Electrical current can be sensed by the G3X system either by Hall Effect current sensors or via the use of a traditional ammeter shunt. The UMA 1C4 ammeter shunt included in Garmin sensor kits (Garmin P/N 909-D0000-00) is a 100 Amp/50 mv shunt. The ammeter shunt has two holes in the insulated base for mounting with #10 screws.