Re: [time-nuts] Poor man's oven

[Bob kb8tq]

Hi


> On Jun 8, 2017, at 2:18 AM, Hal Murray  wrote:
> 
> 
> kb...@n1k.org said:
>> The crystal enclosure may (or may not … who knows ..) be back filled with a
>> low level of helium. It does not take much of a backfill for conduction
>> inside the crystal holder to dominate the heat transfer vs radiation
>> transfer. 
> 
> How does that compare with conduction through the mounting?

That depends a bit on the package (HC-6 vs TO-5 etc).  The number of blank 
mount points gets into it (2 point vs 3 vs 4 vs who knows). The thickness of 
the 
mount is the last thing I can think of on the list. 

A tab mounted rectangular blank will have a *lot* of mount conduction. A 2 
point 
spring mounted HC-6, not so much. 

The simple answer is that the backfill is done because it does matter in a lot 
of 
cases.

Bob

> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] Poor man's oven

[Hal Murray]

kb...@n1k.org said:
> The crystal enclosure may (or may not … who knows ..) be back filled with a
> low level of helium. It does not take much of a backfill for conduction
> inside the crystal holder to dominate the heat transfer vs radiation
> transfer. 

How does that compare with conduction through the mounting?


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Poor man's oven

[Bob kb8tq]

Hi

Keep in mind that on a per cubic inch basis, copper is right up there
for creating a thermal mass ….

Bob
> On Jun 7, 2017, at 5:51 PM, Attila Kinali  wrote:
> 
> Hoi Rick,
> 
> On Wed, 7 Jun 2017 14:21:52 -0700
> "Richard (Rick) Karlquist"  wrote:
> 
> 
>> Actually, the oven mass of the E1938A is much heavier than the
>> 10811 and is made of copper to boot.
> [...]
>> The crystal case is well connected to the oven mass and gets
>> heated by conduction.  I don't think radiation is a player.
> 
> Hmm.. seems like I have misunderstood the design.
> I think I should aquire one of the non-working E1938 and
> pry the can open. 
> 
> Does anyone have a E1938 that's not working anymore
> and would be willing to offer it to science? :-)
> 
> 
>   Attila Kinali
> -- 
> You know, the very powerful and the very stupid have one thing in common.
> They don't alters their views to fit the facts, they alter the facts to
> fit the views, which can be uncomfortable if you happen to be one of the
> facts that needs altering.  -- The Doctor
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Re: [time-nuts] Poor man's oven

[Attila Kinali]

Hoi Rick,

On Wed, 7 Jun 2017 14:21:52 -0700
"Richard (Rick) Karlquist"  wrote:


> Actually, the oven mass of the E1938A is much heavier than the
> 10811 and is made of copper to boot.
[...]
> The crystal case is well connected to the oven mass and gets
> heated by conduction.  I don't think radiation is a player.

Hmm.. seems like I have misunderstood the design.
I think I should aquire one of the non-working E1938 and
pry the can open. 

Does anyone have a E1938 that's not working anymore
and would be willing to offer it to science? :-)


Attila Kinali
-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] Poor man's oven

[Bob kb8tq]

Hi

The crystal enclosure may (or may not … who knows ..) be back filled with a low 
level
of helium. It does not take much of a backfill for conduction inside the 
crystal holder to
dominate the heat transfer vs radiation transfer.

Bob

> On Jun 7, 2017, at 5:21 PM, Richard (Rick) Karlquist  
> wrote:
> 
> 
> 
> On 6/7/2017 1:09 PM, Attila Kinali wrote:
>> 
>> makes the PI loop better behaved. Also the thermal mass of the
>> crystal holder is quite small. Especially compared ot the 10811.
> 
> Actually, the oven mass of the E1938A is much heavier than the
> 10811 and is made of copper to boot.
>> Due to the flat puck design, I assume that the majority of the
>> heat going to the crystal holder is due to radiation (unless I
>> missed some insulation around the crystal). Radiation, albeit being
>> a high "resistivity" transport mechanism, has very low inherent
>> "capacitance". And thus the delay associated with this transport
>> mechanism is low.
> 
> The crystal case is well connected to the oven mass and gets
> heated by conduction.  I don't think radiation is a player.
> 
>> There are probably a lot more small design decisions in the E1938
>> that make it such a superb oven. More than I probably will ever
>> be able to figure out. And, I still am astonished how well it works.
>>  Attila Kinalid
> 
> Rick N6RK
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Re: [time-nuts] Poor man's oven

[Richard (Rick) Karlquist]

On 6/7/2017 1:09 PM, Attila Kinali wrote:


makes the PI loop better behaved. Also the thermal mass of the
crystal holder is quite small. Especially compared ot the 10811.


Actually, the oven mass of the E1938A is much heavier than the
10811 and is made of copper to boot.


Due to the flat puck design, I assume that the majority of the
heat going to the crystal holder is due to radiation (unless I
missed some insulation around the crystal). Radiation, albeit being
a high "resistivity" transport mechanism, has very low inherent
"capacitance". And thus the delay associated with this transport
mechanism is low.


The crystal case is well connected to the oven mass and gets
heated by conduction.  I don't think radiation is a player.


There are probably a lot more small design decisions in the E1938
that make it such a superb oven. More than I probably will ever
be able to figure out. And, I still am astonished how well it works.

Attila Kinalid


Rick N6RK
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Re: [time-nuts] Poor man's oven

[Attila Kinali]

On Tue, 6 Jun 2017 19:07:29 -0700
"Richard (Rick) Karlquist"  wrote:

> In the E1938A oscillator, we used a PIDI^2 loop.  IOW, a PID
> plus a double integrator.  This was Len Cutler's idea.
> Once the constants were dialed in, this worked phenomenally
> well in terms of transient response.  Even dumping in liquid
> nitrogen full throttle into the environmental test chamber
> barely wiggled the crystal temperature/frequency.

The E1938 is kind of special in several ways, IMHO.
Beside having a nice zero-gradient design (I really love
this idea :-) it has also a quite large surface vs volume.
This means that there is a lot of heat flow out of the
can and at the same time the (face) heater is large, which
makes the PI loop better behaved. Also the thermal mass of the
crystal holder is quite small. Especially compared ot the 10811.

Due to the flat puck design, I assume that the majority of the
heat going to the crystal holder is due to radiation (unless I
missed some insulation around the crystal). Radiation, albeit being
a high "resistivity" transport mechanism, has very low inherent
"capacitance". And thus the delay associated with this transport
mechanism is low.

There are probably a lot more small design decisions in the E1938
that make it such a superb oven. More than I probably will ever
be able to figure out. And, I still am astonished how well it works.

Attila Kinalid
-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] Poor man's oven

[Van Horn, David]

You can feed in an external AREF, but look at the data sheet for the particular 
AVR chip.
One thing which is commonly ignored in Arduino-Land is the I/O pin leakage 
current and the maximum source impedance specs.
You are well advised to buffer the voltage you are reading, or make sure the 
source is low enough impedance that those errors won't get you.

All uCs have these issues, I just see this error made a lot in Arduino land.  
My 3D printer is Arduino based, and uses a 100k thermistor driving the Arduino 
directly.
The community makes claims that a degree or two of temperature change is 
important, and yet the circuit isn't capable of that much accuracy.



-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Jim Harman
Sent: Tuesday, June 6, 2017 11:09 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Poor man's oven

On Tue, Jun 6, 2017 at 10:00 AM, Riley, Ian C CTR NSWC Philadelphia, 515 < 
ian.riley@navy.mil> wrote:

> Is there a practical minimum for what voltage you can feed into AREF?
>

It is hard to find on the data sheet, but the minimum voltage for an Arduino's 
AREF is the internal analog reference voltage - 1.1V for the Uno, 2.56V for the 
Leonardo or Micro. The 32U4 chip in the Leo and Micro has options for 
differential analog input and gains of 10, 40, or 200 but they are not 
supported by the Arduino IDE - you have to set the internal registers directly 
to use them. Also the input amplifier is pretty slow.


-- 

--Jim Harman
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Re: [time-nuts] Poor man's oven

[Richard (Rick) Karlquist]

On Jun 6, 2017, at 7:10 PM, Chris Albertson  wrote:


There are more sophisticated control loop designs that can handle this
better, eg by using two temperature sensors, one at the crystal and
one at the heater. But designing them correctly is more difficult
than the normal PID loop.



In the E1938A oscillator, we used a PIDI^2 loop.  IOW, a PID
plus a double integrator.  This was Len Cutler's idea.
Once the constants were dialed in, this worked phenomenally
well in terms of transient response.  Even dumping in liquid
nitrogen full throttle into the environmental test chamber
barely wiggled the crystal temperature/frequency.

Rick N6RK
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Re: [time-nuts] Poor man's oven

[Bob kb8tq]

Hi

The Freescale ADC’s are pretty good compared to a lot of other MCU ADC’s. They 
still are not as good as you might 
think from the audio ENOB numbers. Something in the 10~11 bit range is doing 
quite well at DC in a control loop, even for them. 

Bob

> On Jun 6, 2017, at 8:12 PM, jimlux  wrote:
> 
> On 6/6/17 1:37 PM, Bob kb8tq wrote:
>> Hi
>> 
>> Often when you dig into the details of MCU ADC’s they have a little note 
>> “optimized for audio” or
>> “not recommended for control loops”. It can be a bit of a head scratcher to 
>> work out what they are
>> getting at. The big issues in this case seem to be DC leakage and 1/F noise. 
>> Yes, they do sort of go hand in hand :)
>> You need to be willing to check out the ENOB at DC in order to use them 
>> effectively in a simple
>> OCXO setup. That or be willing to flip the bridge ends on demand and try to 
>> cancel out the issues.
>> Unfortunately that adds both complexity and a string of other fun and games.
>> 
> 
> This one seems to be designed specifically for this kind of DC measurement, 
> sure, it will sample at 100kHz, but not with the amplifier and averaging and 
> such.
> 
> Its based on the Freescale (now NXP, I guess..) Kinetis K20 series
> 
> It has a bewildering variety of peripherals (touch sensors, etc.), as well as 
> the usual multiple UARTs, SPI, I2C, timers, counters, etc. What's nice is 
> that PJRC (who make the teensy series) have written all the drivers and 
> libraries to integrate into the Arduino environment for those that don't live 
> for decoding the 1000 page processor family manual and 600 page package 
> specific manuals that give the specific pinouts and options on the one YOU 
> have in front of you.  Your "time to first light" is much shorter. And then 
> you can hack away.
> 
> I think this is more a chip designed for embedded controllers and the like. I 
> don't know if it has the processor and peripherals to do, say, 3 phase 
> induction motor control or Ultrasound processing, but it might.
> 
> The Atmel processors are nice (and you can actually get one of the Arduino 
> flavor ones in a rad hard version.. for those "control the device in the 
> beamline" applications), but the Kinetis are easily an order of magnitude 
> better - no bit banging to do serial protocols, USB built in, decent ADC, 
> floating point, etc.
> 
> 
> 
> 
>> Op amps are cheap ….
>> 
>> Bob
>> 
>>> On Jun 6, 2017, at 3:54 PM, jimlux  wrote:
>>> 
>>> On 6/6/17 11:47 AM, Chris Albertson wrote:
 Yes, as I wrote.  I would not mess with AREF.  At most you can only get a
 multiplication about 4.   Use an op-amp.   Signal conditioning really
 almost alway is required in the analog domain before any A/D conversion
 
 Also like the uP is not inside the oven and has a cable of some length so
 you'd want a buffered analog signal on the cable, the op-amp can do that
 to.
 
