White Backlight LCD Digital Display USB Ammeter Voltmeter Charging Capacity Detection Table Detector Voltage and Current Measurement: Connect the male USB to a 5V charger and the female connector to your phone to directly read voltage and current parameters. Measure MicroUSB Cable Quality: Connect your phone, then connect the 5V charger with the male connector and note the voltage. Then, connect the charger's MicroUSB cable to the device's MicroUSB port and note the voltage again. The smaller the voltage deviation, the higher the quality of the MicroUSB cable. Measure Mobile Power Supply Output Capacity and Efficiency: Connect the power bank to your phone, turn it on, and press and hold the button until the capacity data resets to zero. Plug in the phone repeatedly until the power shuts off automatically. The displayed capacity is the mAh of the mobile power output when the device is turned on next time. Note that this mAh is the battery voltage. Change Data: Click the button to switch to the next dataset, then double-click to switch to the previous dataset. Clear Data: Hold the button for more than 3 seconds to clear group data. Features: Simultaneously displays voltage, current, and mAh data for easy viewing. Detects mAh mobile power supply output. Multiple sets of test data are saved with power-off function. Does not affect data transmission. High accuracy, current settings do not jump. Male USB and MicroUSB ports are dual-purpose for detecting MicroUSB line quality. 25 milliohm current sampling, less loss. With precise current calibration, current accuracy is higher (it has been calibrated at delivery). Performance Parameters: Input Voltage: 4V-30V Voltage Resolution: 0.01V Test Current: 0-3A Current Resolution: 0.01A Capacity Range: 0-19999mAH Accuracy: plus or minus 1% Line Loss: about 0.1 ohm Test Content: battery voltage, current, discharge capacity (total of 10 sets of data) List: 1x Digital Voltmeter Note: Data are all manual measurements, please allow 1-3 cm error. Due to the light and screen difference, there will be a certain color difference, depending on the physical object received.