This is a standalone DC voltage meter. It measures 3V-30V with 1% accuracy. Best suited for battery level display. Just apply two wires on the power without any extra circuit or components, it gives the reading straight away. Easy to use, and is a good company with robotic applications. Three colors options: green / blue / red. Specification Measure Voltage:3.0-30V DC Refresh Rate:2 Hz Accuracy:1% Shipping List LED Voltage Meter (Blue) x1