| 摘要 |
PROBLEM TO BE SOLVED: To maintain the accuracy of a flow rate even when the kind of a gas species is changed. SOLUTION: This flow-rate measuring apparatus is provided with a transmitter-receiver 5 and a transmitter-receiver 6 which transmit and receive ultrasonic waves to and from a fluid. The measuring apparatus is provided with a measuring circuit 8 which measures the propagation time of their transmission to the downstream from the upstream of a flow or their transmission to the upstream from the downstream. The measuring apparatus is provided with a flow-rate computing means 9 which calculates a flow rate on the basis of the propagation time of the ultrasonic waves. The measuring apparatus is provided with a fluid discrimination means 10 which judges the kind of a fluid inside a flow passage on the basis of the transmitter-receiver. The measuring apparatus is provided with a circuit-constant correction means 11 which changes the constant of the measuring circuit 8 on the basis of the value of the fluid discrimination means 10. Thereby, the measuring circuit which is optimum is selected according to the component of a gas, the ultrasonic waves are changed into a proper signal, and the accuracy of the flow rate can be maintained to be high.
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