The XTRM-3 measures the transformer turns ratio of single phase and three phase transformers using modern electronic techniques. This replaces the Ratio testers using ‘current balancing bridge’ circuits, requiring manual ‘null’ balancing. XTRM-3 incorporates breakthrough technology and design that gives accurate and reliable results repeatedly. It is micro controller operated, user friendly and reliable. XTRM-3 incorporates a large LCD screen for display of menu and results. The entire test is automated and quick. Operator enters the test parameters and XTRM-3 takes over, applies the test voltage, balances the bridge, takes the readings, and displays the results on the LCD screen. The results can be printed on built-in printer after the test is over. A Windows based software is provided for easy operations via USB communication port. LV and HV windings are automatically isolated after the measurement is over. The XTRM-3 is a single unit, lightweight portable design, encased in a hard industrial cabinet weighing only 10 kgs.