Feature: This is the mini USB meter. It can measure voltage, current, power and capacity. 0.91inch OLED Screen design. It is so lightweight which is so portable to be taken. Environmental protecting and low energy consumption. Over-voltage and under-voltage reminding for safe using. Perfect tool that is useful,helpful and so practical. Easy to use and to operate at affordable prices. Description: Voltage range: 3.5V-9V (1% accuracy) Current range: 0-3.3A (accuracy 1%) Working time (0-99Hour) Capacity measurement range:0-99999mAh Color: random Size:59*23*13.5mm Instructions for use: 1.Measuring voltage and current: Plug the USB male connector into the 5V charger, and the female connector into the mobile phone and other devices, and you can directly be alone in the voltage and current parameters 2.Test battery capacity: Use linear charging current such as TP4056 to charge the completely dead battery slowly through this capacity meter, and read the battery capacity in place. This method can also be used to measure the charging capacity of the mobile phone, and even calculate the charging efficiency of the mobile phone Test mobile power output capacity and efficiency: First connect this machine to the mobile power supply, turn on the mobile power supply, press and hold the button until the capacity data is reset to zero, insert the mobile phone to hide and charge until the mobile power supply is out of power and automatically shut down. The next time the machine is turned on, the displayed capacity is the mAH output by the mobile power supply. Note that this mAH is much smaller than the nominal mAH, output mAH*output power 5V/battery mAH*battery power 3.7V=mobile power efficiency 3.Data cleared: The screen display will be reset after pressing the reset button for 3 seconds. Note: 1. The IN-input terminal is connected to the output terminal of the charger. 2. RTZ- Clear button is pressed for 3 seconds and the screen display is cleared. 3. OUT- The USB port where the output end is connected to the data line. 4. Input voltage display window (3-9V) accuracy error 1%. 5. The accuracy error of the charging current display window (0-3A) is 1%. 6. Battery capacity display window (0-99999mAh). 7. Working time display window (0-99H) unit: minute. 8. Working time and capacity display after power off, there is memory function. Package Included: 1 * USB capacity voltage tester