Multi-sensor System Design For Poisonous And Harmful Gases

In recent years,with the gradual expansion of the industrial scale,explosions caused by various hazardous chemical leaks or fires have occurred from time to time.These accidents not only caused serious environmental pollution problems,but also endangered human health,social and economic development,drowning lots of the attentions of relevant departments.Therefore,portable detectors for environmental detection of accident sites and capable of simultaneously detecting multiple gases have become an inevitable requirement for economic and social development.Therefore,a portable multi-sensor system for a variety of toxic gas detection requirements is designed and studied in this thesis.According to the on-site temperature,humidity,smoke and multi-gas detection requirements,the design includes modules of micro air pump,gas flow meter,particle density sensor,temperature and humidity sensor,metal oxide sensor,non-dispersive infrared sensor and power supply.The micro air pump module uses a micro air pump to draw the gas in the environment into the detection chamber;the gas flow meter module uses a gas flow meter to monitor the flow of the inhaled gas;the particle density sensor module uses the H21A3 particle density sensor to detect large particles of smoke,considering that too much smoke particles contained in the gas may affect the detection performance of the gas or even damage the gas sensor,the design uses a filter layer composed of cotton to form a physical layer,which can remove the influence of large particles of smoke and water vapor;the temperature and humidity sensor module utilizes the HTU21D temperature and humidity sensor to detect the temperature and humidity of the gas in the chamber in real time;the MOX sensor module uses the MOX sensor to detect the poisonous gas;the NDIR sensor module uses the NDIR sensor to detect the CO₂in the air,and the KL25 micro processor is adopted as the central processing unit.The system design integrates various types of Figaro gas sensors TGS2611,TGS2602,TGS2600,TGS2603,HTU21D temperature and humidity sensors,H21A3 particle density sensors and self-made NDIR infrared sensors to detect gas parameters.The collected data parameters of all sensors are processed by signal processing and using probabilistic neural network algorithms to obtain specific and accurate parameters such as smoke concentration,temperature,humidity,CO concentration,CO₂ concentration,methane concentration and gas flow rate.The system is tested based on the gas test platform,and the system finally realizes real-time detection and analysis of CO gas detection in the concentration range of10ppm-500ppm,methane gas detection in the concentration range of 0-5000ppm,CO₂ gas detection in the concentration range of 390ppm-10.2%,CO and CO₂ gas mixture concentration detection,CO and methane gas mixture concentration detection,which shows are of great significance to the gas detection industry.