In one of my other incarnations, radio astronomy (definitely amateur if not downright amateurish) an automotive 12 v thermoelectric cooler was converted by one of the group into a servoed "constant" temperature box. Those of time persuasion might want to try that. Note the small auto coolers can just as well be converted to a constant temperature heated box as well. Don
Robert Atkinson > > Interestingly, the packing instructions for the Solartron 7081 81/2 digit > voltmeter shows two "thermal inertia bottles" close to the instument. > These provide a thermal mass that works with the insulation to reduce the > rate of temperature change at the unit. This will also filter short > duration transients. So a cardboard box with a couple of bottles of water > in it would make a good enclosure. Or just leave the beer in the cooler > :-) > > Robert G8RPI. > --- On Tue, 9/6/09, Poul-Henning Kamp <p...@phk.freebsd.dk> wrote: > >> From: Poul-Henning Kamp <p...@phk.freebsd.dk> >> Subject: Re: [time-nuts] Thunderbolt stability and ambient temperature >> To: "Discussion of precise time and frequency measurement" >> <time-nuts@febo.com> >> Date: Tuesday, 9 June, 2009, 9:03 PM >> In message <blu125-w9e23fdf3e1618c93e603ece...@phx.gbl>, >> Mark Sims writes: >> >> >I think that using a well insulated box [...] >> >> The point for timenuts is not just the thermal resistance, >> but more >> importantly the thermal *impedance*: you want to low-pass >> filter >> the thermal changes so that they all happen in the area >> where the >> PLL can cope with them. >> >> Thermal resistance is about insulation, thermal impedance >> is >> about (thermal) mass. >> >> So you significant mass and volume (like a fridge) not >> light and >> small (like a cardboard box). >> >> When metrology people really want to keep things at the >> same >> temperature, they mount them in oil-baths (for good thermal >> contact) >> in the middle of a block of aluminium, typically 2'x2'x1' >> (for >> thermal impedance) which is again insulated with 1" >> styrofoam, all >> of this mounted in a plywoodbox, set on rubber-wheels to >> get it off >> the floor (for thermal resistance). >> >> If they are really into this, they cover the plywood with >> high-quality >> (noble-) metal foil, to maximize reflectivity and minimize >> emissivity, >> so that the black-body radiation from devices and humans in >> the lab >> does not affect the temperature interface as much. >> >> Then they leave it alone for "some weeks" in their >> temperature >> controlled lab so the temperature can stabilize. >> >> At this point they may start to wonder how they can verify >> the pt100 >> temperature sensor they put in the middle of it all >> actually works >> when the temperature never changes... >> >> Poul-Henning >> >> -- >> Poul-Henning Kamp | UNIX >> since Zilog Zeus 3.20 >> p...@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. >> >> _______________________________________________ >> 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. >> > > > > > _______________________________________________ > 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. > -- 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 _______________________________________________ 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.
