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

Don Latham djl at montana.com
Tue Jan 17 19:40:36 EST 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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-- 
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell


Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com






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