Sure, for a clean sinusoidal waveform. But use a 'scope to have a look at the "modified sine wave" that you get on the output of a reasonably priced UPS when it's running on batteries, or the chopped sine wave from a lamp dimmer, or the output of a ferroresonant "constant voltage" transformer. In all of these cases (and many others) you cannot just measure the peak voltage and multiply by 0.707 because doing so will get you terribly inaccurate results.
I agree. That's why I used the NASA reference for qualification. For an ecig mod simpler circuits work fine, IMO. PWM regulators are probably the most common.
For light and motor controllers the desired result is light on or drill turning at a usable speed. In an ecig mod we want our voltage or wattage to be what the display says it is.
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