Our reactionary foulmouthed troll, a.k.a. Always Wrong...

DecadentLinuxUserNumeroUno@decadence.org wrote:

> 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?
>

John Larkin wrote:
> 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!
>

Sure, I'm all in favour of what works. The lower heat leak thing is a
big help if there's forcing above a few percent of the loop bandwidth.

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

Gerhard Hoffmann wrote:
> Am 24.05.22 um 17:06 schrieb Phil Hobbs:
>> 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.
>
> 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.

I invite you to compute the ratio of the bandwidth available to a TEC
loop vs a heater loop as the delta-T goes to zero. ;)
>
> Yes, one could insulate the outside of the TEC, but that is somewhat ill?

You can get TECs in all sorts of sizes.

Heater loops work fine at larger delta-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

On 25/05/2022 04:35, Gerhard Hoffmann wrote:
> Am 24.05.22 um 17:06 schrieb Phil Hobbs:
>> 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.
>
> 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.

You could put another temperature sensor on the outside end of the TEC,
and do some sort of feed-forward as well, to remove most of the effect
before it gets in.

Chris Jones wrote:
> On 25/05/2022 04:35, Gerhard Hoffmann wrote:
>> Am 24.05.22 um 17:06 schrieb Phil Hobbs:
>>> 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.
>>
>> 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.
>
> You could put another temperature sensor on the outside end of the TEC,
> and do some sort of feed-forward as well, to remove most of the effect
> before it gets in.

A really important tool in high-stability temperature control is a local
feedback loop around each actuator. Proportional-only is fine, but what
you really want is super high speed. These days we do a lot of
TEC-based controllers. Our favourite method is to put a bare ENIG pour
on the bottom side of the cold plate board (which usually has a laser or
one or more photodetectors). This contacts the cold side of the TEC via
(usually) silver grease.(*) One end of an 0603 thermistor is soldered
to the pour, and the other goes via a longish skinny trace to the loop amp.

Doing that costs next to nothing, and allows us to make a much faster
simulated actuator with much much lower effective thermal conductance.

Feedforward to the outer loop can also be done, but requires much more
tuning because the speed of the outer loop changes dramatically with
delta-T and Qdot.

Cheers

Phil Hobbs

(*) Thermal silver grease has much much more silver than
electrically-conductive silver paste.

--
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

On Wed, 25 May 2022 23:17:29 +1000, Chris Jones
<lugnut808@spam.yahoo.com> wrote:

>On 25/05/2022 04:35, Gerhard Hoffmann wrote:
>> Am 24.05.22 um 17:06 schrieb Phil Hobbs:
>>> 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.
>>
>> 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.
>
>You could put another temperature sensor on the outside end of the TEC,
>and do some sort of feed-forward as well, to remove most of the effect
>before it gets in.

Bad ovens sometimes sense ambient temp and feed-forward into the
setpoint, to shotgun compensate the badness.

The SRS SC10 is a good example of an oven done wrong. The manual of
rev L is available online.

--

Anybody can count to one.

- Robert Widlar

On 25/05/2022 23:34, Phil Hobbs wrote:
> Chris Jones wrote:
>> On 25/05/2022 04:35, Gerhard Hoffmann wrote:
>>> Am 24.05.22 um 17:06 schrieb Phil Hobbs:
>>>> 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.
>>>
>>> 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.
>>
>> You could put another temperature sensor on the outside end of the
>> TEC, and do some sort of feed-forward as well, to remove most of the
>> effect before it gets in.
>
> A really important tool in high-stability temperature control is a local
> feedback loop around each actuator.  Proportional-only is fine, but what
> you really want is super high speed.  These days we do a lot of
> TEC-based controllers.  Our favourite method is to put a bare ENIG pour
> on the bottom side of the cold plate board (which usually has a laser or
> one or more photodetectors).  This contacts the cold side of the TEC via
> (usually) silver grease.(*)  One end of an 0603 thermistor is soldered
> to the pour, and the other goes via a longish skinny trace to the loop amp.
>
> Doing that costs next to nothing, and allows us to make a much faster
> simulated actuator with much much lower effective thermal conductance.

That scheme makes a lot of sense.

Chris Jones wrote:
> On 25/05/2022 23:34, Phil Hobbs wrote:
>> Chris Jones wrote:
>>> On 25/05/2022 04:35, Gerhard Hoffmann wrote:
>>>> Am 24.05.22 um 17:06 schrieb Phil Hobbs:
>>>>> 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.
>>>>
>>>> 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.
>>>
>>> You could put another temperature sensor on the outside end of the
>>> TEC, and do some sort of feed-forward as well, to remove most of the
>>> effect before it gets in.
>>
>> A really important tool in high-stability temperature control is a
>> local feedback loop around each actuator.  Proportional-only is fine,
>> but what you really want is super high speed.  These days we do a lot
>> of TEC-based controllers.  Our favourite method is to put a bare ENIG
>> pour on the bottom side of the cold plate board (which usually has a
>> laser or one or more photodetectors).  This contacts the cold side of
>> the TEC via (usually) silver grease.(*)  One end of an 0603 thermistor
>> is soldered to the pour, and the other goes via a longish skinny trace
>> to the loop amp.
>>
>> Doing that costs next to nothing, and allows us to make a much faster
>> simulated actuator with much much lower effective thermal conductance.
>
> That scheme makes a lot of sense.

With the thermistor hanging five right at the edge of the pour (right
next to the edge of the cold side of the TEC) the response is faster
than 100 ms.

Thermal diffusion is quadratically slow at large distances, so of course
it's quadratically fast at small ones!

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