Joe wrote: >I know someone who has a General Resistance Dial-a-vider DV-4107 * * * > >The reason I'm interested in this is not so much for use with a DC >reference, as I already have the VS330. I was thinking about using it for >AC, if I can buy or make a reasonably accurate AC reference. It's a basic 7-decade DC Kelvin-Varley divider. The Fluke 720A is generally considered best-of-breed, both for its high quality and its self-calibration features. To my knowledge, no manufacturer of these DC dividers rated them for AC use, and they were not generally built with non-inductive resistors. So it might work OK at very low frequenceis, but everything you did with it would be an "off-label" application. Furthermore, the 100k ohm input resistance demands an ultra-high resistance (impedance) load -- it is designed to be used with a DC null meter. But there is no ultra-high impedance AC null meter, and if there were, stray fields of every sort would wreak havoc on any measurement you tried to make with it. For accurate AC measurements or calibration, metrologists use a "thermal transfer standard" (or "AC/DC transfer standard"), in conjunction with an AC source and an accurate DC source. See: <http://download.flukecal.com/secure/792A____imeng0100.pdf?nvb=20130811035444&nva=20130811040944&token=0aa649a8db6274c6ae587> Best regards, Charles