[Trent M. Wyatt]’s CPUVolt library provides a fast way to measure voltage using no external components, and no I/O pin. It only applies to certain microcontrollers, but he provides example Arduino ...

A common data logging application is measuring voltage or current flowing into or out of a piece of equipment, such as a user monitoring current in solar cells, inverters, or storage batteries. These ...

Measuring a voltage is pretty easy: just place your multimeter’s probes across the relevant pins and read the value. Probing currents is a bit trickier, since you need to open up the circuit and place ...