| 摘要 |
PURPOSE:To enable propagation time of high accuracy having no errors to be obtained by level-converting the ultrasonic waves having received, and measuring propagation time when the level value is within the specified time and level range. CONSTITUTION:A transmitter 2 transmits continuous ultrasonic waves by its transmission driving part 8. When the ultrasonic waves having propagated in the fluid in a pipeline 1 are received 3, they enter an anglog conversion part 5 through a transmission-reception changeover part 4 and whether the analog vlaue thereof is within a reference level or not is judged by the discriminating means consisting of a level judgement part 6 and sampling control part 7. If the time width within the reference level range is insufficient, the transmission is stopped for a fixed time and the edge of this stop and restart is detected 10. From this detecting timing and the corresponding timing of the driving part 8, a time difference is detected 11. By this detection signal and the signal from the control part 9, the propagation time of the ultrasonic waves in a normal flow condition is obtainable. |
