| 摘要 |
PROBLEM TO BE SOLVED: To obtain an electromagnetic flowmeter for open channels which can measure flow rates highly accurately. SOLUTION: A controller 6 continues the measurement by the electromagnetic flowmeter 3 by opening a shut-off valve 5 when the water level of the open channel 1 which is detected by a water gauge 7 becomes not smaller than an upper set value WH, and stops the measurement by the electromagnetic flowmeter 3 by closing the switching valve 5 when the water level becomes not larger than a lower set value WL. The flow rate is measured in a high flow velocity region where the measurement accuracy is good, and the measurement of the flow rate in a low flow velocity region where the measurement accuracy is poor is stopped. The flow rate can be measured highly accurately. COPYRIGHT: (C)2003,JPO
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