| In present, the highway network of china is in a rapid development, however thetraffic accidents caused by fogs and other weather disasters are increasing year andyear, someone even thinks that fog makes block and mist. Fogs, which reduce theatmospheric visibility, hinder the driver’s view and delay the incident judgment on thetiming of the driver, increase the risk of traffic accidents. However, the device whichcan monitor atmospheric visibility has not yet been applied in a large scale, asdomestic measuring device is not yet mature, and foreign products is costly. This articlerelies on the project "things based condition monitoring and road network efficiencytechnology research" of Academy of Transportation Sciences to study visibilitymeasurement for the highway networkThis paper introduces the development of visibility measuring technology andstudies the commonly used methods: scattering and transmission methods, deducesthe measuring principles and selects the latter method for our project, tests andverifies a number of key technical problems, and makes the visibility measuringdevices with a number of eight, which have already been installed for test on G50highway from Shizhu to Zhongxian.The point of the technology is to obtain high sensitivity and long-term stability ofthe measurement results, in order to make it, this paper focuses on the followingpoints:(1) The technique of high stability of the semiconductor laser driver has beenstudied. A semiconductor laser driver based on PID technique and a constant currentdriver for semiconductor laser have been developed.(2) The preamplifier technology has been studied and a preamplifier circuit forphotoelectric detector with a low noise has been developed.(3) The technique of temperature control technology based on the TEC has beenstudied.(5) The long-term stability of the measurement instrument has been studied, anda self-calibration reference based on daylight illumination technique has beenproposed. |
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