COSC question

[roadcarver]

Does the +4/-6 deviation set out by COSC compound over time? I mean,for example if the watch deviates -6 sec / day, so in a month it can go off by 180 seconds (3 min), providing that it is consistent at 6 sec?

Any insight is greatly appreciated.

[mrbieler]

Yes. Assuming your watch is always the same +/-6 seconds, it would be +/-180 seconds over 30 days.

Reality is that watches gain and lose time depending on a many different factors. Some watches are fast/slow on your wrist and the opposite on the nightstand. A watch can be fast or slow depending on which wrist you wear it on.

[roadcarver]

Thanks Jeff. The reason I ask is that my Chrono Avenger appears to be consistently slow by six seconds in a 24 hour period. I know its within COSC, but I'd rather have it be on the plus side.

It does run at +3 on a timing machine, dial up at the AD.

I'll keep on monitoring it.

Originally Posted by mrbieler

Yes. Assuming your watch is always the same +/-6 seconds, it would be +/-180 seconds over 30 days.

Reality is that watches gain and lose time depending on a many different factors. Some watches are fast/slow on your wrist and the opposite on the nightstand. A watch can be fast or slow depending on which wrist you wear it on.

[Launch Mini]

At night, try resting it crown up or crown down, you might be able to pick up a few seconds that way.

[mrbieler]

What they said.

My GMT is slow on my wrist and speeds up crown down on my nightstand. Net result is just under +2 per day.

If you're +3 dial up, keep it that way on your nightstand when you go to bed.

[JJ Irani]

Originally Posted by roadcarver

Does the +4/-6 deviation set out by COSC compound over time? I mean,for example if the watch deviates -6 sec / day, so in a month it can go off by 180 seconds (3 min), providing that it is consistent at 6 sec?

Any insight is greatly appreciated.

Good point, Vernon.

Seriously though, if a watch is worn for at least say 8 hours/day on a regular basis and then put aside each night, the seconds variation per day will fluctuate a wee bit.

Most Rollies BNIB out of box tend to run +1 sec./day. My TT Blue Sub loses 0.5 sec. if kept aside. However, as long it's on the wrist, the running is virtually spot-on!!

Every watch will show different behavioural patterns. You just have to do a bit of experimentation with yours.

Cheers - JJ

[padi56]

The COSC standard is -4 to +7 secs over 24 hours like the others have said try and experiment with different resting positions when off wrist.

[mike]

Originally Posted by roadcarver

Thanks Jeff. The reason I ask is that my Chrono Avenger appears to be consistently slow by six seconds in a 24 hour period. I know its within COSC, but I'd rather have it be on the plus side.

It does run at +3 on a timing machine, dial up at the AD.

I'll keep on monitoring it.

Vernon, that's been my experience also. Rates seem to vary from machine to wrist based on how we wear the watch. Jeff brings up a good point in that which wrist the watch is worn will affect timming.

COSC testing is conducted in six positions over a fifteen day period at a number of different tempratures. While the standard is -4/+6 that standard is not that hard to meet by most modern movements. Indeed Seiko raises the bar on select watches to -3/+5 over a 24 hr. period.

What I have noticed is that if a watch is consistently fast or slow --on my wrist-- it is an accurate watch and will tend to gain or lose the same amount every day.

[montecristo]

Originally Posted by mike

Vernon, that's been my experience also. Rates seem to vary from machine to wrist based on how we wear the watch. Jeff brings up a good point in that which wrist the watch is worn will affect timming.

COSC testing is conducted in six positions over a fifteen day period at a number of different tempratures. While the standard is -4/+6 that standard is not that hard to meet by most modern movements. Indeed Seiko raises the bar on select watches to -3/+5 over a 24 hr. period.

What I have noticed is that if a watch is consistently fast or slow --on my wrist-- it is an accurate watch and will tend to gain or lose the same amount every day.

All the seiko spring drives are rated at:

Time accuracy: Monthly rate within ±15 sec (equivalent to a daily rate of ±1 sec)

http://www.seikospringdrive.com/

[mike]

Originally Posted by montecristo

All the seiko spring drives are rated at:

Time accuracy: Monthly rate within ±15 sec (equivalent to a daily rate of ±1 sec)

http://www.seikospringdrive.com/

Oh Yeah! Springdrives are over the moon! I know of one that is running less than one second a month!

