| 摘要 |
PURPOSE:To make possible temperature correction with high precision by correcting a speed of ultrasonic propagation in terms of temperature based on a distance measurement from an ultrasonic transmitter/receiver to a reflector installed at an already known prearranged distance. CONSTITUTION:If a reflective ultrasonic wave is received from a reflection plate 8 installed at an already known prearranged distance l from a transmitter/receiver 3, 4 of an ultrasonic snowfall depth meter, etc., an elapsed time between transmitted wave and received wave pulses is determined through a drive timer 10, a counter control circuit 12'. Then a clock count value from a clock oscillator 14' which corresponds to a measured distance value of the said time by a counter 13, is compared and identified with a reference value of a reference setter 18 using a magnitude comparator 16 of a temperature compensation circuit 5. As a result of this process, a compensation signal corresponding to a change in the speed of ultrasonic propagation corresponding to a temperature, is generated from an integration circuit 17, controlling the oscillator 14'. Thus it is possible to correct a temperature with high precision without the use of a thermister, etc. |
