How do digital devices know exactly how long a second is?
In: Technology
They have analog circuits that measure time. One of the simplest ways is to wait for a capacitor to charge up through a resistor, but it’s not accurate as each device might have a slightly different amount of capacitance and resistance. The most common way is to use a tiny vibrating quartz crystal, since they can be manufactured with very accurate vibration rates. For even more accuracy, you can wrap a heater around the quartz crystal so it always stays at the same temperature and doesn’t thermally expand. Most devices don’t bother with that. For crazy accuracy, you can plug in an atomic clock.
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