Research On Methane Concentration Detection System Based On Infrared Absorption Spectroscopy Technique

Methane,commonly known as gas,is the main component of natural gas.With the improvement of urbanization level in China,kitchens of urban families will use centralized supply of natural gas to meet their living needs.Real-time detection and early warning of natural gas concentration is related to the safety of personal and property of millions of households.The research and application of methane detection technology are of great significance.Compared with various methane detection technologies,optical detection technology becomes a hot spot in the field of gas detection research because of its excelent stability and high accuracy.Based on infrared absorption spectroscopy,this paper aims to detect methane concentration.By studying the spectral absorption detection method and developing it into the spectral absorption detection system,an infrared detection system for single-wavelength dual optical path was designed.Then the variation of methane measurement value of the system at different temperatures was studied,and the temperature compensation algorithm was designed to eliminate the measurement error of methane.In addition,a wireless communication function was added to the system to realize real-time monitoring and early warning of methane concentration.The main research work of the thesis is as follows:(1)Optical structure and circuit structure of methane concentration detection system are studied and designed.Distributed feedback laser is chosen as infrared light source,double chamber structure is designed,photodiode is chosen as infrared receiver,and detection signal is amplified and filtered after AD sampling.In order to meet the needs of remote warning,the system is designed to connect to the OneNET Internet of Things platform through the narrowband Internet of Things(NB-IoT)based on cellular network,and make APP to obtain real-time detection information of methane concentration remotely and send alarm information in time.(2)The influence of temperature on the measurement accuracy of methane concentration detection system was studied.In order to solve the problem of temperature-dependent drift of concentration measurements,sampling measurements of methane concentration at different temperatures were carried out.A temperature drift compensation mechanism was designed based on the least square theory.Experiments show that the compensation mechanism eliminates the measurement errors caused by temperature changes.