Jump to content

Article: Predicting Crystal Drift Over Time


Recommended Posts

Hello Everyone,

One of the more interesting sections of one of the books I am reading at the moment...

image.png.21468501ae49326e53060df5273fd368.png

...is the section that discusses how manufacturers have to compensate for errors in the quartz oscillators they rely on to provide accurate timing signals to the rest of the quartz circuit.

As almost every quartzophile (is that a word?) knows, the quartz crystal package is supposed to oscillate at 32,768 vibrations per second:

https://en.wikipedia.org/wiki/Quartz_clock#:~:text=Most such quartz clock crystals,frequency of 32768 Hz.

What's interesting (and what I didn't know, but made sense as soon as I read it) was the fact that this isn't always true, and a certain amount of compensation (or regulation) must be  performed by the movement manufacturer, sometimes by by cutting certain traces on the circuit board:

image.png.571aa822d70086598a43a49a98de044e.png

After that, the rate of the crystal was then more or less assumed to be stable over time.

But that's not true.  Apparently, the timing of quartz crystals degrades over time according to a well-known equation (Arrhenius Equation).

https://www.allaboutcircuits.com/technical-articles/using-the-arrhenius-equation-to-predict-aging-of-electronic-components/

I am now quite curious to know if dynamic compensation was implemented (perhaps using a second crystal) to help account for "drift" in the primary crystal.  One could imagine very highly demanding timing environments requiring three crystals and some form of polling system to converge on an "agreed upon" rate of oscillation.  Wow.  Cool!

I am very quickly finding quartz movements ultra, ultra nifty as I learn more about how they work.  Revolutionary is not too strong a word.

(Aside:  One of our sister institutions, MIT at their Media Lab (the parallel to my Department at PolyU) has recently showcased a sculpture that attempts to make what's going on in a quartz movement more accessible to people.  It's called "32,768 Times Per Second" and a small write-up appears on the MIT Media Lab website at:  
https://www.media.mit.edu/projects/32768-times-per-second).

image.png.907bee8efffcb42ee63615326325a553.png 

Sadly, I cannot find any photos of the installation 😞

g.
----

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.



×
×
  • Create New...