5 ms·

What’s the most precise clock I can buy, as an overpaid computer programmer? I suppose anything that shows a human time representation is out of the question.

What’s the most precise clock I can buy, as an overpaid computer programmer? I suppose anything that shows a human time representation is out of the question. It wouldn’t be able to incorporate legal changes to time such as let’s insert a leap second! or days are now divided into 32 hourlets!. I would settle for an output that shows elapsed seconds from an agreed upon datum. I guess having a human readable time would be fine but the science part is more interesting. With a clock of such precision, how could I synchronise it? Or rather: is there something better than NTP that Serious Clock Owners(tm) use? Perhaps what I want is a clock with reasonable-ish accuracy but incredible longevity. Having a long running independent mechanical source of time is appealing, and kind of orthogonal to having an ultra accurate but electrical one.

hnarn 5y ago
There’s nothing wrong with NTP and anything beyond the accuracy of a normal Casio watch is a fools errand in my mind: unless you get a watch that actually NTP syncs itself (like a smart watch), but the battle for an “on-wrist” super accurate watch was won by the digital wrist watch decades ago, there are no serious mechanical competitors.
- kijin 5y ago
  There are differences even among quartz watches, due to the quality of the crystal and the circuitry surrounding it. A normal sub-$50 Casio watch will gain or lose a few seconds every month, accumulating to more than 1 minute of error per year. A particularly bad one I've had gained a minute a month, worse than some of my mechanical watches! Meanwhile, Seiko sells quartz movements that are accurate to within 10 seconds per year. Citizen's top line is accurate to within 1 second per year, uses GPS signals to correct even that little error, and charges itself from any available light source. It's going to be accurate to within a few milliseconds for the next 20 years with no maintenance, all at a price that a typical overpaid programmer can easily afford.
  - hnarn 5y ago
    There's two parts to the original question: - What kind of high precision clocks are there - How do I synchronize them (implying NTP is not for serious use) Since any "smart" device including your "simple" smartphone, smart watch or even your laptop will synchronize itself via NTP, their time keeping abilities are likely already better or at least equal than that of any high tech mechanical watch, because the first question ties into the other: there is no point in perfect accuracy if you can have constant error-correction. While my inability to understand why anyone would care about a 10 second per year loss for personal use -- especially since the time and effort required to recalibrate even a manual clock is tiny if it does matter -- is completely subjective, I don't think the comparison between NTP-enabled devices and "ultra-correct" time keeping devices is. I just don't see a convincing argument for buying something like an atomic watch, or a high-end wristwatch, unless in the first case you yourself plan on hosting an NTP service for example (and you would, of course, even then at least verify it via: NTP!) -- or in the second case if you knew you would for an extended time be without access to any other trustworthy time-keeping device, via the Internet or otherwise. Everyone obviously has their own interests and anyone is free to spend any amount they want on expensive time keeping devices, I just think one should be aware of what the level of normality already is these days for many devices we use, which in my mind is pretty high.
ranma42 5y ago
The most precise for the hobbyist is probably a miniature atomic clock like https://www.sparkfun.com/products/14830 https://www.sparkfun.com/products/14830 "loses a second every 4,000 years or so"
miltondts 5y ago
The most accurate is probably any clock/watch with a GPS sensor.
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NovemberWhiskey 5y ago
Precise is not a term that's often used when considering clocks in the unqualified sense. The two usual dimensions you consider are accuracy and stability. Accuracy is about how well your clock tracks the target timebase over a long period, like a month. If your clock is free-running then this is important to you. Many kinds of clocks have aging effects, meaning that they become less accurate over time. Stability is about whether the individual "ticks" of the clocks have the same duration. Phase noise and clock stability are the same thing, so if you're using your clock to generate radio frequencies, this might actually be more important to you than accuracy. A clock can be accurate but unstable, or stable but inaccurate and so on. The most accurate clock technology is the atomic clock. The high-end of that market is represented by cesium standards, with rubidium standards at the lower-end. The most stable clocks outside the laboratory setting are ovenized crystal oscillators (OCXO). This is fundamentally a quartz crystal inside a metal box with a heater to keep a constant temperature. The next aspect is clock disciplining. Unless you intend to run your clock free and rely on its fundamental accuracy, you're probably going to synchronize it vs a superior standard. A common option for clock discipline is GPS, i.e. you're synchronizing your clock to the atomic clocks of the GPS satellites. NTP is simply a network-based mechanism for disciplining a clock. If you want "better NTP", that's called "PTP" but it's really only a local-area network thing.
zokier 5y ago
Facebooks Time Card is a good starting point if you want to start looking into how higher end timing devices are built: https://github.com/opencomputeproject/Time-Appliance-Project/tree/master/Time-Card https://github.com/opencomputeproject/Time-Appliance-Project... Afaik its not currently available for purchase, so it is more of a diy route. If you want a standalone unit, it probably wouldn't be too big of hassle to ducktape that Time Card to e.g. Raspberry Pi CM4 or similar module with pcie and drive a display (or whatev) that way. Or that FPGA on the Time Card probably has enough spare capacity to do it directly too, for a simplified architecture (and maybe better hard realtime control).

