More expensive, but better

I ordered and tested by 5 euros to 20 euros more USB multimeter. These have been tested with iPhone / iPad at various power supplies, and static load resistance at the DC power supply. Of all this performed best, and the several reasons:

- Very accurate. Already at the factory, but who wants it more precisely: under the sticker on the back is the screw to open the housing. On the board there are two trimmers, I and U, which can be used both to calibrate maximum accuracy.

- Less loop-through resistance. Minimal voltage drop and thus the highest current. No other multimeter let the iPad with full 2.3A load, typically was from 1.7 to 1.9 A.

- Minimum interference during commissioning. Interestingly, the start of the multimeter affect the power of the iPad. Thus, in this multimeter flowed always 2.3 A, while another, yet niederohmigeres, led to a current limit to 1.8 Å. There seems to be important during initialisation and the negotiation of the charging parameters that the multimeter is not even an excessive peak current triggers during initialisation.

- Maximum flexibility. The dual USB socket turns out in practice to be awesome. Charging current of several devices, more branching, additional tap to check measurement - which one might not want to miss one has experienced it once. The second output has short-circuited by the way, the two data pins, and signaled as 'USB Charger' (an iPad invites to the socket firmly with 1.5A). So you can also test the same, flow (normal / USB Charger) which flows in both modes.