A5: Smart energy meter adopts built-in hardware clock circuit with temperature companion function, which has automation conversion function among calendar, time and leap year; the output frequency of internal clock terminals of energy meter is 1 Hz. Within the temperature range of 25~+60℃, the clock accuracy is ≤±1s/d; Under the reference temperature (23℃), the clock accuracy is ≤±0.5s/d. It adopts green environmental protection lithium battery as standby power supply, and the capacity of battery is more than 1.2Ah. During the life cycle of energy meter, the battery needn’t to be changed, and it can make internal clock work correctly for more than 5 years after power outage.