4 ms·

He shows that between 9:50 and 10:50 in the video https://youtu.be/Q07CTj4fUeY?t=592 https://youtu.be/Q07CTj4fUeY?t=592

helsinkiandrew 4y ago
But doesn't that rely on having a strobe flashing at the specific frequency - I thought modern record players do anyway. I'm not sure how this worked on the 1920s machine - unless it assumed 50H mains frequency, or have I missed something?
- hotpotamus 4y ago
  Yeah, I would assume they're using mains frequency as the reference. It was a pretty common thing back in the old days. I remember reading one electrical system engineer talking about how they had to tweak the grid hz in order to make sure that peoples' clocks stayed fairly correct. The grid would typically slow down a bit during times of peak load, so they'd run a bit faster at other times to force clocks to catch up. I think most of those clocks are gone now that there are much better sources, but they were still fairly common when I was a kid in the 90's (though I didn't learn about how they worked until much later).
  - kqr 4y ago
    No, many mains connected clocks still use the power frequency for timing. As recently as four years ago we had the same problem: https://www.nationalgeographic.com/science/article/european-clocks-six-minutes-late-serbia-kosovo-electricity-grid-spd https://www.nationalgeographic.com/science/article/european-...
    - hotpotamus 4y ago
      I wonder where they are still in use? In my world, NTP is king, but there are also radio transmitters in various parts of the world that send out time signals, and satellite navigation systems that broadcast time so accurate, it can be used as a stratum 0 source for NTP. Any time I've checked my phone, it's had essentially 0 error that a human could perceive, and I assumed it was getting that from the cell network. Even my decorative/fashion quartz wristwatches only drift a few seconds a month at most. In my world, tech has certainly moved on, and I'd assumed that was the way for most people too.
      - kqr 4y ago
        I have personally only experienced it with bedside alarm clock radios, and large wall clocks e.g. in schools.
        hotpotamus 4y ago
        Yep, I was thinking of the bedside clocks, but my phone does that job for well over the last decade now. When I was a kid in the 90's, the school clocks were already centrally controlled - you could see them all change in unison sometimes as they corrected them. I'd imagine they might have generally used the 60hz reference and then been corrected as needed, but I wouldn't consider that quite the same thing. It's also interesting to look at Swiss railway clock homages. The design is iconic and quite readable, but the more interesting ones have what are marketed as "stop to go" movements that mimic the actual Swiss clock system. They tick as you would expect, but when the second hand reaches 12 o'clock, it pauses, and the minute hand advances one full minute. It's a strange effect, and then of course you start asking about what happens during that pause and how it was actually counting time around that dial (it would have to be a bit fast, wouldn't it?). From my limited understanding, this is because the system synchronized every minute at the top of the minute, and the system had been around since at least mid-century. Obviously it's just an amusement on a wall clock or wristwatch.
      - junga 4y ago
        Using an iPhone with continuity camera as webcam for work. Can't remember the exact reason why the iPhone can not receive network time in my setup but it effectively can only rely on its local circuits to meassure time. Time is ten minutes off just after a few weeks. It really blew my mind when I first saw this.
      - tgsovlerkhgsel 4y ago
        It's cheap (unlike NTP in a non-internet-connected device and a custom radio circuit), works anywhere where a mains-connected device works (unlike the radio stuff which may not work in a basement/concrete building, or if exported to a different country on the same grid), is unlikely to stop working in the next decade, and is more accurate than quartz over the long term due to the compensation games utilities play.
netsharc 4y ago
Hmm, but how do they make sure the strobe is strobing at the right frequency?
- beAbU 4y ago
  Most likely the 50/60hz mains frequency?
- kqr 4y ago
  As someone else said, the trick is that you can use a slower source to line up the rotation of a faster source to high accuracy. The idea is similar to that of the Vernier scale.

But doesn't that rely on having a strobe flashing at the specific frequency - I thought modern record players do anyway. I'm not sure how this worked on the 1920s machine - unless it assumed 50H mains frequency, or have I missed something?

hotpotamus 4y ago
Yeah, I would assume they're using mains frequency as the reference. It was a pretty common thing back in the old days. I remember reading one electrical system engineer talking about how they had to tweak the grid hz in order to make sure that peoples' clocks stayed fairly correct. The grid would typically slow down a bit during times of peak load, so they'd run a bit faster at other times to force clocks to catch up. I think most of those clocks are gone now that there are much better sources, but they were still fairly common when I was a kid in the 90's (though I didn't learn about how they worked until much later).
- kqr 4y ago
  No, many mains connected clocks still use the power frequency for timing. As recently as four years ago we had the same problem: https://www.nationalgeographic.com/science/article/european-clocks-six-minutes-late-serbia-kosovo-electricity-grid-spd https://www.nationalgeographic.com/science/article/european-...
  - hotpotamus 4y ago
    I wonder where they are still in use? In my world, NTP is king, but there are also radio transmitters in various parts of the world that send out time signals, and satellite navigation systems that broadcast time so accurate, it can be used as a stratum 0 source for NTP. Any time I've checked my phone, it's had essentially 0 error that a human could perceive, and I assumed it was getting that from the cell network. Even my decorative/fashion quartz wristwatches only drift a few seconds a month at most. In my world, tech has certainly moved on, and I'd assumed that was the way for most people too.
    - kqr 4y ago
      I have personally only experienced it with bedside alarm clock radios, and large wall clocks e.g. in schools.
      - hotpotamus 4y ago
        Yep, I was thinking of the bedside clocks, but my phone does that job for well over the last decade now. When I was a kid in the 90's, the school clocks were already centrally controlled - you could see them all change in unison sometimes as they corrected them. I'd imagine they might have generally used the 60hz reference and then been corrected as needed, but I wouldn't consider that quite the same thing. It's also interesting to look at Swiss railway clock homages. The design is iconic and quite readable, but the more interesting ones have what are marketed as "stop to go" movements that mimic the actual Swiss clock system. They tick as you would expect, but when the second hand reaches 12 o'clock, it pauses, and the minute hand advances one full minute. It's a strange effect, and then of course you start asking about what happens during that pause and how it was actually counting time around that dial (it would have to be a bit fast, wouldn't it?). From my limited understanding, this is because the system synchronized every minute at the top of the minute, and the system had been around since at least mid-century. Obviously it's just an amusement on a wall clock or wristwatch.
    - junga 4y ago
      Using an iPhone with continuity camera as webcam for work. Can't remember the exact reason why the iPhone can not receive network time in my setup but it effectively can only rely on its local circuits to meassure time. Time is ten minutes off just after a few weeks. It really blew my mind when I first saw this.
    - tgsovlerkhgsel 4y ago
      It's cheap (unlike NTP in a non-internet-connected device and a custom radio circuit), works anywhere where a mains-connected device works (unlike the radio stuff which may not work in a basement/concrete building, or if exported to a different country on the same grid), is unlikely to stop working in the next decade, and is more accurate than quartz over the long term due to the compensation games utilities play.

netsharc 4y ago

Hmm, but how do they make sure the strobe is strobing at the right frequency?

beAbU 4y ago
Most likely the 50/60hz mains frequency?
kqr 4y ago
As someone else said, the trick is that you can use a slower source to line up the rotation of a faster source to high accuracy. The idea is similar to that of the Vernier scale.