Gas Analytical System With Non-dispersive Infrared Measurement

With the increasing of the number of motor vehicle, the gas of motor vehicle has become main source of air pollution which also makes environment pollution more seriously. So we should measure and control the gas of vehicle by stable and accurate gas analytical system. In this paper, I design a new infrared gas analytical system to measure gas concentration.This gas analytical system is achieved using non-dispersive infrared (NDIR) techniques which are based on the fact that many gases have unique infrared absorption signatures in the 2-14 μm region. It can measure the concentration of carbon dioxide, carbon monoxide and hydrocarbon in the gas at the same time.This gas analytical system consists of the following: infrared light source, sample cell (of known optical length), thin-film interference filter, and infrared detector with its associated electronics. The thin-film interference filter is chosen to allow the detector to selectively monitor only the part of the infrared spectrum that is specifically affected by the gas of interest. As the gas of interest passes between the powered infrared source and the detector, the absorption spectra changes along with the detector's output, which is correlated to gas concentration.By studying a series of results between standard gas concentration and detector's output, we can get the relationship between these variables using Origin software. This paper study several factors which affect the result of measurement, including environmental temperature, gas pressure, change of light source and so on. This paper also study crosstalk among the different contamination, and by compensate to the results the system get more accurate.The results of the measurement using the gas analytical system display that the system is stable and accurate.