2 ms·
That's intriguing! I was under the impression that the mains frequency varied, which is why mains hum is useful for dating recordings. It appears there is some
by phil_k 2y ago
That's intriguing! I was under the impression that the mains frequency varied, which is why mains hum is useful for dating recordings. It appears there is some drift (but why?), although they aim to keep the average stable over a certain period. The article states that the device primarily relies on mains frequency for timekeeping, using the crystal oscillator as a backup. I found that unexpected, though I'm not well-versed in either topic.
- ipieter 2y agoThe mains frequency is literally how fast the generators in power plants are turning. If the load on the grid increases, those generators slow down slightly and more natural gas/coal/heat needs to be added to increase the frequency again. This whole process is quite complicated as not every plant can react in the same time. Some plants are always at 100% capacity, while others are dedicated to governing the frequency. So there are small fluctuations, often between 0.2 Hz around the base frequency, but the average is very close to the theoretical 50/60 Hz. And for an alarm clock that is good enough.
- Tempest1981 2y agoA while back, this happened in the US: The North American Electric Reliability Corporation (NERC) discussed a proposed experiment that would relax frequency regulation requirements. https://www.nerc.com/pa/Stand/Project%2020101422%20Phase%202%20of%20BARC%20%20BAL004%20DL/BAL-004-0_White_Paper_Clean_09242015.pdf https://www.nerc.com/pa/Stand/Project%2020101422%20Phase%202... Was that made permanent, or reverted? I thought I've noticed the accuracy of my older line clock being worse... trending fast. From https://en.wikipedia.org/wiki/Utility_frequency#US_regulations https://en.wikipedia.org/wiki/Utility_frequency#US_regulatio...