| 摘要 |
PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter capable of displaying a measured value of a gas flow rate at an optional temperature in terms of a measured value at a prescribed reference temperature without using a thermometer. SOLUTION: This ultrasonic flowmeter is so composed that an ultrasonic wave is propagated in the flow direction and in the reverse direction in gas, and that time required for propagation to each direction are measured, and that a volume flow rate of the gas is calculated from the measured values. And this ultrasonic flowmeter is equipped with an input means 4 for allowing a user to select whether temperature correction to the measured value is necessary or not, and calculation-output means 1a, 1b, 1c, 3 for outputting a value obtained by substituting a propagation velocity at a reference temperature for a propagation velocity of the ultrasonic wave in a calculation formula by a time difference method as a temperature-corrected measured value, if it is selected that the temperature correction is necessary, and for outputting a calculated value by a reverse time difference method as a measured value, if it is selected that the temperature correction is not necessary.
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