RioRand Mini DC 0-30V Voltage Meter, Red LED digital Voltmeter 2 Wires Volt Tester Gauge Measure 12 24 volt Directly for Checking Car Automotive Battery Powered by RioRand Advanced Technology Variable precision: 10V below , resolution of 0.01 V; 10V above,resolution of 0.1 V Power supply: Don't need the power supply, direct use of the test voltage as a power supply Measurement range: DC 3.50 - 30.0V; Measurement accuracy: +/- (0.5% + 2 Digit) Display mode: Three 0.56 Red LED digital tube