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As an exercise I measured (with a 100MHz 10x probe) the 32.768 kHz crystal signals on a board by varing the Cl1,/Cl2 capacitors.

Here are the results:

12pF

enter image description here

15pF

enter image description here

22pF

enter image description here

Can someone help me interpret these results? The frequency is roughly correct (I do not have an accurate way and instruments to measure it.)

In all the cases, the amplitude increases with 12pF. (I suppose it is a good thing, isn't it?)

JRE
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Paul Lake
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  • [Crystal oscillators - my bare-bones website](http://www.stades.co.uk/XTAL%20Oscillator/XTAL%20Oscillator.html) and [Crystal loading](https://electronics.stackexchange.com/questions/250608/crystal-oscillator-load-capacitance-again/250645#250645) and [crystal feedback resistor](https://electronics.stackexchange.com/questions/384602/feedback-resistor-value-for-a-crystal-oscillator/384613#384613) and [What frequency stability crystal do we need?](https://electronics.stackexchange.com/questions/600887/what-frequency-stability-crystal-do-we-need/600903#600903). – Andy aka Feb 10 '22 at 10:41
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    Does this answer your question? [Crystal oscillator load capacitance, again](https://electronics.stackexchange.com/questions/250608/crystal-oscillator-load-capacitance-again) – Andy aka Feb 10 '22 at 10:45
  • What exactly you need to get interpreted? More loading, less amplitude? The effect to frequency is so small that it can't be measured by scope, but more load will lower the frequency. You need just the right amount of load to get just the right frequency that is within your requirements. – Justme Feb 10 '22 at 11:19
  • well why don't use the scopes measurement facility to measure the frequency? seems to be good enough to measure 32.768 kHz... – schnedan Feb 10 '22 at 12:03
  • As a hint, if you want to measure period on a scope, set the markers to span (for example) 10 periods and divide by 10, don't set them across half a period and multiply by 2. (Or just use the built in measurement feature of the scope) – The Photon Feb 10 '22 at 15:48
  • It still won't be as accurate as using a frequency counter, but it will probably get you an extra signifcant figure. – The Photon Feb 10 '22 at 15:50

0 Answers0