Don't bother with the concrete, just put the dirt back. You can even just bury a vault with a lid under about 2 ft of dirt, will work just fine. Don Chris Albertson > I've got a foundation trench open right now. I've been thinking it is a > great opportunity to keep some electronics at a very stable temperature. > What's better then tossing it in a big hole in the ground then dumping > a > truckload of concrete on top? Likely the only thing I'll burry is a $2 > temperature sensor. In So. California you don't need to go very deep to > reach stable temp. > > > > > On Fri, Jul 13, 2012 at 5:25 PM, Neville Michie <namichie@gmail.com> > wrote: > >> >> You have to go deep into the ground to get stability. >> At 15 metres deep there is a lovely pure sine wave of about 0.3C P-P. >> I measured it on the roof of a cave, its period one year. >> My design for the bolt is to put it in a 1/4 inch thick aluminium box >> which >> is held at a constant temperature by a fan. Switching control is good >> enough as the >> thermal diffusivity of 1/4 inch aluminium will attenuate any spectral >> components shorter than >> a minute. The aluminium box is so conductive that the box is >> isothermal, >> so once the bolt >> has established its internal temperature gradients, nothing changes. >> cheers, >> Neville Michie >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > > > -- > > Chris Albertson > Redondo Beach, California > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- "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 www.lightningforensics.com www.sixmilesystems.com

As someone pointed out, it is dependent on where you are, as well as a number of other factors. I've got a nice chunk of concrete tied to bedrock about 10' below the surface with a thermal variation that is below the threshold of the thermometer i have there. Since I need to put something else on the concrete block (seismograph) I thought it might be interesting to toss a frequency std on it a well. Yet another project...:) On Jul 13, 2012, at 20:25, Neville Michie <namichie@gmail.com> wrote: > > You have to go deep into the ground to get stability. > At 15 metres deep there is a lovely pure sine wave of about 0.3C P-P. > I measured it on the roof of a cave, its period one year. > My design for the bolt is to put it in a 1/4 inch thick aluminium box which > is held at a constant temperature by a fan. Switching control is good enough as the > thermal diffusivity of 1/4 inch aluminium will attenuate any spectral components shorter than > a minute. The aluminium box is so conductive that the box is isothermal, so once the bolt > has established its internal temperature gradients, nothing changes. > cheers, > Neville Michie > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.