Mike Coon wrote:> In article <t6fga4$f2p$1@dont-email.me>, pNaonStpealmtje@yahoo.com > says... >> >> On a sunny day (Sun, 22 May 2022 22:51:09 +0100) it happened Mike Coon >> <gravity@mjcoon.plus.com> wrote in >> <MPG.3cf4c0956a87c90d9896be@usenet.plus.net>: >> >>> My design for a foyer quartz clock back in the early 1960s included a >>> crystal in a thermostatic oven made from Perspex. I have a sketch and >>> isometric of the oven and a note that there were five thermistors in a >>> bridge, but no schematic. I do remember that on first testing the >>> control circuit initially ran at full power heating, then cut off, then >>> gradually settled on steady warmth! >> >> Yes that is overshot, maybe over-compensated > > My definition of over-compensated would be indefinite oscillation, which > is what I was concerned about when I was monitoring the behaviour... No > theory involved! >The usual terminology would be "underdamped" if it's linear, or "windup" if it isn't. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Crystal oven theory
Started by ●May 21, 2022
Reply by ●May 23, 20222022-05-23
Reply by ●May 23, 20222022-05-23
On 5/23/2022 11:46 AM, jlarkin@highlandsniptechnology.com wrote:> On Mon, 23 May 2022 14:11:54 -0000 (UTC), > DecadentLinuxUserNumeroUno@decadence.org wrote: > >> jlarkin@highlandsniptechnology.com wrote in >> news:4hjl8hd5d42lhge1c7lu0kt7m29led31kd@4ax.com: >> >>> On Sun, 22 May 2022 16:46:44 -0400, bitrex <user@example.net> >>> wrote: >>> >>>> On 5/22/2022 2:21 PM, jlarkin@highlandsniptechnology.com wrote: >>>>> On Sun, 22 May 2022 13:24:02 -0400, bitrex <user@example.net> >>>>> wrote: >>>>> >>>>>> On 5/22/2022 4:31 AM, Anthony William Sloman wrote: >>>>>>> On Sunday, May 22, 2022 at 1:15:05 PM UTC+10, >>>>>>> jla...@highlandsniptechnology.com wrote: >>>>>>>> On Sat, 21 May 2022 20:50:12 -0400, bitrex >>>>>>>> <us...@example.net> wrote: >>>>>>>> >>>>>>>>> Here's a paper on the theory of crystal ovens: >>>>>>>>> >>>>>>>>> <http://www.karlquist.com/oven.pdf> >>>>>>> >>>>>>> He didn't survey the literature all that well. >>>>>>> >>>>>>>>> There's a lot more to it than just slapping a crystal & >>>>>>>>> heater in a metal box and calling it a day! There are >>>>>>>>> probably some pathologically bad geometries even a really >>>>>>>>> fast control loop can never stabilize very well. >>>>>>>>> >>>>>>>>> The part about the outer can acting like a Faraday shield is >>>>>>>>> interesting, shunting ambient gradients around the core. >>>>>>>>> Does anyone know how they make the negative space look like >>>>>>>>> a linear tehrmal resistance over a wide range? There's some >>>>>>>>> kind of insulating foam in there, is main heat thermal >>>>>>>>> transfer radiative or conduction? >>>>>>> >>>>>>> Conduction. Foam pretty much stops convection. >>>>>> >>>>>> It was mentioned on another thread that the thermal resistance >>>>>> of radiation between two concentric blackbodies at 300K is >>>>>> about 6mm, interestingly that's very close to the same >>>>>> thickness of foam-filled negative space between the outer and >>>>>> inner shells of the OCXO module on my 5334B. >>>>>> >>>>>> Don't know if that's a coincidence or not, obviously the two >>>>>> aren't at exactly 300K. The interior I think runs about 355K, >>>>>> while the exterior (I haven't measured it) seems cool enough to >>>>>> keep your hand on a while. >>>>>> >>>>> >>>>> In a reasonably close-fitting box, without a lot of space for >>>>> convection, air is a better thermal insulator than foam or >>>>> fiberglass. >>>>> >>>> >>>> Here's a glamour shot of the internals: >>>> >>>> <https://imgur.com/a/W4hmKt4> >>>> >>>> Don't know what the foam is. It doesn't seem to conduct heat too >>>> good. >>>> >>>> >>> >>> The interesting test would be to measure heater power with and >>> without the foam. >>> >>> >>> >> >> The foam is for physical shock absorption, silly. > > None of my ovens depended on foam for mechanical support. Sometimes > long lead wires are bad news too. > > I did mount one OCXO on some custom springs. Mating and unmating an > nearby SMB test connector made my PLL lose lock. > > https://www.dropbox.com/s/0k8agdfyiqlwn84/Spring_2.JPG?raw=1 > > https://www.dropbox.com/s/l2gr4fxas2k05fz/Sprung_Osc_2.JPG?raw=1 > > >> >> Hard to protect against that "floating in air". They should try >> some nice aerogel inserts. I think it has pretty good thermals >> compared to foam. > > Have you done that? Is aerogel rigid enough to support a subassembly? > Would mechanical shocks scrunch it down?The foam inside the HP oven is stiff & brittle. I think it may just be to separate the bits from each other and provide mechanical support, but I don't think I'd want to rely on it to absorb much shock.
