DROK 100A Digital LED Ammeter DC Ampere Meter+ Current Shunt Resistor [Misc.] Dimensions: 79 x 42 x 27 mm Measure range : 0-100A (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