DROK&reg; High Accuracy DC 50A Ammeter Current Ampere Panel Meter Amp Gauge Positive and Negative Current Monitor Amperage Tester 0.56" Red LED Digital Tube Display Dimensions: 79 x 42 x 27 mm Measure range : 0-50A (need an extra shunt) Operating voltage: DC +5 V  5%; Operating Current: &lt;100mA Display: 4 1/2 0.56" Red LED digital tube Can Measure positive and negative amps