3 ms·
> I was expecting a gem-like quartz crystal inside, but found that oscillators use a very thin disk of quartz. Interesting - watches usually use a tuning fork
by nailer 4y ago
> I was expecting a gem-like quartz crystal inside, but found that oscillators use a very thin disk of quartz.
Interesting - watches usually use a tuning fork shape. I wonder why they use a disc here?
> Wristwatches were revolutionized in the 1970s by the use of highly-accurate quartz oscillators.
If you're into highly accurate timepieces you can pick up some amazing quartz pieces from brands like Rolex (the OysterQuartz) and Audemars Piguet (the AP Royal Oak 6005) from this time. Since brands wanted to distinguish their quartz movements from their mechanical ones the cases the quartz pieces come in are very distinct.
- sennight 4y ago> I wonder why they use a disc here? It has been a long time since I've thought about it, so I might be misremembering, but the crystal geometry can influence skew related to orientation and external vibration. A crystal + IC design is using the crystal as more of a bandpass filter than an actual signal source, so it would make no sense to introduce the downsides of a tuning fork for a design that makes no use of the actual tuning fork quality.
- fake-name 4y agoIt's a function of size. Tuning fork crystals generally have frequencies in the range of a few tens of kilohertz (generally 32768 Hz). Quartz discs vibrate at many megahertz. A tuning-fork like structure that oscillated at 100 MHz would be far to small to easily manufacture. ------ One fun note: crystals like this are used for measuring deposited material in vacuum processes like PVD [1] or similar [2]. The crystal is exposed inside the vacuum chamber where it will be deposited on at the same rate as the target, and the change in frequency is a direct function of the mass (and therefore thickness) of the deposited material. Eventually, the exposed crystal has to be replaced as it no longer oscillates properly. 1: https://en.wikipedia.org/wiki/Physical_vapor_deposition https://en.wikipedia.org/wiki/Physical_vapor_deposition 2: https://www.semicore.com/news/72-thin-film-deposition-control-quartz-crystal https://www.semicore.com/news/72-thin-film-deposition-contro...
- melony 4y agoNote 32768 Hz is chosen because it is a power of 2 (the 15th power).
- HPsquared 4y agoAnd therefore you can get a 1 Hz clock from a series of binary frequency dividers (flip-flops). That is, having the crystal oscillate at a power-of-2 frequency simplifies the circuitry a great deal.
- krallja 4y agoThe first power of two that is outside the range of (most) human hearing.
- anotherhue 4y agoA PVD sensor is a very clever use case! Thanks for highlighting.
- deleted 4y ago[deleted]
- adolph 4y agoAlso the Seiko Spring Drive. . . . the Tri-synchro regulator uses three types of energy to regulate the moving parts and establish synchronicity: * Mechanical power, from the mainspring * Electrical power, creating a reference signaling via an IC/quartz oscillator * Electromagnetic power, to apply a brake via a rotor/stator. These three forces work in harmony to regulate the way the spring unwinds and to make possible the precise movement of the second hand. https://www.grand-seiko.com/sg-en/collections/movement/springdrive https://www.grand-seiko.com/sg-en/collections/movement/sprin...