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Siglent SDS6000A DSO's 500MHz-2GHz

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--- Quote from: nctnico on November 01, 2021, 11:39:59 am ---sin x/x does not interpolate

--- End quote ---

 :palm: I must have skipped some lessons...


--- Quote from: tv84 on November 01, 2021, 11:50:18 am ---
--- Quote from: nctnico on November 01, 2021, 11:39:59 am ---sin x/x does not interpolate

--- End quote ---

 :palm: I must have skipped some lessons...

--- End quote ---
Indeed you have  ;). When the Nyquist criteria is met (with some margin) you can prove mathematically that you can draw only 1 waveform through the sampled points which is what sin x/x does. This means you are not interpolating (estimating) but reconstructing.

Yes we are reconstructing by using sin(x)/x to interpolate parts of the curve (or points, in the end there will always be physical plot points on the screen at least) between..

Estimation is not a synonym for interpolation.

Interpolation is a specific type of value estimation, that is closely related  to approximation.
Hence we approximate missing values by using sin(x)/x function, that we curve fit to sampled data points.
Therefore reconstructing the data between sample points.  We say that data was interpolated.

Or I don't understand it right...?

I don't want to drag out this semantic discussion out any further so this is the last thing I'm going to write about it: As I explained before you have to be really careful with the word 'interpolation' because it has a negative tone in combination with using test equipment. And there is reason for it since interpolation means estimation and thus implies inaccuracies / fantasy data. This has become very clear to me in previous discussions so I avoid using the word unless it is actually appropriate.


--- Quote from: Performa01 on November 01, 2021, 09:25:50 am ---The best feature of ESR is that it can be turned off.

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Hardly a ringing endorsement...

--- Quote ---The attached screenshots demonstrate the improved accuracy of transition time measurements in a long record.

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I certainly don't want to dismiss the efforts of some very talented people at LeCroy, as I'm sure this 'feature' is of some use and I certainly don't know enough technically to pass judgement on it.  It's the marketing angle where I'm sure the sales department was giddy with excitement being able to write "10Gsa/s blah blah".  That's an area I know enough to pass judgement on, b/t/w.

As for what it does, according to your explanation, it appears that without ESR the scope only performs the sinx/x interpolation on the screen display (and to adjust the trigger point on the fly) and not the whole capture?  So then ESR is simply using sinx/x to generate points in between the actual captured points so that the measurements can be done in the way they normally are--not using sinx/x interpolation--on a greater number of points.  OK.

However, I can't quite reconcile that with the photo excerpt that I posted from LeCroy's paper.  More samples means more Gibbs ears?  As I commented there, I fail to see the improvement in that case, and since the screen display is already being processed by sinx/x, what are they actually doing?


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