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Watch Accuracy Explained

Contents

Part 1:
A little perspective, please

Part 2:
The enemy of mechanical movement accuracy

Part 3:
Accuracy of mechanical movements

Part 4:
Accuracy of quartz movements

Part 5:
Which is the best movement?

Part 6:
Further reading

A little perspective, please

Early development

Elias Allen (1588–1653), English clockmaker

Let's start this article with a short thought exercise. I'd like you to think about the conditions back in the 1500s when the first watches were coming onto the scene. It boggles the mind (mine at least) to think the watchmakers in those days could craft the gears, shafts, pinions, springs, screws, and the rest to make a functional timepiece.

Keep thinking about it; no electricity, no light except that provided by lamps or candles, no controlled heat or cooling. Their tools were likely primitive, and everything was cut, shaped, and finished by hand. I mean, really, how did they manage to cut the tiny teeth in the gears with precision and repeatability? Our ancestors were remarkable people, and thanks to their genius and skill, we are able to enjoy the fascinating hobby of watch collecting today. Mind exercise over.

The enemy of mechanical movement accuracy

WWI and the interwar years

When it comes to mechanical watches, friction, precision, and gravity conspire to reduce accuracy. The movements convert the energy stored in the mainspring into rotational movement of the gear train. In turn, the gears move the hands and power other complications like chronometer functions and power reserve displays.

The gears are held between plates, and their shafts rotate in tiny holes. For especially critical gears, watchmakers insert minuscule synthetic rubies (which, by the way, are identical to real rubies without the cost). Rubies provide a silky smooth surface that reduces friction considerably.

At other shaft locations, the watchmakers use little drops of oil to reduce friction. Prior to today's synthetic options, the oil could become gummy. This was due to age, disuse, dirt getting inside the case, and so forth. As you expect, gummy oil increases friction. Friction up, accuracy down.

Another enemy of accuracy in mechanical movements is wear and tear on the movement's rotating parts.Over time, the physical interaction of the gears, spring, and plates can lead to wear.

In five short years following Bleriot's flight, Europe and most of the rest of the world was plunged into the horror of WWI. Dirigibles and observation balloons were still in use but eventually succumbed to the rapidly developing airplanes. Watches and compasses now served to guide bombers to targets to deliver their ordnance as accurately as possible.

The airplanes of WWI were often hard to control. That meant the pilot was ill-advised to take his hands off the controls to retrieve his pocket watch. The same value that leads Santos-Dumont to seek a solution carried full force into combat.

Most aerial combat during WWI occurred during the day due to lack of proper instruments and lights. Bad weather almost always grounded the planes of the time. So watches did not need large quantities of luminescence. The just needed to be easy to read. Therefore, the iconic black dial and large contrasting Arabic numerals became standard issue.

As a result of experiences in WWI, U.S. Navy captain Philip Van Horn Weems designed an independently adjustable seconds ring. This feature allowed pilots to accurately synchronize their watch with a radio time signal without stopping the sweep seconds hand. Although "hacking" watch movements to allow everyone in a combat unit to synchronize their watches to the second, the practice could result in throwing pilots off course, ruin missions, and risk the airplane and crew.

Following his successful trans-Atlanic flight in 1927, Charles Lindbergh collaborated with Weems to develop the Hour Angle system which further enabled the wristwatch to determine longitude.

The German military specified a design that set the standard for what we think of as a classic pilot's watch today. By 1936, aviation advances allowed airplanes to fly at all hours and in foul weather (although grounding in severe conditions was common). The result was the Beobachtungsuhr (B-Uhr), or Observer.

"A LIV watch is a precision instrument with hundreds of moving components working together in harmony. In order to ensure that it continues to work for decades to come, regular maintenance is required. We recommend mechanical movement overhauls and services every 20-24 months."

- Chaz Chazanow

Co-Founder at LIV Watches

Accuracy of mechanical movements

So, just how accurate can a mechanical movement be, given the challenges presented by friction, etc.? You might be surprised to find out that mechanical movements can be accurate to within a few seconds per day. Okay, since some accuracy ratings are on the horizon, let's determine how many seconds you have each day:

Total seconds/day = (60 seconds x 60 minutes x 24 hours) = 86,400 seconds.

The quality of the movement will determine the accuracy. Premium Swiss movements like those engineered by ETA and Sellita are accurate to +/- 12 seconds per day. What is the accuracy of a movement that loses this number of seconds?

Accuracy % = (12/86,400) = 0.000138888%, plus or minus.

But wait, there's more. Movement manufacturers can submit their masterpieces to the Contrôle Officiel Suisse des Chronomètres (COSC) for rigorous accuracy testing. This organization will provide a report and certificate documenting the accuracy. A COSC certified mechanical movement can be accurate to within +6/-4 seconds per day.

