The red wire is to connect to the positive pole, the black wire is to connect to the negative pole. No need to worry even if there is any connection mismatch of the wires, the electric circuit wont be a boom because it features reverse polarity protection.

This voltmeter doesn't need external drive working power, it can work with measuring voltage, the working voltages range is 3.5-30V. To reach the best measurement accuracy, this voltmeter will automatically move the decimal points position according to the different measuring voltage. When it measures the voltage below 10V, it will display two places after the decimal point. When it measures the voltage above 10V, it will display one place after the decimal point.

This voltmeter can be used to measure the storage battery's voltage in motorcycles and cars and also can grasp the storage batterys status. It also can be used to measure other voltage. 30V is the voltmeters maximum operating limited voltage, please leave enough margin when working, to avoid voltmeters permanent damage because of an electrical spark, power supply ripple, or other too high abrupt change of voltage.

Very bight and decent LED Display is ready to measure the dc voltages in the range of 3.5V to 30V.

Connections :

Red Wire: source +ve terminal.

Black Wire: Source -ve terminal.

Note: The display weight and Dimensions may have2% error.

Features :

1. Very small and lightweight voltmeter module.
2. Very handy and easy to use.
3. Green LED display.
4. Dont need the external power supply because it is a self-powered version of this display.
5. Best operates in the working voltage range of 5V to 24V
6. 100% Brand new and high quality.

Package Includes :

1 x 0.72 cm (0.28 inch)  3.5-30V Two Wire DC Voltmeter Green