The position of a watch influences accuracy (2020)

https://watchesbysjx.com/2020/02/positional-error-and-accuracy.html

by nequo • 3 years ago

73 40 3 years ago

aredox• 3 years ago

Funny to see a fairly technical article on mechanical watches rank so high on HN.

Yes, quartz watches are simpler and more accurate yadayada, but there is an interesting engineering challenge in trying to improve accuracy (1 second/day = 10 ppm!) through purely mechanical means.

Constraints foster creativity.

yodon• 3 years ago

Long ago my dad (an experimental physicist) had a self-winding mechanical watch.

At the end of the day, he would check if the watch had gained or lost time during the day (compared to the broadcast bell chimes radio stations used to broadcast on the hour).

Based on the observation he would set the watch on its right side or left for the night, causing the spring in the self winding mechanism to be slightly more or less tensioned, leading to a slight gain or loss of time by morning to tune the watch to the precise broadcast signal.

hasoleju• 3 years ago

Thanks for that story. While reading the article I always wondered what the value of the inaccuracy they where talking about really is. I guess it varies for different manufacturers. But seeing this shows me that even in the past it was only a matter of a few seconds.

bacheaul• 3 years ago

Yes! On average, my Orient watch runs about 15-20s fast per week when I lay it flat on its back at night. But when I position it crown down at night, it runs about 4s slow per week. I usually check it every Sunday morning, and if it's running a bit slow, then I'll put it on it's back for a couple of night to let it catch up. Haven't had to pull the crown out and adjust it for about 2 months now with this system.

TheOtherHobbes• 3 years ago

There's more room for creativity with digital technology.

The most accurate quartz movements drift by around 5 secs a year. Chip scale atomic clocks are accurate to around 37ms a year.

Current chip scale atomic clocks are still a little too big for watches, but some applied creativity might change that.

Personally I don't care about clockwork, but I think having an atomic clock on your wrist would be quite cool.

dgacmu• 3 years ago

An interesting race will be improvements to the local oscillator versus continued size and power reductions for grabbing a GPS signal every hour to correct your clock. No predictions here, though, of course, an increasing number of watches do have GPS for other reasons. (And the GPS solution doesn't help you if you live on a submarine)

throw0101a3• 3 years ago

The most accurate quartz movements drift by around 5 secs a year.

See:

* https://www.citizenwatch-global.com/the-citizen/lineup/5sec/...

* https://www.hodinkee.com/articles/the-citizen-eco-drive-the-...

They've gone to ±1 second per year:

* https://www.hodinkee.com/articles/citizen-caliber-0100-eco-d...

* https://www.citizenwatch-global.com/caliber0100/index.html

s0rce• 3 years ago

Are quartz watches really simpler? They require significant technological advancement to create.

JohnBooty3• 3 years ago

Well, both things are true. The technological advancement required to make them was immense. Now that we can stand on the shoulders of those giants, they are ~1 order of magnitude simpler to make.

Lio2• 3 years ago

Something that really blew my mind is how far mechanical accuracy can be taken when money is no object.

It's said that George Daniels could make mechanical watches that were more accurate than the quartz watches of his day[1], 0.4 seconds per year.

Of course that doesn't really matter if the thing is a priceless work of art that no one can afford to wear day to day but it's still really interesting to know how he did it.

Quartz watches' real advantage is just their accuracy but that they are accurate and cheap to make. There's something rather wonderful about a practically disposable Casio like a Bic Biro.

1. https://www.sothebys.com/en/articles/george-daniels-the-worl...

2. https://www.danielslondon.com/daniels-watches/the-space-trav...

formerly_proven2• 3 years ago

Orientation of a quartz watch also influences accuracy. Though a tuning fork watch crystal is probably not good enough to observe that.

ricc• 3 years ago

Maybe for analog and not digital? I believe temperature affects a quartz crystal more.

formerly_proven2• 3 years ago

Typical crystal acceleration sensitivities will range from about 1 x 10-10 per g for specially constructed precision SC-cut and AT-cut resonators to the order of 10-7 per g for tuning fork resonators.

https://www.microwavejournal.com/articles/print/7711-managin...

Demonstration: https://www.youtube.com/watch?v=zILwgQhjC_Q#t=2m36s

HPsquared2• 3 years ago

Mechanical clock accuracy used to be pretty important for navigation to determine longitude. A large prize was offered by the British government to whoever could invent a way to accurately determine longitude.

It's an interesting look at the high-tech world of yesteryear.

https://watchesbysjx.com/2019/09/john-harrison-marine-chrono...

https://en.m.wikipedia.org/wiki/Longitude_rewards

HPsquared2• 3 years ago

(Too late to edit)

And, of course, clock accuracy is even more critical now in the age of GPS.

154573452343• 3 years ago

Technically yes but the user of that system doesn't have to have an accurate clock, the GPS system itself provides the time signal. I think the first stage of GPS positioning is clock signal acquisition and training the local oscillator. Once synced you can proceed with almanac download or whatever comes next.

(The accurate (atomic) clocks are on the satellites and base stations.)

throw0101a3• 3 years ago

Mechanical clock accuracy used to be pretty important for navigation to determine longitude.

Specifically:

One degree of latitude equals approximately 364,000 feet (69 miles), one minute equals 6,068 feet (1.15 miles), and one-second equals 101 feet. One-degree of longitude equals 288,200 feet (54.6 miles), one minute equals 4,800 feet (0.91 mile), and one second equals 80 feet.

* https://www.usgs.gov/faqs/how-much-distance-does-a-degree-mi...

One minute of latitude covers about 1.8 kilometers (1.1 miles) and one second of latitude covers about 32 meters (105 feet).

