Welcome to our store! 1. USB power tester can measure USB charging voltage, current, and discharge capacity over time. 2. Such a tester can be used to check the performance of USB cables, wall chargers, car chargers, and power banks. 3. Compatible with fast charging; the power tester can work up to 20V and does not interfere with fast charging negotiation. 4. Blank display with memory function after power off, the power meter has high performance according to strict rules. 5. With the reset button, pressing for 3-5 seconds can clear the screen. 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: Approx. 0.1Ω IN: The input is connected to the charger's output port. RESET: Reset button, press 3-5 seconds, the screen will clear. OUT: The output is connected to the data line's 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: 0-99 min working time and blank display with memory function after power off Voltage Range: 3.5-20V Maximum Current: 3.3A Resolution: 0.01V, 0.01A, 1mAh 1 x USB Power Tester