Research Of High Precision Gas Measurement System Based On Infrared Pyroelectric

The mixed gas concentration detecting device is indispensable for monitoring gas composition and concentration in the urban pipe network systems.Gas concentration detecting for pipe network has high requirements for accuracy,real-time performance,power consumption and stability.The gas detection device must report and alarm promptly when gas concentrations is abnormal in pipe networks.This system will guarantee operation for pipe network systems,reduce the accident incidence and avoid unnecessary property damage.In this paper,infrared pyroelectric detection method is studied and a high performance mixed gas concentration detection system is designed.This system realizes high-precision concentration detection of each component in the pipe networks.The research content of this paper includes:1、The current methods of mixed gas detection at home and abroad were studied.The advantages and disadvantages of various detection methods were compared.Then,the infrared pyroelectric technology was selected as the gas detection technology.2、Principles of infrared pyroelectric detection technology and the methods of pyroelectric gas measurement were studied.The influences of different infrared excitation frequencies on the electric effect of pyroelectric crystals were calculated and analyzed.Then,the excitation frequency range of the infrared pyroelectric probe is 1～5 Hz.3、The signal characteristics and external influence factors of infrared pyroelectric detection were studied and analyzed,appropriate hardware circuits were selected.Hardware system with low power consumption chip MSP430 was designed,and the feasibility of the hardware system was verified using Multisim software.4、Several digital filtering algorithms of gas detection technology were compared.The real-time performance and stability of different digital filtering algorithms were verified by Matlab simulation.Finally,the second-order sliding Goertzel algorithm was selected as the core digital filtering algorithm.5、An experimental platform was built.Then calibration experiments and gas sensitivity experiments were conducted.The measurement accuracy of four gas(carbon dioxide,ammonia,methane and carbon monoxide)concentration measuring devices was analyzed and calculated.The accuracy is: 0.427%,1.06%,0.941%,and 1.79% respectively.The average power consumption is 78 m A(6V power supply).Linearity is less than ±1%.The results show that the performance of gas detection devices reach the advanced level at home and abroad.Experimental results show that the mixed gas detection device designed in this paper has advantages of high measurement accuracy,high stability and low power consumption.This mixed gas detection device is suitable for gas monitoring in urban pipe network systems.