Measuring accuracy

[NachoNeal]

Originally Posted by ROLEXROLEXROLEXRO

Hello, I just picked up my first Rolex, a new Milgauss! My question on determining accuracy--- the +2/-2 Spd is supposed to be an average over what time frame?

Cheers!

That's one long wait list! You've been a member here for almost a decade!

[ROLEXROLEXROLEXRO]

Originally Posted by NachoNeal

That's one long wait list! You've been a member here for almost a decade!

Ha! I put my name on the list when the Milgauss was reintroduced, I finally just got the call!

[padi56]

Originally Posted by Andad

Why doesn’t Rolex state that their new movements have an accuracy of +/- 2 seconds per day.
Why do they state precision?
They obviously also know the difference.

Is it because the movements could be running 5, 10 or even 8 seconds per day fast or slow consistently (with precision) at +/- 2 seconds per day?

I believe the new movements may run at +/- 2 precision and can also be adjusted for accuracy but I know not many of them do long term.

Exactly in the real world all it means when tested in a controlled environment when tested on a machine perhaps many at a time. At time of test movement did comply to said spec average -2+2, but with the owner and his/hers wearing, watch winding habits now thats a different story. Much like they test the fuel consumptions on cars in a controlled test to get MPG. Its doubtful if most owners will achieve these exact figures quoted as like a wrist watch many many daily variables to overcome. And all this accuracy and precision stuff, for any mechanical movement to run within a few seconds out of 86400 in a day is a mechanical marvel. And what some would call very low end movements like the Chinese made Seagull ST19 after careful regulation, this mechanical movement can perform to a average +2 seconds a day and watch cost just $60.

[thenewrick]

I'm surprised they haven't figured out a mechanical method of self regulating. Knowing when it's running fast and slow itself down, or speed itself up. I suppose it would need a reference point like a wifi/nfc/radio communication with a computer clock.

[Fred48]

And what some would call very low end movements like the Chinese made Seagull ST19 after careful regulation, this mechanical movement can perform to a average +2 seconds a day and watch cost just $60.[/QUOTE]


Yes, correct, could not agree more; have done it myself.

So, why are Rolexes so expensive?!

[Mendota]

https://minus4plus6.com/about.php

To achieve Swiss Chronometer rating it needs to be within -4/+6 seconds per 24 hours, measured over a 10 day period. That's the maximum deviation allowed to receive the rating. Anything better than that is bonus in their eyes.

[thenewrick]

Originally Posted by Fred48

So, why are Rolexes so expensive?!

It's considered a collectible piece of art essentially. There's no inherent value in a Rolex. It doesn't do things better than other things. It's not like a computer or a TV where there's clearly a price/specs relationship.

The A Lange & Sohne Odysseus is selling for $70K+ now and it's still a steel sports watch with a chronometer spec.

The basic watch tiers are fakes<good cheap quartz watches<good cheap mechanical watches<high quality factory/mass produced mechanical<hand finished/rare mechanical watches. Rolex falls in the high quality mass produced in factories category.

[fskywalker]

Originally Posted by ROLEXROLEXROLEXRO

Ha! I put my name on the list when the Milgauss was reintroduced, I finally just got the call!

Congrats on purchase, but where are the pictures of the watch?


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[trfChris]

Originally Posted by ROLEXROLEXROLEXRO

Hello, I just picked up my first Rolex, a new Milgauss! My question on determining accuracy--- the +2/-2 Spd is supposed to be an average over what time frame?

Cheers!

So many replies here and so few answering your actual question.

Here is a detailed overview of how the COSC accuracy test works and how they come up with the -4/+6 number:

https://forums.timezone.com/index.ph...oto=1555&rid=2

In this test the accuracy is measured over 10 days. I would imagine Rolex does something similar to COSC but with a cased up movement instead of a bare movement and with the tighter tolerance of -2/+2.

[Juan Luis]

Originally Posted by thenewrick

I'm surprised they haven't figured out a mechanical method of self regulating. Knowing when it's running fast and slow itself down, or speed itself up. I suppose it would need a reference point like a wifi/nfc/radio communication with a computer clock.

The only thing close to that is the Seiko Spring Drive system. Regulates the mechanical parts with quartz technology.

[bmb15]

Originally Posted by trfChris

So many replies here and so few answering your actual question.

That’s an observation I fully share, true for many threads

The OP' question (post #1) showed a missing understanding of the basic terminology.

Post #1: "My question on determining accuracy--- the +2/-2 Spd is supposed to be an average over what time frame?"

A clarification of the difference between accuracy and precision was delivered in post #29, w/o follow-up or continuation until here.

[Fred48]

Originally Posted by thenewrick

It's considered a collectible piece of art essentially. There's no inherent value in a Rolex. It doesn't do things better than other things. It's not like a computer or a TV where there's clearly a price/specs relationship.

The A Lange & Sohne Odysseus is selling for $70K+ now and it's still a steel sports watch with a chronometer spec.

The basic watch tiers are fakes<good cheap quartz watches<good cheap mechanical watches<high quality factory/mass produced mechanical<hand finished/rare mechanical watches. Rolex falls in the high quality mass produced in factories category.

Not sue I would consider a Rolex a "piece of art", more a very well engineered mechanical device, but good answer.

[Rushhour]

Originally Posted by fskywalker

Congrats on purchase, but where are the pictures of the watch?


Sent from my iPhone using Tapatalk Pro

This! We need pictures damn it!

My Z Blue seems to be in the -1.5 to -2 seconds a day since I got it in July 19.