Reply by ●May 23, 20222022-05-23
On 5/23/2022 5:40 PM, bitrex wrote:>>> Hard to protect against that "floating in air". They should try >>> some nice aerogel inserts. I think it has pretty good thermals >>> compared to foam. >> >> Have you done that? Is aerogel rigid enough to support a subassembly? >> Would mechanical shocks scrunch it down? > > The foam inside the HP oven is stiff & brittle.Basically the consistency of dehydrated "astronaut" ice cream if you've had that stuff..
Reply by ●May 23, 20222022-05-23
On 5/23/2022 9:48 AM, Phil Hobbs wrote:>> The interesting test would be to measure heater power with and without >> the foam. > > Air at room temperature has an alpha of about 0.026 W/m/K. High-density > styrofoam (the kind that crunches when you poke it with your finger) is > about 0.040, and low-density styrofoam (the kind that squeaks) is around > 0.030. > > Cheers > > Phil Hobbs >The way I would describe the "insulating" (or whatever it does) foam in the HP oven is sort of the consistency of freeze-dried ice cream.
Reply by ●May 23, 20222022-05-23
bitrex <user@example.net> wrote in news:QaTiK.4601$8T.2667@fx40.iad:> On 5/23/2022 11:46 AM, jlarkin@highlandsniptechnology.com wrote: >> On Mon, 23 May 2022 14:11:54 -0000 (UTC), >> DecadentLinuxUserNumeroUno@decadence.org wrote: >> >>> jlarkin@highlandsniptechnology.com wrote in >>> news:4hjl8hd5d42lhge1c7lu0kt7m29led31kd@4ax.com: >>> >>>> On Sun, 22 May 2022 16:46:44 -0400, bitrex <user@example.net> >>>> wrote: >>>> >>>>> On 5/22/2022 2:21 PM, jlarkin@highlandsniptechnology.com >>>>> wrote: >>>>>> On Sun, 22 May 2022 13:24:02 -0400, bitrex <user@example.net> >>>>>> wrote: >>>>>> >>>>>>> On 5/22/2022 4:31 AM, Anthony William Sloman wrote: >>>>>>>> On Sunday, May 22, 2022 at 1:15:05 PM UTC+10, >>>>>>>> jla...@highlandsniptechnology.com wrote: >>>>>>>>> On Sat, 21 May 2022 20:50:12 -0400, bitrex >>>>>>>>> <us...@example.net> wrote: >>>>>>>>> >>>>>>>>>> Here's a paper on the theory of crystal ovens: >>>>>>>>>> >>>>>>>>>> <http://www.karlquist.com/oven.pdf> >>>>>>>> >>>>>>>> He didn't survey the literature all that well. >>>>>>>> >>>>>>>>>> There's a lot more to it than just slapping a crystal & >>>>>>>>>> heater in a metal box and calling it a day! There are >>>>>>>>>> probably some pathologically bad geometries even a really >>>>>>>>>> fast control loop can never stabilize very well. >>>>>>>>>> >>>>>>>>>> The part about the outer can acting like a Faraday shield >>>>>>>>>> is interesting, shunting ambient gradients around the >>>>>>>>>> core. Does anyone know how they make the negative space >>>>>>>>>> look like a linear tehrmal resistance over a wide range? >>>>>>>>>> There's some kind of insulating foam in there, is main >>>>>>>>>> heat thermal transfer radiative or conduction? >>>>>>>> >>>>>>>> Conduction. Foam pretty much stops convection. >>>>>>> >>>>>>> It was mentioned on another thread that the thermal >>>>>>> resistance of radiation between two concentric blackbodies >>>>>>> at 300K is about 6mm, interestingly that's very close to the >>>>>>> same thickness of foam-filled negative space between the >>>>>>> outer and inner shells of the OCXO module on my 5334B. >>>>>>> >>>>>>> Don't know if that's a coincidence or not, obviously the two >>>>>>> aren't at exactly 300K. The interior I think runs about >>>>>>> 355K, while the exterior (I haven't measured it) seems cool >>>>>>> enough to keep your hand on a