The Breitling Watch Source Forums

I have a SOHC 46 and use NIST web site or the Breitling application to set time every couple of months. In two months, my watch is off by 2 or 3 minutes. I understand that the accuracy of a COSC certified mechanical movement is a few seconds up or down per day.

My question is how do I go about measuring the time slip to compare against COSC specs. Should I check every 15 days and calculate an average value and see if that is within the COSC specs? Do particular watches "always" run a few seconds fast or slow, or is it that they would run a few seconds fast one day and slower on another, and the average slip is what is important?

I wear my watch about 12 - 15 hours every day, and sometimes wind it manually as well.

Most mechanical watches will always either generally gain or lose time, although the amount they lose or gain isn't always absolutely 100% consistent. There are so many variables to take into account, like temperature, wearing patterns, etc. What I do if ever I'm curious about a watch's timekeep, is set it against a source known to be correct (usually an atomic G-Shock these days) and then check it 24 hours later. Sure it may be fractionally different over the next 24 hour period, but that's as far as I go because if absolute accuracy was that important to me I never would've bought mechanical watches.

To be honest, my advice would be to check it once in a while like I do, and then just forget about it and enjoy your watch. As long as it's within COSC specs I wouldn't worry about it too much. Otherwise if super-accuracy is that important to you, maybe you'd be better off with an SQ model instead.

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Driver8

Site Moderator

+1
They're mechanical and they tend to fluctuate. If I recall correctly, COSC specs runs between -4 to + 6 sec /day.

I agree with Driver that getting anal about the timekeeping of your watch is not worth the time and effort.

At one time, however, I was pretty bored and put together this little spreadsheet with another member of the forum (can't recall his name at this time)

https://docs.google.com/spreadsheet/ccc ... ey=COOl0x0

This should enable you to be as anal as you'd like about how well your watch is keeping time. You can track as many as you like and log several time checks to get a time-weighted average of your watch's performance. It even has a little bit of "if, then" trickery to tell you if the watch is running within COSC tolerance.

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“The only reason for time is so that everything doesn't happen at once.” - Albert Einstein

Thanks for the replies.

My specific question was that is there a home grown regime to sort of check against COSC specs; e.g. measure time slip every 15 days or every month and as long as the slip is between -4xN seconds and 6xN seconds (where N=no. of days since last check) then it is OK, else go check with the AD.

If above is a true / valid way of looking at performance, after one month the watch could run two minutes slow or three minutes fast and that would within the COSC guidelines?

I hope I explained well enough, and once again appreciate all the replies.

Not trying to be anal about accuracy; just very proud to own a precision movement and confirm that it performs as designed

And thanks for the spreadsheet - should give me something to do on cold rainy days in Dubai

COSC is -4 / +6 per day, so if average variation per day is within that range then the watch is fine.

As others have said, if it's going to bother you then get a quartz!

I have a Tag Heuer quartz, its been sitting in it's case since I bought the Breitling. I regretted not buying a mechanical movement just months after buying it but couldn't afford anything else at the time. That said, the Tag performed well for 8 years, only went to the dealers once for a battery change and took lots of accidental knocks.

Been wearing the new watch (SOHC 46) every day for the last 7 months since I bought it.

You guys didn't get it; I like my new watch and want to learn about its optimal performance.

Thanks for all the replies. Helps me learn.

My new Superocean is +4 seconds a day (going on Day 3 of owning it now with regular wear). Which is totally fine by me. My old Sea Dweller got up to +9 minutes every week!!!! unacceptable. But it got tuned up and was better (still wasn't great). That said, the watch was worn under really crazy circumstances where it got jostled a lot (because of running), got shocked a lot at the firing range, and overall never left wrist.

Like everyone else said, time it on your computer clock or an atomic clock or G-Shock. Once a month maybe reset it if you want.

So just note, that depending on what kind of activity you'll be doing, you'll get varied accuracy (YMMV).

There is no one way to go about it. I'm anal - not necessarily about insisting an automatic be accurate, but just about knowing the perameters of a watch's performance. So, if it were me, I would set it against something like http://www.time.gov, or some other source known for accuracy. Then I would check it every 24 hours for a week or so and keep a note of the variation and/or fluctuation, and under what circumstances they occurred. Odds are it will prove academic, and I'm fine with that; it's just a way of knowing how the watch is doing. On the other hand, if it reveals a problem, then it's good I find out. However, if your watch were having a problem keeping time, you probably would have realized it already. Three minutes fast after two months averages out to +3 seconds a day, well within COSC specs.

Thank you all for the replies.

Accuracy is a personal, subjective, & priority oriented animal.
If you need it for professional reasons, then SuperQuartz,
Atomic, Solar, etc. watches are mandatory. If simply for
laid back timing, then auto/mechs will suffice, unless they
run extremely erratically. Fortunately, the advancing tech-
nologies offer many great options. You no longer have to
select watches that require crank winds like old Model A/T
Fords. Plus, today's pacemakers have the most advanced
systems that leave your in-house calibers @ the curb, while
saving & enhancing your lives with pinpoint accuracies. Hope-
fully you won't need implants, but it's reassuring they are available.

If you have a world band / shortwave radio, the following stations broadcast the atomic clock world time every minute:
Station

Location

Frequencies



CHU

Ottawa, Canada

3330, 7850 and 14670 kHz



RWM

Moscow, Russia

4996, 9996 and 14996 kHz (note that RWM transmits pulses rather than ticks)



WWV

Colorado, USA

2500, 5000, 10000 and 15000 kHz



WWVH

Hawaii, USA

2500, 5000, 10000 and 15000 kHz



YVTO

Caracas, Venezuela

5000 kHz



DSHO

São Paulo, Brazil

10000 kHz



BPM

Pucheng, China

2500, 5000, 10000 and 15000 kHz



HLA

Daejeon, South Korea

5000 kHz



HD2IOA

Guayaquil, Ecuador

3810 kHz (not 24/7)



EBC

Cadiz, Spain

4998 and 15006 kHz (not 24/7)



BSF

Taipei, Taiwan

5000 and 15000 kHz

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1997 Aerospace,Repitition Minutes,Titanium & 18k
1998 Colt Chrono Transocean

All this talk of, "if accuracy is that important, you may want to consider quartz," reminds me of what some mall AD salesperson told me once. I was browsing Ben Bridge (God...is there anything so depressing as spending time at the mall? But I digress.) and was looking at some Hamiltons. They weren't COSC certified, so I asked what the accuracy was on them. He said, "Oh, probably about ten seconds a day or so...but if you're really that concerned about accuracy, you should probably consider quartz." Maybe...or maybe I would want to consider a certified mechanical. Accuracy is relative. Yeah, the COSC standard of -4/+6 is relatively inaccurate compared to quartz or radio-control, but it is quite accurate compared to non-chronometer grade mechanical movements. I don't think there is anything wrong with expecting a watch to perform to the standard established by its manufacturer. Beyond that, if I know the reason a non-certified mechanical watch won't keep time as well as a certified watch is because it is made to a lower standard of tolerances, that's going to annoy me. So generally, I want to buy a watch that is a certified chronometer, and I expect it to run within COSC specs. As long as it does that, I'm satisfied.

Well there ya go!