 Those $2 parts I linked to have the ADC referenced to 3.3 volts but have 12
 bits as compared to the arduino which has 10 bits
>>> 
>>> 
>>> or use a Teensy with a 16 bit differential input ADC.  Arduino compatible, 
>>> cheaper, yeah, you probably get 13 bits real performance from the ADC.  
>>> Also has a real analog output (not PWM and a LPF) if you need that.
>>> 
>>> Programmable gain, sample averaging in hardware, etc.   Not bad for <$20.
>>> 
>>> 
 
 
>>> 
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Re: [time-nuts] Poor man's oven

[jimlux]

On 6/6/17 1:37 PM, Bob kb8tq wrote:

Hi

Often when you dig into the details of MCU ADC’s they have a little note 
“optimized for audio” or
“not recommended for control loops”. It can be a bit of a head scratcher to 
work out what they are
getting at. The big issues in this case seem to be DC leakage and 1/F noise. 
Yes, they do sort of go hand in hand :)
You need to be willing to check out the ENOB at DC in order to use them 
effectively in a simple
OCXO setup. That or be willing to flip the bridge ends on demand and try to 
cancel out the issues.
Unfortunately that adds both complexity and a string of other fun and games.



This one seems to be designed specifically for this kind of DC 
measurement, sure, it will sample at 100kHz, but not with the amplifier 
and averaging and such.


Its based on the Freescale (now NXP, I guess..) Kinetis K20 series

It has a bewildering variety of peripherals (touch sensors, etc.), as 
well as the usual multiple UARTs, SPI, I2C, timers, counters, etc. 
What's nice is that PJRC (who make the teensy series) have written all 
the drivers and libraries to integrate into the Arduino environment for 
those that don't live for decoding the 1000 page processor family manual 
and 600 page package specific manuals that give the specific pinouts and 
options on the one YOU have in front of you.  Your "time to first light" 
is much shorter. And then you can hack away.


I think this is more a chip designed for embedded controllers and the 
like. I don't know if it has the processor and peripherals to do, say, 3 
phase induction motor control or Ultrasound processing, but it might.


The Atmel processors are nice (and you can actually get one of the 
Arduino flavor ones in a rad hard version.. for those "control the 
device in the beamline" applications), but the Kinetis are easily an 
order of magnitude better - no bit banging to do serial protocols, USB 
built in, decent ADC, floating point, etc.






Op amps are cheap ….

Bob


On Jun 6, 2017, at 3:54 PM, jimlux  wrote:

On 6/6/17 11:47 AM, Chris Albertson wrote:

Yes, as I wrote.  I would not mess with AREF.  At most you can only get a
multiplication about 4.   Use an op-amp.   Signal conditioning really
almost alway is required in the analog domain before any A/D conversion

Also like the uP is not inside the oven and has a cable of some length so
you'd want a buffered analog signal on the cable, the op-amp can do that
to.

Those $2 parts I linked to have the ADC referenced to 3.3 volts but have 12
bits as compared to the arduino which has 10 bits



or use a Teensy with a 16 bit differential input ADC.  Arduino compatible, 
cheaper, yeah, you probably get 13 bits real performance from the ADC.  Also 
has a real analog output (not PWM and a LPF) if you need that.

Programmable gain, sample averaging in hardware, etc.   Not bad for <$20.







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Re: [time-nuts] Poor man's oven

[Bob kb8tq]

Hi

In the case of a second sensor, “at the crystal” effectively means “inside the 
crystal package”. 
That heads you into all sorts of “interesting” problems. Better to just read 
the papers and do
it the “old fashioned” way.

Bob

> On Jun 6, 2017, at 7:10 PM, Chris Albertson  wrote:
> 
>> There are more sophisticated control loop designs that can handle this
>> better, eg by using two temperature sensors, one at the crystal and
>> one at the heater. But designing them correctly is more difficult
>> than the normal PID loop.
>> 
> 
> Keeping with the thread topic, I think this is the key.For the cost of
> only one more cheap sensor you gain a lot.   Harder design as you say but
> getting help on-line seems to be free.
> 
> I have gotten PID to work myself with linear systems (motor speed) and I
> reading up on Kalman Filters as I need them for navigation using multiple
> sensors.
> 
> I guess one could use the crystal frequency as a measure of its temperature
> to tune the system.  Is there a name to Google to read up on using two
> sensors and a pid-like algorithm?
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] Poor man's oven

[Chris Albertson]

> There are more sophisticated control loop designs that can handle this
> better, eg by using two temperature sensors, one at the crystal and
> one at the heater. But designing them correctly is more difficult
> than the normal PID loop.
>

Keeping with the thread topic, I think this is the key.For the cost of
only one more cheap sensor you gain a lot.   Harder design as you say but
getting help on-line seems to be free.

I have gotten PID to work myself with linear systems (motor speed) and I
reading up on Kalman Filters as I need them for navigation using multiple
sensors.

I guess one could use the crystal frequency as a measure of its temperature
to tune the system.  Is there a name to Google to read up on using two
sensors and a pid-like algorithm?
-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Poor man's oven

[Attila Kinali]

On Tue, 6 Jun 2017 11:00:57 -0700
Chris Albertson  wrote:

> >
> > 1) You want the control loop as stable as possible
> > 2) Stability is directly related to controllability
> > 3) The larger the heat flow, the better the controllability
> > 4) therefore the outside temperature should be as low as possible
> 
> 
> I think you are correct but within reason of course.   It is easy to see
> that the extremes can't work. If the internal set point is very close to
> ambient the oven is uncontrollable.  because you only use the first bit of
> the DAC to control the heater and after a few seconds you have overshoot.

You are looking at one minor issue here. Of course, if your control loop
is only of the bang-bang kind, then you will have a hard time to keep
the system parameter stable. But that is easy to deal with if one knows
the overall system.

I was talking about the control therotical "controllability":
https://en.wikipedia.org/wiki/Controllability

For a simple system like an OCXO that is mostly dependent on
thermal mass vs thermal flow (both in and out) which translates
into "delay" between the heating element and the temperature sensor.
A lot of people assume that adding more thermal mass is going to make
the control more stable. But in reality this might make it unstable
(aka cause oscillations) or make the control error larger.
What happens here is that the mass takes time to heat up. During heat
up you can describe it like a (very slow) transmission line. It will
take time until the signal (heat) reaches the other end (center of the mass).
When the heat reaches the sensor, the control electronics will dial the heater
down. But there is still a heatwave traveling inwards, ie the core will get
warmer and warmer. Thus the heater will be dialed down more and more until
it doesn't heat enough. This will cause a cold wave traveling inwards..

Having a larger thermal flow vs mass helps against this problem.
Good thermal conductivity between heater and sensor helps as well.
(that's why you will read often, that the sensor should be placed
close to the heater and not to the quartz)

> The PID algorithm needs something that is slow to change
> compared to the control loop cycle.  So you want a good size thermal mass
> compared to the amount of heat.

The control loop does not need something slow to change. You need to
factor the termal mass, its insulation etc into PID parameters so you
get a stable loop. As I have shown above, if this is not correctly done
you will get oscilations. One way to avoid them, if your physical system
is fixed, is to lower the loop bandwith and thus make the system respond
much slower to changes than the time it takes to conduct the heat from
the heater to the sensor. But this means also that the control loop will
be slow to react to changes in the environment.

There are more sophisticated control loop designs that can handle this
better, eg by using two temperature sensors, one at the crystal and
one at the heater. But designing them correctly is more difficult
than the normal PID loop. 


Attila Kinali

-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] Poor man's oven

[Bob kb8tq]

Hi

Often when you dig into the details of MCU ADC’s they have a little note 
“optimized for audio” or 
“not recommended for control loops”. It can be a bit of a head scratcher to 
work out what they are
getting at. The big issues in this case seem to be DC leakage and 1/F noise. 
Yes, they do sort of go hand in hand :)
You need to be willing to check out the ENOB at DC in order to use them 
effectively in a simple 
OCXO setup. That or be willing to flip the bridge ends on demand and try to 
cancel out the issues. 
Unfortunately that adds both complexity and a string of other fun and games. 

Op amps are cheap ….

Bob

> On Jun 6, 2017, at 3:54 PM, jimlux  wrote:
> 
> On 6/6/17 11:47 AM, Chris Albertson wrote:
>> Yes, as I wrote.  I would not mess with AREF.  At most you can only get a
>> multiplication about 4.   Use an op-amp.   Signal conditioning really
>> almost alway is required in the analog domain before any A/D conversion
>> 
>> Also like the uP is not inside the oven and has a cable of some length so
>> you'd want a buffered analog signal on the cable, the op-amp can do that
>> to.
>> 
>> Those $2 parts I linked to have the ADC referenced to 3.3 volts but have 12
>> bits as compared to the arduino which has 10 bits
> 
> 
> or use a Teensy with a 16 bit differential input ADC.  Arduino compatible, 
> cheaper, yeah, you probably get 13 bits real performance from the ADC.  Also 
> has a real analog output (not PWM and a LPF) if you need that.
> 
> Programmable gain, sample averaging in hardware, etc.   Not bad for <$20.
> 
> 
>> 
>> 
> 
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Re: [time-nuts] Poor man's oven

[jimlux]

On 6/6/17 11:47 AM, Chris Albertson wrote:

Yes, as I wrote.  I would not mess with AREF.  At most you can only get a
multiplication about 4.   Use an op-amp.   Signal conditioning really
almost alway is required in the analog domain before any A/D conversion

Also like the uP is not inside the oven and has a cable of some length so
you'd want a buffered analog signal on the cable, the op-amp can do that
to.

Those $2 parts I linked to have the ADC referenced to 3.3 volts but have 12
bits as compared to the arduino which has 10 bits



or use a Teensy with a 16 bit differential input ADC.  Arduino 
compatible, cheaper, yeah, you probably get 13 bits real performance 
from the ADC.  Also has a real analog output (not PWM and a LPF) if you 
need that.


Programmable gain, sample averaging in hardware, etc.   Not bad for <$20.







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Re: [time-nuts] Poor man's oven

[Poul-Henning Kamp]

In message 
, Chris Albertson writes:

>The next step up the complexity scale would have you place an I2C
>interlaced ADC inside your oven.  These don't cost much and have several
>ADC channels.

ISOtemp made a version of their OCXO-107 which a built in DAC, but
I've been told the result was less than stellar.

When you do stuff like that, you need to pay a lot of attention to noise.

Personally I would avoid I2C, in preference for SPI to avoid the
sharp flanks required by I2C.

I would also run the SPI as slow as I possibly could and put low-pass
filter the digital signals at the boundary.

SRS uses an interesting trick in several of their instruments, where
they shut down parts or even all of the digital circuits when not
needed, see for instance their digital "all analog" lock-in amplifier.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Poor man's oven

[Hal Murray]

csteinm...@yandex.com said:
> It depends on what you mean by "best."  "Best" can mean "minimizes the
> wander in oven-regulated temperature at a constant (or slowly-changing)
> ambient temperature," or it can mean "fastest recovery when the ambient
> temperature changes more rapidly." 

