DIN EN 60051-3-1991 直接显示的模拟电器测量仪及附件.第3部分:功率表和无功功率表的特殊要求(IEC 51-3-84.第4版)
Direct acting indicating analogue electrical measuring instruments and their accessories; part 3: special requirements for wattmeters and varmeters (IEC 60051-3:1984, edition 4); german version EN 60051-3:1989