| 摘要 |
PROBLEM TO BE SOLVED: To provide a water meter requiring no smoothing capacitor 14 having a large capacity and no high-frequency reference clock.SOLUTION: A rotation detecting portion 6A includes a first coil 4a, a first capacitor 5a, a charge transistor 20, a power supply line 21, a start transistor 22, an output buffer circuit 23, a DA converter 24, a comparator 25, and a counter 26. A first LC resonance circuit includes a start transistor 22 connected to the first coil 4a in series, the first capacitor 5a connected to the first coil 4a in parallel, and the charge transistor 20 for charging the first capacitor 5a. The first LC resonance circuit is started by turning on the charge transistor 20 to charge the capacitor 5a and then turning on the start transistor 22. |
