APM521 网络电力仪表（以下简称仪表）按 IEC 国际标准设计，具有全电量测量、电能统计、电能质量分析事件记录功能及网络通讯等功能，主要用于电网供电质量的综合监控。该系列仪表配有功能丰富的 DI/DO 模块、AO 模块，可以灵活实现电气回路全电量测量及开关状态监控。

The APM521 network power meter (hereinafter referred to as the meter) is designed according to IECinternational standards, featuring full electrical quantity measurement, energy statistics, power quality analysis, eventlogging functions, and network communication capabilities. It is primarily used forcomprehensive monitoring of powersupply quality in power grids. This series of meters is equipped with DI/DO modules and AO modules that offer awealth of  functions,allowing for flexible implementation of full electrical quantity measurement and monitoring of switch statuses in electrical circuits.