| 摘要 |
PURPOSE:To detect snow accurately independently of the snowfall, the ambient temperature, air speed conditions, and difference of snow quality by controlling a device so that the temperature of a snow receiving plate is kept at a preliminarily set prescribed value. CONSTITUTION:The surface temperature of the snow receiving plate is monitored by a thermometer 13 attached to the snow receiving plate, and a difference between this temperature and a preliminarily set optimum temperature Ts of the snow receiving plate is operated by an operating circuit 15, and the temperature error signal is outputted to a current control circuit 16. The circuit 16 controls the supply current to a sheathed heater 3 of the snow receiving plate in accordance with the temperature error signal to set the surface temperature of the snow receiving plate to the preliminarily set optimum value, and a snowfall detection signal S is used for stopping the current to the heater in case of no snowfall. An ambient temperature TE is used for controlling the heater to set the surface temperature of the snow receiving plate to a certain required minimum temperature so that rain or water condensed as dews is not frozen in case of <=+2 deg.C and no snowfall. |
