Purchased from grobotronics. It is very simple and easy to use, and handy for checking the voltage and current of various devices while charging them via USB.
There is an mAh reading, which measures current over time, but it would be much more useful if it showed us the mWh (a unit of energy) directly, since with a non-constant voltage, mAh do not adequately represent the energy received by the device. Minus one star for this.
The most significant problem, and the reason I’m taking off two more stars, is that moving the port ever so slightly causes it to make inconsistent contact, resulting in significant changes to the source’s voltage readings. And as if that weren’t enough, when a load is connected, the meter always shows a voltage drop, which, as you can see in the photos, is not happening at all!
If I were to buy a gadget like this again, I’d get a more expensive one in the hope that it would provide more reliable readings.