while. >>>>>>> >>>>>> >>>>>> In a reasonably close-fitting box, without a lot of space for >>>>>> convection, air is a better thermal insulator than foam or >>>>>> fiberglass. >>>>>> >>>>> >>>>> Here's a glamour shot of the internals: >>>>> >>>>> <https://imgur.com/a/W4hmKt4> >>>>> >>>>> Don't know what the foam is. It doesn't seem to conduct heat >>>>> too good. >>>>> >>>>> >>>> >>>> The interesting test would be to measure heater power with and >>>> without the foam. >>>> >>>> >>>> >>> >>> The foam is for physical shock absorption, silly. >> >> None of my ovens depended on foam for mechanical support. >> Sometimes long lead wires are bad news too. >> >> I did mount one OCXO on some custom springs. Mating and unmating >> an nearby SMB test connector made my PLL lose lock. >> >> https://www.dropbox.com/s/0k8agdfyiqlwn84/Spring_2.JPG?raw=1 >> >> https://www.dropbox.com/s/l2gr4fxas2k05fz/Sprung_Osc_2.JPG?raw=1 >> >> >>> >>> Hard to protect against that "floating in air". They should >>> try >>> some nice aerogel inserts. I think it has pretty good thermals >>> compared to foam. >> >> Have you done that? Is aerogel rigid enough to support a >> subassembly? Would mechanical shocks scrunch it down? > > The foam inside the HP oven is stiff & brittle. I think it may > just be to separate the bits from each other and provide > mechanical support, but I don't think I'd want to rely on it to > absorb much shock. > >Compared to being suspended in air, I am sure it wil absorb more. Just what do you think "mechanical support" is?
Reply by ●May 23, 20222022-05-23
On 5/23/2022 6:05 PM, DecadentLinuxUserNumeroUno@decadence.org wrote:> bitrex <user@example.net> wrote in news:QaTiK.4601$8T.2667@fx40.iad: > >> On 5/23/2022 11:46 AM, jlarkin@highlandsniptechnology.com wrote: >>> On Mon, 23 May 2022 14:11:54 -0000 (UTC), >>> DecadentLinuxUserNumeroUno@decadence.org wrote: >>> >>>> jlarkin@highlandsniptechnology.com wrote in >>>> news:4hjl8hd5d42lhge1c7lu0kt7m29led31kd@4ax.com: >>>> >>>>> On Sun, 22 May 2022 16:46:44 -0400, bitrex <user@example.net> >>>>> wrote: >>>>> >>>>>> On 5/22/2022 2:21 PM, jlarkin@highlandsniptechnology.com >>>>>> wrote: >>>>>>> On Sun, 22 May 2022 13:24:02 -0400, bitrex <user@example.net> >>>>>>> wrote: >>>>>>> >>>>>>>> On 5/22/2022 4:31 AM, Anthony William Sloman wrote: >>>>>>>>> On Sunday, May 22, 2022 at 1:15:05 PM UTC+10, >>>>>>>>> jla...@highlandsniptechnology.com wrote: >>>>>>>>>> On Sat, 21 May 2022 20:50:12 -0400, bitrex >>>>>>>>>> <us...@example.net> wrote: >>>>>>>>>> >>>>>>>>>>> Here's a paper on the theory of crystal ovens: >>>>>>>>>>> >>>>>>>>>>> <http://www.karlquist.com/oven.pdf> >>>>>>>>> >>>>>>>>> He didn't survey the literature all that well. >>>>>>>>> >>>>>>>>>>> There's a lot more to it than just slapping a crystal & >>>>>>>>>>> heater in a metal box and calling it a day! There are >>>>>>>>>>> probably some pathologically bad geometries even a really >>>>>>>>>>> fast control loop can never stabilize very well. >>>>>>>>>>> >>>>>>>>>>> The part about the outer can acting like a Faraday shield >>>>>>>>>>> is interesting, shunting ambient gradients around the >>>>>>>>>>> core. Does anyone know how they make the negative space >>>>>>>>>>> look like a linear tehrmal resistance over a wide range? >>>>>>>>>>> There's some kind of insulating foam in there, is main >>>>>>>>>>> heat thermal transfer radiative or conduction? >>>>>>>>> >>>>>>>>> Conduction. Foam pretty