Description: -This voltmeter's wiring is simple,it only need to connect two wires,the red wire is to connected to positive pole,the black wire is to connected to negative pole. -There is protection when the wires aren't correctly connected,the electric circuit won't be bumed. -This voltmeter doesn't need external drive working power,it can work with measuring voltage,the working voltage's range is 4.5-30V. -To reach the best measurement accuracy,this voltmeter will automatically move the decimal point's position according to the different measuring voltage. When it measures the voltage below 10V,it will display two places after decimal point. When it measures the voltage above 10V,it will display one place after decimal point. -This voltmeter can be used to measure the storage battery's voltage in motorcycles and cars and also can grasp the storage battery's status. It also can be used to measure other voltage. Specifications: Measuring range: 4.5-30V Allowable error: accurate to 0.01V below 10V, accurate to 0.1V above 10V, allowable error of 1% (+/-1 words) Display mode: 3-digit 0.56 LED digital tube Display color: Red/Green/Blue (Optional) Refresh rate: about 200mS/time Power supply: No required Current consumption: less than 20mA, generally 5-15mA Working temperature: -10C~65C Dimensions:48 x 29 x 16mm / 1.89 x 1.14 x 0.63inch Opening size: 46x27mm / 1.81 x 1.06inch Lead length :20cm / 7.9inch Precautions: 30V is the voltmeter's maximum operating limited voltage,please leave enough margin when working,to avoid voltmeter's permanent damage because of electrical spark ,power supply ripple,or other too high abrupt change of voltage. Package included: 1pcs Digital Voltmeter