| 摘要 |
PROBLEM TO BE SOLVED: To provide a water meter capable of detecting an abnormality caused by an approaching magnet over a wide range at a lower cost than before. SOLUTION: The water meter 10 is provided with a magnetic sensor 20 on the impeller 12 with a magnet 16, rotating proportionally to the flow of the tap water. The flow rate of the tap water is obtained by counting the number of rectangular waves generated, based on the detection signal of the magnetic sensor 20. Abnormalities are detected based on whether the duty ratio of the rectangular signal agrees with the reference value. By utilizing the rectangular wave signal for both the flow-rate measurement and the abnormality detection, lower cost can be expected, as well as the abnormality caused by the approaching magnet over a whole range, where the rectangular signal used for measuring the flow-rate of the tap water to be affected can be detected. COPYRIGHT: (C)2006,JPO&NCIPI
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