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

Bob Camp lists at rtty.us
Tue Jan 17 16:53:56 EST 2012


Hi

Since they used a magnetic outer case I'd keep it in place. Rb's are
sensitive to magnetic field. Anything that attenuates external fields is
helping you out.

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of paul swed
Sent: Tuesday, January 17, 2012 4:02 PM
To: beale; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] 5680A update (temperature stabilization)

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
temperature.
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. ;-)
Regards
Paul
WB8TSL

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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> >
>
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