Author Topic: Scope and Probes - Measuring Crystal  (Read 3265 times)

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Offline tautech

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Re: Scope and Probes - Measuring Crystal
« Reply #75 on: August 27, 2019, 07:57:56 am »
I think oscilloscope is a bad choice to test crystals. It's better to use VNA. With VNA you can see parallel and serial resonance frequency, Q factor of crystal and it's equivalent circuit values and all parasitic resonances. With oscilloscope it will be almost impossible.

I am afraid that you have to read more than just (quite misleading) subject of the thread. Measuring oscillators is actual topic here and VNA is wrong tool for that.
Well yes and no.
An in-circuit active crystal, well yes a scope can give you information to see it's working  as expected.

Yet SFRA or a VNA can also give you info on the crystal outside the circuit.
From this post:
https://www.eevblog.com/forum/testgear/siglent-sds1204x-e-released-for-domestic-markets-in-china/msg2447832/#msg2447832
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Offline ogden

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Re: Scope and Probes - Measuring Crystal
« Reply #76 on: August 27, 2019, 08:09:32 am »
Yet SFRA or a VNA can also give you info on the crystal outside the circuit.

That post is about measuring *crystals*. I already said that you do not measure *oscillator* using VNA. How crystal measurements you mention helps to pick proper drive level and load capacitors? Please elaborate.
 

Offline David Hess

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Re: Scope and Probes - Measuring Crystal
« Reply #77 on: August 27, 2019, 11:29:32 pm »
For those unaware - he is talking about 20+ years old events & tech which is long gone. Oscillators and crystals are way different today.

The only thing which might have improved is the awareness of the IC designers and I am dubious about that when it involves analog circuits.  Crystals are the same but with a smaller selection and CMOS oscillators on lower voltage processes are worse.

It still happens that designers report with crystal oscillator problems on new microcontrollers.  Some have even done so on EEVBlog.
 


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