Discussion:
Any guesses as to how Citizen is claiming ±1 second/year with using this AT-cut 8.4MHz XTAL?
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t***@joshreply.com
2018-04-11 16:26:27 UTC
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That comes out to about 30ppb, and this is a pocket watch so they don’t seem
to depend on the temp stabilization of being attached to a human wrist.



https://www.ablogtowatch.com/wp-content/uploads/2018/03/Citizen-Cal-0100-Eco
-Drive-Movement-04.jpg



I’ve been reading about the new watch that contains this crystal for about a
month, but just saw some more detail today…

---

AT-CUT QUARTZ CRYSTAL OSCILLATOR

While AT-cut quartz crystals have indeed been in production and use since as
early as 1934, the technology is more common in larger applications and not
necessarily wristwatches. To address the needs of individuals seeking only
the most accurate performance in a wristwatch, Citizen sought to apply and
optimize this available technology in a way that could serve watch consumers
on a more direct and personal level. When working to reach the accuracy of
the Cal.0100, Citizen opted for an AT-cut quartz oscillator instead of a
more traditional tuning fork shape (XY cut). Perhaps most notably, AT-cut
variations allow for greater temperature tolerances, specifically in the
range of -40°C to +125°C. Additionally, this configuration allows for
reduced deviations caused by wearer orientation, which can cause significant
changes in accuracy that aren't negligible when attempting this kind of
performance. As a result, wearers will not have to worry about errors caused
by spatial orientation and positioning becomes less of a concern. The same
can be said about durability, which Citizen also improved upon in
conjunction with the AT-cut oscillator. After all, shock experienced in
day-to-day situations could easily prove detrimental even for quartz
movements. And when the goal is an annual accuracy of ±1 second, that just
isn't acceptable.



https://www.ablogtowatch.com/citizen-cal-0100-eco-drive-watch-movement/

---



Is this possible with an MXCO running across this wide temp range? How are
they compensating for aging at this level of precision?



Thanks!

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Poul-Henning Kamp
2018-04-11 20:15:42 UTC
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--------
That comes out to about 30ppb, and this is a pocket watch so they don't seem
to depend on the temp stabilization of being attached to a human wrist.
For an application where neither phase noise nor jitter matters,
it is certainly feasible to measure the tempco of the X-tal at the
factory and let a micro-power computer use temperature measurements
to model the "perfect" frequency and phase.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
***@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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Bob kb8tq
2018-04-11 20:24:19 UTC
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Hi

Guess at the aging

Cut the crystal so it’s fairly flat at 25 to 35C

Do a basic / simple temperature compensation (TCXO)

…. and count on the errors to average out.

The success of all that will depend a lot on how close your wrist is to the
environment they used for their guesswork. Did they count on you taking
the watch off at night or not? What temperature is the room at? …..

Before you say it can’t be done, the whole “average out” thing is how time
pieces have been done for hundreds of years. The device may swing this
way and that …. done properly it eventually averages out. How well it works
for you … that depends.

