Acta Optica Sinica, Volume. 41, Issue 18, 1812004(2021)
Measuring Method of Atmospheric Carbon Dioxide Based on Tunable Fabry-Perot Interferometer
In order to meet the needs of accurate, fast and portable measurement of greenhouse gases such as CO2 and CH4, a multi-wavelength greenhouse gas measurement system based on tunable Fabry-Perot interferometer (FPI) sensor is introduced in this paper. Using FPI as wavelength selective element, the continuous measurement in band of 3100--4400 nm (wavenumber range is 3226--2273 cm -1) is realized through interference filter. The correlation coefficient is obtained by fitting the measured absorption spectrum with the absorption cross section of CO2, and then the gas concentration of CO2 can be calculated. To correct the non-linear absorption effect that caused by the low resolution of the instrument, the iterative algorithm is used to optimize the CO2 absorption cross section. The results show that the measurement error is reduced by 18% compared with the direct fitting calculation when concentration of CO2 is 4.08×10 -4. The interference optimization, precision, the limit of detection and other parameters of the system are verified. The experimental results show that the concentration of residual CO2 in the air chamber is less than 1×10 -6, the instrument precision is ±1.32×10 -6, and the detection limit is 1.13×10 -6 (2σ, 2 times standard deviation) when the time resolution is 10 minutes. Moreover, the system is used to carry out outdoor measurement in Hefei Science Island for one week, and the daily variation results and diurnal characteristics of concentrations of CO2 are obtained, which verified the stability and reliability of the system.
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Hongcheng Ji, Pinhua Xie, Jin Xu, Ang Li, Zhaokun Hu, Yeyuan Huang, Xin Tian, Xiaomei Li, Bo Ren, Hongmei Ren. Measuring Method of Atmospheric Carbon Dioxide Based on Tunable Fabry-Perot Interferometer[J]. Acta Optica Sinica, 2021, 41(18): 1812004
Category: Instrumentation, Measurement and Metrology
Received: Mar. 11, 2021
Accepted: Apr. 16, 2021
Published Online: Sep. 3, 2021
The Author Email: Xie Pinhua (phxie@aiofm.ac.cn), Xu Jin (jxu@aiofm.ac.cn)