丙丁烷TDLAS测量系统的吸收峰自动检测

Automatic Absorption Peak Determination in LPG Detection System Based on TDLAS

摘要:

基于丙丁烷在3.37μm处的基频吸收峰,使用相应中心波长的连续带间级联激光器和长光程吸收池,研制了基于波长调制技术的丙丁烷气体检测系统。为自动确定波长调制过程中的锯齿波中心值参数,基于电流与输出光频率的线性关系,通过均匀增加激光器驱动电流获得直接吸收光谱。使用基于洛伦兹线型的拟合算法确定吸收峰值对应电流,使锯齿波输出光以其为中心覆盖吸收峰。实验证明,以拟合结果31.94mA为中心值的锯齿波,在叠加频率为20000Hz、幅值为0.03V的高频正弦调制波后,系统二次谐波峰值超过100mV。算法全过程不依赖标气和F-P标准具等精密光学器件,可适应实际生产条件下的系统自动定参。

Abstract:

Based on the fundamental frequency absorption peak at 3.37μm of propane butane, a propane butane gas detection system based on wavelength modulation technology was developed by using a continuous interband cascade laser(ICL) with corresponding center wavelength and an absorption cell with a long optical path.In order to automatically determine the center value of sawtooth wave in the wavelength modulation process, based on the linear relationship between current and output frequency, the direct absorption spectrum was obtained by uniformly increasing the driving current of the laser.The Lorenz profile fitting algorithm was used to determine the current corresponding to the absorption peak so that the sawtooth output light can cover the absorption peak with its center. The experimental results show the sawtooth wave with the fitting result of 31.94mA as the central value, after the high-frequency sinusoidal modulated wave with the superposition frequency of 20000Hz and amplitude of 0.03V, the second harmonic peak exceeds 100mV. The whole process of the algorithm does not depend on precise optical devices such as gas and F-P etalon.