ORIGINAL RESEARCH
Design of High Precision Temperature and Pressure Closed-Loop Control System for Methane Carbon Isotope Ratio Measurement by Laser Absorption Spectroscopy
Liu Xu 1,2,3
,
 
Zhang Zhirong 1,2,4,5
,
 
,
 
,
 
Pang Tao 1,4
,
 
Xia Hua 1,4
,
 
Wu Bian 1,4
,
 
,
 
 
 
 
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1
Anhui Provincial Key Laboratory of Photonic Devices and Material, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Science, Hefei 230031, China
2
University of Science and Technology of China, Hefei 230026, China
3
School of Electronic and electrical Engineering, Bengbu University, Bengbu 233030, China
4
Key Lab of Environmental Optics & Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
5
Advanced Laserer Tenonology Laboratory of Anhui Province, Heifei 230037, China
6
School of Atmospheric Physics, Nanjing University of Information Science & Technology, Ningliu Road No. 219, Nanjing, China, 210044
7
Department of Safety Health and Environmental Engineering, Yunlin University of Science and Technology, Yunlin, Taiwan 64002, China
CORRESPONDING AUTHOR
Zhang Zhirong   

Anhui Provincial Key Laboratory of Photonic Devices and Materia, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Science, China
Submission date: 2021-04-30
Final revision date: 2021-07-06
Acceptance date: 2021-07-17
Online publication date: 2021-12-20
Publication date: 2022-01-28
 
Pol. J. Environ. Stud. 2022;31(1):969–978
 
KEYWORDS
TOPICS
ABSTRACT
In order to achieve the accurate measurement of gas stable isotope, according to the structure of gas cavity and the characteristics of optical elements, a constant temperature and pressure gas isotope measurement experimental system based on tunable diode laser absorption spectroscopy (TDLAS) technology is designed, which can achieve high-precision and stable control of temperature and pressure in the box. The hardware circuit system including high-precision constant-current source, two-channel temperature sampling module, conditioning circuit and pressure control circuit is designed in the system. The corresponding system closed-loop control software is developed to ensure the stability of the temperature and pressure of the optical cavity. Through the experimental verification, the temperature is controlled at 35ºC and the pressure is controlled at 150 mbar in the present work. The measurement results verified the stability of the temperature and pressure system, as follows: the optimal temperature fluctuation control is ±0.005ºC and the pressure stability is ±0.1 mbar. Then, in our experiment, the CH4 standard gas is introduced to measure carbon isotope (12CH4 and 13CH4). The results clearly show that the control system is sufficiently stable to be used and the δ13C value can reach 0.52‰ according to the Allan variance.
eISSN:2083-5906
ISSN:1230-1485