voltmeter - TOOGOO(R)KW-202 Digital Display USB portable tension tester voltmeter battery tester for Power Bank Cell Mobile Phone Transparent 100% brand new and high quality it can testing USB power supply unit easy to use and practical. Compact and portable. Need no power supply, plug and play. It can easily measure the output voltage of the USB port and the operating voltage or load voltage. Test any USB charger, USB, household charger, car charger.