TDLAS一氧化碳浓度检测系统误差分配

Error distribution for TDLAS carbon monoxide concentration measurement system

在利用可调谐二极管激光吸收光谱技术测量一氧化碳(CO)气体浓度时,反演精度受光强、温度、压强等的影响,需要对系统的总体误差进行分析与分配。为了提高TDLAS的测量精度,降低多项误差对测量的影响,本文提出了对系统各个测量误差的分配方法。首先建立了CO浓度反演的误差模型,基于二次谐波测量原理引入了二次谐波峰值、光强、驱动电流、温度、压强和光程几项误差;其次,利用随机化方法分别研究了系统各项误差对浓度误差的影响,并通过数值拟合的方法推导了浓度误差与各项误差的关系,比较了浓度误差对各项误差变化的灵敏度;最后,根据求得的灵敏度关系,综合考虑浓度测量要求以及现有器件的工艺水平,对各项误差进行了合理、有效的分配。利用蒙特卡洛法对本文所提出的各项误差分配方案进行了仿真,仿真结果表明,在CO体积分数为2.5%时,该误差分配方案可使浓度测量的绝对误差小于0.025%。在实验室条件下对体积分数为2.5%的CO进行了测量,其绝对误差小于0.01%,实现了对CO气体浓度的高精度反演。本文的研究结果保证了TDLAS浓度检测系统在多项误差影响下的测量精度,同时,可有效降低系统的设计难度和经济成本,对仪器的开发和应用具有重要的指导意义。

The inversion accuracy of carbon monoxide(CO)concentration measurement using tunable diode laser absorption spectroscopy(TDLAS)technology is affected by various measurement errors,such as those pertaining to laser intensity,temperature,and pressure. To improve the measurement accuracy of TDLAS and reduce the influence of multiple errors on measurements,an error distribution method for each measurement error was proposed. First,an error model for CO concentration inversion was established. It included common error terms such as the peak value of the second harmonic,laser intensity,driving current,temperature,pressure,and optical path,based on the second harmonic measurement principle. Second,the influence of various error sources on the measured concentrations was studied separately using a randomized numerical fitting method,enabling the relationship between the concentration error and each error to be derived and the sensitivity of the concentration error to each error to be compared.Lastly,the various errors were effectively distributed by considering the sensitivity relationships,concentration measurement requirements,available devices,and technical complexity. Simulation of the error distribution scheme was performed using the Monte Carlo method. The simulation results show that when the gas volume fraction is 2. 5%,the absolute error of concentration measurement is less than 0. 025% under the error distribution scheme. Experiments to measure CO with a volume fraction of 2. 5% show that the absolute error is less than 0. 01%,demonstrating the high inversion accuracy inversion of CO concentration measurement. The results of this research show that the proposed error distribution method ensures high measurement accuracy for a TDLAS concentration detection system under the influence of multiple errors. In addition,the method can effectively decrease the design difficulty and cost of the systems,which is significant for the development and application of such instruments.