Fangrui Product Details 1. The Voltmeter Has Simple Wiring. It Usually Uses Two Wires, Red For Positive And Black For Negative. It Has Reverse Connection Protection, So It Wont Burn If Connected In Reverse. 2. It Doesnt Need An External Power Supply. It Can Work Directly With The Measuring Voltage. The Measuring Voltage Range Is 2.4v-32v For Two Lines. 3. It Works With A Wide Voltage. The Minimum Measuring Voltage Of Red Is 2.4v, And The Maximum Safe Pressure Can Reach 40v. It May Be Damaged If It Exceeds 40v. 4. When Measuring Voltage Below 10v, Two Decimal Places Are Displayed; When Measuring Voltage Above 10v, One Decimal Place Is Displayed. Measuring Range: Two-wire Dc2.4-32v Power Supply Range: No Need For Separate Power Supply Test Voltage Test Accuracy: Greater Than 10v Error Plus Or Minus 0.2v Less Than 10v Plus Or Minus 0.03v Input Impedance: Greater Than 50k Working Current: Less Than 30ma Refresh Rate: About 100ms Once Display Specifications: Three-digit 0.36led Digital Tube Lead Length: Default 15cm Opening S