This is Two-Wire Voltmeter. Voltage Test Range: DC 5-120V (others: up to 30V). No need for an independent power supply.
Measurement Accuracy: ± 0.1 (5 - 9.99V) / ± 0.3 (10.0 - 99.9V)/ ± 1 (100 - 120V). Easy to CALIBRATE: Turn the screw on the back of meter to Calibrate it slightly.
Bright and Clear Reading: three-digit 0.56'' digital LED tube; Display Color: BLUE; Refresh rate: about 300ms / time; Operating Temperature: -4 F ~149 F (-20°c to 65°c).
Reverse Polarity Protection: The meter won't burn out if reverse polarity is applied, but the screen will display nothing.
NOTE: When measured voltage is larger than 120V, the voltmeter will be damaged.