A na-eji GDDO-20C AC / DC Electric Meter Calibration Device iji chọpụta njehie bụ isi nke ngwa eletriki eletrik dị iche iche na sistemụ ike, gụnyere voltmeter, ammeter, wattmeter, ohmmeter, otu oge & mita AC ike atọ (nhọrọ) na njehie bụ isi nke DC volt mita na ammeter.