Is there any reason why my basic Radio Shack multimeter might consistently read high when I use it to test the output voltage of an AC->DC wall adapter? I try it on a 4.5V adapter rated for a few hundred mA and it reads close to 10V... I try it on a 6V one and it reads around 12V... but then I try it on a known-good charged car battery and get the 12.6V I expect. (And no, I am not messing up the range setting :) as all three readings come off the 0-25 scale without touching the range setting). I am testing the adapters with no load. Is it possible that they rectify the output badly enough to confuse this multimeter?