Yep, measuring stuff always has lots of traps buried in there

A thing I wanted to underline in measurements: take the example when it is sinking 80mA at 6:26.

I will be ignorant for now and just take the voltage, current & power measurements from the PSU and load.

In: 5.00*0.234 = 1.17W

Out: 11.80*0.080 = 0.944W

So that's 80.6%, nice.

As shown in the video the BK precision doesn't have great resolution. 80mA could have been 79.5 or 80.5, and just to show:

11.80 * 0.0795 = 0.938W -> 80.2%

11.80 * 0.0805 = 0.950W -> 81.2%

Oops, that's +/- 0.5% right there.

In fact; this is not entirely correct neither. The BK only gives us 2 significant digits for current, and so our measurement can only be 2 significant digits.

So with that measurement we can only conclude it's 81%, but not better. Luckily the BK also only shows 0.94W, because all other digits behind that are bogus. 0.94W is not the same as 0.940W or 0.94000W

This is a little trap and in practice I think often ignored, aside probably from the voltnuts who already know this. Of course you aren't also going to round off numbers and look at some bouncy graphs, but it's always nice to know what degree of precision measurements were taken.

But the introduction of the SMU outlines that the BK Precision electronic load isn't a perfect fit for this measurement. That load really shines if you have a few amps to measure because then you do get 4 significant digits.