I bought a 29 range digital multimeter from radio shack "22-813" (Link to Owners Manual) 1. What is a "AC voltage riding on a DC source bias" mean? 2. The specifications say that it can measure AC 600 V RMS Maximum at 50/60Hz. Does that mean that it can't measure any voltage above 50/60Hz or it just can't measure 600V at 50/60Hz? I am trying to measure what should be 4.5 V AC at 58kHz and am not getting an accurate reading. Is it possible my multimeter is just a piece of crap?