Features Wide Application: The USB power tester can measure USB charging voltage, current and discharge capacity over time. Such tester can be used to check the performance of USB cables, wall chargers, car chargers and power banks. High Performance: The USB power meter is with high performance according to strict rule. The larger the load capacity, the better the quality. Real time detection of the charging state of the electrical appliance, and the voltage, current, power and other indicators are clear at a glance. Compatible: The USB power can compatible with fast-charger compatible, power tester can work under upto 20V and it does not interfere with fast charge negotiation. Power Off Storage: The USB power empty display with memory function after power off. The capacity and energy data can be stored when the mobile power supply is cut off, which is convenient for subsequent viewing and measurement of the capacity and energy of the mobile power supply. Reset Button: The USB power tester with reset button, press 3-5 seconds can make that the screen will be cleared. You can do the next test quickly without waiting too long. Specification:Item Type: USB power tester Model: KWS-V21 Voltage: Input / Output Voltage: 3.5-20v, Voltage Resolution: 0.01V Current: Input / Output Current: 0-3.3A, Current Resolution: 0.01A Accuracy: ±1% Line Loss: Aabout 0.1Ω IN: Input is connected to the charger's output port. RESET: Reset button, press 3-5 seconds, the screen will be cleared. OUT: Output terminal is connected to the data line USB port. Input Voltage Display Window: 3.5-20V Charging Current Display Window: 0-3.3A(accuracy + 1%) Battery Capacity Display Window: 0-99999mAh Working Time Display Window: 0-99min working time and empty display with memory function after power off Voltage Range: 3.5-20V Maximum Current: 3.3A Resolution: 0.01V, 0.01A, 1mAh Package List: 1 x USB Power Tester Package List 1 x USB Power Tester