[time-nuts] uC ADC resolution (was: Poor man's oven)

Bob kb8tq kb8tq at n1k.org
Wed Jun 7 22:35:51 EDT 2017


Metal actually makes things a bit worse since it has a lower thermal resistance than glass. 
This is also why a high performance dewar is made from glass rather than metal.  Yes, you
can go to weird stuff like titanium (it has been done). You can’t afford that ….

If you fill the entire dewar with a heat conductor you make things worse still. The idea is to
*block* heat flow out of the heated area. Even without fill,  the wall of the dewar goes from the outside 
world to the heart of the heated area. It is the perfect “sneak" path into the oven. Actually
it’s not that much of a sneak path since it’s a well known effect :) 

Again, none of this is particularly original. Take a hammer to any dewar based OCXO and
the details are going to be similar. 

> On Jun 7, 2017, at 9:51 PM, Chris Albertson <albertson.chris at gmail.com> wrote:
> On Wed, Jun 7, 2017 at 3:18 PM, Bob kb8tq <kb8tq at n1k.org> wrote:
>> Hi
>> Consider that a lot of the heat flow is through the glass wall of the
>> vacuum gizmo. You want to tie your heater(s) to it in order to create
>> an iso-thermal “wall”. Often this is done by gluing the whole assembly
>> together.
> Not glass walls.  Stainless steel.  The metal wall make it uniform.
> I occurred to be that you could fill the container with a liquid.
> Something that has good thermal conductivity and it would be very uniform
> inside.   I don't know what, transformer oil perhaps?
> -- 
> Chris Albertson
> Redondo Beach, California
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