| 摘要 |
PURPOSE:To accurately measure the snowfall amount by a method wherein an ultrasonic wave is radiated, and the reflected wave from the snow surface is converted into an electric signal, which is amplified in a plurality of amplifiers connected in a multistage manner. CONSTITUTION:The microprocessor 3 outputs a signal via an input/output interface 4 to a transmission controlling circuit 2, and the transmitter-receiver 1 radiates an ultrasonic wave toward the road surface. The reflected wave from the road surface is converted into an electric signal by the electrostrictive oscillator of the transmitter- receiver 1 and added to an amplifier 5. After the amplifier 5, amplifiers 6, 7 and 8 are connected. The electric signal from the transmitter-receiver 1 is synthesis of the portion 14 reflected by the snow surface and the portion 15 reflected by the road surface. When said signal is amplified in the amplifiers 5, 6, 7 and 8, the portion 15 is saturated to become a signal waveform 16 of gentle riser and then becomes a signal waveform 17 of sharp riser. The period of time from the radiation of the ultrasonic wave to the reception of the reflected wave is measured by the microprocessor 3 to calculate the thickness of snowfall. Because conventional apparatuses can obtain only the waveform 18, an error Ta appears. |
