Monitoring The Concentration Of Carbon Dioxide By Tunable Diode Laser Absorption Spectrometer

The environment pollution is the focus problem all the world care about in recent years, so it is very important to monitor the pollution air on-line. Carbon dioxide is one of the main green-house gases. Through on-line monitor the carbon dioxide, it has the leading function towards on-line monitoring other pollution air.This thesis takes Beer- Lambert as the theoretical foundation. By combining the line-type theories and Beer- Lambert law, formula on carbon dioxide concentration were deduced, and a various data evaluation methods were given. Under a condition of normal temperature and pressure, the peak of the carbon dioxide absorb spectrum can representative the concentration of the carbon dioxide, we get a more favorable way to get the concentration of the carbon dioxide is that the area of carbon dioxide absorb spectrum.Direct absorption spectrum has been adopted under some different conditions, and some conclusions were got by optical spectrum analysis. Under the normal temperature and pressure, the peak of the carbon dioxide absorb spectrum linear with the concentration of the carbon dioxide. Under constant temperature and pressure above 0.5atm, the peak of the carbon dioxide absorb spectrum relates with the sample cell length and carbon dioxide concentration. Under any conditions and optical path constant, the area of carbon dioxide absorb spectrum can only representation the concentration of the carbon dioxide. Modulation absorption spectrum do these experiments again, at the normal temperature and pressure, the peak of second harmonic signal linear with the carbon dioxide concentration.The last experiment is saturated absorb study, light power is about 0.5 mw, saturated coefficient is about 0.1 by interpretation. It has big influence in precision measure. The same kind product in our country hasn't discussed this problem at all, but limiting of experiment condition, we can only give some conclusions, follow-up work is need.Our work carried out on-line monitor of the carbon dioxide, have the leading function towards carrying out on-line monitor the other pollution air.