Bob
Post by t***@joshreply.com
That comes out to about 30ppb, and this is a pocket watch so they don’t seem
to depend on the temp stabilization of being attached to a human wrist.
https://www.ablogtowatch.com/wp-content/uploads/2018/03/Citizen-Cal-0100-Eco
-Drive-Movement-04.jpg
I’ve been reading about the new watch that contains this crystal for about a
month, but just saw some more detail today
---
AT-CUT QUARTZ CRYSTAL OSCILLATOR
While AT-cut quartz crystals have indeed been in production and use since as
early as 1934, the technology is more common in larger applications and not
necessarily wristwatches. To address the needs of individuals seeking only
the most accurate performance in a wristwatch, Citizen sought to apply and
optimize this available technology in a way that could serve watch consumers
on a more direct and personal level. When working to reach the accuracy of
the Cal.0100, Citizen opted for an AT-cut quartz oscillator instead of a
more traditional tuning fork shape (XY cut). Perhaps most notably, AT-cut
variations allow for greater temperature tolerances, specifically in the
range of -40°C to +125°C. Additionally, this configuration allows for
reduced deviations caused by wearer orientation, which can cause significant
changes in accuracy that aren't negligible when attempting this kind of
performance. As a result, wearers will not have to worry about errors caused
by spatial orientation and positioning becomes less of a concern. The same
can be said about durability, which Citizen also improved upon in
conjunction with the AT-cut oscillator. After all, shock experienced in
day-to-day situations could easily prove detrimental even for quartz
movements. And when the goal is an annual accuracy of ±1 second, that just
isn't acceptable.
https://www.ablogtowatch.com/citizen-cal-0100-eco-drive-watch-movement/
---
Is this possible with an MXCO running across this wide temp range? How are
they compensating for aging at this level of precision?
Thanks!
_______________________________________________
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and follow the instructions there.
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Mike Cook
2018-04-11 22:03:44 UTC
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I have a Citizen A660 movement which was spec’d at +/- 5 secs per year. I monitored it from when I bought it in December 2010 until its battery failed on 03/11/2012.
It was in spec when both on and off the wrist (off the wrist it was in a drawer at a constant temperature and the accuracy was a stability was lower) .
The error in the first 18 months gave a yearly rate of +1,2 secs. Not bad. So maybe the new movement is just getting the advantage of higher frequency so that their cycle hops are finer grained.
Post by Bob kb8tq
Hi
Guess at the aging
Cut the crystal so it’s fairly flat at 25 to 35C
Do a basic / simple temperature compensation (TCXO)
…. and count on the errors to average out.
The success of all that will depend a lot on how close your wrist is to the
environment they used for their guesswork. Did they count on you taking
the watch off at night or not? What temperature is the room at? …..
Before you say it can’t be done, the whole “average out” thing is how time
pieces have been done for hundreds of years. The device may swing this
way and that …. done properly it eventually averages out. How well it works
for you … that depends.
Bob
Post by t***@joshreply.com
That comes out to about 30ppb, and this is a pocket watch so they don’t seem
to depend on the temp stabilization of being attached to a human wrist.
https://www.ablogtowatch.com/wp-content/uploads/2018/03/Citizen-Cal-0100-Eco
-Drive-Movement-04.jpg
I’ve been reading about the new watch that contains this crystal for about a
month, but just saw some more detail today
---
AT-CUT QUARTZ CRYSTAL OSCILLATOR
While AT-cut quartz crystals have indeed been in production and use since as
early as 1934, the technology is more common in larger applications and not
necessarily wristwatches. To address the needs of individuals seeking only
the most accurate performance in a wristwatch, Citizen sought to apply and
optimize this available technology in a way that could serve watch consumers
on a more direct and personal level. When working to reach the accuracy of
the Cal.0100, Citizen opted for an AT-cut quartz oscillator instead of a
more traditional tuning fork shape (XY cut). Perhaps most notably, AT-cut
variations allow for greater temperature tolerances, specifically in the
range of -40°C to +125°C. Additionally, this configuration allows for
reduced deviations caused by wearer orientation, which can cause significant
changes in accuracy that aren't negligible when attempting this kind of
performance. As a result, wearers will not have to worry about errors caused
by spatial orientation and positioning becomes less of a concern. The same
can be said about durability, which Citizen also improved upon in
conjunction with the AT-cut oscillator. After all, shock experienced in
day-to-day situations could easily prove detrimental even for quartz
movements. And when the goal is an annual accuracy of ±1 second, that just
isn't acceptable.
https://www.ablogtowatch.com/citizen-cal-0100-eco-drive-watch-movement/
---
Is this possible with an MXCO running across this wide temp range? How are
they compensating for aging at this level of precision?
Thanks!
_______________________________________________
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.
Don’t worry about how powerful the machines are. Worry about who the machines are giving power to.

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Richard (Rick) Karlquist
2018-04-11 21:38:59 UTC
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The aging spec on the 10811 is 5 parts in 10^10 per day.
After 60 days, it could be off 30 ppb. So what we
have here is a non-ovenized AT cut that is better
than an ovenized SC cut. I'm sure.

I am reminded of the old Accutron ads. The headlines
guaranteed so many seconds a day or whatever it was.
The fine print says they don't actually guarantee that.
The only remedy under that guarantee is that they
agree to adjust the watch to be in spec at the
watch repair shop and hand it back to you. Thus,
they didn't have to worry about aging. Just come
into the shop as often as necessary :-)

