KKmoon Mini 2 Wires DC 3.3-30V LED Panel Digital Display Voltage Meter Voltmeter Yellow Light Digital voltmeter with precision automatic adjustment. It only have two wires, you can connect to the measure power directly. It have the polarity reverse protection, won't damage the meter. Minimum input: DC3.3(Below this voltage, it will show measurement inaccurately, or doesn't show). Maximum Input: DC30V(please do not exceed 30V,otherwise,the meter would be damaged).