* https://education.nationalgeographic.org/resource/latitude/

When using a sextant:

Sextants measure the angle between the sea horizon and a celestial body. These angles are measured in degrees and minutes of arc (1/60th of a degee). Measuring this angle to an accuracy of 1 minute of arc (1') will result in a positional accuracy of 1 nautical mile. Accurate sextants can measure this angle to an accuracy of 0.2'. This means that theoretically one can determine their position to 1/5 of a mile [~320m]. Additionally, a good clock is required to accurately compute the GP of the celestial body. An error of 1 second in the clock will create a positional error of up to 1/4 of a mile [~400m].

* http://www.cse.yorku.ca/~amana/personal/navigation/

Airplanes also used to use sextants for trans-oceanic flights (when beyond radio beacon range). Part 63 of FAA regulations has a section on Flight Navigators:

* https://www.ecfr.gov/current/title-14/chapter-I/subchapter-D...

Doing a search for FAA-H-8083-18 will lead you to The FAA Flight Navigator Handbook.

WalterBright2• 3 years ago

My dad was navigator on a B-17 in WW2. The B-17 crews had to fly their own birds from Newfoundland to England. Many crews and their airplanes were lost without a trace on this trip. (There was no hope of rescue if you went down in the North Atlantic. You just prayed nothing went wrong with the engines or the navigation.) My dad was proud he crossed the coast of Ireland within a mile of where he was aiming for.

His tool was a sextant and math.

He was made lead navigator for his bomb group.

He wanted to be a pilot, but because he was a math nerd, the Air Corps told him he was gonna be a navigator.

kqr• 3 years ago

Indeed, airliners used to have a domed window on top, just behind the cockpit, where the navigator could stick their head and take star fixes. The Apollo astronauts also did this when they needed to realign their gyros.

Terr_• 3 years ago

In an alternate universe, people might've discovered simple radio first, and skipped all the fancy clock developments!

1. Set up a big transmitter in some major city that fires off a big noisy pulse at every day at solar-noon.

2. Equip your long-distance ships with mediocre clock and a radio-receiver that is just good enough to detect the pulse if a crewmember is waiting and listening for it.

3. Using the low-accuracy clock, measure the difference between (A) solar noon where the ship is and (B) when the radio-pulse is received. Every 4 minutes is 1 degree of longitude.

P.S.: The pulse-listener will have to shift their listening-window as the ship travels, but it shouldn't be too tough since they already have a so-so clock and know their latitude. Sailing 200km/day along the equator means the pulse-listener would have to adjust their listening-window by ~8 minutes/day to keep "centered" on the pulse moment.

JohnBooty3• 3 years ago

The more I learn about old-timey maritime navigation, the more I realize that (like a lot of skilled trades) it must have been nearly indistinguishable from literal magic to laypeople.

I wonder if that fact inspired the mysterious and bizarre Guild Navigators in Dune.

mannykannot• 3 years ago

The article mentions, but does not describe, tourbillons, which are ingenious mechanisms to continuously rotate the escapement around one or more axes, so that the effects of orientation are averaged out.

https://youtu.be/O-6KhwwM66k?si=W0-jQ033m_kkv7-R&t=200

pard68• 3 years ago

My uncle always said you have to put your watch onto the rest/stand that comes with it as those are designed to hold the watch at the optimal position.

I never understood what he meant since I've always worn a Casio F-91 for as long as I can remember.

stevekemp• 3 years ago

That's a little interesting, if only because a lot of watches don't come with stands/cases - I remember when I was a kid I got a couple of watches that had little plastic holders, that they were packaged with.

These days I've got watches ranging from the low-end Casio Terrorist Watch to mid-range Rolexes, and a lot in between, and they typically come in boxes or cases without a stand of any kind.

bvan• 3 years ago

Watch mechanics are fascinating. If only software was developed with such care and accuracy..

bluescrn• 3 years ago

People spend vast amounts on luxury mechanical watches, when a $10 digital watch does the job of timekeeping just as well, if not better.

'Luxury Software' hasn't become a thing (beyond ludicrously priced free-to-play whalebait)

eru• 3 years ago

There's some really expensive software for CAD etc.

And there's bespoke software, that can be almost arbitrarily ludicrous in terms of cost. I'm talking about eg corporate in-house software that has whole teams developing it, but only a few users.

But I guess these examples are mostly just very expensive, but you don't use this software to brag to your mates.

Terretta• 3 years ago

'Luxury Software' hasn't become a thing

And yet, arguably, that's exactly what most app store subscriptions are, priced at several multiples of what that lightweight utility would have cost to purchase before the subscription model.

throw0101b• 3 years ago

'Luxury Software' hasn't become a thing […]

* https://en.wikipedia.org/wiki/I_Am_Rich

JohnBooty3• 3 years ago

Do you think that people buying mechanical watches are under the illusion that they're more accurate?

Some people surely buy them for the status symbol aspect, and those are definitely the ones we notice because their watches are big and tacky.

There are far more mechanical watches who don't wear brazen Rolex-esque "look at me" watches. You may not notice us because we're wearing Seikos, Citizens, Timexes, etc.

Ironically the accuracy and ubiquity of mobile phone based timekeeping has made mechanical watches more practical. You don't need your wristwatch to be hyperaccurate if you're carrying a phone.

    when a $10 digital watch does the job of timekeeping just as well

Surely not everything in your life is chosen strictly on terms of absolute performance?

I'm sure you own some articles of clothing that were chosen despite the existence of cheaper alternatives that are functionally equivalent for your use cases.

Lio2• 3 years ago

I wonder, how does orientation affect a watch with a Coaxial escapement?

Since they're a relatively modern innovation I'd guess they were never really used in commercial applications like marine chronometers.

https://en.wikipedia.org/wiki/Coaxial_escapement

The position of a watch influences accuracy (2020)

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