<VV> voltmeter problem explanation

[John McMahon]

Hi,

Some people have asked what the original problem was with my digital 
voltmeter.  It was NOT that it wasn't working at all, but that when I tried 
to measure the voltage with the motor on, the reading was all over the 
place, just a bunch of random numbers flashing.  If the motor was off, it 
read just fine.  I don't have the time to learn exactly why a battery is 
needed for this, but I am grateful for the experts on the list who chimed in 
to give me the executive summary.  Viva VV!

Thanks again,

John