[time-nuts] Thunderbolt temperature

Don Latham djl at montana.com
Mon Aug 27 18:56:42 UTC 2012

Charles: Yes, these methods will work equally well. As you have mounted
the TB, it is in radiative equilibrium with the cast box. Thus,
controlling the box temp will quite nicely control the TB temperature.
I've been lurking for a while on this topic (well, it comes up wit great
regularity). Investigate the characteristics of nested radiative
equilibrium, you'll see that this technique is very good, especially if
you use say wire-wrap wire to carry the signals and power. If you
suspend your cast box inside a small peltier six-pack cooler and
regulate that, the system would be very nice indeed. There are of course
convective currents inside the nested boxes, but if the temperatures are
reasonably steady, they will settle into reliable transfer patterns. I
confess I have not done the homework to see what proportion of the heat
is transferred by convection, but it might be small. Certainly in the
setup you have, conduction plays a very small part indeed in the total
heat flow. Someday, when my decks are cleared, I'd like to try just the
setup you have devised. I think it promises to be the best.

Charles P. Steinmetz
> Michael wrote:
>>I'm still not entirely sure this is a good idea though, seems like a
>>low-temp oven for the whole tbolt would be better if you want
>>thermal stability.
> Precisely because it is not clear that holding the backplate of a
> Tbolt at a constant temperature is the best way to keep the interior
> of its crystal oven at the most constant temperature (which is the
> ultimate goal), I mounted mine on thermally insulating standoffs in a
> cast aluminum box with about 1" of clearance on all sides, and
> control the air temperature inside the cast box.
> For another Tbolt mounted similarly, I control the surface
> temperature of the cast box, which seems to work equally well.
> In both cases, I adjust the controller for whatever measured
> temperature produces a Tbolt internal temperature reading (via the
> Tbolt's DS1620) of about 45C -- safely above any ambient temperature
> to which the mounted units will be exposed, to avoid the need for
> active cooling (Peltier, etc.), but not excessively so, to keep the
> internal electronics as cool as is practicable.
> Best regards,
> Charles
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"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell

Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304

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