Historical
IEC 61557-5 Ed. 1.0 b:1997
Electrical safety in low voltage distribution systems up to 1000 V a.c. and 1500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 5: Resistance to eart
Specifies requirements for equipment for measuring the earth resistance using an a.c. voltage
International Electrotechnical Commission [iec]