Feature: 1. USB power tester can measure USB charging voltage, current and discharge capacity over time. 2. Such tester can be used to check the performance of USB cables, wall chargers, car chargers and power banks. 3. Compatible with fast-charger compatible, power tester can work under upto 20V and it does not interfere with fast charge negotiation. 4. Empty display with memory function after power off, power meter is with high performance according to strict rule. 5. With reset button, press 3-5 seconds can make that the screen will be cleared . 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