基于超窄线宽激光器的多气体光声光谱检测研究

Multi-component gas high accuracy detection based on photoacoustic spectrometry and ultra-narrow-linewidth laser

针对多组分痕量气体检测中精确度差、灵敏度低等问题,设计了基于光源波长扫描技术的光声光谱式多组分痕量气体检测系统。系统采用单一超窄线宽半导体激光器作光源,设计了一阶纵向共振式多光程吸收光声池,通过正弦信号对光源波长进行调制,并结合二次谐波信号检测技术和超窄线宽激光特性,有效地消除了吸收池内的背景噪声和光源抖动的影响,实现了C2H2、CO和CO2多组分低浓度气体同时检测。实验结果表明,C2H2、CO和CO2多组分气体浓度测量线性相关度为0.99,最大相对误差小于2%,极限检测灵敏度分别为5×10-6、12×10-6和15×10-6;长时间稳定性实验,多组分气体浓度最大相对波动小于1.5%。系统精确度好、灵敏度高并具有较好的稳定性,可用于电力变压器故障气体实时在线监测。

In order to solve the problem of low accuracy and sensitivity in multi-component trace gas detection, a kind of multi-component trace gas detection system based on wavelength scanning and photoacoustic spectrometry is designed. A semiconductor laser with ultra-narrow-linewidth and tunable wavelength is utilized as light source and a first-longitudinal resonant photoacoustic cell with multi-optical path is also used in this system. By taking the sine signal to modulate the wavelength of laser and combining the second harmonic signal detection technique with characteristics of ultra-narrow-linewidth laser, the detection of low concentration multi-component gases is achieved. The system is able to effectively eliminate the background noise and the influence of intensity fluctuation. The experiment results indicate that the relative measurement error is less than 2% and the linearity relevance coefficient is 0.99. The results of long time stability monitoring also show that the maximum relative fluctuation is less than 1.5%. Finally the sensitivity detection limits are determined to be： 5×10^-6 for acetylene, 12 ×10^-6 for carbon monoxide and 15×10^-6 for carbon dioxide. The system has advantages of high accuracy, high sensitivity and good stability,which can be used in power transformer fault gases on-line monitoring in real time.