much stops convection. >>>>>>>> >>>>>>>> It was mentioned on another thread that the thermal >>>>>>>> resistance of radiation between two concentric blackbodies >>>>>>>> at 300K is about 6mm, interestingly that's very close to the >>>>>>>> same thickness of foam-filled negative space between the >>>>>>>> outer and inner shells of the OCXO module on my 5334B. >>>>>>>> >>>>>>>> Don't know if that's a coincidence or not, obviously the two >>>>>>>> aren't at exactly 300K. The interior I think runs about >>>>>>>> 355K, while the exterior (I haven't measured it) seems cool >>>>>>>> enough to keep your hand on a while. >>>>>>>> >>>>>>> >>>>>>> In a reasonably close-fitting box, without a lot of space for >>>>>>> convection, air is a better thermal insulator than foam or >>>>>>> fiberglass. >>>>>>> >>>>>> >>>>>> Here's a glamour shot of the internals: >>>>>> >>>>>> <https://imgur.com/a/W4hmKt4> >>>>>> >>>>>> Don't know what the foam is. It doesn't seem to conduct heat >>>>>> too good. >>>>>> >>>>>> >>>>> >>>>> The interesting test would be to measure heater power with and >>>>> without the foam. >>>>> >>>>> >>>>> >>>> >>>> The foam is for physical shock absorption, silly. >>> >>> None of my ovens depended on foam for mechanical support. >>> Sometimes long lead wires are bad news too. >>> >>> I did mount one OCXO on some custom springs. Mating and unmating >>> an nearby SMB test connector made my PLL lose lock. >>> >>> https://www.dropbox.com/s/0k8agdfyiqlwn84/Spring_2.JPG?raw=1 >>> >>> https://www.dropbox.com/s/l2gr4fxas2k05fz/Sprung_Osc_2.JPG?raw=1 >>> >>> >>>> >>>> Hard to protect against that "floating in air". They should >>>> try >>>> some nice aerogel inserts. I think it has pretty good thermals >>>> compared to foam. >>> >>> Have you done that? Is aerogel rigid enough to support a >>> subassembly? Would mechanical shocks scrunch it down? >> >> The foam inside the HP oven is stiff & brittle. I think it may >> just be to separate the bits from each other and provide >> mechanical support, but I don't think I'd want to rely on it to >> absorb much shock. >> >> > > Compared to being suspended in air, I am sure it wil absorb more. > Just what do you think "mechanical support" is?Do u require mechanical support: <https://www.mayoclinic.org/tests-procedures/penis-pump/about/pac-20385225>
Reply by ●May 23, 20222022-05-23
On Mon, 23 May 2022 17:41:12 -0400, bitrex <user@example.net> wrote:>On 5/23/2022 5:40 PM, bitrex wrote: > >>>> � Hard to protect against that "floating in air".� They should try >>>> some nice aerogel inserts.� I think it has pretty good thermals >>>> compared to foam. >>> >>> Have you done that? Is aerogel rigid enough to support a subassembly? >>> Would mechanical shocks scrunch it down? >> >> The foam inside the HP oven is stiff & brittle. > >Basically the consistency of dehydrated "astronaut" ice cream if you've >had that stuff..Dehydrated ice cream? I'm glad I didn't become an astronaut. -- If a man will begin with certainties, he shall end with doubts, but if he will be content to begin with doubts he shall end in certainties. Francis Bacon
Reply by ●May 23, 20222022-05-23
