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: [email protected] >>>> [mailto:[email protected]] 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 <e182724b9fce4b9f9e914bcc4f374...@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 >>>> [email protected] | TCP/IP since RFC 956 >>>> FreeBSD committer | BSD since 4.3-tahoe >>>> Never attribute to malice what can adequately be explained by >>>> incompetence. >>>> > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- 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 _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
