| 摘要 |
PROBLEM TO BE SOLVED: To surely determine the received wave arrival timing and measure the flow velocity with high accuracy by integrating the waves of one or both polarities of the received waves, and setting the time when the integrated output reaches the reference value to the received wave arrival timing for measuring the propagation time difference. SOLUTION: Received waves from transceivers 2, 3 are half-wave shaped by a half-wave shaping circuit 7 through an amplifying circuit 5, and the integrated output from an integrating circuit 8 is compared with the reference voltage from a reference voltage generating circuit 10 by a comparing circuit 9. The reference voltage is set to the middle value where the integrated output rises synchronously with the rise of the half wave of the second wave, thus the integrated output reaches the reference voltage value at the middle time when it rises along the rise of the second wave beyond the peak value of the first wave, and the received wave arrival signal is outputted from the comparing circuit 9 at this time. When the received signal is integrated, the integrated output can be increased in response to the received wave-form, and the first wave of the received wave is not required to be captured. |
