[time-nuts] Thunderbolt stability and ambient temperature

Pete Lancashire pete at petelancashire.com
Thu Jun 11 14:19:27 EDT 2009


I use to have a similar on from GR but was lost in a fire.
It had a large GR metal name plate on one side.

I sanded and varnished the box and had it on display for
quite a long time.

GR was great at stretching the mechanical limits of material
to get electrical specs.

-pete

> I have a General Radio 100KHz crystal oven that is inside a crafted wood
> box. The oven uses a mercury thermometer with a pair of wires sealed in
> the side to implement a bang-bang servo. The wood box will thus smooth out
> the square wave heat pulse. I think it came from something like an LR-1
> Navy signal generator as a calibration standard. I need to put an
> oscillator circuit on it in order to characterize its behavior. It's on
> the FIFO to-do stack...
> Don
>
> Arnold Tibus
>> Ed,
>> and the big group
>>
>> I did run such a 10811 without the outer heater connected and without
>> any insulation around as replacement for the original insulation and box
>> but I did not see any fluctuations beside the normal behaviour of a
>> 10811.
>>
>> (I have to admit that I did not yet run precision records, neither for
>> the
>> heater current nor for the frequency output. I see what I have to do
>> soon!)
>>
>> This model is obviously adjusted inside to work best in an encreased
>> environment of around 40 to 45 deg. C .
>>
>> I think as Ulrich does explain, blocking the heat flow significantly
>> must
>> deteriorate the regulating loop parameters. The life time of the
>> oscillator
>> electronics outside the stabilized crystal element will as well
>> decrease...
>>
>> A good idea in fact to put the standard in a stable area and very slow
>> varying temp range of around 15 deg. C underneath the house
>> fundaments...I will think about!
>>
>> Did anybody ever think to apply wood as stabilizing element around an
>> oscillator? Wood behaves a bit strange, it is on one side a not bad
>> insulator and it does have as well a quite high heat storage capacity!
>>
>> (Oak with around 2.4 J/g, K., Lambda 0.17 W/m.K,,
>> Pine around 2.7 J/g.K., Lambda 0.14 W/m.K.
>> Water around 4.18 J/g.K., Lambda 0,604 W/m.K.
>> Copper has 0.385 2.4 J/g, K., Lambda 401 W/m.K. at 25 deg. C. )
>> I consider wood a very intersting material, cheap and easy to work...
>>
>> Arnold
>>
>>
>>
>> On Thu, 11 Jun 2009 09:22:00 -0600, Ed Palmer wrote:
>>
>>>Ulrich, when you changed the thermal characteristics around your 10811,
>>>how 'crazy' did it become?
>>
>>>According to your theory, there should be differences in the schematics
>>>of the oven controllers between the single and double oven variants of
>>>the 10811.  Last year I picked up a couple of those double oven 10811s
>>>from China that had the outer insulation removed.  I wonder if I could
>>>see any anomalies in its operation with no outer insulation and only the
>>>inner oven operating.
>>
>>>Ed
>>
>>>Ulrich Bangert wrote:
>>>>> I'm not talking about crystal ovens, I'm talking about
>>>>> timekeeping kit in general: how to filter high frequency
>>>>> temperature fluctuations out, so the PLL does not have to
>>>>> deal with them.
>>>>>
>>>>
>>>> Ok, but in this general case you have to accept the fact, that
>>>> filtering
>>>> high temperature fluctuations is only ONE part of the engineering job.
>>>> The
>>>> second task (which I tried to point at) is: When you do already have a
>>>> closed loop temperature regulation system inside what you plan to
>>>> built
>>>> around it, then you need to manage the filtering without mal
>>>> interaction of
>>>> the local temperature controller with your additional filtering stuff.
>>>> The
>>>> art is to make the closed temperature loop inside see only smaller
>>>> temperature fluctuations but No changes otherwise.
>>>>
>>>> If you apply an overall change in temperature insulation to the
>>>> ambient
>>>> you
>>>> will make the work of the inside temperature controller a lot harder
>>>> because
>>>> it is not prepared for that. In the aluminium box that i wrote about I
>>>> have
>>>> for an experiment replaced the air between the 10811 and the outer box
>>>> with
>>>> a material that has a significant lower temperature conductivity than
>>>> standing air. You can easily watch the temperature controller go crazy
>>>> with
>>>> that. For a second experiment I have replaced the air with a material
>>>> having
>>>> lots more of thermal conductivity than air and you can watch the
>>>> temperature
>>>> controller go crazy with that too. You don't need sophisticated
>>>> temperature
>>>> measurement equipment to see the controller go crazy, just watch the
>>>> frequency of the oscillator. This will tell you all about it.
>>>>
>>>> Things are different, if you have an influence on the controller's
>>>> regulation parameters (which you do not have with a ready bought
>>>> device). If
>>>> you do have, then your additional provisions for filtering and
>>>> insulation
>>>> can easily be included into the thermal model that the temperature
>>>> controller has to handle and will lead to different operation
>>>> parameters of
>>>> the controller. That will of course work and that is why I compared
>>>> your
>>>> suggestions to designing a new oven (for xtal or rubidium or
>>>> whatever).
>>>>
>>>> Best regards
>>>> Ulrich Bangert
>>>>
>>>>
>>>>> -----Ursprungliche Nachricht-----
>>>>> Von: time-nuts-bounces at febo.com
>>>>> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Poul-Henning Kamp
>>>>> Gesendet: Donnerstag, 11. Juni 2009 12:50
>>>>> An: Discussion of precise time and frequency measurement
>>>>> Betreff: Re: [time-nuts] Thunderbolt stability and ambient
>>>>> temperature
>>>>>
>>>>>
>>>>> In message <E182724B9FCE4B9F9E914BCC4F374401 at athlon>, "Ulrich
>>>>> Bangert" writes:
>>>>>
>>>>>>> For PLL steered devices, you want your device enclosed by a
>>>>>>> thermal mass which is again enclosed by a layer of thermal
>>>>>>> isolation.  The goal is to filter/average all rapid (daily ?)
>>>>>>> external temperature influences, only letting through such
>>>>>>> slow variations (seasonal ?) which the PLL can comfortably
>>>>>>>
>>>>> cope with.
>>>>>
>>>>>> My impression with this thread is that two sligthly different things
>>>>>> are being discussed here:
>>>>>>
>>>>>> Some posters explain how a crystal oven shall be designed as
>>>>>> Poul-Henning does with his words above. Absolute correct, no doubt
>>>>>> about it!
>>>>>>
>>>>> I'm not talking about crystal ovens, I'm talking about
>>>>> timekeeping kit in general: how to filter high frequency
>>>>> temperature fluctuations out, so the PLL does not have to
>>>>> deal with them.
>>>>>
>>>>> The above advice applies to GPSDO's and Rb's and Cs's as well
>>>>> as TCXOs, OCXOs and voltage references.
>>>>>
>>>>> Poul-Henning
>>>>>
>>>>> --
>>>>> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
>>>>> phk at FreeBSD.ORG         | TCP/IP since RFC 956
>>>>> FreeBSD committer       | BSD since 4.3-tahoe
>>>>> Never attribute to malice what can adequately be explained by
>>>>> incompetence.
>>>>>
>>
>>
>>
>>
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>
>
> --
> 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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