[volt-nuts] Sub PPM 10V transfer standard

[Poul-Henning Kamp]

In message <BLU160-W589E11CA52703B9DEA19E7911A0 at phx.gbl>, m k writes:

>But for 0.1ppm you need to address opamp heating and unintended
>thermocouples everywhere.

Actually, if you go that far anyway, adding a peltier and ntc to
hold the temperature constant is not a big deal.

Build the PCB (both Vref & Tctl) as surface-mount with no through-hole
and attach it directly to the Peltier with a thermal pad

The Peltier needs very little power if the temperature difference
is on the order of a few degrees and the power dissipation in the
controlled volume is low.

When I ran the MAX6350 experiment, the 12V Peltier was running
at slightly less than 1V most of the time.

I would let the Tctl output an analog control voltage and put the
Peltier power-driver outside the controlled volume.

I would recommend preregulating the input power with a linear
regulator (also outside the controlled volume) so that the power
dissipation in the controlled volume is as constant as possible.

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