The REDARC hall effect current sensor is an electronic device which is designed to measure the current flowing in a circuit and output the value of that current as a voltage signal. (i.e. can monitor the amount of current to or from your main or auxiliary battery). The REDARC Hall effect current sensor is a high performance, compact cable mounted current sensor suitable for installation into rugged environments where a fully sealed product is required to assure reliability. This REDARC device is 100A rated and cannot be damaged by overload. If there is an alternator or system failure, the voltage reading will be low and drop as the battery discharges. In the case of an overcharge condition, the gauge will climb above its normal zone. There are pre-set alert levels to notify of these changes, altering the gauge backlight to programmable amber or red. The GS-AMPS is an optional sensor that is compatible with both REDARC gauges: the G52-VVA and G52-VA.