Development Of Three-team Automobile Exhaust Gas Concentration Sensor

Nowadays, with the increasing of the number of city automobilevehicle, it brings convenience to people’s daily life at the same time, alsocaused serious pollution for our living environment. The exhaust emission ofautomobile has become the main source of air pollution and it’s one of themajor factors affecting urban air quality. To control the automobile vehicleemissions, the best way is that it must be started with the sources of pollutionand enhance the detection and control of automobile exhaust emissions. Forthis reason, China began to develop vehicle emissions standards from1981.Then as more and more rigorous new national standards promulgated, thecontrol index is gradually approaching with the international advanced index.Therefore, it requires the exsiting exhaust detect instrument to have higheraccuracy and more stability. An automobile exhausts gas sensor developed inthis paper is just used to measure the pollutants concentration in vehicleemissions, providing a strong protection for the vehicle emission control. Itimproves the analysis of vehicle exhaust testing technology, and to a cer tainextent it also would improve the atmospheric environment and people’s livingenvironment. It plays a positive role on energy conservation and emissionreduction, especially for the promotion of high pollution and high emissionvehicles’ out updates, and protection of the increasingly nervous petroleumresources.A gas sensor using to analyze the concentration information ofautomobile exhaust emission is developed based on Non-Dispersive Infrared(NDIR) techniques in this paper. It could quickly detect the concentration ofCO2, CO and HC in the emission exhaust at the same time.Based on the analysis of status quo of vehicle exhaust testing andnon-dispersive infrared detection technique, this article establishes a fullsystem test scenario and designs a detection system structure. Choose the right infrared lamp, infrared detectors, gas chamber, window films, etc. as theoptical, pneumatic system components. According to the characteristics ofthe infrared light source, we design a steady-voltage light source drivencircuit. And according to the IR thermopile detector output characteristics, aweak signal amplification filter circuit is designed in this paper. Then wedesigned the following A/D conversion circuit, MCU control circuit andperipheral circuit. By developing the program of hypogynous machine andepigynous machine, complete the whole design of sensor system platform.In this paper, the calibration experiment of sensor system platform isstudied. By measuring a series of standard gases of each component, we canget the relationship between each channel voltage signal data andcorresponding gas concentration. By analyzing the experimental data andprocessing, fitting out of the three components CO, HC, CO2concentrationcurves using Origin software. The system is within±5%of the relative error,±1%of the repeatability and stability, and its response time is within3second. And by detailed analysis of the factors influencing the system,compensate to the main affecting factors like environment temperature andpressure, and finally present the error sources of influencing the system.