An ETA 252.611 Movement's Temperature Correction Method Unveiled - Page 3
Like Tree2Likes

Thread: An ETA 252.611 Movement's Temperature Correction Method Unveiled

Page 3 of 4 FirstFirst 1 2 3 4 LastLast
Results 21 to 30 of 32
  1. #21
    Member Bruce Reding's Avatar
    Join Date
    May 2005
    Location
    Wilmington, North Carolina
    Posts
    2,929

    Re: An ETA 252.611 Movement's Temperature Correction Method Unveiled

    Quote Originally Posted by Catalin View Post
    I initially thought about that but I doubt it - right now we have two secondary corrections each at half inhibition apart , if we would have a 3rd the logic would be slightly more complex (not to mention that any symmetry would be lost).
    I agree about the symmetry breaking, and suspect that you're right. However, in principle, symmetry is not a requirement for a successful scheme, and this would be a possible explanation for the temperature dependence of the primary correction.

  2. #22
    Member dwjquest's Avatar
    Join Date
    Jul 2006
    Location
    Oklahoma, USA
    Posts
    638

    Re: Great work as ever !!!

    Quote Originally Posted by DaveM View Post
    Very interesting !
    I struggle as well

    As previously discussed 8 minutes inhibition gives about 2s per year adjustment resolution, which seems sensible.
    But this may be slower than the watch thermal time-constant (I doubt if this matters under real-world conditions). So to get over this you could thermal-adjust 3 times as often and 'round up' the 1/3 count errors until they generated a full count.
    But in this case I would expect to see (in dwjquest example)
    1077 - 1150 +21+21+21 = -10 (ie apart from rounding-error each inhibition makes the same temperature-compensation).

    So I cannot see why they do it like this.
    I am also surprised that the 'primary adjustment vs temperature' curve is so smooth. My understanding is that it can only have values mutiplied up from 2.01 seconds per year (for 32768Hz xtal).

    Can dwjquest tell us
    a) Is each data-point the average of several readings ? If so how many.
    b) What is the time and temperature-increment when doing the temperature curve ?

    Let us assume that the thermal-adjustments are 'fractional-count compensated', say to 1/4 of a primary count. The compensation-resolution is now 0.5s, and this would explain dwj's curve (assuming that it is the average of several readings).

    If there is anybody from COSC out there perhaps they ought to offer dwjquest a consultancy contract!
    The raw rate is typically an average of 20-30 readings. Three readings are available during each cycle. Thus, the readings are the average over about 7-10 cycles or 56-80 minutes.

    The primary correction is an average of about 15-20 data cycles.

    The secondary corrections are an average of 8 cycles.

  3. #23
    Member ppaulusz's Avatar
    Join Date
    Feb 2006
    Location
    Budapest, Hungary
    Posts
    3,431

    Re: Great work as ever !!!

    Quote Originally Posted by Bruce Reding View Post
    ...Make it fast enough and you won't have to worry about inhibition not working.
    Exactly!

  4. Remove Advertisements
    WatchUSeek.com
    Advertisements
     

  5. #24
    Member
    Join Date
    Jan 2009
    Posts
    3,107

    Re: Great work as ever !!!

    Quote Originally Posted by South Pender View Post
    So, Catalin, are you saying that the movement cannot run slow within that temperature range? Is that what you mean by "as ETA is set"?
    The ETA raw oscillator seems to be set at around 40 seconds / MONTH fast and everywhere in the 'normal' temperature range is at least 10-20 seconds / MONTH fast - so that part can not run slow unless you do very exotic stuff with it ...

    The final values after all the corrections CAN be slow ...

  6. #25
    Member
    Join Date
    Jul 2008
    Location
    Vancouver, Canada
    Posts
    2,266

    Re: Great work as ever !!!

    Quote Originally Posted by Catalin View Post
    The ETA raw oscillator seems to be set at around 40 seconds / MONTH fast and everywhere in the 'normal' temperature range is at least 10-20 seconds / MONTH fast - so that part can not run slow unless you do very exotic stuff with it ...

