We are fortunate to have John here :-)

Sep 04, 2011,16:04 PM

John, as always, wonderful and informative post.  We learn so much here from you!


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question for the geeks.......

 By: JMan : September 4th, 2011-07:47
Folks, I have a question regarding amplitude of a watch which is used as a measure for the accuracy. I understand why the deviation of amplitude would represent accuracy but often the total amplitude seems to be used synonymously. As in "....change increa... 


 By: ei8htohms : September 4th, 2011-09:19
Hello JMan, Discussions of amplitude very often take place between two people with a less than completely thorough understanding of the subject. I once had a US watch industry executive (NOT my current employer) relay to me a story wherein he bragged to h... 

Great and highly educating post, a true classic! ...

 By: Marcus Hanke : September 4th, 2011-09:32
...thanks, John! I printed it and put it into my copy of Raymondin/Monnier, because your expalantion is so much easier to understand than the stuff written there. Regards, Marcus

Great information!

 By: mkvc : September 4th, 2011-10:54
Thanks for much improving my understanding of the subject.

Had to read it twice to make sure I was following...

 By: Zhege : September 4th, 2011-11:24
Thanks for posting, very informative. I almost wrote "useful", but the only real use it has is to make me more aware of something I know very little about

Excellent post, John

 By: nickd : September 4th, 2011-13:29
Excellent post! As you say, amplitude is more of an indicator of good design and manufacturer, and I wonder if things like balance wheel inertia, "power curve" and reserve de marche would be better indicators of potential performance? If people can obsess... 

What I'd love to see

 By: ei8htohms : September 4th, 2011-14:48
I'd love to see curves like these published across entire power reserves....  

Any chance of...

 By: BDLJ : September 4th, 2011-16:29
seeing the source data for that graph? Thanks for the posts, John. Informative and fascinating as ever.

it just looks like ~4000 rows of this

 By: ei8htohms : September 4th, 2011-16:38
t [s] Rate [s/d] Amplitude [°] 2 12.8 290.0 4 12.5 290.0 6 12.3 291.0 8 11.8 291.0 10 11.7 292.0 12 11.8 293.0 14 11.5 294.0 16 11.3 295.0 18 11.7 296.0 20 11.7 296.0 22 11.5 297.0 24 11.7 298.0 26 12.0 298.0 28 12.0 298.0 30 12.1 298.0 32 12.2 297.0 34 1... 

That's exactly..

 By: BDLJ : September 4th, 2011-21:50
...what I'd like to see You'd then be able to interrogate the data by manipulating the scales....but as you wrote, you'd need a fair few samples and a decent amount of background info before you could make any inferences....fascinating, though.

Per watch...?

 By: nickd : September 4th, 2011-23:54
I can see the use of this on a per-watch basis, but could you do it as a generalisation for all instances of a movement if it's so sensitive to adjustment, or are some production movements so consistent that it's feasible? nick

realistically? probably yes

 By: ei8htohms : September 5th, 2011-07:24
Hi Nick, This is only a couple hours worth of data, so it's definitely only useful on a per watch basis and even then more for curiosity's sake. If you look at the total amplitude and rate trace over the full run-down of a watch it tells you a little more...  


 By: nickd : September 5th, 2011-08:33
Hi John, I'd wondered if people used FF transforms for watch analysis. It's used for precision clocks, and I love the idea of long term studies of precision clocks such as various Shortts or the Littlemore showing the earth's natural resonant frequencies ... 

Now that...

 By: BDLJ : September 5th, 2011-16:51
...is some interesting data. My FFT skills are almost dead, but that's the kind of analysis/tool I'd love to see more of. Brilliant work, John

I've thought about trying to put together some sort of

 By: grumio : September 5th, 2011-22:09
optical pickup for measuring rate & ampltiude myself. I've built home-made optical pickups for other purposes before using the light source and receivers from an old fashioned 'roller ball' computer mouse. Positioning the pickup to work reliably, and cali... 

If you end up putting something like that together...

 By: ei8htohms : September 6th, 2011-09:58
Send me the "how to". The I'd love to have something like that! _john

There's a chapter...

