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Reminds me of a highly accurate clock used in broadcasting. This clock sends out a time signal around the building to various clocks on walls and equipment, e.g. 'VT machines' (or whatever is used now).
I had the pleasure of adjusting this clock for GMT/BST twice a year. The great thing about this clock was that it did not actually tell the time itself. One would have to walk out of the machine room and through a couple of corridors, up a flight of stairs and into a gallery to actually see the alleged time with one's own eyes. All it had was a MODEM socket hidden in the back of a 19U rack, with the wires in U.S. configuration rather than what we have in the U.K.
So, to change the time you could 'conveniently' solder up a lead that would actually connect to the box, telnet in, remembering to get the password right, then set the time zone using the obscure command procedure provided.
This would be a simple enough task, however, there would be two of these clocks and they would talk to each other. So changing the time on one would not be good enough, the other would correct it or set it ahead/back by another hour. For added convenience the other 'master' clock would be in an entirely different part of the building and need to stay 'on' the whole time.
When it comes to extreme horology, I think that the most stupendously over-the-top accurate timepieces should not actually be able to tell the time with something as cheap and tacky as a display. If the time does have to be displayed then it should be in UNIX epoch time as that is the most convenient for all concerned.
A bit off-topic, but this is one BBC Horizon documentary I enjoyed, "Do you know what time is?"
http://www.dailymotion.com/video/x18wcfo_horizon-2008-do-you...
Basically, we, the human race, still have no clue at all what time is and why it only moves forward.
Even further off-topic and even more insightful is the Weekly Wipe' Moments of Wonder on Time:
www.youtube.com/watch?v=NvpbW7JRu0Q
;)
If the time does have to be displayed then it should be
in UNIX epoch time as that is the most convenient for all
concerned.
http://en.wikipedia.org/wiki/Unix_time
TAI is used for atomic clocks, then converted to UTC or unix time for consumption by ordinary time consumers.
I am actually very pleased to have learned that snippet of useful information!
FYI when I wrote my comment I had just added an attribute to a product catalog that uses [very large number] - [product creation date in epoch format] so that I could have a latest added as the sort order without having to go through the bother of having DESC on my SQL query.
I assure you that only on HN could you find someone that is delighted to know about how 'unix time is not monotonic'... - thanks!
Also see this experiment from the same site: http://leapsecond.com/great2005/
Quote: "So, yes, not only do we live in a time when atomic clocks are altimeters, but when relativity is child's play. It was the best extra 22 nanoseconds I've ever spent with the kids."
This got me thinking: How can you tell that two clocks are 22 nanoseconds apart? I mean, it's not like you can look at a display or anything.
This is a bit of a rhetorical question, I'm sure Google holds many answers involving decaying isotopes or measuring laser pulses or something.
This entry from "Time and Frequency from A to Z" published by NIST should get you started.
How can you tell that two clocks are 22 nanoseconds apart?
If the clocks are in the same room and you have a fast oscilloscope at hand, it's easy.
If the clocks are more than about 6 metres apart, it really is impossible.
For a little bit of context, leapsecond.com is the website of Tom Van Baak, one of the "Time Nuts", people striving (sometimes: obsessed with) to maintain precise clocks and oscillators, mostly for the fun of it.
Here's a recent talk of him, at the ARRL and TAPR Digital Communications Conference, 2013.
https://www.youtube.com/watch?v=MT2reYXPvGg
Also interesting, the state of the art in amateur timekeeping (but already 2003):
http://leapsecond.com/ptti2003/index.htm
...and clock powers of ten.
Thanks for posting those! I came across the leapsecond site years ago and enjoyed it but haven't been back in a while. If I wasn't already so over-hobbied I'd probably be a time nut. My father is a ham radio operator and always set the clocks in the house from the WWV broadcasts, thus establishing in me at a young age an appreciation of accurate clocks.
Haha, good for increasing your arm strength. There does seem to be some slightly more portable ones:
http://www.microsemi.com/products/timing-synchronization-sys...
Also you can get fairly cheap rubidium clocks from ebay that tend to output around 10MHz for fairly cheap. They would be less accurate that the one he's sporting however.
Yeah, someone's doing a Kickstarter for an atomic watch based on a similar module but they seem to have sold out of them already: https://www.kickstarter.com/projects/846511652/the-worlds-fi...
Can someone explain me use of those atomic watches... with analog displays and tuned by hand?
Re the radio synchronized watches, it's annoying that most of them listen to things like WWV, which is geographically limited.
