| 摘要 |
<p>In the measurement of the distance between two immersed points using ultrasonic signals, a control beacon is located at one point and a servo-beacon at the other point. The control beacon emits a first signal which is received by the servo-beacon. After a set period of time T sufficient for the disappearance of all echoes, the servo-beacon emits a signal which is received by the control beacon. Measurement apparatus associated with the control beacon determines the distance as a function of the time between emission of the first signal by the control beacon and reception of the signal from the servo-beacon, and the velocity of the ultrasonic signal which is determined in the region of the control beacon.</p> |
