Description: The voltage meter is displayed with a 0.36-inch digital tube. It has an -small size and is similar in size to a 5-point coin manufactured by fully automatic SMD process, with lean process and accurate voltage display. Display and measurement effects defeat the general digital meter. The voltmeter wiring is simple, the power supply and the measurement input are combined into one, only two wires need to be connected, and the reverse protection is provided, and the reverse connection is not burned. Measuring range of this voltmeter is 3.5-30v, the resolution is 0.1v, and the actual error will be slightly greater than 0.1v. This voltmeter needs external power supply, without which the voltmeter will not work. working power supply has a wide range of voltage up to 3.5-30v. Specification: Material: electronic components Measuring Range: DC 3.5-30V Display: three 0.36inch digital tube Display color : Red Green Blue optional Measurement rate: 500mS / times. Measurement Accuracy: 1% Operation Temperature: -10℃-+65℃ Dimensions Length 32x Width 14x Thickness 10mm Opening size 23x14mm Mounting hole distance 28mm Screw size M2.0x12 self-tapping screws (customer-supplied) Lead length 15cm Net weight 5g Gross weight 8g (including packaging) Power supply No power supply, use the measured voltage directly as the power supply. Package Includes: 1 Piece Digital Voltmeter(4 Pack) Note: Alarm value adjustment method: There is a red button on the back of the board. Press the button for 3 seconds to display 1-U, release the button, press 1 second to display 2-L, release the button, press again for 1 second to display 3-H, loose Press the button again, press 1 second to display 4-S again; press 1 button for 1 second to display the trimming voltage value, then press and hold again, the voltage value will be fine-tuned upwards, stop and press again, fine-tune downward After the adjustment is completed, the digital save will automatically save and exit; when the 2-L is displayed, the lower limit alarm value can be adjusted; when 3-H is displayed, the upper limit alarm value can be adjusted; when 4-S is displayed, the sound alarm time can be adjusted, the is forwarded in 1 second; in any state, short press the button for half a second, to turn off the audible alarm, short press again for half a second, two times to restart the audible alarm.