| CO2 is a main kind of pollution gases discharged from coal-fired power station and automotive vehicles. Serious gas pollution not only leads to tremendous economic lose, but also endangers human subsistence. So it is of importance to monitor atmosphere pollution for environment protection and controlling. In this paper, CO2 is the detected object. The absorption curves carrying concentration information are changing with different pressure and temperature, which is studied. This technology can be extended to other pollution possessing infrared spectral absorption characteristic.Gas sensor based on spectral absorption is applied widely because of remarkable advantages. All kinds of gas detection technologies and the research status are narrated in this paper, and then tunable diode laser spectral technology is selected. The method of harmonic detection can tune some frequency signal by high frequency. It scans the measured characteristic signal. In signal processing system, the modulation signal or its double frequency is the reference signal. Then the phase-locked amplifier notes the characteristic message. This method has high-sensitivity, anti-electromagnetism interference and is not influential by other environment gases easily.In the paper, the center absorption wave, the absorption shape, the gap between the adjacent lines and the intensity of absorption line are analyzed using the theories of quantum mechanics and molecular spectrum. It gives the mathematics description of the Beer-Lambert law and integral absorption and peak value coefficient.Based on theoretic analysis, light source and photoelectric detector are selected, the working mode of phase-locked amplifier is determined in experiment. Experiment scheme, steps and data processing method are designed.At last the absorption experiments of CO2 at room temperature and standard pressure, changing pressure, changing temperature validate the feasibility of the measurement system. |
PDF Full Text Request