[time-nuts] Temperature stability for Thunderbolt: results

Paramithiotti, Luciano Paolo S luciano.paramithiotti at hp.com
Wed Jan 26 09:18:21 UTC 2011

Can you show us some picture of your assembly and, what is your final conrtrol loop setting?

Luciano P. S. Paramithiotti

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Achim Vollhardt
Sent: mercoledì 26 gennaio 2011 9.12
To: time-nuts at febo.com
Subject: [time-nuts] Temperature stability for Thunderbolt: results

After some tweaking of the temperature controlled fan setup (not always to the better), I finally settled on a setup with great results.

- Peak-peak variations in stable environments are down to 0.02K.
- opening window for few minutes disturbs only 0.03K down.
- TBolt sits now nice and stable at 36 degC.

Summarizing the important points (and please if somebody wants to add/correct, feel free!):

- Using Lady Heather's temperature controller helps A LOT.
- Using a too small fan results in too small control range. Large temperature disturbances cannot be compensated.
- Direction of flow DOES make a difference. First attempt blew the air from the (warmer) power supply to the TBolt.. which make you kind of wondering why the temperature shoots up while the fan is running 100%.
- I minimized the thermal mass *between* the fan and the TBolt. It is still in his own case, but no passive shielding around. Slows down the control loop and seems to make things worse. Some thermal mass around the fan control loop might be a different story.
- Once the temperature has settled, 'ka4' optimizes the controller parameters. Another improvement in response speed and temperature residuals.

A big thank you to Warren and Mark for implementing this feature (sorry if I forgot somebody) and all others who helped in this list. I think this feature is a must-have for all TBolt setups out there..

73s Achim, DH2VA

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