They are all off base here. Actually I am surprised Phil didn't mention it.    
      
   Compare the readings with the same peak to peak value o a sine wave and a   
   square wave. If they read the same it is not true RMS. If it is true RMS on a   
   square wave it will read approximately ½ the P-P value but on a sine wave it   
   will read lower, 0.70711    
   of ½ the P-P value. Almost any meter has the resolution to discern 1 volt   
   from 0.71 volt.    
      
   You do have a scope right ? If not you'll have to figure out a way to clip a   
   sine wave. You don't need any power behind it, a Zener or stack  of diodes   
   will do. A scope is the best way though. If you have to wing it come back and   
   I will try to figure out    
   the easiest way.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)