The Seiko Astron is probably the best alternative, since GPS sync works over the whole planet. Unfortunately, expensive. (http://www.seiko-astron.com/)
There are a lot of digital GPS watches (Garmin, Suunto, etc.), but some of them (for some reason) don't sync the displayed watch time to GPS time.
Watches actually listen to WWVB, not WWV. (WWV is on HF, WWVB is on LF.)
On a good propagation day, you can probably hear WWV around the world. If it wasn't for other countries broadcasting their time stations on the same frequency, that is.
Ultimately, LF time synchronization is a good idea. It doesn't depend on additional ionospheric information to get an accurate time transfer, since signals do not travel through the ionosphere. HF signals take different routes at different times of day, and GPS time transfer requires an accurate site survey and accurate ionospheric delay constants.
There's also these: http://www.ablogtowatch.com/citizen-satellite-eco-drive-watc...
Btw. I happen to know the guy who directed the ad. I just don't understand why Japanese watchmakers don't market their GPS watches more heavily and in a much lower price range. I feel that there is a huge market gap for well made $300-700 watches with GPS synched time. There's cheap quartz that aren't synched, there's the expensive Seikos and Citizen watches ($1000-$3000), there's mechanical Swiss watches you have to set up yourself ($500 to whatever you want to pay) and there's mechanical watches with perpetual calendar (start at $10k or so). As a result, Swiss watchmakers get most of world's earnings. Others just try to either emulate the Swiss or cheap Japanese quartzes from the past.
Casio is coming out with their first GPS/WWV hybrid watch: http://www.ablogtowatch.com/casio-g-shock-gpw1000-first-watc...
Since that post is quite old, I was surprised that this wasn't a reference to Bathy's recent efforts to make a wristwatch out of a chip scale atomic clock that is much closer to actual wristwatch scale (though still very large).
http://www.ablogtowatch.com/bathys-hawaii-cesium-133-atomic-...
There is now a 17cm3 atomic clock chip on the market for about $2300, well under the price of a high-end watch. I'm surprised nobody's made a wristwatch with that.
The chip: CSAC SA.45s.
Datasheet here:
http://www.chronos.co.uk/files/pdfs/sym/sa.45s.pdf
120mW, 3.3V? Totally doable as a wristwatch.
Because a >>$2300 wristwatch is a piece of jewelry, not a way to tell accurate-to-the-second time. Typically, it will have an intricate mechanical movement and be almost as accurate as a $5 quartz-driven electronic watch from the gift shop.
Given that they're advertising military applications, I wouldn't be surprised if there are export regulations on such components.
Shame that it's so huge!
I would love to have a small form factor real atomic clock wristwatch.
Then I could impress people like "your watch may have a touch screen and smartphone integration, but, mine is ATOMIC!"
Well, I think all watches are made of atoms and hence ATOMIC. I think most just don't intentionally include an atom of cesium, ask it to resonate, and then measure the frequency. ;)
The really sad thing is how the "old" HP was so cool but now it's gone.
They designed and built so many fantastic products, and then wrote amazingly detailed articles about them in the Hewlett-Packard Journal. http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/hpjindex.html
Rather less silly, actually an atomic watch and close to wristwatch size: http://www.ablogtowatch.com/bathys-hawaii-cesium-133-atomic-...
edit: grammar
This story is tacked up on the wall inside the clock room at the Arecibo Radio Observatory. The "Keeper of the Clocks" here eagerly awaits a true atomic watch based off the CSAC SA.45s chip that @daniel-cussen mentioned.
How go the repairs there? I loved visiting the observatory and museum hall on my first few trips to PR.
Did they manage to keep all or most of it open to the public or is it now purely a science installation?
Edit: Ah, I found a link to the visitor's center ( http://www.naic.edu/outreach/describe_fset.htm ). Happy to see it is still serving the public and looking forward to taking my kids there next trip down.
If you want something that would have an accuracy that's relatively close to an atomic watch, get one that synchronizes its time using GPS.
Relatively close? What is this, horse shoes or hand grenades? I need precision dammit!
Technically this is an underarm-watch, not a wristwatch. Imprecise terminology is almost as bad as clock drift!
Who would wear that, seriously
Someone who needs that, seriously!
Chuck Norris' watch
Where do I order one? I'm hooked!
I can't help but feel this is a little impractical.
Perhaps a bit, but the boldness and style quickly make up for that.
If the goal is to show that people upvote without looking at the link, then I think it's quite successful.
This is fake. Do you see the power cable on the photos? They do not use batteries on their photos!!! And I thought it is finally true ;)
The HP5071 has built in rechargeable batteries.