I think it also depends on whether you are using an existing system or get to 
tweak the design to take advantage of the new rules.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Poor man's oven

[Chris Albertson]

Yes, as I wrote.  I would not mess with AREF.  At most you can only get a
multiplication about 4.   Use an op-amp.   Signal conditioning really
almost alway is required in the analog domain before any A/D conversion

Also like the uP is not inside the oven and has a cable of some length so
you'd want a buffered analog signal on the cable, the op-amp can do that
to.

Those $2 parts I linked to have the ADC referenced to 3.3 volts but have 12
bits as compared to the arduino which has 10 bits

The next step up the complexity scale would have you place an I2C
interlaced ADC inside your oven.  These don't cost much and have several
ADC channels.  then your oven has full digital interface and a much higher
quality DAC.  But this adds another 2 or 3 dollars to the design.   Maybe
worth it as now all the analog stuff is inside a temperature stable metal
tin can. But you have to watch this feature-creep as you can drive up
cost with little to show for it.

Also I'd not want the analog stuff designed to work only with ADC built
into one specific development board.  The I2C serial interface is pretty
much universal

I'm thinking something like this:
http://www.ebay.com/itm/12-Bit-I2C-4-CH-ADS1115...

Notice that the chip has programmable gain, it can scale the input over a
small range before sampling.
For $2 it's still a "poor man's part and you do NOT need to make a PCB to
use it.

On Tue, Jun 6, 2017 at 10:08 AM, Jim Harman  wrote:

> On Tue, Jun 6, 2017 at 10:00 AM, Riley, Ian C CTR NSWC Philadelphia, 515 <
> ian.riley@navy.mil> wrote:
>
> > Is there a practical minimum for what voltage you can feed into AREF?
> >
>
> It is hard to find on the data sheet, but the minimum voltage for an
> Arduino's AREF is the internal analog reference voltage - 1.1V for the Uno,
> 2.56V for the Leonardo or Micro. The 32U4 chip in the Leo and Micro has
> options for differential analog input and gains of 10, 40, or 200 but they
> are not supported by the Arduino IDE - you have to set the internal
> registers directly to use them. Also the input amplifier is pretty slow.
>
>
> --
>
> --Jim Harman
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-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Poor man's oven

[Bob kb8tq]

Hi

As you point out, there really is no answer that is obviously better than all 
the others. 
If you keep the outside warm (say 40C) you will reduce the strain on the heater 
devices
and likely not degrade the MTBF of anything outside the OCXO by very much. 

Bob

> On Jun 6, 2017, at 7:26 AM, Poul-Henning Kamp  wrote:
> 
> 
> In message , Bob kb8tq writes:
> 
>> In an OCXO design, the gotcha
>> is matching the PTC oven temperature to the crystal turn. You can do that if
>> you have a substantial inventory of material and custom fab the oven after
>> the crystal is built. 
> 
> Bob, you of all people must be able to answer this:
> 
> OCXO's have specified temperature ranges for instance
> -40...+70°C for the heavy duty stuff.
> 
> But I cant imagine the ovens used are so perfect that they have the
> same regulation performance at all temperatures.
> 
> I can choose the exterior temperature, which I should prefer ?
> 
> Disregard aging of electronics and materials, we all know that
> stuff, what I'm interested in is at which exterior temperature
> OCXO ovens work best ?
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] Poor man's oven

[Richard (Rick) Karlquist]

On 6/6/2017 4:26 AM, Poul-Henning Kamp wrote:


But I cant imagine the ovens used are so perfect that they have the
same regulation performance at all temperatures.

I can choose the exterior temperature, which I should prefer ?

Disregard aging of electronics and materials, we all know that
stuff, what I'm interested in is at which exterior temperature
OCXO ovens work best ?



My experience has been that, while ovens may not be perfect,
they are inherently linear.  So the exterior temperature is
a don't care.

I extensively characterized the E1938A oven.  By adjusting
the ratio of heat to the top/bottom vs edge, I was able to
get the thermal gain into the millions.  At that point,
finally a modicum of non-linearity showed up and the thermal
gain varied with ambient temperature.  It might be 2 million
at the ambient where I adjusted it, and drop to 1.5 million
when well away from that temperature.  Or it might change
sign at some ambient.  (Yes, you can have negative thermal
gain).  You shouldn't need to worry about this for any ordinary oven.

Rick N6RK
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Re: [time-nuts] Poor man's oven

[Bob kb8tq]

Hi

For a variety of reasons, if you go the MCU ADC route, put an op amp in between 
the
thermistor bridge and the ADC. It takes care of a whole lot of issues. 

Bob

> On Jun 6, 2017, at 12:13 PM, Adrian Godwin  wrote:
> 
> The specs for the ADC are pretty vague : most of the errors are around 2
> LSB but all are quoted with vref at 4V. If you reduce vref (there's an
> internal option of 1.1V) you'll increase gain but some of those errors are
> going to stay physically the same. In general, I'd tend expect to get more
> precision but also more noise. Averaging may help a bit.
> 
> 
> On Tue, Jun 6, 2017 at 3:00 PM, Riley, Ian C CTR NSWC Philadelphia, 515 <
> ian.riley@navy.mil> wrote:
> 
>> Chris,
>> 
>>> The trick with using a uP and it's built-in A/D converters is scale.  You
>>> want the limited 10-bits of revolution to fall over the operating range
>>> which is very narrow, like 1C.   Anything outside of that is either 
>> or
>>>  and only seen at start-up.,  So at start up the the controller is on
>>> "bang-bang" mode then later you have milli-degree resolution over your 1C
>>> range.   Basically you are measuring noise. but your $2 uP can take
>> 100,000
>>> measurments per second and putt tour a digital filter.
>> 
>> I have seen but not used the AREF pins on Arduino and similar uPs; as you
>> lower AREF, do you lose any sort of accuracy? Is there a practical minimum
>> for what voltage you can feed into AREF?
>> 
>> -Ian R.
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Re: [time-nuts] Poor man's oven

[Charles Steinmetz]

Poul-Henning wrote:


what I'm interested in is at which exterior temperature
OCXO ovens work best ?


Jim replied:


Here's my guess...
1) you want minimal gradients across the device for a variety of reasons
2) therefore you want least amount of heat from the heater
3) therefore somewhat below the setpoint of the heater.


It depends on what you mean by "best."  "Best" can mean "minimizes the 
wander in oven-regulated temperature at a constant (or slowly-changing) 
ambient temperature," or it can mean "fastest recovery when the ambient 
temperature changes more rapidly."


Minimum heater power tends to favor the first, but be careful -- this 
means a low *available* (maximum) power, not just using a high-powered 
heater at a lower output.  This is because the rate of temperature 
change for full-scale heater swings is proportional to maximum heater 
output, not to the ambient-to-oven differential, and this "granularity" 
of the heater control function is what determines the oven wander at a 
constant (or slowly-changing) ambient temperature.


A higher differential between the set point and ambient, and higher 
maximum heater output, are necessary for fast recovery from larger 
and/or faster changes in ambient temperature (i.e., to achieve a higher 
dTemp/dTime).


Note that the above is why, for an oven controller with decent loop 
gain, it is not necessary to control the ambient temperature very 
tightly -- it is only necessary to slow down the *rate of change* in 
ambient temperature to the point that the loop can track it to the 
required tolerance.  See previous list discussions of "cast aluminum 
boxes" and "thermal capacitance."


Best regards,

Charles


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Re: [time-nuts] Poor man's oven

[Chris Albertson]

On Tue, Jun 6, 2017 at 7:34 AM, Attila Kinali  wrote:

>
> 1) You want the control loop as stable as possible
> 2) Stability is directly related to controllability
> 3) The larger the heat flow, the better the controllability
> 4) therefore the outside temperature should be as low as possible


I think you are correct but within reason of course.   It is easy to see
that the extremes can't work. If the internal set point is very close to
ambient the oven is uncontrollable.  because you only use the first bit of
the DAC to control the heater and after a few seconds you have overshoot.
Moving the set point up lets us use the full range of current on the heater
can gives us 8 or 10 bits of control and the rate of change is slow enough
that we have time take thousands of samples and see a rate of change in
temperature.  The PID algorithm needs something that is slow to change
compared to the control loop cycle.  So you want a good size thermal mass
compared to the amount of heat.


At the other extreme, where the set point to far above ambient we would
need to run the heater full time and also loose control.  So I disagree
with #4 above.   The heater would have to run full-on at 100% duty cycle.
 (In other words avoid using liquid nitrogen baths)

There is an optimum were it peaks but I don't know how to find it.Look
at the specific heat of the thermal mass (likely you are using aluminum)
and multiply that by the mass and I think you want that to be large
compared to the heat from a full-on heater so that the rate of change looks
slow compared to your control loop cycle.





-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Poor man's oven

[Jim Harman]

On Tue, Jun 6, 2017 at 10:00 AM, Riley, Ian C CTR NSWC Philadelphia, 515 <
ian.riley@navy.mil> wrote:

> Is there a practical minimum for what voltage you can feed into AREF?
>

It is hard to find on the data sheet, but the minimum voltage for an
Arduino's AREF is the internal analog reference voltage - 1.1V for the Uno,
2.56V for the Leonardo or Micro. The 32U4 chip in the Leo and Micro has
options for differential analog input and gains of 10, 40, or 200 but they
are not supported by the Arduino IDE - you have to set the internal
registers directly to use them. Also the input amplifier is pretty slow.


-- 

--Jim Harman
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Re: [time-nuts] Poor man's oven

[Adrian Godwin]

The specs for the ADC are pretty vague : most of the errors are around 2
LSB but all are quoted with vref at 4V. If you reduce vref (there's an
internal option of 1.1V) you'll increase gain but some of those errors are
going to stay physically the same. In general, I'd tend expect to get more
precision but also more noise. Averaging may help a bit.


On Tue, Jun 6, 2017 at 3:00 PM, Riley, Ian C CTR NSWC Philadelphia, 515 <
ian.riley@navy.mil> wrote:

> Chris,
>
> > The trick with using a uP and it's built-in A/D converters is scale.  You
> > want the limited 10-bits of revolution to fall over the operating range
> > which is very narrow, like 1C.   Anything outside of that is either 
> or
> >  and only seen at start-up.,  So at start up the the controller is on
> > "bang-bang" mode then later you have milli-degree resolution over your 1C
> > range.   Basically you are measuring noise. but your $2 uP can take
> 100,000
> > measurments per second and putt tour a digital filter.
>
> I have seen but not used the AREF pins on Arduino and similar uPs; as you
> lower AREF, do you lose any sort of accuracy? Is there a practical minimum
> for what voltage you can feed into AREF?
>
> -Ian R.
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Re: [time-nuts] Poor man's oven

[Riley, Ian C CTR NSWC Philadelphia, 515]

Chris,

> The trick with using a uP and it's built-in A/D converters is scale.  You
> want the limited 10-bits of revolution to fall over the operating range
> which is very narrow, like 1C.   Anything outside of that is either  or
>  and only seen at start-up.,  So at start up the the controller is on
> "bang-bang" mode then later you have milli-degree resolution over your 1C
> range.   Basically you are measuring noise. but your $2 uP can take 100,000
> measurments per second and putt tour a digital filter.

