Randy Leifer wrote: > Bigger Volt-nut here. > ...albeit, less knowledgeable than most of you. > I have been in the chase for the perfect volt. > I have 2 JRL SCO-105 saturated cell references running 24/7. > But checking it's accuracy....I must rely on my cal'd HP3457 meter. > Although, those cells (6 total, 3 in each cabinet) are pretty stable, and > good for determining drift of the Vrefs I build. > I have a Geller 5v, and I've built a few of my own refs using some > National LM399AH-50 along with a chopper buffer. > (these LM399's come with a 1000 hr burn-in and a drift plot) > I am getting a 10uV drift with these circuits, but that is over a +/- 15* F > ambient temp range (as is the voltmeter)...and they're only in plastic cases > in open air--not shielded yet. > http://i5.photobucket.com/albums/y177/Midiot/my_lm399_ref.gif > > I am currently building/testing/tweaking a temp stable insulated enclosure, > using a Peltier, a 5 watt controller, and 0.1% glass thermistors.....to house > my Vrefs and some standard resistors. > I am shooting for 25* C, but the outside air still has an slight effect on > the internal air (+/- 0.5* C on the inside).....not bad but I think I can do > better. I put a low-ohm thermistor outside the box, in series with the main > sensing thermistor inside, and this helps. But this may be a whole new topic. > I'm up for a Vref project. How about you? > > =Randy= > > An LTZ1000 or LTZ1000A based reference will have better long term stability. One can even build in a thermal conditioning cycle to "anneal" out voltage shifts that occur when starting up after the reference loses power.
Bruce _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