On 5/23/2022 6:54 PM, John Larkin wrote:> On Mon, 23 May 2022 17:41:12 -0400, bitrex <user@example.net> wrote: > >> On 5/23/2022 5:40 PM, bitrex wrote: >> >>>>> Hard to protect against that "floating in air". They should try >>>>> some nice aerogel inserts. I think it has pretty good thermals >>>>> compared to foam. >>>> >>>> Have you done that? Is aerogel rigid enough to support a subassembly? >>>> Would mechanical shocks scrunch it down? >>> >>> The foam inside the HP oven is stiff & brittle. >> >> Basically the consistency of dehydrated "astronaut" ice cream if you've >> had that stuff.. > > Dehydrated ice cream? I'm glad I didn't become an astronaut. >Yeah, freeze-dried. No idea if this stuff was actually used on space flights or when. My mother used to buy it for me at science museum gift shops when I was a kid, we didn't have much money but she didn't like to turn me down for a few souvenirs so long as they were "educational"! It was sweet at least and most sweet stuff tastes good to an 8 y/o: <https://youtu.be/gmGDBmeyBIs> The pull-back racer Space Shuttle toy was another classic gift shop crowd-pleaser. <https://www.amazon.com/5-Diecast-Pullback-Space-Shuttle/dp/B003PATHLU/>
Reply by ●May 23, 20222022-05-23
On Mon, 23 May 2022 10:09:23 -0700 (PDT), whit3rd <whit3rd@gmail.com> wrote:>On Monday, May 23, 2022 at 8:46:31 AM UTC-7, jla...@highlandsniptechnology.com wrote: >> On Mon, 23 May 2022 14:11:54 -0000 (UTC), >> DecadentLinux...@decadence.org wrote: > >> >The foam is for physical shock absorption, silly. > >> None of my ovens depended on foam for mechanical support. Sometimes >> long lead wires are bad news too. >> >> I did mount one OCXO on some custom springs... > >> > Hard to protect against that "floating in air". They should try >> >some nice aerogel inserts. I think it has pretty good thermals >> >compared to foam. > >> Have you done that? Is aerogel rigid enough to support a subassembly? >> Would mechanical shocks scrunch it down? > >Some aerogels are foam-like quartz, quite strong enough for most uses, and >relatively tough. You could use 'em to support, and they're good in vacuum (if >you want a good insulator, ditch the air). On the other hand, a perforated >section of fiberglass PCB should likewise be a thermal break. How >stingy on heater power do you want to be?Heater power is seldom an issue. Heat loss is bad because it makes an assembly non-isothermal, so that some bits are not at the same temperature as the feedback sensor. And the difference will vary with heater power, namely ambient temp. -- Anybody can count to one. - Robert Widlar
Reply by ●May 24, 20222022-05-24
On a sunny day (Mon, 23 May 2022 17:34:33 +0100) it happened Mike Coon <gravity@mjcoon.plus.com> wrote in <MPG.3cf5c7f82510056d9896bf@usenet.plus.net>:>In article <t6fga4$f2p$1@dont-email.me>, pNaonStpealmtje@yahoo.com >says... >> >> On a sunny day (Sun, 22 May 2022 22:51:09 +0100) it happened Mike Coon >> <gravity@mjcoon.plus.com> wrote in >> <MPG.3cf4c0956a87c90d9896be@usenet.plus.net>: >> >> >My design for a foyer quartz clock back in the early 1960s included a >> >crystal in a thermostatic oven made from Perspex. I have a sketch and >> >isometric of the oven and a note that there were five thermistors in a >> >bridge, but no schematic. I do remember that on first testing the >> >control circuit initially ran at full power heating, then cut off, then >> >gradually settled on steady warmth! >> >> Yes that is overshot, maybe over-compensated > >My definition of over-compensated would be indefinite oscillation, which >is what I was concerned about when I was monitoring the behaviour... No >theory involved!http://panteltje.com/pub/under_and_over_compensated_IXIMG_0818.JPG
