Products > Test Equipment
Oscilloscope Zoom Out Quirk
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jemangedeslolos:

--- Quote from: tv84 on June 15, 2020, 05:00:54 pm ---Dave's video already shows the "problem" explicitly (at least for my knowledge level).

The rest of the rumblings are different ways of explaining the thing (with more or less expert details) but, in the end, after all the juice has been squeezed, all come down to the same.

Those that disagree with this analysis, have misunderstood the simplicity of the bad/wrong (strike the one that makes you itchy) implementation that Dave's has showed in the video.

--- End quote ---

Yes, I think everyone has understood the problem since Dave posted the video.
But this is a problem that has been discussed here for years, often on the initiative of nctnico when we talk about the operation or the choice of an oscilloscope but rarely with a demonstration as explicit as Dave's one.

Despite this, there still seems to be misunderstandings between some here and on the real impact on real cases.
It would be great if nctnico could show us a case that we can solve with a GW Instek or an R&S and that we cannot with a Siglent or a Lecroy or with or with more steps or less efficiency.
maginnovision:
It's not about can or can not, it's about the time it takes. You can decode serial data even without the scope doing it. It just takes longer.
2N3055:

--- Quote from: nctnico on June 15, 2020, 04:19:08 pm ---
--- Quote from: 2N3055 on June 15, 2020, 03:29:01 pm ---
--- Quote from: nctnico on June 15, 2020, 02:35:45 pm ---You choose an example in which you can still see both signals on an oscilloscope with very little memory. Set the bitrate to 1Mbit/s (100 times higher) with a much higher packet rate as well and try to do the same with the top zoom window set to 5ms/. You'll see a contigous colored band. If you set the zoom window to 50us/ in order to see the packets a Siglent scope will shorten the memory depth and there is nothing you can do about it. You have a choice between either having long memory but not being able to see the packets in the zoom window OR seeing the packets but not have deep memory.

--- End quote ---

No it won't. I showed you example from my Pico where I sampled 100 MPoints in 200ms and shown it zoomed in to 20ns /div, zoom factor of  1M X. Yes, one million times.
Tautech posted one image above, where he got 50 MPoints at 20 ms/div (200 ms total) and is showing details at 20 us/div.

This is how it works but you don't seem to understand. On main timebase you grab big chunk of data, and zoom shows a subset of that, in such a detail that is only defined by sampling rate. Which will be limited by memory size.

But zooming in won't change anything from how timebase and sampling is set, only what are you looking at.

So you enable 100 MPoints, set timebase to use all 100 MPoints, and you can zoom in to every single point...
And zoom will not shorten or change anything.

What are you saying is SIMPLY NOT TRUTH. Just look at the overwhelming evidence shown here..

--- End quote ---
Sorry, but again you are not understanding the problem; you should try the steps I wrote on a Siglent or Lecroy oscilloscope and you'll see the limitations for yourself. You think you achieve the same but you don't. It is true there are many routes to Rome. You keep insisting the taking the long route to Rome is that same as taking the short route to Rome. That simply isn't true. It is no my fault you can't see the short route to Rome.

--- End quote ---

I DID show you that I accomplish the same with Picoscope.. With 1 million factor zoom.. Simultaneously capturing 100 Mpoints of data with 500 MS/sec and at the same time looking at it at trigger point (or any other point relative to trigger) at 20 ns /div.... Here it is 10 ms/div timebase , looking at it at 1,2 us/div, while simultaneously decoding 100 Mpoints worth of data sampled at 1GS/sec.



If I wanted to speculate I would simply think that you don't know how to use zoom properly, so you didn't set timebase to long enough before pressing zoom.
Or that you did try that on some previous Siglent scope that DID behave like this, and had some weird behaviour. 
That would explain why are you so adamant at repeating what is proven (with images) that is not true.

Entering zoom mode doesn't change any of parameter of sampling that is set previously with max mem depth and timebase. It simply opens new view to buffer with separate time axis on which it plots smaller subset of data on different time axis from timebase.

tv84:

--- Quote from: jemangedeslolos on June 15, 2020, 06:09:07 pm ---It would be great if nctnico could show us a case that we can solve with a GW Instek or an R&S and that we cannot with a Siglent or a Lecroy or with or with more steps or less efficiency.

--- End quote ---

That is another matter and goes deeply into each other's way of using a scope. Based on all the information in this forum it's perfectly clear that it will never be a consensus in the way people use a so generic instrument as a scope is. And, specially, people with lots of experience and accustomed to use it in a certain way.

Of course, it's not only about the people's way but also the type of signal analysis and/or glitches that are being searched that influence the best way to handle the scope.

If Siglent corrects this "quirk" i'm sure it will not be only nctnico that will be happy  :). That will benefit even the current Siglent advocates! And some/many of them have yet to understand that benefit.
2N3055:

--- Quote from: tv84 on June 15, 2020, 05:00:54 pm ---Dave's video already shows the "problem" explicitly (at least for my knowledge level).

The rest of the rumblings are different ways of explaining the thing (with more or less expert details) but, in the end, after all the juice has been squeezed, all come down to the same.

Those that disagree with this analysis, have misunderstood the simplicity of the bad/wrong (strike the one that makes you itchy) implementation that Dave's has showed in the video.

--- End quote ---

What Dave have shown is good explanation how Siglent scope works. I agree that they should add manual memory management if they can, just because. It can't hurt.
I'm not disagreeing with Dave's findings.
I'm fine with the fact that Nico uses something and it works for him.

My problem with Nico's interpretation is that he keeps saying things that are simply not true... I show example with 1 million zoom factor that disproves his statements, he says that if I chose different timebase it would be different. It wouldn't. I know how my scope works, I'm the one that use it on daily basis. He says Siglent scopes can't show zoomed data without losing detail few posts down from image from Elasia that clearly shows  it can do it.. I really don't care much for that.

I know I can be very stubborn sometimes. Not very often, but I simply cannot stand that incorrect is being sold as correct by repetition, false argumentation and misdirection.
It ain't truth. Simple as that.  I can stop, but it will never be truth. Never.
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