Mini DC Digital Voltmeter 0.28" Voltage Tester Mini DC Three Wire Voltmeter 0V-100V - 5 Colors

3 wire connection (but it can also change three lines in 2 wire connection), with reverse polarity protection. 2 Connection Methods: 3 wires are connected separately to measure voltage and power (red and yellow for positive, black for negative); 3 wires are used as 2 wires, connected to measure voltage below 30V (red yellow can be paired for positive, black for negative) Max. Input Voltage: DC 100V Above 100V, there is a risk of burning. 0.28 inch LED display. Small size and lightweight, quite easy and convenient to make. And with fine tension adjustment function. The screw on the back can be adjusted to calibrate --- turn clockwise to lower the tension.