Forced air will generally be turbulent, which means that the air speed and pressure at any point will follow a somewhat normal (or not) random distribution. That is not good for something that needs stable cooling. Air flow resulting from convection cooling on the other hand is usually laminar, which means it is much more stable.
Didier Sent from my Droid Razr 4G LTE wireless tracker. -----Original Message----- From: Bob Camp <[email protected]> To: Discussion of precise time and frequency measurement <[email protected]> Sent: Sun, 16 Dec 2012 7:47 PM Subject: Re: [time-nuts] Z3805A cooling requirements? Hi The gotcha here is that an un-cooled piece of gear will heat up and cool down as it's work load changes. There is no "magic bullet" that keeps the temperature constant with zero airflow in a normal design. Yes, I'm old enough to remember oil cooled computers. Still no constant temperature and you have turbulence. Bob On Dec 16, 2012, at 8:40 PM, Magnus Danielson <[email protected]> wrote: > On 12/17/2012 02:21 AM, Bob Camp wrote: >> Hi >> >> When you blow on a TCXO you are setting up variable airflow. A fan produces >> a constant airflow. A variable flow gives you a variable temperature. A >> constant flow keeps things pretty uniform. >> >> Environnemental chambers have pretty massive airflow. TCXO's and OCXO's do >> quite well inside them. > > The trouble with airflows over a TCXO or OCXO compared to still air, is that > you provide a better connectivity to the ambient air and it's variations. > Hence, I get to monitor the AC in the building or testlab that way. Just > tossing very mild isolation and it is almost quiet in comparison. A good > quality environmental chamber doesn't have drastic "puffs" of heat-up, where > as lesser onces do that. When testing TCXOs I learned more about the > environment chamber in use than on the TCXO itself... > > Again, your mileage WILL vary. > > Oh, I do know some folks that are looking into the effect of turbulence of > forced air on crystal "noise". I could find some flaws in their line of > reasoning. > > Cheers, > Magnus > > _______________________________________________ > 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. _______________________________________________ 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. _______________________________________________ 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.
