On Mon, 23 May 2022 08:23:05 GMT, Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote:>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-compensatedHeaters usually run at some limited full power after cold-start, so the initial temperature curve is linear, slew-limited. If you have a well-tuned PID loop, the integrator rails and it will usually overshoot at the end of the slew. That can be fixed but it's usually not worth the trouble. -- Anybody can count to one. - Robert Widlar
Crystal oven theory
Started by ●May 21, 2022
Reply by ●May 23, 20222022-05-23
Reply by ●May 23, 20222022-05-23
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. 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.
Reply by ●May 23, 20222022-05-23
On Mon, 23 May 2022 09:48:57 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>jlarkin@highlandsniptechnology.com wrote: >> 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. > >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 HobbsI just did some tests and noted the heater power. -- Anybody can count to one. - Robert Widlar
Reply by ●May 23, 20222022-05-23
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? -- Anybody can count to one. - Robert Widlar
Reply by ●May 23, 20222022-05-23
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-compensatedMy definition of over-compensated would be indefinite oscillation, which is what I was concerned about when I was monitoring the behaviour... No theory involved!
Reply by ●May 23, 20222022-05-23
jlarkin@highlandsniptechnology.com wrote:> Anybody can count to one. > > - Robert WidlarI don't get it. allintext:"Anybody can count to one" "Robert Widlar" Produces four results, all of them from John Larkin.
Reply by ●May 23, 20222022-05-23
mandag den 23. maj 2022 kl. 17.46.31 UTC+2 skrev jla...@highlandsniptechnology.com:> On Mon, 23 May 2022 14:11:54 -0000 (UTC), > DecadentLinux...@decadence.org wrote: > > >jla...@highlandsniptechnology.com wrote in > >news:4hjl8hd5d42lhge1c...@4ax.com: > > > >> On Sun, 22 May 2022 16:46:44 -0400, bitrex <us...@example.net> > >> wrote: > >> > >>>On 5/22/2022 2:21 PM, jla...@highlandsniptechnology.com wrote: > >>>> On Sun, 22 May 2022 13:24:02 -0400, bitrex <us...@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?https://youtu.be/o5nzYpRdY4g
Reply by ●May 23, 20222022-05-23
jlarkin@highlandsniptechnology.com wrote in news:2gan8hdp7v3lhp44joaa278gmtktgva985@4ax.com:> 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 shieldis>>>>>>>>> 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 enoughto>>>>>> 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 asubassembly?> Would mechanical shocks scrunch it down? >The word for today is scrunch. I don't know. it isn't a foam. so scrunching of any kind would be a different animal with it. One has to wonder how it reacts to thermals though. There were/are several ISS exterior exposure tests taking place. For micro-meteor impact data and I think there were some thermal tests. Someone will make some carbon nanotube matrix thing that beats it all because we will be able to shape it. Oh wait. that's conduction. even electrical. They could come up with an idealized resistance medium and make big high wattage "carbon comp" resistors again for certain applications. Less noisy than what we used for so many decades. Or, a nice 'clean' noise... the sound of things going bump in the night (day too). Insulation... right. Aerogel. Maybe they make a Hydrogel or Nitrogel. Or Xenon... apply juice and get a glow gel.
Reply by ●May 23, 20222022-05-23
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?
Reply by ●May 23, 20222022-05-23
John Dope <always.look@message.header> wrote in news:t6gdmo$or8$6@dont- email.me:> jlarkin@highlandsniptechnology.com wrote: > >> Anybody can count to one. >> >> - Robert Widlar > > I don't get it. > > allintext:"Anybody can count to one" "Robert Widlar" > > Produces four results, all of them from John Larkin. >Widlar was an engineer, idiot. Consider yourself 'flipped off'. You have to be a complete idiot to search and not find Widlar info.
