Hi, I'm interested in the possibility of developing a reasonably priced reference that has significantly better long term drift than the LTZ1000 - long term drift seems to be the biggest problem with voltage references. I've come up with some ideas that might make that possible, but haven't filled in the detail yet. What do people think? The circuit will be in an oven so temperature coefficients of components won't be crucial. The 'oven' will actually be a cooler using a small Peltier device to hold a constant low temperature within a well insulated compartment. I understand high temperatures increase the rate of aging and hence long term drift so presumably the opposite is true for low temperatures. The voltage reference device will be as low cost as possible so that several can be built into the 'oven' and their outputs averaged. Could a temperature compensated zener plus op amp be good enough, for example. Am I wasting my time or is this a great idea? Alan

At 02:21 PM 11/29/2009, Alan Scrimgeour wrote... >I'm interested in the possibility of developing >a reasonably priced reference that has >significantly better long term drift than the >LTZ1000 - long term drift seems to be the >biggest problem with voltage references. The older Motorola buried zener references, as used in the Fluke 732a have "drift rates [which] are normally distributed with a mean of 0.47·10-6 / yr and a standard deviation of 0.5·10-6 / yr." - http://assets.fluke.com/appnotes/Calibration/deaver_msc01.pdf Since those rates are actually for the entire system, the reference itself may be even better (or worse, if there are offsetting drifts in the surrounding circuitry, I suppose). That's better than the LTZ1000, in spec and practice (ibid). NLA, except by scavenging existing equipment (which should also mean they've "settled down"). The same ones appear to have been used in the Fluke 332* Voltage Standards, which can sometimes be found on eBay for ~$100.

Alan, Short answer is you are wasting your time ! If your concept had value the commercial world would have done it. They do not. It is easier and cheaper to heat something then it is to cool it and maintain that temperature to very accurate levels. ACUTALLY, they (scientific community) have done it but you will need between $150,000 and $300,000 to do it yourself. The current World voltage standard is the Josephson Junction array which is cooled down to very near absolute ZERO temperature. It requires a cesium frequency reference and a bunch of expensive microwave equipment to mention but a few items. Here are two references to read on the subject to give you an idea of the difficulty. http://www.scientificamerican.com/article.cfm?id=what-are-josephson-juncti http://en.wikipedia.org/wiki/Josephson_effect Bill....WB6BNQ Alan Scrimgeour wrote: > Hi, > > I'm interested in the possibility of developing a reasonably priced reference that has significantly better long term drift than the LTZ1000 - long term drift seems to be the biggest problem with voltage references. > I've come up with some ideas that might make that possible, but haven't filled in the detail yet. What do people think? > > The circuit will be in an oven so temperature coefficients of components won't be crucial. > > The 'oven' will actually be a cooler using a small Peltier device to hold a constant low temperature within a well insulated compartment. I understand high temperatures increase the rate of aging and hence long term drift so presumably the opposite is true for low temperatures. > > The voltage reference device will be as low cost as possible so that several can be built into the 'oven' and their outputs averaged. Could a temperature compensated zener plus op amp be good enough, for example. > > Am I wasting my time or is this a great idea? > > Alan > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there.

In message <4B12E3D9.45D68A75@cox.net>, WB6BNQ writes: >[...]The current >World voltage standard is the Josephson Junction array which is >cooled down to very near absolute ZERO temperature. It requires a >cesium frequency Actually, that's the nice part: it doesn't, GPSDRB is perfectly fine. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.