    The final values after all the corrections CAN be slow ...
    Got it! Thanks Catalin and Bruce.
    Vancouver

  7. #26
    Member Eeeb's Avatar
    Join Date
    Jul 2007
    Location
    Great Lakes - USofA
    Posts
    18,115

    Re: Great work as ever !!!

    Quote Originally Posted by Catalin View Post
    The ETA raw oscillator seems to be set at around 40 seconds / MONTH fast and everywhere in the 'normal' temperature range is at least 10-20 seconds / MONTH fast - so that part can not run slow unless you do very exotic stuff with it ...

    The final values after all the corrections CAN be slow ...
    This entry on the Sinn vocabulary page is interesting.

    Inhibition cycle

    Correction interval in quartz movements.

    A range of different techniques has been used in different developments to optimize the accuracy of quartz movements. In the past manufacturers tried to produce the quartz as precisely as possible, to grind it or to set the precise oscillation frequency by depositing layers of vaporized gold and then removing it by laser. Today, quartz crystals are ground in such a way to produce a significant gain in the movement. This gain is then measured in each individual movement at room temperature. Subsequently the movement is programmed so that the gain is corrected every one to four minutes (depending on the caliber). The movement is briefly "paused" to compensate for the gain of the quartz oscillation. In quartz chronometer movements there is also temperature compensation. The temperature sensor on the movement plate then helps to determine the current temperature in the watch and to calculate a correction value accordingly. The correction value which is applied once the inhibition cycle is complete is therefore not constant in quartz chronometer movements; rather it is continually adjusted in line with the current movement temperature.
    "Forever is composed of nows." - Emily Dickinson

    "The watch has to be surrounded by a history.
    You need more than just a great design. You need to create an atmosphere around the product.
    Who is the company behind it? Why are they using this material?
    People need to be able to identify the watch with themselves. It's based on emotion." - Ralph Furter

    ...that's just my opinion and I've been wrong before and will be again and might be now!

  8. #27
    Member Hans Moleman's Avatar
    Join Date
    Sep 2007
    Location
    New Zealand
    Posts
    1,586

    Re: Great work as ever !!!

    I can see around a 0.031 millisecond gain every second.
    That happens to be exactly one tick.
    One quartz vibration that takes 1000/32768 milliseconds.

    Left uncorrected that would add up to 900 seconds per year.

    So I think ETA counts to 32767 when counting for a second. And thus ensuring the clock runs fast.
    And that way they don't have to select crystals.

    All speculation off course!

    The end result remains the same: The clock runs fast, and the corrections slow it down.
    Last edited by Hans Moleman; September 8th, 2009 at 03:56.

  9. #28
    HAQ and AW moderator
    Join Date
    May 2005
    Posts
    6,744

    Re: An ETA 252.611 Movement's Temperature Correction Method Unveiled

    Why not get closer to 2^15 Hz and decide to add or subtract counts?

  10. #29
    Member Hans Moleman's Avatar
    Join Date
    Sep 2007
    Location
    New Zealand
    Posts
    1,586

    Re: An ETA 252.611 Movement's Temperature Correction Method Unveiled

    If you only subtract when applying corrections you don't need to have signed numbers. A bit cheaper I believe. Or at that time anyway. They were fighting for every bit at that time.

  11. #30
    Member
    Join Date
    Jan 2009
    Posts
    3,107

    Re: An ETA 252.611 Movement's Temperature Correction Method Unveiled

    Quote Originally Posted by Hans Moleman View Post
    If you only subtract when applying corrections you don't need to have signed numbers. A bit cheaper I believe. Or at that time anyway. They were fighting for every bit at that time.
    Honestly I believe it would still be a lot simpler / cleaner to just set the oscillating circuit fast in the all-analog part and then count 32768 ticks ...

Page 3 of 4 FirstFirst 1 2 3 4 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

    Posting Permissions

    • You may not post new threads
    • You may not post replies
    • You may not post attachments
    • You may not edit your posts
    •