Study Of Dynamic Characteristic Of The Scattering Visibility Meter And Its Device Design

In recent years, with the rapid economic development, air pollution problem is getting more and more serious, as an important physical characterization of near-earth air pollution level, visibility is also increasingly been of concern. The visibility meter is the major equipment to measure air visibility, and dynamic characteristics is one of the important features of the visibility meter. In the actual project, it changes linearly between input and output, otherwise it will affect normal read of the measurement results of the visibility meter. So, how to improve the dynamic characteristics is a very important significance for improving measuring distance and measuring accuracy of the visibility meter.This paper analyzed work principle of the forward scattering visibility meter, and built a detection system. According to the comparison and selection of key device, light of this system was a semiconductor laser,and photodiode detector was PIN photodiode. Optical signal was modulated by exerting pulse signal to laser tube, and forward scattered light was received by photodiode detector, ultimately, signal was processed by signal processing circuit. The signal processing circuit mainly included the photoelectric detection circuit, the filter circuit, the RMS converting circuit and the post-amplifier circuit.In the test part, the dynamic characteristics of the signal processing circuit and its every module was measured, according to the comparison of the linear dynamic range between each module and the system, the dynamic characteristics of photoelectric detection circuit was the most significant. The analysis of the photoelectric detection circuit showed that the linear dynamic range of the system was improved effectively by decreasing the load resistance.