The Research And Development Of CO Online Detection System Base On TDLAS

Large power factories and mines exhaust a great deal of flammable, explosive and poisonous gases which seriously threaten human's living environment and personal safety. How to detect these gases quickly and real-time has very important meaning to safe production, poisonous gases recycle and environment protection. So by taking carbon monoxide's online detection as a goal, the implement principles and methods of whole instrument were analyzed. Based on these works, an experimental sample machine was made. The sample machine has several advantages such as high sensitivity, fast response speed, burn-proof, explosion prevention and electromagnetic interference prevention and so on.The basic theory about system realization, which was gas molecule's selective absorption and Lambert-beer's law, was analyzed. The methods about how to distinguish the different gases based on the characteristic absorption wavelength of gases were pointed out. Meanwhile the methods about how to calculate the gases' concentration based on the absorption were also presented. Brief presentations about related knowledge such as spectrum line broadening mechanism, spectrum line width and spectrum line intensity were introduced.The carbon monoxide and some other usual background gases were analyzed. A conclusion which is the right absorption peak's center wavelength of this project is 1.57μm is made.The mathematical model of the carbon monoxide detection system especially the method of harmonic detection was analyzed. Two conclusions were pointed out: the gas concentration was proportional to the second harmonic and the ratio of the second harmonic to the first harmonic could be used to eliminate the system error caused by several factors such as unstable light source and so on. Also the influence of gas' temperature and pressure on the absorption coefficient was analyzed.After analyzed the whole instrument's physical realization circuit especially the laser drive and the circuit which core was lock-in amplifier, theoretical analysis or simulation analysis on some important circuit were made and so did the matching software's realization flow.The hardware and software which were used to the implementation of instrument human-computer interaction were brief analyzed.At the end the feasibility of entire project by experimenting on the sample instrument was verified and then the solution of the problems about the sample instrument was presented.