hnarn 5y ago

There’s nothing wrong with NTP and anything beyond the accuracy of a normal Casio watch is a fools errand in my mind: unless you get a watch that actually NTP syncs itself (like a smart watch), but the battle for an “on-wrist” super accurate watch was won by the digital wrist watch decades ago, there are no serious mechanical competitors.

kijin 5y ago
There are differences even among quartz watches, due to the quality of the crystal and the circuitry surrounding it. A normal sub-$50 Casio watch will gain or lose a few seconds every month, accumulating to more than 1 minute of error per year. A particularly bad one I've had gained a minute a month, worse than some of my mechanical watches! Meanwhile, Seiko sells quartz movements that are accurate to within 10 seconds per year. Citizen's top line is accurate to within 1 second per year, uses GPS signals to correct even that little error, and charges itself from any available light source. It's going to be accurate to within a few milliseconds for the next 20 years with no maintenance, all at a price that a typical overpaid programmer can easily afford.
- hnarn 5y ago
  There's two parts to the original question: - What kind of high precision clocks are there - How do I synchronize them (implying NTP is not for serious use) Since any "smart" device including your "simple" smartphone, smart watch or even your laptop will synchronize itself via NTP, their time keeping abilities are likely already better or at least equal than that of any high tech mechanical watch, because the first question ties into the other: there is no point in perfect accuracy if you can have constant error-correction. While my inability to understand why anyone would care about a 10 second per year loss for personal use -- especially since the time and effort required to recalibrate even a manual clock is tiny if it does matter -- is completely subjective, I don't think the comparison between NTP-enabled devices and "ultra-correct" time keeping devices is. I just don't see a convincing argument for buying something like an atomic watch, or a high-end wristwatch, unless in the first case you yourself plan on hosting an NTP service for example (and you would, of course, even then at least verify it via: NTP!) -- or in the second case if you knew you would for an extended time be without access to any other trustworthy time-keeping device, via the Internet or otherwise. Everyone obviously has their own interests and anyone is free to spend any amount they want on expensive time keeping devices, I just think one should be aware of what the level of normality already is these days for many devices we use, which in my mind is pretty high.

ranma42 5y ago

The most precise for the hobbyist is probably a miniature atomic clock like https://www.sparkfun.com/products/14830 https://www.sparkfun.com/products/14830 "loses a second every 4,000 years or so"

miltondts 5y ago

The most accurate is probably any clock/watch with a GPS sensor.

deleted 5y ago

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deleted 5y ago

[deleted]

NovemberWhiskey 5y ago

Precise is not a term that's often used when considering clocks in the unqualified sense. The two usual dimensions you consider are accuracy and stability. Accuracy is about how well your clock tracks the target timebase over a long period, like a month. If your clock is free-running then this is important to you. Many kinds of clocks have aging effects, meaning that they become less accurate over time. Stability is about whether the individual "ticks" of the clocks have the same duration. Phase noise and clock stability are the same thing, so if you're using your clock to generate radio frequencies, this might actually be more important to you than accuracy. A clock can be accurate but unstable, or stable but inaccurate and so on. The most accurate clock technology is the atomic clock. The high-end of that market is represented by cesium standards, with rubidium standards at the lower-end. The most stable clocks outside the laboratory setting are ovenized crystal oscillators (OCXO). This is fundamentally a quartz crystal inside a metal box with a heater to keep a constant temperature. The next aspect is clock disciplining. Unless you intend to run your clock free and rely on its fundamental accuracy, you're probably going to synchronize it vs a superior standard. A common option for clock discipline is GPS, i.e. you're synchronizing your clock to the atomic clocks of the GPS satellites. NTP is simply a network-based mechanism for disciplining a clock. If you want "better NTP", that's called "PTP" but it's really only a local-area network thing.

zokier 5y ago

Facebooks Time Card is a good starting point if you want to start looking into how higher end timing devices are built: https://github.com/opencomputeproject/Time-Appliance-Project/tree/master/Time-Card https://github.com/opencomputeproject/Time-Appliance-Project... Afaik its not currently available for purchase, so it is more of a diy route. If you want a standalone unit, it probably wouldn't be too big of hassle to ducktape that Time Card to e.g. Raspberry Pi CM4 or similar module with pcie and drive a display (or whatev) that way. Or that FPGA on the Time Card probably has enough spare capacity to do it directly too, for a simplified architecture (and maybe better hard realtime control).