| 摘要 |
PURPOSE:To enable the measurement of wide range with good accuracy and to make the instrument small-sized by transmitting alternately two adjacent frequencies and by finding the difference of detected phase of reflected waves from the aiming substance. CONSTITUTION:An oscillator 10 is oscillated in frequencies f1 and ultrasonic wave W1 is irradiated from a transmitter 20. The wave reflected on an aiming substance 1 is detected as W'1 by a wave reciver 30 and the phase difference between W1 and W'1 is found by a phase detector 40 and is made phi1. Also the oscillator 10 is oscillated in frequencies f2 adjacent to f1 and the phase difference phi2 is found in the similar way. Then using the difference between phi1 and phi2 with an arithmetic unit 50, a distance (d) is found. |
