| 摘要 |
PROBLEM TO BE SOLVED: To miniaturize a watt-hour meter without requiring the replacement of a battery by providing a charging means charging a power failure compensating battery. SOLUTION: The voltage of a power failure compensating battery 6 is monitored by a battery voltage monitoring circuit 7, and the battery 6 is automatically charged when the voltage of the battery 6 drops. The voltage of the power failure compensating battery 6 is inputted to the comparing circuit 7a of the battery voltage monitoring circuit 7 and is compared with the reference voltage, and the comparing circuit 7a outputs a signal indicating a voltage drop to a control circuit section 41 when the voltage of the power failure compensating battery 6 is lower than the reference voltage. When the control circuit section 41 receives this signal, it closes the charging circuit switch 51a of a charging circuit section 51 for a prescribed time, and the power failure compensating battery 6 is charged from a charging power supply connected to the charging circuit section 51. The voltage drop of the power failure compensating battery 6 is detected, and it can be surely charged automatically. |
