I'm sure we are all used to the 4 meters and a calculator drill to measure efficiency. So being tired of that, especially when trying to get an idea of efficiency under various conditions like e.g. a dc/dc converter under different loads, input voltages etc, I thought it would be useful to construct a device to do all the work.
Originally I thought DC only, 0-30V 0-5A, but then it wouldn't require much to include AC, as that allows all sorts of interesting calculations based on voltage vs current phase, real vs apparent power with a power factor.
But if doing AC it makes most sense if it will do mains voltage, then we are talking 120/230Vac, so essentially 0-260Vac or
+/-370V peaks. That will of course require some more attention to safety.
Anyway, quick overview of what I have in mind:
This is of course just a rough sketch. Also I'd probably like to add a USB connection for both charging and data collection, but to keep it safe I think best to make this double insulated, as in another DC/DC plus isolator for data, then if enclosed in a plastic box that should satisfy the requirements for a proper double insulated device.
For ADC I think 16 bits should be sufficient and maybe a decent 5milliohm shunt to achieve 10A current capability.