| 摘要 |
PURPOSE:To measure the flow speed and the flow rate, by repeating the transmission and reception of ultrasonic waves in the forward direction and the reverse direction, counting the time interval of the ends of the repeating transmission and reception, thereby removing the effects of the sound speed and electric and acoustic delay times. CONSTITUTION:The transmission and reception in the forward direction are repeated (n) times during the period between the times t1 and t2, and the transmission and reception in the reverse direction are repeated (n) times during the period between the times t3 and t3 and t4. The counted value of a counter 5a and the counted value of a counter 5b are compared in a comparator. The counter 5b is reset by the signal of the comparator 5c. A counter 7a stops the counting when the counted values of both counters 6a and 6b are agreed in a comparator 6c. A counter 8a starts the counting when the agreement signal of the comparator 6c is outputted, and stops counting based on the agreement signal of the comparator 7c. At this time, the flow speed is computed based on a counted value N2 held in the counter 8a. |
