| 摘要 |
PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter which accurately measures a flow rate of a fluid, irrespective of a flow velocity. SOLUTION: The ultrasonic flowmeter propagates ultrasonic waves S<SB>1</SB>and S<SB>2</SB>in the right and reverse directions of the flow of the fluid W, in a first sensor part 11, and calculates a volume flow rate of the fluid W, based on a propagation time difference between the ultrasonic waves S<SB>1</SB>and S<SB>2</SB>. It propagates an ultrasonic wave S<SB>3</SB>in the direction parallel to the flow of the fluid W, in a second sensor part 12, and obtains signal strengths of reflected waves S<SB>31</SB>and S<SB>32</SB>reflected on inner wall surfaces 14b and 14c respectively. The acoustic impedance of the fluid W is determined, based on each signal strength and the acoustic impedance of the material composing a measuring tube 14, and further the density is determined, based on that acoustic impedance. A mass flow rate of the fluid W is determined by multiplication of the density and the volume flow rate. COPYRIGHT: (C)2011,JPO&INPIT
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