| 摘要 |
PURPOSE:To make it possible to measure flow speed with a sensor which is small- size and has no movable part, by detecting the acoustic wave, which the acoustic wave generator provided in a fluid pipe generates, by receivers in the upper stream and the lower stream of flow and by measuring the arrival time difference between both receivers. CONSTITUTION:Ultrasonic wave generator A is fitted into pipe P where fluid flows, and receivers B and C are arranged in the upper stream and the lower stream, thereby measuring the arrival time difference between both receiving waves. When the flow speed of fluid and the sound speed are denoted as v(m/s) and c(m/s) respectively and distances and angles are expressed with l1, l2, theta1, and theta2 as shown in the figure, arrival time difference dt of the acoustic wave between receivers B and C is expressed by dt=[c(l1 sin theta2-l2 sintheta1)+v(l1+ l2)]/c<2> sintheta1 sintheta2. Further, if l1=l2=l and theta1=theta2=theta are made true, dt=2lv/c<2> sin<2>theta is true, so that flow speed v can be measured by measuring time difference dt as the above. |