Rick N6RK
Post by t***@joshreply.com
That comes out to about 30ppb, and this is a pocket watch so they don’t seem
to depend on the temp stabilization of being attached to a human wrist.
https://www.ablogtowatch.com/wp-content/uploads/2018/03/Citizen-Cal-0100-Eco
-Drive-Movement-04.jpg
I’ve been reading about the new watch that contains this crystal for about a
month, but just saw some more detail today…
---
AT-CUT QUARTZ CRYSTAL OSCILLATOR
While AT-cut quartz crystals have indeed been in production and use since as
early as 1934, the technology is more common in larger applications and not
necessarily wristwatches. To address the needs of individuals seeking only
the most accurate performance in a wristwatch, Citizen sought to apply and
optimize this available technology in a way that could serve watch consumers
on a more direct and personal level. When working to reach the accuracy of
the Cal.0100, Citizen opted for an AT-cut quartz oscillator instead of a
more traditional tuning fork shape (XY cut). Perhaps most notably, AT-cut
variations allow for greater temperature tolerances, specifically in the
range of -40°C to +125°C. Additionally, this configuration allows for
reduced deviations caused by wearer orientation, which can cause significant
changes in accuracy that aren't negligible when attempting this kind of
performance. As a result, wearers will not have to worry about errors caused
by spatial orientation and positioning becomes less of a concern. The same
can be said about durability, which Citizen also improved upon in
conjunction with the AT-cut oscillator. After all, shock experienced in
day-to-day situations could easily prove detrimental even for quartz
movements. And when the goal is an annual accuracy of ±1 second, that just
isn't acceptable.
https://www.ablogtowatch.com/citizen-cal-0100-eco-drive-watch-movement/
---
Is this possible with an MXCO running across this wide temp range? How are
they compensating for aging at this level of precision?
Thanks!
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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Bob kb8tq
2018-04-11 23:16:01 UTC
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HI
Post by Richard (Rick) Karlquist
The aging spec on the 10811 is 5 parts in 10^10 per day.
After 60 days, it could be off 30 ppb. So what we
have here is a non-ovenized AT cut that is better
than an ovenized SC cut. I'm sure.
As a practical point - they didn’t leave the factory until they hit that spec, Manufacturing
being what it is, having OCXO’s hang around was not a popular thing. The 5x10^-10
per day at 5 or 10 days might well drop by quite a bit a month or two later. Back in the
day, this was a “who knows / who cares / meets spec” sort of thing.

I’m not sure that everybody buys the “log rule” for aging. I think there are a lot of reasonable
objections to it. That aside, if there *is* a rule that applies to 80% of your crystals …. that’s
doing very well. By watch standards that is “perfection”. Measure something over a 10 day
period and plug that into the firmware. Yes, the watch sits in test for 10 days … .and you
charge for that.
Post by Richard (Rick) Karlquist
I am reminded of the old Accutron ads. The headlines
guaranteed so many seconds a day or whatever it was.
The fine print says they don't actually guarantee that.
The only remedy under that guarantee is that they
agree to adjust the watch to be in spec at the
watch repair shop and hand it back to you. Thus,
they didn't have to worry about aging. Just come
into the shop as often as necessary :-)
I wonder how many watch shops are set up to re-shoot the memory in a watch CPU?
Most of them seem to have a hard time swapping a battery and keeping things dry enough
that the watch doesn’t fog up in the cold ….

Bob
Post by Richard (Rick) Karlquist
Rick N6RK
Post by t***@joshreply.com
That comes out to about 30ppb, and this is a pocket watch so they don’t seem
to depend on the temp stabilization of being attached to a human wrist.
https://www.ablogtowatch.com/wp-content/uploads/2018/03/Citizen-Cal-0100-Eco
-Drive-Movement-04.jpg
I’ve been reading about the new watch that contains this crystal for about a
month, but just saw some more detail today
---
AT-CUT QUARTZ CRYSTAL OSCILLATOR
While AT-cut quartz crystals have indeed been in production and use since as
early as 1934, the technology is more common in larger applications and not
necessarily wristwatches. To address the needs of individuals seeking only
the most accurate performance in a wristwatch, Citizen sought to apply and
optimize this available technology in a way that could serve watch consumers
on a more direct and personal level. When working to reach the accuracy of
the Cal.0100, Citizen opted for an AT-cut quartz oscillator instead of a
more traditional tuning fork shape (XY cut). Perhaps most notably, AT-cut
variations allow for greater temperature tolerances, specifically in the
range of -40°C to +125°C. Additionally, this configuration allows for
reduced deviations caused by wearer orientation, which can cause significant
changes in accuracy that aren't negligible when attempting this kind of
performance. As a result, wearers will not have to worry about errors caused
by spatial orientation and positioning becomes less of a concern. The same
can be said about durability, which Citizen also improved upon in
conjunction with the AT-cut oscillator. After all, shock experienced in
day-to-day situations could easily prove detrimental even for quartz
movements. And when the goal is an annual accuracy of ±1 second, that just
isn't acceptable.
https://www.ablogtowatch.com/citizen-cal-0100-eco-drive-watch-movement/
---
Is this possible with an MXCO running across this wide temp range? How are
they compensating for aging at this level of precision?
Thanks!
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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Dan Rae
2018-04-12 00:45:02 UTC
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Way back in 1960 something Braun in Germany made a little alarm clock
using a 4.194304 MHz crystal which could reach this level of accuracy. 
I had one and it certainly met the Harrison level of timekeeping when I
used it for navigation.  I think that the crystal cut used had a
temperature coefficient at room temperatures that had minimal variation
at around this frequency.   Way better than the 32+ kHz crystals used now.

The clock died in the end but I still have the crystal somewhere :^)

Dan


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