I am trying to figure out how long my project will last on a single battery. It's powered by a single AA battery with an NCP1402 3.3 volt boost converter. I've determined that the target circuit draws around 75 µA at rest and around 250 µA for 35 ms per second. I could just run that number, assume the boost converter is 80% efficient and go with the result (which is around 2 years or so), but I would like, if possible, to validate that experimentally.
I have a µCurrent Gold, and hooked it up to my Rigol DS1052 scope to get the numbers above (with a bench 3.3 volt supply and the circuit on a breadboard). But when I repeat the experiment with the boost converter, what I see is a complex waveform with peaks at around 1 mA which decays down to 0. Not only that, but it's quite irregular. I can't make any sense out of it.
I've discovered my scope does have an averaging function, but it doesn't help - it can't gather enough samples into the average to make a difference.
My big concern is that the boost converter efficiency may be way, way lower than 80% at such a low draw, but I can't really verify that.
I did try just using a multimeter (still with the µCurrent Gold), and I get an answer of 450 µA. That would last around 9 months - still acceptable, but is it correct?