RioRand 2 Wires Digital Voltmeter DC Volt Tester 12V 24V Battery Power Monitor Car/Motorcycle Motor Bus Vehicle 0.56" Red LED Display DC 2.5-30V Panel Meter Powered by RioRand Advanced Technology Measure DC 2.5-30V directly (two wires Access), do not need extra power source Precision automatic adjustment: Measure 10V Below, Display as x.xx; 10V Above, Display as xx.x 0.56" Digital Tube with Big, bright Red LED display. Perfect for solar project to monitor Battery voltage. The power consumption is &lt;=12mA when in use Very nice to check the voltage and charging system on cars. There is a small calibration adjustment