A New Forward-Scatter Visibility Sensor Based on a Universal Frequency-to-Digital Converter

Traffic delays attributable to weather conditions may cause an increase in fuel consumption and then an increase in CO2 emissions to the environment. Visibility reduction in roads due to dense fog is a main cause of traffic accidents and possible environmental pollution, hence the importance of deploying fog warning systems. In this article, we present a forward-scatter visibility sensor that uses a quasi-digital photodetector and a universal frequency-to-digital converter instead of a conventional analog-to-digital converter as data acquisition system. This feature has allowed the design of a low-cost, robust, and simple sensor-to-microcontroller interface as demanded by Intelligent Transportation Systems (ITS) applications. An optical system to limit light interference is proposed. The visibilimeter was calibrated from a self-calibrated transmissometer using the same frequency-to-digital technique. This new instrument is capable of a 41–662.5 m visibility range detection and to transmit the information wirelessly to a 100 m distance.