I have seen but not used the AREF pins on Arduino and similar uPs; as you lower 
AREF, do you lose any sort of accuracy? Is there a practical minimum for what 
voltage you can feed into AREF? 

-Ian R. 
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Re: [time-nuts] Poor man's oven

[Attila Kinali]

On Tue, 6 Jun 2017 05:52:56 -0700
jimlux  wrote:

> > Disregard aging of electronics and materials, we all know that
> > stuff, what I'm interested in is at which exterior temperature
> > OCXO ovens work best ?
> 
> Here's my guess...
> 
> 1) you want minimal gradients across the device for a variety of reasons
> 2) therefore you want least amount of heat from the heater
> 3) therefore somewhat below the setpoint of the heater.
> 
> How far below? I've no idea.

I counter that guess! :-)

1) You want the control loop as stable as possible
2) Stability is directly related to controllability
3) The larger the heat flow, the better the controllability
4) therefore the outside temperature should be as low as possible

Do we have to battle now, to see who is right? :-)


Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Poor man's oven

[jimlux]

On 6/6/17 4:26 AM, Poul-Henning Kamp wrote:






OCXO's have specified temperature ranges for instance
-40...+70°C for the heavy duty stuff.

But I cant imagine the ovens used are so perfect that they have the
same regulation performance at all temperatures.

I can choose the exterior temperature, which I should prefer ?

Disregard aging of electronics and materials, we all know that
stuff, what I'm interested in is at which exterior temperature
OCXO ovens work best ?


Here's my guess...

1) you want minimal gradients across the device for a variety of reasons
2) therefore you want least amount of heat from the heater
3) therefore somewhat below the setpoint of the heater.

How far below? I've no idea.

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Re: [time-nuts] Poor man's oven

[Poul-Henning Kamp]

In message , Bob kb8tq writes:

>In an OCXO design, the gotcha
>is matching the PTC oven temperature to the crystal turn. You can do that if
>you have a substantial inventory of material and custom fab the oven after
>the crystal is built. 

Bob, you of all people must be able to answer this:

OCXO's have specified temperature ranges for instance
-40...+70°C for the heavy duty stuff.

But I cant imagine the ovens used are so perfect that they have the
same regulation performance at all temperatures.

I can choose the exterior temperature, which I should prefer ?

Disregard aging of electronics and materials, we all know that
stuff, what I'm interested in is at which exterior temperature
OCXO ovens work best ?

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Poor man's oven

[Bob kb8tq]

Hi

For a while, a couple of outfits made TO-5 and TO-8 “cap heaters” with 
PTC material. There are still a few obscure places that people do the same
sort of thing with a mini-pcb based design. In an OCXO design, the gotcha
is matching the PTC oven temperature to the crystal turn. You can do that if you
have a substantial inventory of material and custom fab the oven after the 
crystal 
is bult. 

Bob

> On Jun 6, 2017, at 12:13 AM, David  wrote:
> 
> I have never been able to find a reference to them on the internet but
> there was a similar product intended for TO-99 packages that could be
> used with operational amplifiers.
> 
> On Mon, 5 Jun 2017 08:35:35 + (UTC), you wrote:
> 
>>   The Crystal heater clip wasa Murata "Posistor" soldered onto a clipand 
>> they were marketed by Murata.
>> I once purchased a small amount of theseand used them as "poor man's ovens".
>> Although not perfect by far, they did theirjob and kept my UHF gear stable.
>> Murata dropped that product many yearsago and I have not been able to 
>> findany similar product. The Posistors arelisted by eg. Digi-key but they do 
>> not stock them.
>> Ulf - SM6GXV
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Re: [time-nuts] Poor man's oven

[Jon Iza]

Folks,
with tongue firmly stuck in cheek, may I propose an old technique to
stabilize
xtal oscillators?You only need a "satellite" oscillator placed under your
armpit...
http://www.qsl.net/on7yd/136narro.htm#NihilNovum
jon, ea2sn
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Re: [time-nuts] Poor man's oven

[David]

I have never been able to find a reference to them on the internet but
there was a similar product intended for TO-99 packages that could be
used with operational amplifiers.

On Mon, 5 Jun 2017 08:35:35 + (UTC), you wrote:

>  The Crystal heater clip wasa Murata "Posistor" soldered onto a clipand they 
>were marketed by Murata.
>I once purchased a small amount of theseand used them as "poor man's ovens".
>Although not perfect by far, they did theirjob and kept my UHF gear stable.
>Murata dropped that product many yearsago and I have not been able to findany 
>similar product. The Posistors arelisted by eg. Digi-key but they do not stock 
>them.
>Ulf - SM6GXV
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Re: [time-nuts] Poor man's oven

[Charles Steinmetz]

Chris wrote:


Today all you need is a reliable way to measure the error
between the crystals' current temperature and the set  point.


That's all that's ever been needed.  But it is devilishly difficult to 
measure the actual quartz temperature, or even to find a good proxy that 
is easier to measure.


There is a fair body of published research on these topics, including 
Rick's (et al.) work on zero-gradient ovens.


Keep this in mind when someone says they are controlling the "oven 
temperature" to 0.001C (or even 0.1C).  They are measuring *something*, 
and may even be holding whatever it is "constant" within fairly tight 
tolerances.  But they have no idea what the quartz temperature is, and 
no way to know with precision the relationship between the measured 
temperature and the actual quartz temperature.


Some years ago, I consulted for a research group that was using a number 
of non-contact technologies to measure the temperature of oscillating 
quartz crystals.  The results were promising, but there were some issues 
with measuring the temperature (which is, essentially, quantifying tiny 
random molecular motions within the crystal lattice) against the 
background of the hugely greater macro motion of the vibating quartz.  I 
never knew the final conclusions, nor am I aware of any systems designed 
using these principles or methods.  But it is something to think about 
if you *really* want a temperature-stable oscillator.


Best regards,

Charles


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Re: [time-nuts] Poor man's oven

[Bob kb8tq]

Hi

That paper is the basis for the MCXO. It is an interesting way to do a TCXO. 
The drift between the two modes makes it a difficult thing to master in an OCXO.
Plating a pair of electrodes (one pair per mode) is also an approach that has 
been
tried. 

Bob

> On Jun 5, 2017, at 7:20 PM, Chris Caudle  wrote:
> 
> On Mon, June 5, 2017 5:38 pm, Charles Steinmetz wrote:
>> Some years ago, I consulted for a research group that was using a number
>> of non-contact technologies to measure the temperature of oscillating
>> quartz crystals.
> 
> In most cases what you really care about is the stability of the
> frequency, and the temperature of the crystal is just a proxy for that,
> correct?
> I thought there was some effect where different modes of oscillation
> shifted by different amounts with temperature, and if you had two
> oscillation circuits running from the same crystal but different modes,
> you could use the shift in difference frequency between the two modes to
> infer the temperature change.
> 
> Found a reference in the Vig tutorial:
> S. Schodowski, "Resonator Self-Temperature-Sensing Using a
> Dual-Harmonic-Mode Crystal Oscillator," Proc. 43rd Annual Symposium on
> Frequency Control, pp. 2-7, 1989, IEEE Catalog No. 89CH2690-6.
> 
> From page 48 of Vig tutorial version 8.5.5.3 May 2013:
> As is shown in chapter 4, see “Effects of Harmonics on f vs. T,” the f
> vs. T of the fundamental mode of a resonator is different from that of
> the third and higher overtones.  This fact is exploited for
> “self-temperature sensing” in the microcomputer compensated crystal
> oscillator (MCXO). The fundamental (f1) and third overtone (f3)
> frequencies are excited simultaneously (“dual mode” excitation) and a
> beat frequency fb is generated such that fb = 3f1 - f3 (or fb = f1 -
> f3/3). The fb is a monotonic and nearly linear function of
> temperature, as is shown above for a 10 MHz 3rd overtone (3.3. MHz
> fundamental mode) SC-cut resonator.
> 
> The graph shows a line with slope of around 80ppm/deg C.  Not sure what
> that translates to in terms of what you could realistically measure and
> use for frequency compensation.  I guess you could use that information to
> either control an oven or just let the crystal run free and control a
> synthesizer for the used output.
> 
> -- 
> Chris Caudle
> 
> 
> 
> 
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Re: [time-nuts] Poor man's oven

[Bob kb8tq]

Hi

For further info on just why the crystal temperature is such a crazy thing to 
track, check out
Rick’s paper. At first glance it *seems* like it’s a trivial thing. In reality, 
gradients are a very
big deal.

Bob

> On Jun 5, 2017, at 6:38 PM, Charles Steinmetz  wrote:
> 
> Chris wrote:
> 
>> Today all you need is a reliable way to measure the error
>> between the crystals' current temperature and the set  point.
> 
> That's all that's ever been needed.  But it is devilishly difficult to 
> measure the actual quartz temperature, or even to find a good proxy that is 
> easier to measure.
> 
> There is a fair body of published research on these topics, including Rick's 
> (et al.) work on zero-gradient ovens.
> 
> Keep this in mind when someone says they are controlling the "oven 
> temperature" to 0.001C (or even 0.1C).  They are measuring *something*, and 
> may even be holding whatever it is "constant" within fairly tight tolerances. 
>  But they have no idea what the quartz temperature is, and no way to know 
> with precision the relationship between the measured temperature and the 
> actual quartz temperature.
> 
> Some years ago, I consulted for a research group that was using a number of 
> non-contact technologies to measure the temperature of oscillating quartz 
> crystals.  The results were promising, but there were some issues with 
> measuring the temperature (which is, essentially, quantifying tiny random 
> molecular motions within the crystal lattice) against the background of the 
> hugely greater macro motion of the vibating quartz.  I never knew the final 
> conclusions, nor am I aware of any systems designed using these principles or 
> methods.  But it is something to think about if you *really* want a 
> temperature-stable oscillator.
> 
> Best regards,
> 
> Charles
> 
> 
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Re: [time-nuts] Poor man's oven

[Chris Caudle]

On Mon, June 5, 2017 5:38 pm, Charles Steinmetz wrote:
> Some years ago, I consulted for a research group that was using a number
> of non-contact technologies to measure the temperature of oscillating
> quartz crystals.

In most cases what you really care about is the stability of the
frequency, and the temperature of the crystal is just a proxy for that,
correct?
I thought there was some effect where different modes of oscillation
shifted by different amounts with temperature, and if you had two
oscillation circuits running from the same crystal but different modes,
you could use the shift in difference frequency between the two modes to
infer the temperature change.

Found a reference in the Vig tutorial:
S. Schodowski, "Resonator Self-Temperature-Sensing Using a
Dual-Harmonic-Mode Crystal Oscillator," Proc. 43rd Annual Symposium on
Frequency Control, pp. 2-7, 1989, IEEE Catalog No. 89CH2690-6.

