The DTRŽ Model 8510 is a portable digital transformer ratiometer designed for on-site testing of power, potential and current transformers. When connected to a non-energized transformer, the DTRŽ Model 8510 accurately measures primary to secondary turns ratio, while simultaneously displaying polarity and excitation current. The DTRŽ is fully automatic and uses an ANSI/IEEE compliant test method. No user calibration, range selection, hand cranking or tedious balancing is required. At each measurement, the DTRŽ automatically self-calibrates and checks for open windings/connections/circuit breakers, short circuits (excess excitation current), incorrect test lead placement, and reverse polarity. Measurements are displayed quickly and accurately.