What I did was set it as best a human can to an atomic clock (as an aside humans ain’t perfect) and watched (can’t believe I said that) for several days. And just came up with an average - though no time during that time frame did I see it loose more than 2 sec each day.

Now I did not try to compute the delay from looking at an iPhone on the atomic clock to my watch. But the error, which obviously was there, remained static.

I have done it a few times over the time I have had it. It has been the same - though nowadays I usually have a nice Fosters or Stella next to me when sitting in the porch watching the young ladies going to the beach (post setting on the atomic clock of course). I can’t believe that method would skew anything .

Just my 02.


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[bmb15]

Originally Posted by Rushhour

This! We need pictures damn it!

Just my 02.

Value max 0,00002

[jamesbondOO7]

Atomic Clock and Watch Accuracy is an excellent app

[padi56]

In over 50 years of wearing Rolex watches never felt the need for any of today's phone apps to check my watches every day/hour for accuracy.Myself check mine once a month or so and then if a minute or so off will adjust thankfully my life was never ran to the exact second.And in all those years of wearing cannot recollect being late for any appointment,or missed a bus,train, or plane.Even if my watch was COSC tested to AVERAGE -4+6 seconds or any other test on this planet.

[jamesbondOO7]

After over 30 years of wearing Rolex watches, I still have pleasure checking their accuracy.
I make a point of always being on time. Small pleasures in life should always be grasped.

[HogwldFLTR]

Set it to a known standard (time.is) and track it for a week. That should give you the answer for which you look.

[EEpro]

Originally Posted by HogwldFLTR

Set it to a known standard (time.is) and track it for a week. That should give you the answer for which you look.

This is exactly what the WatchTracker app does. All the user does is tell it what time is displayed on your watch. It does the math and shows you the data as plots.

[ricardo-sf]

when i check my watches i first make sure its been worn for at least 4 weeks before taking measurements.

then i measure across 30 days. -- making sure the watch is daily worn.

[Jerrocop]

This from the wikipedia for COSC:
Each uncased movement is individually tested for fifteen days, in five positions, at three different temperatures. The movements are fitted with a seconds hand and the automatic winding mechanisms are disengaged for the tests. Measurements are made daily with the aid of cameras. Based on these measurements, seven eliminatory criteria are calculated, each of which must be met (e.g., for movements of a diameter over 20 mm, the requirements, indicated in seconds/day, are noted in the table below). There is no ISO standard for quartz timepieces, but there is development in this field. ISO 10553:2003 specifies the procedure for evaluating the accuracy of quartz watches, individually and by lot, and the relationship between the accuracy tested and the accuracy classification given by the manufacturer. It applies to quartz watches having accompanying documents on which the accuracy classification is indicated. Nevertheless, COSC has also developed its own standard for testing quartz chronometers with eight eliminatory criteria, also noted in the table below.

From Rolex website:

The green seal accompanying every Rolex watch is a symbol of its status as a Superlative Chronometer. This exclusive designation attests that it has successfully undergone a series of specific final controls by Rolex in its own laboratories according to its own criteria, in addition to the official COSC certification of its movement. This unique testing of the chronometric precision of the cased-up movement, as well as of the watch’s waterproofness, self-winding and power reserve, pushes back the boundaries of performance and makes Rolex the benchmark for excellence in mechanical watches. The green seal is coupled with a five-year guarantee which applies to all Rolex models.

I'd say it's an average over at least 15 days.

[dchernikoff]

One of the ways that I enjoy my Rolexes is to watch how they behave over time. There's an app for iPhone called "WatchTracker" that you can use to observe how your watch performs over time. I used it for a few months with my DJ, checking it against WatchTracker in the morning right after I get up, and then at night right before taking it off for bed. My DJ was gaining +2 seconds a day, average. But the interesting part was seeing the graph that WatchTracker produced. It clearly ran slower at night, sitting on my bedside table, and faster when on my wrist, but it all averaged out to a very respectable +2 seconds a day.

Note that I do this for fun, I don't worry about it or feel bad about it or obsess over it or think "less" of my mechanical watch because it's not quartz accurate. I work with data for a living, and enjoy analysing data sets as a hobby! These are tiny mechanical marvels we wear on on wrists, I feel we should enjoy the technology as much as the style/beauty/functionality! (Otherwise just get a quartz watch and be done with it!)

-Dan

[bmb15]

I come back to the OP's initial question "....on determining accuracy--- the +2/-2 Spd is supposed to be an average over what time frame"

In my view this thread has not yet given a clear answer; the question shows a fundamental misinterpretation of the +/- 2 seconds per day (Spd or s/d) published by Rolex.

I don't know any document where Rolex guarantees the ACCURACY of their modern watches. The reason why is absolutely clear: ACCURACY can strongly depend on wearing pattern and many other factors, as already explained quite often in this forum.

Instead, Rolex guarantees a PRECISION of +/- 2 s/d. The difference between ACCURACY and PRECISION I explained here in post # 29, and at several places in literature.

All measurement results presented in this thread are ACCURACY measurements, which need a reference time to compare with, e.g. an atomic watch to which an app refers.

Therefore, all these data are not comparable with the +/- 2s/d PRECISION guaranteed by Rolex.

To determine the PRECISION you need to do many (&gt;&gt; 2-3) measurements, then analyse the results, determine the average value and its standard deviation.

In other words, the spread of the measured values (standard deviation) is called PRECISION. This is completely independent of the ACCURACY!

One can have all combinations of ACCURACY and PRECISION, as sketched below.



PS: I do not claim the need of super high accuracy Rolex movements! It's just my passion to better understand these calibers and contribute to an interesting discussion. I hope that helps a bit.