[time-nuts] Thermal Time Constant
Brooke Clarke
brooke at pacific.net
Tue Mar 9 23:52:57 UTC 2010
Hi:
For some time I've considered surrounding a free running 32678 Hz
oscillator (like a Dallas 32khz, or one of the newer Maxim units) with
thermal mass and insulation in order to get the time constant into the
range of some days. To get a feel for it a simple experiment shows that
a half inch diameter brass rod 3.75" long (102 grams) has a thermal time
constant of about 6 min 35 seconds when wrapped lightly in a towel.
Is there a way to calculate the amount of aluminum and Styrofoam needed
to get a time constant of say 100 hours?
This came up in relation to WWVB clocks that free run for most of the
time. When you compare WWVB clocks it's not uncommon to see tens of
seconds difference between them. http://www.prc68.com/I/Loop.shtml#TC
--
Have Fun,
Brooke Clarke
http://www.PRC68.com
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