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

Wed Jan 18 00:40:36 UTC 2012

Electronic Goldmine has nickel-iron magnetic shielding sheet, 6"x9"
x.005" for 6 bucks p/n G18646 peel and stick at that.
Don

Bob Camp
> 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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-- 
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