[time-nuts] "The Penultimate HP5065 A15"

[Poul-Henning Kamp]

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timeok at timeok.it writes:

>    A better C field generator is necessary and the LM399 remains a good solution. It would be interesting to add
>  barometric pressure compensation.

I don't think I can fit that also :-)

> Two types of setting could be used to adjust the C field, one with fixed high
>  stability resistors resistors that can be switched for the coarse and a potentiometer for fine tuning in order 
> to mitigate its low temperature stability.

already got that.

>    Excellent solution of two separate power supplies for the lamp and the rest of the electronics but I have 
> doubts about the LM317. Since we already have the LM399 available for the CField, why not use this reference
> voltage already present on the board to drive two low noise regulators?

That's precisely the plan, but I like the LM317 style short-circuit and thermal protection, so I will probably
do it by setting the LM317 voltage with a voltage divider, and then drive the midpoint with an op-amp
relative to the LM399

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