OKRAY 4A 20V Dual USB 2.0 Voltage Amp Power Meter Tester Multimeter, Charging Current Voltage Monitor, Test speed of charger cable, capacity of power bank, Watt Meter, 9 Modes Tester (White ) USB Tester Monitor : OKRAYs USB Voltage Tester can be used to measure current, voltage, active power when the Power Supply Unit is on load or no load and the USB terminal unit is working. Using this tester, you can judge whether the performance of USB charger and cable is meet with your requirement of quality. Automatically Protection : The screens voltage data will flash and the buzzer will alarm when the device is over voltage and over current. The USB port will be shut down automatically in order to protect your device. Please notice that input Voltage must not over 20V, or it will destroy the item. Power supply voltage must be 4.6-15V. If you use "USB load resistance" must not work for a long time during electric current over 3A. Special USB Port Function and Compatibility : USB 1 port have universal USB fast charging adapter features. USB 2 can be used for data transmission and also charging. Support to test your iPhone or Android phone. Simple But Useful Design: It is small, easy and convenient to use for your device. The data of current and voltage will show circularly in the screen. Having it means that you have a safer partner when you use your device. What You Get : 1 pack USB Voltage Tester, A piece of product instruction, Friendly 24-hours prompt customer service and 12-month Warranty.