[padi56]

Originally Posted by mike

Oh Yeah! Springdrives are over the moon! I know of one that is running less than one second a month!

Yes Mike agree great accuracy but have we progressed in timekeeping mechanically all that much.So guys next time your watch is perhaps a few seconds fast or slow just outside COSC spec, think about John Harrison's watches made almost 300 years ago.No computer aided graphic designs no machine robots to cut the precision parts. Only his bare hands and by todays standards very primitive tools.Now when Harrison's son William set sail for the West Indies, with the Harrison H4 marine chronometer, aboard the ship Deptford on 18 November 1761. They arrived in Jamaica on 19 January 1762, where his watch was found to be only 5 seconds slow! in almost 2 months accuracy three times better, than that required to win the £20,000 Longitude prize,in them days £20000 must have been quite a sum of money.So next time when your Rolex or any watch is just a few seconds out simply think of John Harrison who made a mechanical watch almost 300 hundred years ago that was more accurate than most mechanical wrist watch today,better than some quartz.

[roadcarver]

Thanks for concurring, Mike. I left the watch resting dial up last night. I will check with the usual site for time accuracy later on today.

Originally Posted by mike

Vernon, that's been my experience also. Rates seem to vary from machine to wrist based on how we wear the watch. Jeff brings up a good point in that which wrist the watch is worn will affect timming.

COSC testing is conducted in six positions over a fifteen day period at a number of different tempratures. While the standard is -4/+6 that standard is not that hard to meet by most modern movements. Indeed Seiko raises the bar on select watches to -3/+5 over a 24 hr. period.

What I have noticed is that if a watch is consistently fast or slow --on my wrist-- it is an accurate watch and will tend to gain or lose the same amount every day.

[Welshwatchman]

Originally Posted by padi56

Think about John Harrison's watches made almost 300 years ago.No computer aided graphic designs no machine robots to cut the precision parts. Only his bare hands and by todays standards very primitive tools.Now when Harrison's son William set sail for the West Indies, with the Harrison H4 marine chronometer, aboard the ship Deptford on 18 November 1761. They arrived in Jamaica on 19 January 1762, where his watch was found to be only 5 seconds slow!

Thanks for the info, Pete. It is quite amazing to think of the engineering skills of this man.

The thing that intrigues me is how they were able to determine that the watch was so accurate?

Today we have the Atomic clock as an absolute reference. What did they have then which was so accurate to the second?

[montecristo]

Originally Posted by Welshwatchman

Thanks for the info, Pete. It is quite amazing to think of the engineering skills of this man.

The thing that intrigues me is how they were able to determine that the watch was so accurate?

Today we have the Atomic clock as an absolute reference. What did they have then which was so accurate to the second?

A wall clock maybe?

My main concern now is that why didn't they up the COSC standard being that if seiko can crank out watches thats ±1 sec a day, why should they still use that old COSC standard?

[padi56]

Originally Posted by montecristo

A wall clock maybe?

Dont think they had too many clock around in those days nearly 300 years ago

My main concern now is that why didn't they up the COSC standard being that if seiko can crank out watches thats ±1 sec a day, why should they still use that old COSC standard?

Well the Swiss COSC is just a bench test for Swiss mainly made watches,now the Japanese chronometer standard is slightly higher,as with the European Din standard for watches.Today the COSC is just totally down to marketing,and almost any modern day movement can obtain the COSC standard with a bit of patience and careful regulation.
.

Originally Posted by Welshwatchman

Thanks for the info, Pete. It is quite amazing to think of the engineering skills of this man.

The thing that intrigues me is how they were able to determine that the watch was so accurate?

Today we have the Atomic clock as an absolute reference. What did they have then which was so accurate to the second?

They had two watches that were set astronomically with each other, now not sure about the science involved, and how they worked it out.But his watch was started and run, quite recently, and the accuracy tested then was quite unbelievable, and far better than the swiss COSC or any other standard for mechanical watches.

[mike]

Originally Posted by montecristo

A wall clock maybe?

