Keweisi 3v-9v 0-3a Usb Charger Power Detector Battery Capacity Tester Voltage Current Meter It can measure the USB-powered devices empty and easy to use and practical. Compact and easy to carry, no additional power supply, plug and play. It can easily measure the output voltage of the USB port and the device operating current or load voltage. Detect any USB charger such as PC USB, home charger, car charger. Wide range of applications, any phone, any electronic product. Suitable for factories, laboratories and personal use.