| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter having constant flow sensitivity irrelevant to a type or temperature of fluid. <P>SOLUTION: In a so-called propagation time difference type ultrasonic flowmeter, annular ultrasonic vibrators 2 and 3 are provided separated at a constant interval L from each other, on an upstream side and a downstream side of a straight measurement tube 1; each of the annular ultrasonic vibrators alternately operates one as an ultrasonic transmitter and the other as an ultrasonic receiver, and measures a time difference ΔT between a downstream-directional ultrasonic propagation time T<SB POS="POST">1</SB>and an upstream-directional ultrasonic propagation time T<SB POS="POST">2</SB>to calculate a flow rate v. An acoustic velocity c<SB POS="POST">0</SB>of fluid is represented as a predetermined function f(c) of the propagation speed c of an ultrasonic wave, and the flow rate v of the fluid is calculated by an expression: v=f<SP POS="POST">'</SP>(c)*c<SP POS="POST">2</SP>*ΔT/2L incorporating derivatives of the function, using the actually measured propagation speed c and propagation time difference ΔT. <P>COPYRIGHT: (C)2013,JPO&INPIT |