>From page 48 of Vig tutorial version 8.5.5.3 May 2013:
As is shown in chapter 4, see “Effects of Harmonics on f vs. T,” the f
vs. T of the fundamental mode of a resonator is different from that of
the third and higher overtones.  This fact is exploited for
“self-temperature sensing” in the microcomputer compensated crystal
oscillator (MCXO). The fundamental (f1) and third overtone (f3)
frequencies are excited simultaneously (“dual mode” excitation) and a
beat frequency fb is generated such that fb = 3f1 - f3 (or fb = f1 -
f3/3). The fb is a monotonic and nearly linear function of
temperature, as is shown above for a 10 MHz 3rd overtone (3.3. MHz
fundamental mode) SC-cut resonator.

The graph shows a line with slope of around 80ppm/deg C.  Not sure what
that translates to in terms of what you could realistically measure and
use for frequency compensation.  I guess you could use that information to
either control an oven or just let the crystal run free and control a
synthesizer for the used output.

-- 
Chris Caudle




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Re: [time-nuts] Poor man's oven

[Chris Albertson]

On Mon, Jun 5, 2017 at 3:38 PM, Charles Steinmetz 
wrote:

> Chris wrote:
>
> Today all you need is a reliable way to measure the error
>> between the crystals' current temperature and the set  point.
>>
>
> That's all that's ever been needed.  But it is devilishly difficult to
> measure the actual quartz temperature, or even to find a good proxy that is
> easier to measure.
>
> There is a fair body of published research on these topics, including
> Rick's (et al.) work on zero-gradient ovens.
>
> Keep this in mind when someone says they are controlling the "oven
> temperature" to 0.001C (or even 0.1C).  They are measuring *something*, and
> may even be holding whatever it is "constant" within fairly tight
> tolerances.  But they have no idea what the quartz temperature is, and no
> way to know with precision the relationship between the measured
> temperature and the actual quartz temperature.
>

How much does this matter?  What we measure is the ambient temperature
inside the insulated box that contains the crystal.   The assumption is
that given some time the temperature will be uniform. OK, so the assumption
is not 100% correct but lets say the crystal is held to a range of 0.1C
 This is a reasonable goal for a home shop made controller.

Here is another question:
Lets assume we place the operating point on the flat part of the curve with
say a 1.0 C absolute error and can hold the relative temperature to 0.1C
 What does this mean in terms of frequency.?

This is a "Poor Man's" oven.   So really the question is this:  I have a
$10 budget, shouldI blow half my budget on a better sensor or is the 75
cent part good enough.  Or is it worth buying a second 75 cent sensor so I
can detect a temperature gradient  With a poor man's budget, I think the
trick is to use a good size thermal mass, chunks of scrap meter are cheap.




>
> Some years ago, I consulted for a research group that was using a number
> of non-contact technologies to measure the temperature of oscillating
> quartz crystals.  The results were promising, but there were some issues
> with measuring the temperature (which is, essentially, quantifying tiny
> random molecular motions within the crystal lattice) against the background
> of the hugely greater macro motion of the vibating quartz.  I never knew
> the final conclusions, nor am I aware of any systems designed using these
> principles or methods.  But it is something to think about if you *really*
> want a temperature-stable oscillator.
>
> Best regards,
>
> Charles
>
>
>
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-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Poor man's oven

[Chris Albertson]

Look at the dates on the uses of these exotic temperature controllers.
Organic compounds and positive temp coefficients and so on.  All these were
used before the current era.  Today all you need is a reliable way to
measure the error between the crystals' current temperature and the set
point.

Those exotic methods were good back when controllers were analog devices
build with op-amps and precision resisters and every math operation cost
you one more op-amp.   Today we can do a million floating point operations
per second for the cost of one kind good op-amp.

The trick with using a uP and it's built-in A/D converters is scale.  You
want the limited 10-bits of revolution to fall over the operating range
which is very narrow, like 1C.   Anything outside of that is either  or
 and only seen at start-up.,  So at start up the the controller is on
"bang-bang" mode then later you have milli-degree resolution over your 1C
range.   Basically you are measuring noise. but your $2 uP can take 100,000
measurments per second and putt tour a digital filter.

Today we can do things the old-time designers even as recent as the 1980's
would not even dream of doing and it cost under $10.

On Mon, Jun 5, 2017 at 1:35 AM, Ulf Kylenfall via time-nuts <
time-nuts@febo.com> wrote:

>   The Crystal heater clip wasa Murata "Posistor" soldered onto a clipand
> they were marketed by Murata.
> I once purchased a small amount of theseand used them as "poor man's
> ovens".
> Although not perfect by far, they did theirjob and kept my UHF gear stable.
> Murata dropped that product many yearsago and I have not been able to
> findany similar product. The Posistors arelisted by eg. Digi-key but they
> do not stock them.
> Ulf - SM6GXV
>
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> mailman/listinfo/time-nuts
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>



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] poor-man's oven

[Chris Albertson]

Yes,  Agree.  I wrote tin the first post that "for your use a resistive
heater would be better"

But everything else, I'd do over.  Drill the aluminum block and use thermal
epoxy to hold the sensor in place.   Use a vacuum insulated mug or bowl for
a cover and let a micro controller run a PID loop to control temperature..
  You can keep it within 0.1C without the need to be a control theory
expert. Another order of magnitude would really hard and expensive

The last temperature controller I made was not as good but keeps a rubidium
oscillator within about a degree.   I put a thruster in the Rb's heat sink
and a micro controller adjusts the fan speed.  The self heat from the Rb
unit is enough. The Rb is about the size and shape of an old 3.5 inch
disk drive so I put it n an old disk drive enclosure that already had a
place for a fan.As crude as this is, it is much better then what I had
which was not control.  The Rb output is better then I have means to
measure now.

So same with the poor man's oven.   It can be very good with very little
effort.What has happened is that now we have nearly free micro
controllers and can use daily sophisticated control algorithms that HP
could not use back in the day. We can actually model non linearities in
the sensor.   We can use a full on PID solution rather then the simple
on/off thermostat.

But no you don't want to cool a crystal, I was not suggesting that.   We
happened to have a high gain amplifier that was in effect counting
electrons.

On Mon, Jun 5, 2017 at 2:15 AM, Attila Kinali  wrote:

> On Sun, 4 Jun 2017 22:01:45 -0700
> Chris Albertson  wrote:
>
> > Voltage is proportional to the product of resistance and absolute
> > temperature.   As an experiment place a voltage across a high value
> > resister like say one 1M  raise the volts until you are near the limit of
> > the resister and connect it via a coupler cadaster to an audio amplifier.
> > You will hear white noise in the speakers.
>
> Yes, Johnson noise increases by about 20% (or about 0.8dB)
> when going from 25°C to 90°C. But Johnson noise is usually
> not the first limiting noise one runs into when designing
> a crystal oscillator. I would rather use a simpler,
> "high temperature" oven and invest the time saved into a
> desgining better oscillator structure.
>
>
> > There is a similar effect in semi conductors.  The best example of this
> is
> > visual noise in digital camera, when you tern the gain way up (set the
> ISO
> > high) you can see it in the photo.
> >
> > All of this is proportion; to absolute.
> >
> > As I remember we ran the "oven" at -20C There was a valve used to flash
> out
> > the air inside with inert welding gas to reduce ice.
>
> If the -20°C was used on the camera, then this is not to reduce Johnson
> noise, but the dark current noise. While the former is due to thermal
> vibration of the atom lattice, the later is due to spontaneous forming
> of electron-hole pairs in the p-n junction region. Thus also their
> temperature characteristics differ: While Johnson noise is linear
> in temperature, dark current noise is (almost) exponential in temperature.
> Going down from room temperature to 0°C is something like a factor 100
> (IIRC, from memory, could be wrong) in noise for a CCD. While for
> a resistor, the difference is almost negligible.
>
> Attila Kinali
> --
> You know, the very powerful and the very stupid have one thing in common.
> They don't alters their views to fit the facts, they alter the facts to
> fit the views, which can be uncomfortable if you happen to be one of the
> facts that needs altering.  -- The Doctor
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>



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Poor man's oven

[Adrian Godwin]

Wax is also used for thermostatic valves in engine cooling systems and
domestic heating systems.

On Mon, Jun 5, 2017 at 1:13 PM, Tim Shoppa  wrote:

> Here is a national new-technology of the art crystal oven from 1956:
>
> http://tf.boulder.nist.gov/general/pdf/1642.pdf
>
> Using the phase change properties of p-dibromobenzene it keeps temperature
> constant to 0.01C. It notes other organic compounds can be used for
> different temperature ranges.
>
> Did this oven technology ever get beyond lab use and into the real crystal
> oven world?
>
> I know in the past decade "thermowax" has been used in Honda lawnmower
> auto-chokes. I don't think it's ever supposed to be anything but solid, but
> it undergoes a phase change that causes it to expand by a large fraction.
>
> Tim N3QE
>
>
>
> Sent from my VAX-11/780
> > On Jun 5, 2017, at 5:16 AM, Clint Jay  wrote:
> >
> > There's a few 'OCXO' designs out there, I'm not qualified to comment on
> the
> > timenutty quality of them but someone else mentioned Hans Summers
> offerings
> > and I would offer Roman Black's simple design (if it's not been mentioned
> > already):
> >
> > http://www.romanblack.com/xoven.htm
> >
> > I've no idea if it's useful but it's ridiculously simple to implement.
> >
> > Both Hans' and Roman's designs are 'on the list' of things to try for
> > myself at some point.
> >
> >> On 5 June 2017 at 09:56, Stephen Tompsett  wrote:
> >>
> >> Not quite as simple as the PTC, an alternative may be:
> >>
> >> http://shop.kuhne-electronic.de/kuhne/en/shop/accessoires/
> >> crystal-heater/Precision+crystal+heater+40%C2%B0+QH40A/?card=724
> >>
> >> No it probably doesn't hold the crystal at it's optimum turn over
> >> temperature, but it will keep the temperature of a crystal approximately
> >> constant especially on a windswept hilltop.
> >>
> >>
> >>> On 05/06/2017 09:35, Ulf Kylenfall via time-nuts wrote:
> >>>  The Crystal heater clip wasa Murata "Posistor" soldered onto a clipand
> >> they were marketed by Murata.
> >>> I once purchased a small amount of theseand used them as "poor man's
> >> ovens".
> >>> Although not perfect by far, they did theirjob and kept my UHF gear
> >> stable.
> >>> Murata dropped that product many yearsago and I have not been able to
> >> findany similar product. The Posistors arelisted by eg. Digi-key but
> they
> >> do not stock them.
> >>> Ulf - SM6GXV
> >>>
> >>> ___
> >>> time-nuts mailing list -- time-nuts@febo.com
> >>> To unsubscribe, go to https://www.febo.com/cgi-bin/
> >> mailman/listinfo/time-nuts
> >>> and follow the instructions there.
> >>>
> >>
> >> --
> >> Stephen Tompsett
> >>
> >> ___
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> >> mailman/listinfo/time-nuts
> >> and follow the instructions there.
> >>
> >
> >
> >
> > --
> > Clint.
> >
> > *No trees were harmed in the sending of this mail. However, a large
> number
> > of electrons were greatly inconvenienced.*
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
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> mailman/listinfo/time-nuts
> > and follow the instructions there.
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Re: [time-nuts] poor-man's oven

[jimlux]

On 6/4/17 10:01 PM, Chris Albertson wrote:

Voltage is proportional to the product of resistance and absolute
temperature.   As an experiment place a voltage across a high value
resister like say one 1M  raise the volts until you are near the limit of
the resister and connect it via a coupler cadaster to an audio amplifier.
You will hear white noise in the speakers.