+ Accuracy % = (6/86,400) = 0.000069444%
- Accuracy % = (4/86,400) = 0.000046396%

These seem like reasonable accuracy rates on a daily basis.

Accuracy of quartz movements

Drumroll, please. Now it is time to show how accurate a quartz movement can be. The invention of the quartz movement was revolutionary, and it nearly destroyed the Swiss watch industry. Fortunately, nearly is the operative term. The Swiss watch industry is robust and thriving. It offers both mechanical and quartz movements.

Unlike their mechanical counterparts, friction, gravity, and wear don't impact accuracy, particularly in digital movements. However, these movements are not without their accuracy enemies. Temperature is one culprit. Extremes of temperature can affect accuracy. Battery performance is another one. Most batteries run until they stop. If something impacts the discharge rate of the battery, accuracy can suffer.

Regular quartz movements boast an accuracy of +/- 100 seconds per year. Time for more math.

Seconds per year = (86,400 x 365) = 31,536,000 second.

Accuracy % = (100/31,536,000) = my calculator doesn't have enough display room. Let's just say you are not likely to notice this level of inaccuracy.

Quartz movements can receive a COSC rating too. There are also thermally compensated movements that offer accuracies between +/- 5 to +/-25 seconds per year.

A LIV watchamker

"Want more accuracy? I recommend investing in the latest atomic clock. Apparently, the best atomic clocks are accurate within +/- 1 second per 15 billion years. But if you're after a beautiful quartz watch, consider a LIV GX1."

- Esti Chazanow

Co-Founder at LIV Watches

Which is the best movement?

Each movement type has its own legions of fans. And there really is no wrong choice. Purists love the mechanical movement with its elegant micro-engineering and roots in the origins of horology. Quartz fans are no less passionate about their timepieces. Quartz watches are "set and forget" with their battery power. And the use of electronics engineering enables these watches to provide functions and complications you cannot replicate using a mechanical movement.

Here at LIV, we offer both types of movements, sourced from the best Swiss movement makers. Your collection has room for both and should have examples of each. If you are running late for an appointment, be sure to strap on your mechanical favorite. Your excuse for tardiness? "Hey, this thing is only accurate to +/- 12 seconds per day. Cut me some slack." Let us know how that works out for you.

The Crafting of a LIV Watch in Stabio, Switzerland

Further reading

Contents

Part 1:
A little perspective, please

Part 4:
Accuracy of quartz movements

Part 2:
The enemy of mechanical movement accuracy

Part 5:
Which is the best movement?

Part 3:
Accuracy of mechanical movements

Part 6:
Further reading

Early development

A little perspective, please

Let's start this article with a short thought exercise. I'd like you to think about the conditions back in the 1500s when the first watches were coming onto the scene. It boggles the mind (mine at least) to think the watchmakers in those days could craft the gears, shafts, pinions, springs, screws, and the rest to make a functional timepiece.

Keep thinking about it; no electricity, no light except that provided by lamps or candles, no controlled heat or cooling. Their tools were likely primitive, and everything was cut, shaped, and finished by hand. I mean, really, how did they manage to cut the tiny teeth in the gears with precision and repeatability? Our ancestors were remarkable people, and thanks to their genius and skill, we are able to enjoy the fascinating hobby of watch collecting today. Mind exercise over.

Given the fact that Santos-Dumont was a regular participant at the airshows of the day, other pilots exhibited one of the earliest known examples of wrist envy. As a result, the pilot's watch soon became a "must-have" instrument in the cockpit. And, not just for "keeping up the the Santos-Dumonts" reasons. Advances in powered flight were enabling planes to fly further and faster. With a reliable watch and a compass, pilots had the tools they needed to calculate time-speed-distance, determine when to move to the next leg of a flight, judge how much fuel was left, and generally be safer in the air.

Pilot Louis Bleriot wore a Zenith wristwatch when he made aviation history being the first to fly an airplace across the English Channel in July of 1909. Taking advantage of the feat for marketing purposes, Bleriot commented upon landing that he was very satisfied with his Zenith and would recommend it to others. The records are unclear on the point of Bleriot's comment being spontaneous or rehearsed.

WWI and the interwar years

"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua."

- Chaz Chazanow

Founder at LIV Watches

Advances during WWII

French watchmaker Zenith continued to manufacture their pilot's watches. Striking a neutral stance, Zenith sold its watches to both the Allies and the Axis. They used their 1939 Type Montre d"Aeronef design as the basis of their wristwatch. It featured the black dial and white arabic numerals with the large onion-style crown at 3 o'clock.

The United States did not produce a purpose-made pilot's watch. One of the most widely produced models supplied to American forces was the A-11. Manufactured by Bulouva, Waltham, and Elgin, the watch featured the required high-visibility black dial with white Arabic numerals. The manually wound movement featured a hacking function for synchronization. Some A-11s were waterproof, some were dust proof, some had luminous hands, , and some did not. All had a larger crown at 3 o'clock, but not in the onion style.

