Research On Sulfor Dioxide Concentration Baded On Fluorescent Technology

Sulfur dioxide is one of the main substances that cause air pollution, and it also brings about great damage to the ecological environment. All the countries in the world regard the sulfur dioxide as an important indicator of the detection level of air pollution. So it plays an important role in the evaluation of the environment. Accurate measurement of the sulfur dioxide’s concentration has important significance for improving air quality and improving human surrounding environment. Fluorescence detection technology is a widely used measurement technique.Measuring the concentration of the sulfur dioxide in the atmosphere based on the fluorescence detection mainly refers that when the light emitted from the UV irradiates on the sulfur dioxide, sulfur dioxide gas is excited and produces a certain wavelength of fluorescence. By analyzing the proportional relationship between the fluorescence intensity and the concentration of sulfur dioxide, sulfur dioxide can be quantitative analyzed and measurement. The main contributions are as follows:The mathematical model of measuring sulfur dioxide by fluorescence and the linear relationship between the fluorescence intensity and the concentration of sulfur dioxide are established on the basis of the principle of fluorescence and the senior research. Combined double chambers with the optical fiber sensing technology, the constructure can reduce the fluorescence noise and make the measurement more stable and anti-interfering.The total scheme of fluorescence measurement systerm was designed, and the principle and characteristic of excited light source, optical filter, lens, optical detector and optical fiber are discussed. At the same time the module by using to detect the weak electrical signal is designed, which includes Ⅰ/Ⅴ changing cicuit and the filter amplifier circuit.The embedded control systerm based on the STM32F103is designed to make the measurement systerm smaller and more intelligent. The systerm include some subsysterms such as the temperature control sysyterm by PWM, the A/D collection systerm and the usart communication systerm. At last, a friendly GUI which can display the real-time data of the fluorescence signal is programmed by the MATLAB.The filter algorithm called Boxcar is discussed and applied on the basis of characteristic of fluorescence. The fluorescence signal is separately filtered by the wavelet fliter, EMD filter and Boxcar filter, and the result show that the signal filtered by the Boxcar filter has a very better effect than the other two filters.