[time-nuts] Thunderbolt stability and ambient temperature

Poul-Henning Kamp phk at phk.freebsd.dk
Wed Jun 10 18:42:33 EDT 2009


In message <4A3033FC.6070806 at xtra.co.nz>, Bruce Griffiths writes:
>Hal Murray wrote:

>Thermal wave reflection at boundaries/interfaces does occur:

If your frequency or voltage standard is in a physical environment
where these effects are relevant, you have much bigger problems to
deal with before thermal reflection becomes your number one priority :-)

Lets stay real here.

Summary:

For PLL steered devices, you want your device enclosed by a thermal
mass which is again enclosed by a layer of thermal isolation.  The
goal is to filter/average all rapid (daily ?) external temperature
influences, only letting through such slow variations (seasonal ?)
which the PLL can comfortably cope with.

Even if you use active temperature control, peltier or otherwise,
it is still a good idea to employ a thermal mass to cope gracefully
with power-failuers and other equipment glitches.

Poul-Henning

PS: The thermal mass need not be solid blocks of metal, regular
ceramic bricks or tiles work fine.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.




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