| 摘要 |
PURPOSE:To certainly measure the distance up to a reflecting article, by tracking the rising of the specific carrier ultrasonic wave contained in ultrasonic burst. CONSTITUTION:The ultrasonic wave from a transmitting ultrasonic transducer T is received by the distance calibrating ultrasonic transducer R0 provided at a position at a known distance L0. The output signal (r) thereof is converted to a rectangular wave signal (s) through an amplifying circuit a and a circuit RW for forming a reference wave into a rectangular wave and the phase difference between the signal (s) and the output signal of an oscillation circuit OSC is detected by a phase detector PHD. The output signal of the circuit PHD is converted to voltage by a phase/voltage converting circuit P/V to be held to a sample holding circuit S/H for a predetermined time, for example, only for a time divided at each burst rising point of time. The circuit OSC is constituted of a voltage control oscillation circuit and frequency changes so as to make the output (t) of the circuit PHD constant. The phase difference of ultrasonic waves is calibrated on the basis of the known distance L0 and the calibrated distance L is displayed on a display part DISP. Therefore, even when the collapse of the wave form of the rising part of ultrasonic burst is marked, an ultrasonic propagation time is measured and the distance up to a reflecting article is measured.
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