| 摘要 |
<p>PURPOSE:To achieve an accurate detection of accumulated snow while eliminating malfunctioning, by setting the frequency of detecting accumulated snow detection signals and that of detecting non-accumulated snow detection signals properly to control a snow melting apparatus depending on the resulting frequency of detection. CONSTITUTION:An ultrasonic wave with the cycle thereof set by a wave transmission setting circuit 101 is transmitted to the surface of accumulated snow to detect the presence of the accumulated snow exceeding a specified level from a delay time in the reflected wave thereof. Then, when an accumulated snow detection signal is detected with a counter 113 (n) times continuously, a first accumulated snow detection signal is outputted. When the snow detection signal is outputted once, an OFF signal is outputted from a counter 114. The counter 114 operates after a non-accumulated snow detection signal is detected (m) times continuously. The frequencies (n) and (m) are set properly to meet optimum requirements; this eliminates malfunctioning caused by weather condition, foreign matter such as tree leaf and animal such as bird, thereby enabling accurate detection of accumulated snow.</p> |
