser was used as the light source in this research.A multi-mode diode laser system based on correlation spectroscopy and wavelength modulation spectroscopy(TMDL-COSPEC-WMS) was used to measure carbon dioxide in ambient air around 1 570 nm.The carbon dioxide concentrations were derived from the relationship between the normalized WMS-2f signal peak heights of the measurement and reference signals which selected based on high signal to noise ratio and correlation coefficient.All measurements were performed with controlled carbon dioxide and nitrogen mixtures in which carbon dioxide concentrations range from 0.6%to 30%.The calculation results showed that there was a high linear relationship between the measured and actual carbon dioxide concentration,the linearity was 0.998 7 and the fitted slope was1.061+0.016 8 respectively over the tested range.A detection limit of 335 ppm ? m was achieved.The standard deviation of0.036 7%was achieved using 20 successive measurements with each measurement time taking ~10 s during 20 minutes,which demonstrated good stability of the system.Good agreements between the measurements of the system and actual values confirm the accuracy and potential utility of the system for carbon dioxide detection.
Tunable diode laser absorption spectroscopy(TDLAS) technology is a kind of fast time response,large-range,continuous on-line monitoring gas detection technique.It is the mainstream technology of gas detectioa In this paper the multimode laser diode was used as light source.Multi-mode laser combined with correlation spectroscopy can improve the test reliability and stability.It can also conquer the problem of the central wavelength change of the single mode diode laser due to thermal or mechanical fluctuations in durable working process.A FP laser was used as the light source in this research.A multi-mode diode laser system based on correlation spectroscopy and wavelength modulation spectroscopy(TMDL-COSPEC-WMS) was used to measure carbon dioxide in ambient air around 1 570 nm.The carbon dioxide concentrations were derived from the relationship between the normalized WMS-2f signal peak heights of the measurement and reference signals which selected based on high signal to noise ratio and correlation coefficient.All measurements were performed with controlled carbon dioxide and nitrogen mixtures in which carbon dioxide concentrations range from 0.6%to 30%.The calculation results showed that there was a high linear relationship between the measured and actual carbon dioxide concentration,the linearity was 0.998 7 and the fitted slope was1.061+0.016 8 respectively over the tested range.A detection limit of 335 ppm ? m was achieved.The standard deviation of0.036 7%was achieved using 20 successive measurements with each measurement time taking ~10 s during 20 minutes,which demonstrated good stability of the system.Good agreements between the measurements of the system and actual values confirm the accuracy and potential utility of the system for carbon dioxide detection.
引文
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