Richard Moore wrote: > What to do? Seems like a possible stable, yet low-cost source would > be to buy 10 or so LM399s and hook them up to a power supply to age > for 6 to 12 months, then use two or four in parallel (with suitable > resistor buffering) driving a chopper amp like the LT1050 to give > gain. Powered by a good, stiff regulated supply, and kept away from > stray air currents, this arrangement wouldn't cost as much as a > single LTZ1000A (which in singles is over $100 USD) LTZ1000A list price is about $54 (excluding freight and taxes) when ordering from Linear Technology. The LTC1050 is a bit marginal unless you bootstrap its power supply the LTC1151 is a better fit. > and -- dang it, > there's always a catch -- after lab calibration, could be a source > that might need adjustment only once every few years to stay within 5 > or 10ppm or so. Paralleling more LM399s would be better, and with an > initial purchase of 10, you could throw away the stinkers and > parallel all the rest. So, short of having a Fluke 732A or those > 8-1/2 digit meters, that's my recommendation for a low-cost V > standard. Unless you know someone, it'll cost less to build than to > calibrate... > > Dick Moore > > > Bruce
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