Features:
This voltmeter uses 0.36 inch LED digital tube without casing.
The voltmeter is super thin with small shape and low price and stable performances. It can display well.
Wide measurement range: DC 0-100V. It needs outer working power supply and the voltage is DC 2.5-30V.
When the voltage is under 10V, there will 2 readings after decimal point, which mean the accuracy is 0.01 when it is under 10V; when it is above 10v, the accuracy is 0.1. 
Reverse Polarity Protection: The meter won't burn out if reverse polarity is applied, but the screen will display nothing.
Application: Motorcycle, Car, E-bike, ATV, scooter, 18650 battery, Li-battery and so on. 
Wiring:
Red: Power Supply +,(2.5~ 30V DC)
Blue: Measure Voltage +,(0~ 100V DC)
    Black: Power Supply -, Measure Voltage - 
Note:
1. This voltmeter's measurement range is 0-100V, this voltage is just measurement signal and it can't be regarded as voltmeter's working power supply. 
2. The maximum input voltage can not exceed 30V, otherwise there is danger of burning.