 By: nickd : September 6th, 2011-10:57
...in Robert Matthy's Accurate Clock Pendulums on both the sensors and the electronics for use on clock pendulums. The book itself is worth the read for the sheer pleasure (if you're that way inclined). nick

thanks for the book reference

 By: JMan : September 7th, 2011-13:02
Hi Nick or John, Are there any other books that you could recommend that explain the technical design aspects of a watch? In the vein that is being discussed in the currently? Thanks. J.

Daniels Watchmaking is quite good

 By: ei8htohms : September 8th, 2011-04:10
The portions of the book specifically dedicated to these issues are pretty small (most of the book focuses on hand fabrication of watch components) but very informative. DeCarle's Practical Watch Adjusting is also an excellent resource. _john

Too much or virtually nothing...

 By: nickd : September 8th, 2011-05:11
If you speak French and have university-level maths/physics there's a set of four tomes from the EICN at le Locle (swiss technology university department specializing in microtengineering, with a sub-speciality of horlogery). Its' called Théorie de la con... 


 By: JMan : September 8th, 2011-07:27
The Theory of Horology seems like the right kind of book. A bit on the expensive side though........ J.

Send me details!

 By: BDLJ : September 6th, 2011-20:28
Interesting project...

Doesn't Brian Mumford..

 By: Tom the Tinkerer : September 8th, 2011-02:38
already make an optical pickup for watches? and the interface for converting it to a usable signal with the micro set thingy? (Never seen one, touched one or used one, but like the ideas) Tom


 By: nickd : September 8th, 2011-03:14
Brian does make them, but the cost is not negligible, and for some applications they're overkill. nick

iA quick look at his website...

 By: grumio : September 8th, 2011-03:43
suggests that the optical pickups available for the Microset machines are used for timing clock pendulums. Again, never actually seen one, only read about them online. There is one attachement he sells for vibrating bare hairsprings, but I can't immediate... 

We are fortunate to have John here :-)

 By: KIH : September 4th, 2011-16:04
John, as always, wonderful and informative post. We learn so much here from you! Ken

Indeed. My thanks to John . . .

 By: Dr No : September 5th, 2011-10:06
. . . for sharing his valuable holiday time with us. Gratefully, Art

Thanks for this, John!

 By: Gary G : September 4th, 2011-19:09
A great exposition of a topic that was previously completely opaque to me. I now sense the fog lifting just a bit... Best, Gary G

appreciate the thorough response.......

 By: JMan : September 4th, 2011-19:27
John: Thanks for the education. I just finished my first read. But the topic is technical enough that I need to re-read your response to completely digest all the information you have presented. But it was my initial inclination that there was not going t... 

Very informative.....

 By: David Elliott : September 4th, 2011-19:39
It's definitely a complicated subject, and you definitely educated me a bit more on it. Thanks. Dave

Hi John, I assume that you're an engineer or in a related field?

 By: patrickmaniac : September 5th, 2011-01:07
Great post and truly educational. If accuracy is needed, folks could get an atomic clock and think about how to mini it. Some things are better left with in-perfections, albiet not too much. cheers PAt

I'm a watchmaker (nt)

 By: ei8htohms : September 5th, 2011-02:19

Thank you for an outstanding answer

 By: nilomis : September 5th, 2011-04:40
At the same time you explained clearly the amplitude and the effect of a high beat. Great. And what about the "lift angle". How this relates, or not? Warm thanks. We need more posts of this caliber.

lift angle

 By: ei8htohms : September 5th, 2011-07:04
Hello nilomis. Lift angle is the angle within which the roller jewel is interacting with the pallet fork, so is the portion of the "swing" of the balance where it is not truly free, but subjected to exterior influences. Lift angle contributes to escapemen... 

Thank you

 By: nilomis : September 5th, 2011-07:10
John, Just copy/paste your two answers on a single document that is now part of my small reference set. Great and direct answers. Cheers and enjoy your holiday

What an outstanding post!

 By: Ornatus-Mundi : September 5th, 2011-05:35
Thanks John for taking the time to put it together. I am astonished how little I knew about the matter! Cheers, Magnus

Mr. Ohms....

 By: Six13 : September 5th, 2011-12:46
John, Your response to this op is well reasoned and insightful, as usual. Real world experience has shown us that cross caliber comparisons based on amplitude alone are very difficult indeed. You and I have seen very stable modern movements with relativel...