| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a propagation time difference type ultrasonic flowmeter that measures a flow rate in such a manner that it is immediately determined which one of measuring methods of a triggering method and a correlation method is used for measuring depending on a waveform characteristic of a received wave and a previous measurement value. Ž<P>SOLUTION: An ultrasonic wave transmitted from a transmission section 1 is received by a sensor 2 (16) from a sensor 1 (13) via a fluid and is received by a reception section 2. The received signal is amplified by an amplifier 5, and then digitally converted by an A/D 6. A reception wave control processing section 7 applies a process to the converted digital signal, the process being for a case where the reception signal is small. A switching determination processing section 8 determines which one of measuring methods of the triggering method 20 and the correlation method 30 is used for measuring. A propagation time difference Δt measured by the measuring method is obtained, and the value is converted into a flow speed by a flow speed computation processing section 10. The obtained flow speed is converted into a flow rate by a flow rate computation processing section 11. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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