| 摘要 |
PROBLEM TO BE SOLVED: To provide a flow measuring apparatus capable of maintaining flow-quantity accuracy even when the type of gas is changed. SOLUTION: The flow measuring apparatus includes transmitters/receivers 5 and 6 for transmitting and receiving ultrasonic waves to and from a fluid; a measuring circuit 8 for measuring the propagation delay time of transmission from the upstream side to the downstream side of a flow or transmission from the downstream side to the upstream side; a flow computation means 9 for computing the quantity of flow on the basis of ultrasonic-wave propagation delay time; a fluid determination means 10 for determining the type of fluid in a channel from the transmitters/receivers; and a circuit constant correction means 11 for changing a constant of the measuring circuit 18 on the basis of a value of the fluid determination means 10. An optimal measuring circuit is thereby selected according to the components of gases to convert ultrasonic waves into appropriate signals and highly accurately maintain flow-quantity accuracy. COPYRIGHT: (C)2009,JPO&INPIT
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