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Building my own scope

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tggzzz:

--- Quote from: tautech on October 25, 2022, 08:34:53 am ---
--- Quote from: pcprogrammer on October 25, 2022, 08:19:14 am ---
--- Quote from: tautech on October 25, 2022, 08:12:12 am ---Of course they do. Why else would their sampling capability be listed in every datasheet in GSa/s ?

--- End quote ---

Read David his post.

The way I read it, is that according to him sampling is charging a capacitor with an analog value, not the turning it into a digital value. It is semantics.

--- End quote ---
I did also Mech's, rob77's and tggzzz's earlier all with some amusement.

But you just can't get away from facts, a DSO samples.....fast !

--- End quote ---

Not the old CCD-based Tek scopes! If you had a 1s sweep and 1000 capacitors in the CCD, then each capacitor contained the average voltage in a 1ms interval. A 1MHz oscillation would be invisible - and that was a problem.

More modern ADCs have a constant sampling rate even at slow sweep speeds, and that is the reason they can have "peak detect" modes which can show the presence of a 1MHz oscillation as a "noise" band.

tggzzz:

--- Quote from: pcprogrammer on October 25, 2022, 08:08:57 am ---So the distinction basically is that sampling means charging a capacitor to the analog voltage at the input and not the conversion to digital to make a digital sample.

--- End quote ---

Sampling means representing a signal at discrete intervals of time.

Some scopes simply display those discrete representations.

Some scopes digitise the representations, then store and digitally process them before displaying them.

pcprogrammer:

--- Quote from: tautech on October 25, 2022, 08:48:53 am ---Do you think the sampling dots in a DSO in Dot mode are just invented ?

--- End quote ---

Actually the original FNIRSI-1013D does invent (calculates) them when the input is above 44MHz  :-DD

tggzzz:

--- Quote from: gf on October 25, 2022, 09:00:03 am ---
--- Quote from: pcprogrammer on October 25, 2022, 08:56:27 am ---And what he, and me too, wonders about how this works for a high speed ADC. Does it use a sample and hold circuit or not.

--- End quote ---

Virtualy any ADC does. Continuous-time sigma-delta ADCs are the only exception i'm aware of.

--- End quote ---

And they also produce samples, of course.

I have an ADC that produces one sample every 50 seconds (a Solartron 7081). If the signal isn't constant within a sampling period then the output is the average of the input over that period.

pcprogrammer:

--- Quote from: tggzzz on October 25, 2022, 09:25:06 am ---Sampling means representing a signal at discrete intervals of time.

--- End quote ---

In this context yes. Sampling has many meanings. You can sample food or drinks, or take a sample of something you send to the printers to see if it matches the quality you require.

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