Keweisi USB & MicroUSB Tester - Voltage Current Power Meter with OLED Display

Description
KCX-017 USB Power Detector is a measurement device which specialized testing and measuring the output voltage and current of any USB port, such as USB port of power banks, phone chargers, PCs, wall chargers, etc. Of course it can be used for measuring the voltage and current anywhere, but in the range of  3 to 9 V and 0.05 to 3.5 A. The best preference of the KCX-017 is easy measuring of voltage and current, simultaneously. It can display mobile power output in mAh unit.

Features
Input voltage: 3V-9V
Voltage resolution: 0.01V
Test current: 0.05A-3.50A
Current resolution: 0.01A
Capacity range: 0-19999mAH
Accuracy: plus or minus 1%
Line loss: about 0.1 ohms

Functions
A) Measuring USB port voltage and current:
The USB male plugs in the 5V charger, You can see the voltage and current of the charger output, in no load.
For measuring the current and voltage of the charger in charging state, after plug in the male connector in charger, by a charge cable, connect a mobile phone  into the female USB port of the tester, to directly read the voltage and current parameters.
B) Measuring the quality of the MicroUSB line:
First, connect the tester in the USB port of the charger and read and remember the voltage and current.
Second, now connect MicroUSB line to the MicroUSB port of the tester and the USB port of charger.
This difference between the first stage and the second stage depends on  the quality of the MicroUSB line, Lower gap means better quality.
C) Measuring the output capacity and efficiency of mobile phone power:
First connect the tester to the USB mobile power
Turn on the mobile power, long press the button until the capacity data are zeroed,
Insert the phone to charge multiple times until the mobile power is turned off automatically.
When the tester is turned on again, it shows the capacity (mAh of the mobile power output) 
Note that this mAh may be much smaller than the nominal mAh,
Mobile power efficiency mAh * battery voltage 3.7V 
D) Data switching:
Click the button to switch to the next set of data, and double-click the button to switch to the previous set of data.
E) Data clearing:
Press and hold the button for more than 3 seconds to clear the group data.