> A while back I cam across a site that detailed using the HP3458A > voltage reference board (which show up regularly on Ebay). I can't > find where I saw that info. Does anybody have this info? The site you're probably thinking of is at http://www.maxmcarter.com/vref . I bought one of the boards when they were first advertised; as of my last confidence check, it had moved a bit over 0.5 ppm. This site shows how the author built a stand alone voltage reference system using the HP board. Mostly, he just assembled it into a box fitted with a biploar regulated power supply to run the board. Pretty simple, actually, but he did a good job of documenting how he built it. David dgminala at mediacombb dot net