| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent fluctuation in detecting sensitivity due to change in the reference light quantity of a sensor caused by degradation of the sensor and the fluctuation in ambient temperature and the like, related to a snowfall sensor comprising a light-projecting part and a light-receiving part for infrared light. SOLUTION: A signal processing part which processes the output signal of the light-receiving part to which infrared light is projected for sensing snowfall before outputting signal is provided with a function which feedback-controls the infrared light irradiation amount at the light-projecting part so that the infrared light reception amount at the light-receiving part has always an initial value.</p> |
