Research On CO₂ Concentration Analyzer With Non-dispersive Infrared Measurement

Carbon dioxide is one of the important components of the atmosphere, it is closely linked with people’s production and daily life. With the continuous development of science-technology and the continuous improvement of productivity, the concentration of CO2 detection becomes more and more important in the field of mine safety production etc.In the thesis, through the comparison and analysis of the advantages and disadvantages of all kinds of gas concentration detection method, combined with the characteristics of CO2 absorption of infrared light, choose the infrared spectrum absorption method to determine the concentration of the gas. The design adopts German PerkinElmer IRL715 light source and PYS3228 G2/G20 pyroelectric infrared detector which has double light path, designed a dual channel non-dispersive infrared CO2 gas concentration detector with no moving parts.According to the characteristics of the selected light source and detector, designed the power supply circuit, light source modulation circuit, basic amplifier and filter circuit, MSP430 single chip microcomputer control circuit, liquid crystal display circuit, serial communication circuit, RS485 communication module circuit and so on.The thesis using C language for programming in IAR Embedded Workbench for MSP430 integrated environment. Combined with the feature of signal and function of the hardware circuit the design write the main program of the system, driving program of IRL715 source, AD conversion program, liquid crystal display and communication program.First of all, in order to take a calibration test for the existing conditions of the laboratory, the thesis analyzed the reasons of the completing errors and the gas measurement errors. In the end, after improving the measurement circuit of the instrument, the thesis reached the conclusion that the absolute error of the instrument is 0.21% and the response time is 6 seconds.