The Model 5220A is a transconductance amplifier designed to operate as either a stand alone unit or an extension of the Fluke Model 5100 Series Calibrator. Functionally, the instrument operates as a precision ac/dc current source for calibrating current shunts and/or current meters. As the name (transconductance amplifier) implies, the output current level is a function of an input control voltage. The input/output ratio is established at 1:1 so that a voltage input in the range of -20 to +20 volts will produce a proportional current output of -20 to +20 amperes. Input voltages may be either dc or ac levels, depending on the output requirements. Bandwidth for ac operation is dc to 5 kHz. Control of the 5220A can be handled locally using front panel controls or remotely by way of the 5100 Series Calibrator. (The 5100 must be equipped with a Model Y5000 Interface.) Control mode selection is accomplished using two front-panel push button switches, INPUT and LOCAL. The INPUT switch allows selection of either front or rear control-voltage input connections. The LOCAL switch is used to recall the 5220A from remote to local operation. A series of front panel indicators are used to visually display both the control and operating status of the 5220A. Control indicators include OPER (operate), STDBY (standby), FRONT input, REAR input, REMOTE, and LOCAL LOCKOUT. The combination of lit LEDs indicates the present status of the control mode. Status indicators include THERMAL CUT-OFF, OVER COMPLIANCE, and OVER CURRENT. When any one of these indicators is lit, an overload condition has been detected causing the 5220A to switch to standby operation. All indicators are active regardless of the selected control mode, local or remote. Current output connections are provided on both the front and rear panels. However, only one set of terminals is active. Selection of the desired set is accomplished internally and is, therefore, not considered an operator function. Neither local nor remote operation is affected by the selection of front or rear output. Forced-air circulation is incorporated in the 5220A to ensure adequate cooling of the current output stage. Air is pulled in through a rear-panel filter, passed over the output stage heat sink, and exhausted through the unit's side panels. The 5220A is designed to operate from ac line voltages within the range of 90 V ac to 264 V ac, 50 to 60 Hz. One-of-eight specific voltages (100, 110, 115, 120, 200, 220, 230, 240 V ac +10 %) can be selected to ensure compatibility with the local line voltage. The selection switches are inside the 5220A. Accessories available for use with the 5220A are listed and described in Table 1-1. The rack mounting kits are designed for use with a standard 19-inch equipment rack. The Model Y5020A is a precision current shunt recommended for use in calibrating the 5220A. Specify both model number and description when ordering accessories.