[time-nuts] Improving the stability of crystal oscillators
brooke at pacific.net
Sun Oct 14 23:05:39 EDT 2007
All the papers are for depths on the order of a few feet, aimed at plant
growth, nevertheless in all cases the temperature was changing by at least 1
deg c at the deepest depth recorded.
I've heard there is some depth that building foundations need to be so they
don't get winter frost heave that might be on the order of a couple of feet,
but that's far different from an constant temperature depth.
I'm guessing that 10 or 15 feet may be required to get fractional degree temp
stability where I am. The Wisconsin data was in loam which I think means a
fairly good insulator. They had the widest temperature variation (15 c delta @
120 cm down). I've got sand and clay after the first foot or so which may be a
better thermal conductor implying less variation.
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam
Bruce Griffiths wrote:
> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+brooke=pacific.net at febo.com RETRY
> Brooke Clarke wrote:
>>Details on your experiment please.
>>Hole/pipe diameter, material?
>>Delta T at different depths vs surface ambient?
> Unable as yet to find my data, it was published in some very obscure
> publication if I remember correctly.
> However there was extensive series of records kept in England from the
> time of Lord Kelvin.
> More recent data is available from the US forest service among others:
> Above is for Wisconsin, not directly applicable to California.
> Above paper by CSIRO is for an Australian site.
> Analysis is fairly comprehensive.
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