To calibrate your PA, I'd recco this strategy.
Pick yourself up a 10 dollar digital multimeter from the automotive electric section of your favorite big box store.
Set it to whatever setting it has for between 2 and 10 volts DC (VDC). My meter has settings in logs of 2 (2, 20, 200), so I use 2, because you want to read to 100ths of a volt (X.XX, 1.23, etc).
Find your favorite batteries and charge them up, and take a reading after it's been out of the charger for 5 minutes. Then set your PA to duplicate that voltage. You may have to go a bit lower than that, because I imagine there's some voltage sag in a AA during 15 amps of current draw (ya think?), which the PA would have less of, if any at all.
My favorite batts are at 1.47-1.48V when fresh, but rested as I describe. That's enough voltage to make microhitting dangerous, and give you a nice constant draw speed that produces nice vapor clouds. Those are the batts i give to noobs and tell them to hit it like a glass spoon and they choke on it
This should give you a reasonably accurate place to start. The mutimeter will help you dial in on the different voltage settings so you can lower the temp to a late bowl level to play safe from scorching.
Hope this helps!