In message <[email protected]>, 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 [email protected] | 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 -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