My main concern now is that why didn't they up the COSC standard being that if seiko can crank out watches thats ±1 sec a day, why should they still use that old COSC standard?

Ken, I think it's mostly marketing.

Here's an explanation I found,
http://forums.timezone.com/index.php...oto=2063&rid=2

[mrbieler]

Seiko's production #'s for the springdrives is much lower then the mass produced Rolex and other brands using COSC standards. These watches are built by their top 5 most skilled craftsmen/women.

The Seiko is also a hybrid. It mixes mechanical and quartz technology to achieve the results.

It's amazing technology. Seiko raised the bar with this one.

COSC is a marketing standard. A good one and it works. It would also cost companies a lot more money if they tightened the standards.

[TNRonin]

I thought COSC was -4+6 secs/day?

[diablojota]

My watch likes to run 5 minutes fast. I don't take it off very often. But I'll set it, and it will run 5 minutes fast and pretty much stay there.

[Goodwatch]

Each officially certified COSC chronometer is unique, and identified by a serial number engraved on its movement and a certification number given by the COSC.

Testing criteria is based on ISO 3159 which provides the definition of a wrist-chronometer with spring balance oscillator. Only movements which meet the precision criteria established under ISO 3159 are granted an official chronometer certificate.

Each movement is individually tested for fifteen days, in five positions, at three different temperatures. Based on these measurements, seven eliminatory criteria are calculated, the minima of which must all be met e.g. for movements of a diameter over 20 mm, indicated in seconds/day:

Average daily rate: -4 +6
Mean variation in rates: 2
Greatest variation in rates: 5
Difference between rates in H & V positions: -6 +8
Largest variation in rates: 10
Thermal variation: +-0.6
Rate resumption: +-5

COSC have developed their own standard for testing quartz chronometers with eight eliminatory criteria:

Average daily rate at 23 °C: +-0.07
Rate at 8 °C: +-0.2
Rate at 38 °C: +-0.2
Rate stability: 0.05
Dynamic rate: +-0.05
Temporary effect of mechanical shocks +-0.05
Residual effect of mechanical shocks +-0.05, 200 shocks equivalent to 100 G (981 m/s²)
Rate resumption +-0.05
Measurements are based on a time base established by two independent atomic clocks synchronised on GPS time.

Over 1 million official chronometer certificates are delivered each year, representing only 3% of the Swiss watch production, a proportion that underscores the exceptional nature of a chronometer. To earn chronometer certification, a movement must not only be made from the highest quality components, but also be the object of special care on part of the finest watchmakers and timers during assembly.

Sources: courtesy of "Contrôle Officiel Suisse des Chronomètres", CH-2301 La Chaux-de-Fonds, Switzerland, email: [email protected]

[fat-sam]

i always thought you got a certificate with a load of details about your watch's individual perfomance, with my new planet ocean i got a credit card is this normal?

[Goodwatch]

Originally Posted by fat-sam

i always thought you got a certificate with a load of details about your watch's individual perfomance, with my new planet ocean i got a credit card is this normal?

Yes. What you are talking about is the 'Bulletin le marche'. I've written Rolex SA many years ago to ask about my BLM but they answered that all individual records off all watches are stored in a database and cannot be made available to the customer anymore.

[fat-sam]

Originally Posted by Goodwatch

Yes. What you are talking about is the 'Bulletin le marche'. I've written Rolex SA many years ago to ask about my BLM but they answered that all individual records off all watches are stored in a database and cannot be made available to the customer anymore.

i'm guessing omega will be just as helpfull!

[mike]

Originally Posted by fat-sam

i always thought you got a certificate with a load of details about your watch's individual perfomance, with my new planet ocean i got a credit card is this normal?

You did in the old days, but like Frans said not anymore.

Omega WILL send a copy of the cert. if you contact them.

[Goodwatch]

Originally Posted by fat-sam

i'm guessing omega will be just as helpfull!

Well, the whole idea of individual and handwritten (pen and ink, ) certificates is a bit romantic but you might expect some effort on their part. Alas

[fat-sam]

werhoo!
i'm doing that monday!

Originally Posted by mike

You did in the old days, but like Frans said not anymore.

Omega WILL send a copy of the cert. if you contact them.