The instrument GF312D1 is a precision 0.05% AC energy meter testing instrument, mainly used to test three phase energy meter error on site, measure all various of AC parameters and CT ratio & phase error, it is also as three phase reference energy meter in the laboratory. Mainly using test single phase or three phase meter error on site. GF312D1 energy meter calibrator is an ideal test tool for the metrological service of electricity power company.