As in Johnson noise - vrms = sqrt(4kTR)



There is a similar effect in semi conductors.  The best example of this is
visual noise in digital camera, when you tern the gain way up (set the ISO
high) you can see it in the photo.


I believe that's a different mechanism, shot noise.



All of this is proportion; to absolute.

As I remember we ran the "oven" at -20C There was a valve used to flash out
the air inside with inert welding gas to reduce ice.

Some people use vacuum and get to cryogenic temperatures.  But that is
expensive and way-hard without an institutional size budget.




cryogenic (as in LN2 temps) is very hard with TEC it takes many stacked 
devices that wind up looking like a ziggurat.


near vacuum isn't that tough at home - refrigeration vacuum pumps are 
inexpensive.  If it's a one time thing, a sorption pump and one time Ln2 
or Dry Ice can get you pretty empty as a one shot. Then you seal it off 
and it's done.
the Bell Jar - http://www.belljar.net/  is a handy reference of vacuum 
hacking stuff








What is the reason why you'd expect less noise with a TEC?

Attila Kinali

--
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] Poor man's oven

[Tim Shoppa]

Here is a national new-technology of the art crystal oven from 1956: 

http://tf.boulder.nist.gov/general/pdf/1642.pdf

Using the phase change properties of p-dibromobenzene it keeps temperature 
constant to 0.01C. It notes other organic compounds can be used for different 
temperature ranges.

Did this oven technology ever get beyond lab use and into the real crystal oven 
world?

I know in the past decade "thermowax" has been used in Honda lawnmower 
auto-chokes. I don't think it's ever supposed to be anything but solid, but it 
undergoes a phase change that causes it to expand by a large fraction.

Tim N3QE



Sent from my VAX-11/780
> On Jun 5, 2017, at 5:16 AM, Clint Jay  wrote:
> 
> There's a few 'OCXO' designs out there, I'm not qualified to comment on the
> timenutty quality of them but someone else mentioned Hans Summers offerings
> and I would offer Roman Black's simple design (if it's not been mentioned
> already):
> 
> http://www.romanblack.com/xoven.htm
> 
> I've no idea if it's useful but it's ridiculously simple to implement.
> 
> Both Hans' and Roman's designs are 'on the list' of things to try for
> myself at some point.
> 
>> On 5 June 2017 at 09:56, Stephen Tompsett  wrote:
>> 
>> Not quite as simple as the PTC, an alternative may be:
>> 
>> http://shop.kuhne-electronic.de/kuhne/en/shop/accessoires/
>> crystal-heater/Precision+crystal+heater+40%C2%B0+QH40A/?card=724
>> 
>> No it probably doesn't hold the crystal at it's optimum turn over
>> temperature, but it will keep the temperature of a crystal approximately
>> constant especially on a windswept hilltop.
>> 
>> 
>>> On 05/06/2017 09:35, Ulf Kylenfall via time-nuts wrote:
>>>  The Crystal heater clip wasa Murata "Posistor" soldered onto a clipand
>> they were marketed by Murata.
>>> I once purchased a small amount of theseand used them as "poor man's
>> ovens".
>>> Although not perfect by far, they did theirjob and kept my UHF gear
>> stable.
>>> Murata dropped that product many yearsago and I have not been able to
>> findany similar product. The Posistors arelisted by eg. Digi-key but they
>> do not stock them.
>>> Ulf - SM6GXV
>>> 
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/
>> mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>> 
>> 
>> --
>> Stephen Tompsett
>> 
>> ___
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>> mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
> 
> 
> 
> -- 
> Clint.
> 
> *No trees were harmed in the sending of this mail. However, a large number
> of electrons were greatly inconvenienced.*
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Re: [time-nuts] Poor man's oven

[Bob kb8tq]

Hi

The posistor approach to heating a crystal was originally pioneered in Russia. 
Morion was 
building vacuum insulated / PTC controlled OCXO’s long before the PTC parts 
started showing
up more generally in the 1970’s. 

Bob

> On Jun 5, 2017, at 4:35 AM, Ulf Kylenfall via time-nuts  
> wrote:
> 
>   The Crystal heater clip wasa Murata "Posistor" soldered onto a clipand they 
> were marketed by Murata.
> I once purchased a small amount of theseand used them as "poor man's ovens".
> Although not perfect by far, they did theirjob and kept my UHF gear stable.
> Murata dropped that product many yearsago and I have not been able to findany 
> similar product. The Posistors arelisted by eg. Digi-key but they do not 
> stock them.
> Ulf - SM6GXV
> 
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Re: [time-nuts] Poor man's oven

[Clint Jay]

There's a few 'OCXO' designs out there, I'm not qualified to comment on the
timenutty quality of them but someone else mentioned Hans Summers offerings
and I would offer Roman Black's simple design (if it's not been mentioned
already):

http://www.romanblack.com/xoven.htm

I've no idea if it's useful but it's ridiculously simple to implement.

Both Hans' and Roman's designs are 'on the list' of things to try for
myself at some point.

On 5 June 2017 at 09:56, Stephen Tompsett  wrote:

> Not quite as simple as the PTC, an alternative may be:
>
> http://shop.kuhne-electronic.de/kuhne/en/shop/accessoires/
> crystal-heater/Precision+crystal+heater+40%C2%B0+QH40A/?card=724
>
> No it probably doesn't hold the crystal at it's optimum turn over
> temperature, but it will keep the temperature of a crystal approximately
> constant especially on a windswept hilltop.
>
>
> On 05/06/2017 09:35, Ulf Kylenfall via time-nuts wrote:
> >   The Crystal heater clip wasa Murata "Posistor" soldered onto a clipand
> they were marketed by Murata.
> > I once purchased a small amount of theseand used them as "poor man's
> ovens".
> > Although not perfect by far, they did theirjob and kept my UHF gear
> stable.
> > Murata dropped that product many yearsago and I have not been able to
> findany similar product. The Posistors arelisted by eg. Digi-key but they
> do not stock them.
> > Ulf - SM6GXV
> >
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> > and follow the instructions there.
> >
>
> --
> Stephen Tompsett
>
> ___
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> mailman/listinfo/time-nuts
> and follow the instructions there.
>



-- 
Clint.

*No trees were harmed in the sending of this mail. However, a large number
of electrons were greatly inconvenienced.*
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Re: [time-nuts] poor-man's oven

[Attila Kinali]

On Sun, 4 Jun 2017 22:01:45 -0700
Chris Albertson  wrote:

> Voltage is proportional to the product of resistance and absolute
> temperature.   As an experiment place a voltage across a high value
> resister like say one 1M  raise the volts until you are near the limit of
> the resister and connect it via a coupler cadaster to an audio amplifier.
> You will hear white noise in the speakers.

Yes, Johnson noise increases by about 20% (or about 0.8dB)
when going from 25°C to 90°C. But Johnson noise is usually
not the first limiting noise one runs into when designing
a crystal oscillator. I would rather use a simpler,
"high temperature" oven and invest the time saved into a
desgining better oscillator structure.


> There is a similar effect in semi conductors.  The best example of this is
> visual noise in digital camera, when you tern the gain way up (set the ISO
> high) you can see it in the photo.
> 
> All of this is proportion; to absolute.
> 
> As I remember we ran the "oven" at -20C There was a valve used to flash out
> the air inside with inert welding gas to reduce ice.

If the -20°C was used on the camera, then this is not to reduce Johnson
noise, but the dark current noise. While the former is due to thermal
vibration of the atom lattice, the later is due to spontaneous forming
of electron-hole pairs in the p-n junction region. Thus also their
temperature characteristics differ: While Johnson noise is linear
in temperature, dark current noise is (almost) exponential in temperature.
Going down from room temperature to 0°C is something like a factor 100
(IIRC, from memory, could be wrong) in noise for a CCD. While for
a resistor, the difference is almost negligible.

Attila Kinali
-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] Poor man's oven

[Stephen Tompsett]

Not quite as simple as the PTC, an alternative may be:

http://shop.kuhne-electronic.de/kuhne/en/shop/accessoires/crystal-heater/Precision+crystal+heater+40%C2%B0+QH40A/?card=724

No it probably doesn't hold the crystal at it's optimum turn over
temperature, but it will keep the temperature of a crystal approximately
constant especially on a windswept hilltop.


On 05/06/2017 09:35, Ulf Kylenfall via time-nuts wrote:
>   The Crystal heater clip wasa Murata "Posistor" soldered onto a clipand they 
> were marketed by Murata.
> I once purchased a small amount of theseand used them as "poor man's ovens".
> Although not perfect by far, they did theirjob and kept my UHF gear stable.
> Murata dropped that product many yearsago and I have not been able to findany 
> similar product. The Posistors arelisted by eg. Digi-key but they do not 
> stock them.
> Ulf - SM6GXV
>
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[time-nuts] Poor man's oven

[Ulf Kylenfall via time-nuts]

  The Crystal heater clip wasa Murata "Posistor" soldered onto a clipand they 
were marketed by Murata.
I once purchased a small amount of theseand used them as "poor man's ovens".
Although not perfect by far, they did theirjob and kept my UHF gear stable.
Murata dropped that product many yearsago and I have not been able to findany 
similar product. The Posistors arelisted by eg. Digi-key but they do not stock 
them.
Ulf - SM6GXV

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Re: [time-nuts] poor-man's oven

[Chris Albertson]

Voltage is proportional to the product of resistance and absolute
temperature.   As an experiment place a voltage across a high value
resister like say one 1M  raise the volts until you are near the limit of
the resister and connect it via a coupler cadaster to an audio amplifier.
You will hear white noise in the speakers.

There is a similar effect in semi conductors.  The best example of this is
visual noise in digital camera, when you tern the gain way up (set the ISO
high) you can see it in the photo.

All of this is proportion; to absolute.

As I remember we ran the "oven" at -20C There was a valve used to flash out
the air inside with inert welding gas to reduce ice.

Some people use vacuum and get to cryogenic temperatures.  But that is
expensive and way-hard without an institutional size budget.





> What is the reason why you'd expect less noise with a TEC?
>
> Attila Kinali
>
> --
> You know, the very powerful and the very stupid have one thing in common.
> They don't alters their views to fit the facts, they alter the facts to
> fit the views, which can be uncomfortable if you happen to be one of the
> facts that needs altering.  -- The Doctor
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> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> and follow the instructions there.
>



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] poor-man's oven

[Bruce Griffiths]

Yes, I have a TEC mounted on a convection heatsink that illustrates that point.
Initially ice forms on the cold surface but eventually the heatsink temperature 
rises sufficiently that the ice melts. A larger blown heatsink or perhaps a 
water cooled heatsink would be necessary if this setup was intended for 
anything other than a demonstration of this issue.

