| 摘要 |
PROBLEM TO BE SOLVED: To determine a true propagation time of an ultrasonic wave by removing a delay time peculiar to an ultrasonic element. SOLUTION: A forward-direction one-way measuring time T<SB>a1</SB>is measured (step S101), and a forward-direction round-trip measuring time T<SB>a2</SB>is measured (step S102), and a reverse-direction one-way measuring time T<SB>b1</SB>is measured (step S103), and reverse-direction round-trip measuring time T<SB>b2</SB>is measured (step S104). A transmission delay time differenceΔT<SB>t0</SB>of the ultrasonic element at zero flow rate is determined beforehand, and a propagation time difference proportional to the flow rateΔT=T<SB>du</SB>-T<SB>ud</SB>is determined from the expressionΔT=(T<SB>b2</SB>-T<SB>a2</SB>)+(T<SB>b1</SB>-T<SB>a1</SB>)+ΔT<SB>t0</SB>(step S105), and the flow velocity v and the flow rate Q are operated by using the result (step S106, S107). COPYRIGHT: (C)2007,JPO&INPIT
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