4 ms·
> cut costs by using less accurate crystals Maybe... but how much money could they possibly be saving? Quartz oscillators like the ones used in cheap digital w
by monochromatic 9y ago
> cut costs by using less accurate crystals
Maybe... but how much money could they possibly be saving? Quartz oscillators like the ones used in cheap digital watches are plenty accurate and completely abundant. I can't imagine they cost very much.
Maybe the issue has to do with miniaturization? If you're trying to make smaller and smaller devices, there could be an acceptable tradeoff between size and precision.
- agoetz 9y agoMost RTCs do use the same crystals that are in wristwatches, which is actually the source of their error. The tuning fork crystal design used in wrist watches has a parabolic temperature coefficient, which means that the clock is only really accurate at room temperature. This isn't a problem for wristwatches, because, presumably your wrist is at approximately room temperature, but it does become a problem for electronics that operate with large temperature swings. (like the inside of a phone or computer, for instance). https://www.maximintegrated.com/en/app-notes/index.mvp/id/58 https://www.maximintegrated.com/en/app-notes/index.mvp/id/58
- Florin_Andrei 9y agoThe vast majority of quartz references in consumer devices could be a lot better, but they are not fine-tuned at the factory. They're just "close enough". So they drift a lot. A simple tuning procedure could make almost all quartz clocks you own a heck of a lot better. But in many cases this is hard to do because the manufacturer never put the tuning components (a variable capacitor or the like) on the PCB.
- monochromatic 9y agoThat’s interesting. I’d never thought about it, but of course there’s a temperature dependence, and of course attaching it to a wrist mitigates it.