INTRODUCTION The Model Y5020 is a precision, four-terminal, current shunt designed for use in calibrating ac/dc current sources in the range of 0 to 20 amps, do to 5 kHz. The shunt is housed in a forced-air cooled, PTI (Portable Test Instrument) case. This case is compatible with all instruments in the Fluke PTI product line and can be stacked with other PTI products to form a portable test system. Forced-air cooling is accomplished by a fan mounted on the rear panel. Air is pulled in through the fan, passed over the shunt, and exhausted through the rear panel. Power for the fan is derived from the power line. Two voltage configurations are available, 115 or 230V ac ±10%, 50 to 60 Hz. Four front panel terminals provide electrical access to the shunt; two are current input terminals and two are voltage output (sense) terminals. When the shunt is connected into a circuit and operating at its maximum current limit (20 amps), the input connections and the shunt present a burden voltage of less than 0.25V dc.