Bruce  

> On 05 June 2017 at 13:58 Bob kb8tq  wrote:
> 
> 
> Hi
> 
> Many times people underestimate the amount of heat sinking required with a 
> TEC. If you get into fans, they 
> introduce a whole new set of issues ….It’s not just the heat you are getting 
> out of the “oven”. The TEC it’s self
> makes a pretty good thermal short (compared to foam insulation). You have to 
> “pump” across that as well. 
> 
> Bob
> 
> > On Jun 4, 2017, at 9:38 PM, Ellen Franke  wrote:
> > 
> > My concern with using a TEC is that, heating or cooling, you are left with 
> > one cold surface and that surface will collect condensation which is a 
> > source for corrosion.
> > John WA4WDL
> > 
> > 
> >> On June 4, 2017 at 8:12 PM Attila Kinali  wrote:
> >> 
> >> 
> >> Moin Chris,
> >> 
> >> On Sun, 4 Jun 2017 13:49:29 -0700
> >> Chris Albertson  wrote:
> >> 
> >>> We used the pelter because we preferred a cool "oven" to a hot one.   The
> >>> theory has that we get less electronic noise so we ran the TEC in cooling
> >>> mode.   But for your use a resistive heater would be cheaper.   But in
> >>> either case you see a coffee mug with a round chunk of Al shoved in and
> >>> heat sink fins showing.
> >> 
> >> What is the reason why you'd expect less noise with a TEC?
> >> 
> >>Attila Kinali
> >> 
> >> -- 
> >> You know, the very powerful and the very stupid have one thing in common.
> >> They don't alters their views to fit the facts, they alter the facts to
> >> fit the views, which can be uncomfortable if you happen to be one of the
> >> facts that needs altering.  -- The Doctor
> >> ___
> >> time-nuts mailing list -- time-nuts@febo.com
> >> To unsubscribe, go to 
> >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> >> and follow the instructions there.
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> > and follow the instructions there.
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Re: [time-nuts] poor-man's oven

[Bob kb8tq]

Hi

Many times people underestimate the amount of heat sinking required with a TEC. 
If you get into fans, they 
introduce a whole new set of issues ….It’s not just the heat you are getting 
out of the “oven”. The TEC it’s self
makes a pretty good thermal short (compared to foam insulation). You have to 
“pump” across that as well. 

Bob

> On Jun 4, 2017, at 9:38 PM, Ellen Franke  wrote:
> 
> My concern with using a TEC is that, heating or cooling, you are left with 
> one cold surface and that surface will collect condensation which is a source 
> for corrosion.
> John WA4WDL
> 
> 
>> On June 4, 2017 at 8:12 PM Attila Kinali  wrote:
>> 
>> 
>> Moin Chris,
>> 
>> On Sun, 4 Jun 2017 13:49:29 -0700
>> Chris Albertson  wrote:
>> 
>>> We used the pelter because we preferred a cool "oven" to a hot one.   The
>>> theory has that we get less electronic noise so we ran the TEC in cooling
>>> mode.   But for your use a resistive heater would be cheaper.   But in
>>> either case you see a coffee mug with a round chunk of Al shoved in and
>>> heat sink fins showing.
>> 
>> What is the reason why you'd expect less noise with a TEC?
>> 
>>  Attila Kinali
>> 
>> -- 
>> You know, the very powerful and the very stupid have one thing in common.
>> They don't alters their views to fit the facts, they alter the facts to
>> fit the views, which can be uncomfortable if you happen to be one of the
>> facts that needs altering.  -- The Doctor
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
> ___
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Re: [time-nuts] poor-man's oven

[Bruce Griffiths]

Really??

The circuitry employed is something of a joke surely?

Relying on the   MOSFET characteristics to limit warm up current is unwise.

The temperature sensor also would appear to suffer from large variations in 
output from one part to another.

Bruce

> 
> On 05 June 2017 at 01:21 "R. Kuehn"  wrote:
> 
> Maybe you want to check out the work of Hans Summers he has done some
> impressive low cost stuff:
> http://www.hanssummers.com/ocxosynth.html
> http://www.qrp-labs.com/ocxokit.html
> 
> Ralph
> 
> On Sun, Jun 4, 2017 at 07:19 jimlux  wrote:
> 
> > > 
> > I recall some years ago folks were talking about putting a PTC
> > thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the 
> > frequency
> > as a sort of poor-man's OCXO.
> > It's also referenced at
> > http://www.setileague.org/askdr/xtaloven.htm
> > where he says "order of magnitude improvement" with no numbers 
> > (from 1%
> > to 0.1% or from 1 ppb to 0.1 ppb?)
> > 
> > I wonder how well that actually works.
> > 
> > Say you bought an inexpensive (perhaps non TC) XO and an equally
> > inexpensive thermistor, glued on on the other, hooked em both up to 
> > 3.3
> > or 5V.
> > 
> > Yeah, there's issues with room air blowing on it, and tolerances in 
> > both
> > the XO and thermistor, so your absolute frequency accuracy may not 
> > be so
> > hot. But what sort of medium to long term performance can one 
> > expect.
> > 
> > I did some searches, because I'm sure we've discussed this before, 
> > but I
> > couldn't find it. There was some stuff from Oct 2007, but that was 
> > in
> > the context of a more complex circuit, and the thermistor was the
> > sensor. (discussions of TE devices too)
> > 
> > ___
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> > and follow the instructions there.
> > 
> > > 
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Re: [time-nuts] poor-man's oven

[Ellen Franke]

My concern with using a TEC is that, heating or cooling, you are left with one 
cold surface and that surface will collect condensation which is a source for 
corrosion.
John WA4WDL


> On June 4, 2017 at 8:12 PM Attila Kinali  wrote:
> 
> 
> Moin Chris,
> 
> On Sun, 4 Jun 2017 13:49:29 -0700
> Chris Albertson  wrote:
> 
> > We used the pelter because we preferred a cool "oven" to a hot one.   The
> > theory has that we get less electronic noise so we ran the TEC in cooling
> > mode.   But for your use a resistive heater would be cheaper.   But in
> > either case you see a coffee mug with a round chunk of Al shoved in and
> > heat sink fins showing.
> 
> What is the reason why you'd expect less noise with a TEC?
> 
>   Attila Kinali
> 
> -- 
> You know, the very powerful and the very stupid have one thing in common.
> They don't alters their views to fit the facts, they alter the facts to
> fit the views, which can be uncomfortable if you happen to be one of the
> facts that needs altering.  -- The Doctor
> ___
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> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] poor-man's oven

[Attila Kinali]

Moin Chris,

On Sun, 4 Jun 2017 13:49:29 -0700
Chris Albertson  wrote:

> We used the pelter because we preferred a cool "oven" to a hot one.   The
> theory has that we get less electronic noise so we ran the TEC in cooling
> mode.   But for your use a resistive heater would be cheaper.   But in
> either case you see a coffee mug with a round chunk of Al shoved in and
> heat sink fins showing.

What is the reason why you'd expect less noise with a TEC?

Attila Kinali

-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] poor-man's oven

[Chris Albertson]

Look at the temperature coefficient of your XO.  Then figure a very simply
control loop and a thermistor will keep a block of aluminum within 0.1C of
a set point.  Use a decent size block and insulation

We drilled a deep hole then epoxied the thermistor.  I think this step is
important as you want to measure the center of the black, not the surface..
   Then epoxied a TEC (aka Peltier device) to the Al Block.  TECs are nice
because they can both cool and heat.   On the other side other TEC was a
rather large heat sink (or heat source depending on the polarity) a uP and
a PID loop controlled the output current.   Place an insulator over the
controlled end of the block.   I think a stainless steel vacuum insulated
coffee mug works well.

I think cheap thermistors are OK as they will never, in use, see
temperature swings of more then 0.1C so who care if they are linear or not.
They are all linear enough over a short range.  What you pay for is being
perfect over a 100C range, you don't need that.


We used the pelter because we preferred a cool "oven" to a hot one.   The
theory has that we get less electronic noise so we ran the TEC in cooling
mode.   But for your use a resistive heater would be cheaper.   But in
either case you see a coffee mug with a round chunk of Al shoved in and
heat sink fins showing.

When I was doing some contraction work, I thought of it would be fun to
toss an XO in the big hole that was going to get a truckload of concrete
poured into it.  The temperature down there would be very stable.



On Sun, Jun 4, 2017 at 5:13 AM, jimlux  wrote:

> I recall some years ago folks were talking about putting a PTC thermistor
> on the TCXO of a FlexRadio SDR1000 to stabilize the frequency as a sort of
> poor-man's OCXO.
> It's also referenced at
> http://www.setileague.org/askdr/xtaloven.htm
> where he says "order of magnitude improvement" with no numbers (from 1% to
> 0.1% or from 1 ppb to 0.1 ppb?)
>
> I wonder how well that actually works.
>
> Say you bought an inexpensive (perhaps non TC) XO and an equally
> inexpensive thermistor, glued on on the other, hooked em both up to 3.3 or
> 5V.
>
> Yeah, there's issues with room air blowing on it, and tolerances in both
> the XO and thermistor, so your absolute frequency accuracy may not be so
> hot. But what sort of medium to long term performance can one expect.
>
> I did some searches, because I'm sure we've discussed this before, but I
> couldn't find it.  There was some stuff from Oct 2007, but that was in the
> context of a more complex circuit, and the thermistor was the sensor.
> (discussions of TE devices too)
> ___
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> and follow the instructions there.
>



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] poor-man's oven

[R. Kuehn]

Maybe you want to check out the work of Hans Summers he has done some
impressive low cost stuff:
http://www.hanssummers.com/ocxosynth.html
http://www.qrp-labs.com/ocxokit.html

Ralph

On Sun, Jun 4, 2017 at 07:19 jimlux  wrote:

> I recall some years ago folks were talking about putting a PTC
> thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the frequency
> as a sort of poor-man's OCXO.
> It's also referenced at
> http://www.setileague.org/askdr/xtaloven.htm
> where he says "order of magnitude improvement" with no numbers (from 1%
> to 0.1% or from 1 ppb to 0.1 ppb?)
>
> I wonder how well that actually works.
>
> Say you bought an inexpensive (perhaps non TC) XO and an equally
> inexpensive thermistor, glued on on the other, hooked em both up to 3.3
> or 5V.
>
> Yeah, there's issues with room air blowing on it, and tolerances in both
> the XO and thermistor, so your absolute frequency accuracy may not be so
> hot. But what sort of medium to long term performance can one expect.
>
> I did some searches, because I'm sure we've discussed this before, but I
> couldn't find it.  There was some stuff from Oct 2007, but that was in
> the context of a more complex circuit, and the thermistor was the
> sensor. (discussions of TE devices too)
> ___
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Re: [time-nuts] poor-man's oven

[Bob kb8tq]

Hi

If you have not done so already, you might try bumping the temperature a bit to 
search for the 
upper turn in the crystal curve. Based on the data in the plots, you do have an 
AT that is cut 
with an upper turn. 

Bob

> On Jun 4, 2017, at 11:30 AM, Dan Rae  wrote:
> 
> 

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Re: [time-nuts] poor-man's oven

[Dan Rae]

The attached plot shows the sort of improvement in warm up time and 
stability of a simple "oven" made by attaching a Darlington heater 
transistor and thermistor to a Crystek 100 MHz oscillator, adjusted to 
set the osc temp to around 35C and wrapping it all in foam.  In this 
application, a DDS clock for an HF transceiver, the result was well 
worthwhile.


