[time-nuts] 5680A update (temperature stabilization)

paul swed paulswedb at gmail.com
Tue Jan 17 16:01:51 EST 2012

Well done.
You have answered a couple of questions for me. The heat sink inside is
small so its easy to see why all sides of the case should be close in
Like you in tinkering, I attached 4 reasonable size heat sinks with the
case off and noticed I could drop the internal heat sink to 115 degrees.
Granted everything cooks inside but it seems a bad way to run things.
Though the xtal does need the stability.
I think I may follow your lead and attach an external sink to dump extra
heat from the regulators. No fan just open air.
I hate fans. ;-)

On Tue, Jan 17, 2012 at 3:44 PM, beale <beale at bealecorner.com> wrote:

> I tried a simple bang-bang controller (LM35 temp sensor+comparator+pass
> transistor to drive a small fan) with the LM35 taped to the center of a
> large finned heatsink. The FE-5680A+heatsink are sitting upside down, so
> heatsink fins point up. LM35 leads wired with 34 gauge wire, which is taped
> along heatsink surface. The fan cycle time was about 20 seconds, and the
> peak variation measured at the LM35 was about 0.2 degrees. Now, of course
> what I am controlling is the top surface of the heatsink. What's the
> temperature variation inside? Well, another temperature sensor, a
> thermistor full bridge attached to the center top surface of the 5680A
> (which is underneath, in my setup) indicates that surface varies only 4
> millidegrees C in the short term (one fan cycle) due to the thermal mass of
> the assembly. However, long term it drifts much more along with ambient,
> because I do not have good insulation around the body of the 5680A. I plan
> to put it in a well-insulated box with just the heatsink exposed, so nearly
> all the heat transfer happens at the heatsink fin surface, which I am
> controlling. I am guessing I can manage 0.01 C stability inside the box
> that way.
> -John Beale
> >  -------Original Message-------
> >  From: WarrenS <warrensjmail-one at yahoo.com>
> >  To: Discussion of precise time and frequency measurement <
> time-nuts at febo.com>
> >  Subject: Re: [time-nuts] 5680A update
> >  Sent: 17 Jan '12 11:52
> >
> >  to Chris
> >  What I've seen is that holding 0.1 C AT the SENSOR is pretty easy,
> >  (Lady Heather will hold the TBolt's sensor to 0.01 deg using just a
> fan),
> >  AND if you blow a lot of air around, then keeping the air gradients
> inside a
> >  closed 'oven box' below 0.1 deg is also NO problem.
> >
> >  to Bert
> >  Have you measure what the Temperature coeff is over normal room changes
> with
> >  and without the addition of the temp controller?
> >  What is the best configuration to keep the fe5680 freq constant?
> >  For the LPRO, what I found by experiment worked best for me is to place
> the
> >  unit upside down so the heat sink was on top.
> >  If any air was blown on the non heat sink side, that would greatly
> effect
> >  the frequency stability in a bad way.
> >
> >  A way to get around the compromise of where the best place is to put the
> >  sensor, either close to the heat source or close to the device.
> >  Best answer is BOTH. The way to get high end control and a much more
> stable
> >  control loop, is to use TWO temperature sensors.
> >  Put one temperature sensor near the Heat source and a second one at the
> >  place you want to hold constant.
> >  Then in effect 'AC couple' the heat source sensor, so that it does the
> >  course temperature control.
> >  One way to do this is to set it up so that the heat source sensor is the
> >  feed-forward or "D" input for the main sensor PID control loop.
> >  Another way to set it up is so that the device sensor's error slowly
> changes
> >  the temperature set-point of the heat source's temperature control loop.
> >
> >  ws
> >
> >  ***************
> >  >I am, as I reported previously using a SMD LM335 away from the fan and
> held
> >  > down with a screw and a small bracket and I get consistent .1 C. I do
> not
> >  >think that I would get 1 E-12  over weeks when my lab has seen more
> than
> >  >5C temperature changes if my temperature readings are not correct.
> >  >Do not forget this was a quick and dirty setup, the final product will
> look
> >  > more professional.
> >  >Bert Kehren
> >
> >  *************
> >  albertson.chris at gmail.com writes:
> >
> >  On Tue,  Jan 17, 2012 at 8:38 AM,  <EWKehren at aol.com> wrote:
> >  >>> I am  using a fan that holds it within .1 C Its been month since I
> >  >>>measured it but I did report it here and I think it is 42.7C.
> >
> >  >>0.1C is very good  for just using a fan.     What is the  fe5680
> >  >>mounted  to?  just the heat sink or is there a thick metal plate.
> >  >>Also what are  you using as a heat sensor.  Is the sensor press fit to
> >  >>the heat sink  or.    I do remember reading about your temperature
> >  >>controlled  fan but not the 0.1C part.   I'd have guessed you could
> only
> >  >>do  about 2.0C with a setup like yours.
> >
> >  >>Chris Albertson
> >  >>Redondo  Beach,  California
> >
> >
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