[time-nuts] Voltage standards

[Bruce Griffiths]

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