Dan - ac6ao




Crystek Test.doc
Description: MS-Word document
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Re: [time-nuts] poor-man's oven

[Bob kb8tq]

Hi

There is no way to know how every outfit makes their products. My guess is that
the temperature compensation “stuff” is pretty stable. At least it has been on 
all 
the product I’ve designed :) I’d bet that the crystals in the TCXO’s are the 
culprit. 
In some of the factories I’ve visited, they package their own crystals. They 
bring in the
blanks pre-sorted and take it from there. The aging pretty much all comes from 
the
plating / packaging process. It would not surprise me to find that long term 
aging is 
not a major focus on parts headed for sort lifespan consumer electronics ...

Bob

> On Jun 4, 2017, at 9:45 AM, Tim Shoppa  wrote:
> 
> Bob, at the same time, look at all the guys here who absolutely insist that
> the only way to use a double-oven OCXO is to put it in a tightly
> temperature controlled environment. "Nuts", yes, but that's why we're here!
> 
> I myself have been extremely disappointed with the aging characteristics of
> low-end TCXO's. They seem to age even worse than plain old crystal
> oscillators, My theory, is this is because the temperature compensation
> components are themselves aging more than an AT cut crystal does by itself,
> but I've never ripped into one (they're way too tiny to rip into anyway!).
> 
> Tim N3QE
> 
> On Sun, Jun 4, 2017 at 9:36 AM, Bob kb8tq  wrote:
> 
>> Hi
>> 
>> The gotcha is that you have multiple systems working against each other.
>> The crystal in the TCXO has
>> one temperature characteristic. The compensation in the TCXO has a
>> temperature characteristic. They
>> cancel each other out to a limited degree. The residual slope may (or may
>> not) be as shallow as you
>> might think. Your PTC is at an arbitrary point on the residual curve. A
>> somewhat more subtle issue is
>> the gradient between your PTC, the crystal, and the compensation as it
>> cycles.
>> 
>> If the TCXO really isn’t a full TCXO, then some of this goes away. A +/- 2
>> ppm 0-50C “TCXO" may not have
>> any compensation in it at all. Some 0 to 70C parts are done as 2 ppm 0 to
>> 50 and only compensated at the
>> hot end. They actually may be worse with the PTC than at room...
>> 
>> Yes this all assumes an AT cut in the TCXO. That’s a pretty good bet ….
>> 
>> Bob
>> 
>> 
>>> On Jun 4, 2017, at 8:13 AM, jimlux  wrote:
>>> 
>>> I recall some years ago folks were talking about putting a PTC
>> thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the frequency as
>> a sort of poor-man's OCXO.
>>> It's also referenced at
>>> http://www.setileague.org/askdr/xtaloven.htm
>>> where he says "order of magnitude improvement" with no numbers (from 1%
>> to 0.1% or from 1 ppb to 0.1 ppb?)
>>> 
>>> I wonder how well that actually works.
>>> 
>>> Say you bought an inexpensive (perhaps non TC) XO and an equally
>> inexpensive thermistor, glued on on the other, hooked em both up to 3.3 or
>> 5V.
>>> 
>>> Yeah, there's issues with room air blowing on it, and tolerances in both
>> the XO and thermistor, so your absolute frequency accuracy may not be so
>> hot. But what sort of medium to long term performance can one expect.
>>> 
>>> I did some searches, because I'm sure we've discussed this before, but I
>> couldn't find it.  There was some stuff from Oct 2007, but that was in the
>> context of a more complex circuit, and the thermistor was the sensor.
>> (discussions of TE devices too)
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
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>> mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
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>> and follow the instructions there.
>> 
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Re: [time-nuts] poor-man's oven

[Tim Shoppa]

Bob, at the same time, look at all the guys here who absolutely insist that
the only way to use a double-oven OCXO is to put it in a tightly
temperature controlled environment. "Nuts", yes, but that's why we're here!

I myself have been extremely disappointed with the aging characteristics of
low-end TCXO's. They seem to age even worse than plain old crystal
oscillators, My theory, is this is because the temperature compensation
components are themselves aging more than an AT cut crystal does by itself,
but I've never ripped into one (they're way too tiny to rip into anyway!).

Tim N3QE

On Sun, Jun 4, 2017 at 9:36 AM, Bob kb8tq  wrote:

> Hi
>
> The gotcha is that you have multiple systems working against each other.
> The crystal in the TCXO has
> one temperature characteristic. The compensation in the TCXO has a
> temperature characteristic. They
> cancel each other out to a limited degree. The residual slope may (or may
> not) be as shallow as you
> might think. Your PTC is at an arbitrary point on the residual curve. A
> somewhat more subtle issue is
> the gradient between your PTC, the crystal, and the compensation as it
> cycles.
>
> If the TCXO really isn’t a full TCXO, then some of this goes away. A +/- 2
> ppm 0-50C “TCXO" may not have
> any compensation in it at all. Some 0 to 70C parts are done as 2 ppm 0 to
> 50 and only compensated at the
> hot end. They actually may be worse with the PTC than at room...
>
> Yes this all assumes an AT cut in the TCXO. That’s a pretty good bet ….
>
> Bob
>
>
> > On Jun 4, 2017, at 8:13 AM, jimlux  wrote:
> >
> > I recall some years ago folks were talking about putting a PTC
> thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the frequency as
> a sort of poor-man's OCXO.
> > It's also referenced at
> > http://www.setileague.org/askdr/xtaloven.htm
> > where he says "order of magnitude improvement" with no numbers (from 1%
> to 0.1% or from 1 ppb to 0.1 ppb?)
> >
> > I wonder how well that actually works.
> >
> > Say you bought an inexpensive (perhaps non TC) XO and an equally
> inexpensive thermistor, glued on on the other, hooked em both up to 3.3 or
> 5V.
> >
> > Yeah, there's issues with room air blowing on it, and tolerances in both
> the XO and thermistor, so your absolute frequency accuracy may not be so
> hot. But what sort of medium to long term performance can one expect.
> >
> > I did some searches, because I'm sure we've discussed this before, but I
> couldn't find it.  There was some stuff from Oct 2007, but that was in the
> context of a more complex circuit, and the thermistor was the sensor.
> (discussions of TE devices too)
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Re: [time-nuts] poor-man's oven

[Bob kb8tq]

Hi

The gotcha is that you have multiple systems working against each other. The 
crystal in the TCXO has
one temperature characteristic. The compensation in the TCXO has a temperature 
characteristic. They
cancel each other out to a limited degree. The residual slope may (or may not) 
be as shallow as you
might think. Your PTC is at an arbitrary point on the residual curve. A 
somewhat more subtle issue is 
the gradient between your PTC, the crystal, and the compensation as it cycles. 

If the TCXO really isn’t a full TCXO, then some of this goes away. A +/- 2 ppm 
0-50C “TCXO" may not have
any compensation in it at all. Some 0 to 70C parts are done as 2 ppm 0 to 50 
and only compensated at the 
hot end. They actually may be worse with the PTC than at room...

Yes this all assumes an AT cut in the TCXO. That’s a pretty good bet ….

Bob


> On Jun 4, 2017, at 8:13 AM, jimlux  wrote:
> 
> I recall some years ago folks were talking about putting a PTC thermistor on 
> the TCXO of a FlexRadio SDR1000 to stabilize the frequency as a sort of 
> poor-man's OCXO.
> It's also referenced at
> http://www.setileague.org/askdr/xtaloven.htm
> where he says "order of magnitude improvement" with no numbers (from 1% to 
> 0.1% or from 1 ppb to 0.1 ppb?)
> 
> I wonder how well that actually works.
> 
> Say you bought an inexpensive (perhaps non TC) XO and an equally inexpensive 
> thermistor, glued on on the other, hooked em both up to 3.3 or 5V.
> 
> Yeah, there's issues with room air blowing on it, and tolerances in both the 
> XO and thermistor, so your absolute frequency accuracy may not be so hot. But 
> what sort of medium to long term performance can one expect.
> 
> I did some searches, because I'm sure we've discussed this before, but I 
> couldn't find it.  There was some stuff from Oct 2007, but that was in the 
> context of a more complex circuit, and the thermistor was the sensor. 
> (discussions of TE devices too)
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

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Re: [time-nuts] poor-man's oven

[Mike Naruta AA8K]

My SDR-1000 showed substantially less "WWV drift" after adding 
the PTC thermistor to the TCXO.  Sorry, no measurements because 
that was before I had a GPSDO.


Mikr - AA8K


On 06/04/2017 08:13 AM, jimlux wrote:
I recall some years ago folks were talking about putting a PTC 
thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the 
frequency as a sort of poor-man's OCXO.

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Re: [time-nuts] poor-man's oven

[John Ackermann N8UR]

We did this years ago on a 430 MHz data radio with an utterly uncompensated 
crystal that would drift through the passband.  After building our own for a 
while, we discovered that Yaesu had something even better available through 
their replacement parts shop -- a spring clip with PTC that snapped tightly 
over the crystal case.  I never did any formal measurements, but it did improve 
stability quite a bit for radios that were sitting in uncontrolled environments.

John

On Jun 4, 2017, 8:18 AM, at 8:18 AM, jimlux  wrote:
>I recall some years ago folks were talking about putting a PTC 
>thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the
>frequency 
>as a sort of poor-man's OCXO.
>It's also referenced at
>http://www.setileague.org/askdr/xtaloven.htm
>where he says "order of magnitude improvement" with no numbers (from 1%
>
>to 0.1% or from 1 ppb to 0.1 ppb?)
>
>I wonder how well that actually works.
>
>Say you bought an inexpensive (perhaps non TC) XO and an equally 
>inexpensive thermistor, glued on on the other, hooked em both up to 3.3
>
>or 5V.
>
>Yeah, there's issues with room air blowing on it, and tolerances in
>both 
>the XO and thermistor, so your absolute frequency accuracy may not be
>so 
>hot. But what sort of medium to long term performance can one expect.
>
>I did some searches, because I'm sure we've discussed this before, but
>I 
>couldn't find it.  There was some stuff from Oct 2007, but that was in 
>the context of a more complex circuit, and the thermistor was the 
>sensor. (discussions of TE devices too)
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>time-nuts mailing list -- time-nuts@febo.com
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[time-nuts] poor-man's oven

[jimlux]

I recall some years ago folks were talking about putting a PTC 
thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the frequency 
as a sort of poor-man's OCXO.

It's also referenced at
http://www.setileague.org/askdr/xtaloven.htm
where he says "order of magnitude improvement" with no numbers (from 1% 
to 0.1% or from 1 ppb to 0.1 ppb?)


I wonder how well that actually works.

Say you bought an inexpensive (perhaps non TC) XO and an equally 
inexpensive thermistor, glued on on the other, hooked em both up to 3.3 
or 5V.


Yeah, there's issues with room air blowing on it, and tolerances in both 
the XO and thermistor, so your absolute frequency accuracy may not be so 
hot. But what sort of medium to long term performance can one expect.


I did some searches, because I'm sure we've discussed this before, but I 
couldn't find it.  There was some stuff from Oct 2007, but that was in 
the context of a more complex circuit, and the thermistor was the 
sensor. (discussions of TE devices too)

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