| 摘要 |
PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter capable of improving the measurement accuracy by increasing the propagation distance without increasing the size of a measurement tube. SOLUTION: A measurement tube 1 has a double tubular structure comprising an outer tube 1a and an inner tube 1b for fluid to be measured flowing in the measurement tube 1. A pair of ultrasonic wave transmitter-receivers 2a and 2b transmit ultrasonic waves to the measurement tube 1 (the outer tube 1a) at a predetermined angle with respect to the axial direction, and allow the ultrasonic waves to spirally propagate in a flow passage of an annular section formed between the outer tube 1a and the inner tube 1b. The ultrasonic wave propagation times t1 and t2 in the forward direction and the backward direction to the flow of the fluid are measured by an ultrasonic wave propagation time measurement circuit 3. A flow rate operation circuit 4 obtains the flow speed Vg of the fluid based on the ultrasonic wave propagation time, and the volumetric flow rate of the fluid is operated by multiplying the flow speed by the sectional area of the measurement tube (the flow passage) with the fluid flowing therein. COPYRIGHT: (C)2004,JPO&NCIPI
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