D08000 RUGGED, PORTABLE DIGITAL TRANSFORMER WINDING RESISTANCE OHMMETER RESISTANCE MEASURING INSTRUMENTS The DO8000 can measure and save more than 10,000 high resolution test results, along with transformer nameplate data. With its expansive memory, bright LCD screen, and concise reports from its built in printer, this model sets the standard in test equipment. The DO8000 can store hundreds of files, each containing a virtually unlimited number of resistance measurements, with tap and winding details, and several fields of information about the transformer, its location, and the operator. The file manager makes this information easy to locate, open, view, and print past results. The DO8000 features 4.5 digit resolution and 0.25% accuracy for precise measurement of winding resistance. Input channels have sophisticated sigma-delta D/A converters and notch filters to eliminate the effects of substation noise. key feature DO8000 True 4 measurement eliminates lead resistance errors n Wide measuring range 0.1 milli ohm to 2 kilo ohm n Resolution 0.1 micro ohm on 2 milli ohm range n 2 channel measurement for primary and secondary windings n High accuracy 0.25% rdg + 0.25% fs n Open circuit limit mode 20 mV / 50 mV maximum n Interface RS232 and USB n Data logging with large colour alpha numeric storage for test results n Robust power supply for fast testing of large power transformers n Bracken Hill, South West Industrial Estate, Peterlee, County Durham, SR8 2SW United Kingdom Tel: +44 (0) 191 586 3511 Fax: +44 (0) 191 586 0227 Email: [email protected] Web: www.cropico.com

Operating Principle The resistance of windinRgess iosl umtieoansured by passing DC current through the unknown resistance, and measuring the resulting voltage drop. The DO8000 calculates the resistance by the formula R = E/I. Winding resistance challenges Measuring small resistance in a highly inductive environment can be a challenging task. The voltage across an indicator is defined by the formula V = L di/dt. Some power transformers have inductance (L) of over 1000 henrys, therefore minute changes in current will result in undesirable voltage swings that can make it impossible to measure the...