Q. What's the maximum current the Centech USB Power Meter will safely measure?
A. 2.00 Amp current maximum rating, 0.05 Amp minimum for a reading and uses 0.01 Amp power
Q. Does this device tell you the available power from a given port or does it actually measure what the plugged-in device is actually drawing?
A. It measures the current being drawn by the device.
Q. Will I be able to determine the battery health of my iPhone compared with my brother's iPhone using this?
A. No, the USB Power Meter won't tell you battery health. It's possible that by monitoring the charge amperage at different phases you could see one is problematic but that would not be conclusive. If you live withing range of an Apple store, simply make a Genius Bar appointment and ask them to diagnose your battery. They have an app that gives them access to your phone's diagnostics and will show them the battery health. They can tell you exactly how health the battery is and it's free. The Meter will tell you the rate at which your charger and cable is delivering power to the phone. Above 80% the phone reduces the charge rate but below 80% it should charge at a full 1Amp (5 watts.)