The Triplett USB-Bug is designed to test the power, voltage, and current of USB 2.0 or USB 3.0 charging ports. Connect the USB-Bug inline between the power source and the device you are trying to charge. Test current from 0 to 3 Amps. If the current is over 3 Amps, the USB-Bug will flash the decimal point quickly. Test voltage from 3.2 VDC to 30 VDC. If the voltage is greater than or equal to 5.6 VDC, the decimal point indicator on the voltage measurement will flash quickly. If the voltage is less than 4.4 VDC, the decimal point indicator on the voltage measurement will flash slowly. Test power from 0 to 99.9W.