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On Sunday, May 22, 2022 at 4:57:25 PM UTC-7, jla...@highlandsniptechnology.com wrote:
... I\'ve experimented with heated gadgets inside a deep-drawn
aluminum box, which has a low emissivity. My testing usually showed
that I got less heater power dissipation with air, as opposed to
styrafoam or fiberglas.
It\'s not a difficult experiment. I think most people just assume that
insulation always helps.
Insulation in the sense of low-conductivity material is NOT the intended function of
fiberglass; it is used to reduce air convection, which (thermal convection is
delta-T squared heat transfer) is a tiny effect in a low-temperature-gradient system.
In a house-on-fire, fiberglass in the walls is not tiny, but a big help in getting out alive.
In a very real sense, fiberglass filled cavities are air-insulated.
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
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.
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 Hobbs
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.
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
Anybody can count to one.
- Robert Widlar
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?
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 word for today is scrunch.
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?
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.
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!
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?
 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.
jlarkin@highlandsniptechnology.com wrote:
he Mach-Zender electro-optical modulator.
https://www.dropbox.com/sh/knkoywpv6563mj5/AACy1sLNcyqIO8Eik4NRCC9Da?dl=0
We have lots of heater power available so we can stabilize to
millikelvins in about a half hour.
One of the less-frequently remarked advantages of thermoelectrics is
that anywhere near room temperature they can have considerably better
forcing resistance than heater-only loops with a given bandwidth.
A heater-only loop gets its negative slewing exclusively from the heat
leak, which of course leaks in both directions, whereas a TEC can pull
as well as push, so a TEC-based loop can be better insulated for the
same control bandwidth and slew rate.
John Dope <always.look@message.header> wrote in news:t6hvrj$kq3$3@dont-
email.me:
Bob Widlar was a big engineer.
Now, what is the significance of \"Anybody can count to one\"?
Seems not to be a famous quote.
John Dope is still in the dark. You never knew electronics and have
been a mere interloper all these years, at best.
The actual quote is \"Every idiot can count to one.\"
So even your google skill sucks. John Dope lives up to his name
every time he posts into SED.
Am 24.05.22 um 17:06 schrieb Phil Hobbs:
jla...@highlandsniptechnology.com wrote:
he Mach-Zender electro-optical modulator.
https://www.dropbox.com/sh/knkoywpv6563mj5/AACy1sLNcyqIO8Eik4NRCC9Da?dl=0
We have lots of heater power available so we can stabilize to
millikelvins in about a half hour.
One of the less-frequently remarked advantages of thermoelectrics is
that anywhere near room temperature they can have considerably better
forcing resistance than heater-only loops with a given bandwidth.
A heater-only loop gets its negative slewing exclusively from the heat
leak, which of course leaks in both directions, whereas a TEC can pull
as well as push, so a TEC-based loop can be better insulated for the
same control bandwidth and slew rate.
But a TEC has a thermal low-impedance-path from inside to the
outside. That is unwanted and one of the reasons for their bad efficiency.
That means that heat transients on the outside get in
immediately and must be activly regulated away, AFTER they have happened.
The proper quote helped.
John Dope <always.look@message.header> wrote in news:t6j8sq$61v$3@dont-
email.me:
The proper quote helped.
You are a fucking total retard. ALL that was EVER needed was the
guy\'s name. So you are dumber than a 5 year old. It does not get
dumber than you John Dope.
Kids know how to use the hardware better than you do and they get
better results too.
Aren\'t you the total retard trying to power a bicycle with a drill
motor?
On Tue, 24 May 2022 11:06:16 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:
jlarkin@highlandsniptechnology.com wrote:
On Tue, 24 May 2022 08:41:01 +0100, Mike Coon
gravity@mjcoon.plus.com> wrote:
In article <t6hrnr$2ac$1@dont-email.me>, pNaonStpealmtje@yahoo.com
says...
On a sunny day (Mon, 23 May 2022 17:34:33 +0100) it happened Mike Coon
gravity@mjcoon.plus.com> wrote in
MPG.3cf5c7f82510056d9896bf@usenet.plus.net>:
In article <t6fga4$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
Thanks for that idiosyncratic illustration! You could also have reminded
me of the calculus of feedback theory which I studied for my degree back
in the early 1960s. It was merely the modern (?) terminology I was
querying. \"Windup\" indeed; that\'s a gramophone!
We usually tune thermal loops in the classic linear style, for
critically-damped small signal disturbance. They will typically
overshoot at cold-start powerup because the integrator winds up and
rails. Rob did a lot of fancy math to define the software control
loop; I just Spice things like that.
The oven that I pictured has a 2nd order plant response, about 75
minutes tau for the huge aluminum block and about another 17 for the
platform and e/o modulator inside. Spacers set the second time
constant; aluminum, stainless, or plastic.
One goal was to force minimal thermal gradients along the length of
the Mach-Zender electro-optical modulator.
https://www.dropbox.com/sh/knkoywpv6563mj5/AACy1sLNcyqIO8Eik4NRCC9Da?dl=0
We have lots of heater power available so we can stabilize to
millikelvins in about a half hour.
One of the less-frequently remarked advantages of thermoelectrics is
that anywhere near room temperature they can have considerably better
forcing resistance than heater-only loops with a given bandwidth.
A heater-only loop gets its negative slewing exclusively from the heat
leak, which of course leaks in both directions, whereas a TEC can pull
as well as push, so a TEC-based loop can be better insulated for the
same control bandwidth and slew rate.
We only run at 30c, and ambient is very reliably 22. We considered
TECs but that was too complex and expensive. We sure don\'t want a fan
anywhere close to our optics.
The dpak mosfet heaters are cheap!