The DTR? Model 8500 from AEMC Instruments 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 DTR? Model 8500 accurately measures primary to secondary turns ratio, while simultaneously displaying polarity and excitation current. The DTR? 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 DTR? automatically self-calibrates and checks for open windings/connections/ circuit breakers, shortcircuits (excess excitation current), incorrect test lead placement, and reverse polarity. Measurements are displayed quickly and accurately. The DTR? Model 8500 is designed with operator safety in mind. Tests are performed at low voltage and, unlike other ratiometers, step-down excitation is employed. This method, in conjunction with an integral H/X, reverse protection circuit, guards against the generation of hazardous test voltages normally associated with transformer ratio measurement instruments. A large, dual-line alpha-numeric LCD with adjustable contrast and backlight guarantees day/night readability. Power is supplied by an integral NiCD battery (included) or by an AC line. Batteries are charged automatically during AC operation. Both rugged and reliable, the DTR? Model 8500 is built into an attractive, sealed structural polypropylene case designed to withstand the rigors of utility and industrial field use. Constructed using only the highest quality electrical and mechanical components, the DTR? Model 8500 sets the standard in advanced design, engineering, and workmanship, and it will provide the user with years of accurate and reliable measurements.