Digital multimeter and current loop calibrator combined to give process technicians double the power in one tool the fluke 789 has a 24 v loop supply for reducing the need to take a separate power supply when doing offline transmitter testing and thanks to its built in selectable 250 ohm hart resistor it also eliminates the need to carry a separate resistor for calibrating hart instruments with you all this means that process technicians can now do a lot more while carrying a lot less