Since its introduction over 25 years ago the USB port has become the de-facto standard for communications between a PC and its peripheral equipment. In the meantime, in an effort to reduce the plethora of non-standard wall-wart mains adapters, most other devices with built-in rechargeable batteries like mobile phones, tablets etc. use the 5 V supply pins of this port for charging. It’s even possible to fit a mains outlet wall plate with a built-in 5 V supply and USB socket. With the introduction of Quick Charge the power supply communicates with the device being charged to negotiate an output voltage. A compliant charger can output a higher voltage and current beyond the typical 5 V / 2 A rating of the standard USB charger. With so many essential devices relying on a fully-functioning charger and so many different fast-charge standards emerging it is convenient to have a single unit that can quickly check that the charger is doing everything it should...