Instruments RD-30, RD-31 and RD-33 (further RD-3X) are the three-phase model (standard) counters of electric power with the accuracy of measurement by 0,01% and with the accuracy of measurement - 0,04%, with the total influence of all destabilizing factors. Before the instrument is used the analog-to-digital converter (ATsP) Of dytronic, which works together with the electronic- compensated input transformers of current and voltage and the airtight entrances for achievement of high stability and accuracy.