USB Voltage Current Mobile Battery Multimeter (3V-7V) Power Tester with LCD Display for Smartphone Tablet Detection Tool (White) It can test current and voltage of phone, mobile power bank etc With a USB port and micro USB interface, convenient to test devices With LCD screen, easy to see the current and voltage of the devices Press the small circle button and the data will be zero, then you can test next data It can show you the USB charging current and voltage instantly. which gives you the fastest charging performance! Flexible, easy to use.