Postwar evolution

Elias Allen (1588–1653), English clockmaker

The enemy of mechanical movement accuracy

When it comes to mechanical watches, friction, precision, and gravity conspire to reduce accuracy.The movements convert the energy stored in the mainspring into rotational movement of the gear train. In turn, the gears move the hands and power other complications like chronometer functions and power reserve displays.

The gears are held between plates, and their shafts rotate in tiny holes. For especially critical gears, watchmakers insert minuscule synthetic rubies (which, by the way, are identical to real rubies without the cost). Rubies provide a silky smooth surface that reduces friction considerably.

At other shaft locations, the watchmakers use little drops of oil to reduce friction. Prior to today's synthetic options, the oil could become gummy. This was due to age, disuse, dirt getting inside the case, and so forth. As you expect, gummy oil increases friction. Friction up, accuracy down.

Another enemy of accuracy in mechanical movements is wear and tear on the movement's rotating parts.  Over time, the physical interaction of the gears, spring, and plates can lead to wear.

"A LIV watch is a precision instrument with hundreds of moving components working together in harmony. In order to ensure that it continues to work for decades to come, regular maintenance is required. We recommend mechanical movement overhauls and services every 20-24 months."

- Chaz Chazanow

Founder at LIV Watches

Accuracy of mechanical movements

So, just how accurate can a mechanical movement be, given the challenges presented by friction, etc.? You might be surprised to find out that mechanical movements can be accurate to within a few seconds per day. Okay, since some accuracy ratings are on the horizon, let's determine how many seconds you have each day:

Total seconds/day = (60 seconds x 60 minutes x 24 hours) = 86,400 seconds.

The quality of the movement will determine the accuracy. Premium Swiss movements like those engineered by ETA and Sellita are accurate to +/- 12 seconds per day. What is the accuracy of a movement that loses this number of seconds?
Accuracy % = (12/86,400) = 0.000138888%, plus or minus.

But wait, there's more. Movement manufacturers can submit their masterpieces to the Contrôle Officiel Suisse des Chronomètres (COSC) for rigorous accuracy testing. This organization will provide a report and certificate documenting the accuracy. A COSC certified mechanical movement can be accurate to within +6/-4 seconds per day.

+ Accuracy % = (6/86,400) = 0.000069444%
- Accuracy % = (4/86,400) = 0.000046396%

These seem like reasonable accuracy rates on a daily basis.

"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua."

- Esti Chazanow

Co-Founder at LIV Watches

Accuracy of quartz movements

Drumroll, please. Now it is time to show how accurate a quartz movement can be. The invention of the quartz movement was revolutionary, and it nearly destroyed the Swiss watch industry. Fortunately, nearly is the operative term. The Swiss watch industry is robust and thriving. It offers both mechanical and quartz movements.

Unlike their mechanical counterparts, friction, gravity, and wear don't impact accuracy, particularly in digital movements. However, these movements are not without their accuracy enemies. Temperature is one culprit. Extremes of temperature can affect accuracy. Battery performanceis another one. Most batteries run until they stop. If something impacts the discharge rate of the battery, accuracy can suffer.

Regular quartz movements boast an accuracy of +/- 100 seconds per year. Time for more math.

Seconds per year = (86,400 x 365) = 31,536,000 second.

Accuracy % = (100/31,536,000) = my calculator doesn't have enough display room. Let's just say you are not likely to notice this level of inaccuracy.

Quartz movements can receive a COSC rating too. There are also thermally compensated movements that offer accuracies between +/- 5 to +/-25 seconds per year.

"Want more accuracy? I recommend investing in the latest atomic clock. Apparently, the best atomic clocks are accurate within +/- 1 second per 15 billion years. But if you're after a beautiful quartz watch, consider a LIV GX1."

- Esti Chazanow

Co-Founder at LIV Watches

Which is the best movement?

Each movement type has its own legions of fans. And there really is no wrong choice. Purists love the mechanical movement with its elegant micro-engineering and roots in the origins of horology. Quartz fans are no less passionate about their timepieces. Quartz watches are "set and forget" with their battery power. And the use of electronics engineering enables these watches to provide functions and complications you cannot replicate using a mechanical movement.

Here at LIV, we offer both types of movements, sourced from the best Swiss movement makers. Your collection has room for both and should have examples of each. If you are running late for an appointment, be sure to strap on your mechanical favorite. Your excuse for tardiness? "Hey, this thing is only accurate to +/- 12 seconds per day. Cut me some slack." Let us know how that works out for you.

The Crafting of a LIV Watch in Stabio, Switzerland