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New Tektronix 3 Series MDO

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Wuerstchenhund:


--- Quote from: snoopy on April 29, 2020, 02:29:19 am ---
--- Quote from: Wuerstchenhund on April 28, 2020, 03:22:57 pm ---InstaVu was a crutch where high update rates were achieved in a special mode using data reduction, and which made it impossible to run measurements or any other analysis on the waveform.

It was only an "industry first" in a sense that no-one else implemented such a mode, very likely because of it's limitations. At around the same time, HP came out with its first MegaZoom equipped scope (HP 54645A/D, the 'D' also being the "industry first" MSO), which achieved excessive update rates in normal operation, with no limitations on measurements.

And when it comes to emulating analog functionality, there simply is nothing which better resembles an analog scope than MegaZoom (if that's what you want). It's as simple as that.

--- End quote ---

That's not why you would use InstaVu. InstaVu was used to show up rarely occurring glitches that other scopes were blind to or may take hours sitting in front of the scope before  you would capture a single glitch !
--- End quote ---

So in which way is this different than any other high waveform rate technology like MegaZoom?

And while your trust in InstaVu is admirable, the reality is that even at 400k wfms/s your scope is still blind >90% of the time! Even scopes like the Keysight DSO-X3000T which achieve up to 1'030'000 waveforms/s are blind 89.70% of the time. Which means there is a 9 out of 10 chance your scope will miss an event on every acquisition.

Which means the *only* way to find rare events (or to make sure there are none!) is to use triggers.

And this is the reason why the only market segment that actually cares about update rates is the low-end/entry-level segment, mostly because this is what serves people coming from analog scopes and who prefer analog scope derived methodology. Above that, the update rate is pretty much irrelevant, and most high end scopes achieve only comparably low trigger rates. Which, again, doesn't matter, because no-one spends $3k on a scope to search for glitches by staring at a screen.


--- Quote ---And lets cut to the chase of the first megazoom scopes. What acquisition rates are you talking about here ? Please give us a figure !
--- End quote ---

The original HP 54645A/D back then only had 200MSa/s, however it already offered 1Mpts memory. But this model did satisfy the needs of most engineers who came from a standard analog bench scope, which often had less than 100MHz BW anyways. The 54645 handled like an analog scope in normal mode, and could perform measurements and FFT on data captured.

Of course the TDS700 had higher sample rates and BWs, it was part of Tek's high end offerings and did cost a lot more than the HP 54645A/D. However, InstaVu worked with data decimation which notably reduced the amount of data that was used, which also means the waveform on the screen doesn't necessarily reflect the actual signal (bit like Peak Detect), something that isn't the case with MegaZoom.

Teh main point however is that for a scope in this class high update rates were pretty low on the list of expected functionality. It's a good example how Tek got the priorities wrong.


--- Quote ---Also later scopes such as TDS7000 allowed Fast Acquisition and measurements on the display at the same time.
--- End quote ---

Yes, you can do measurements in Fast Acquisition mode, but you can't zoom, you can't use math, and the sample rate drops to 1.25GSa/s.

The TDS7000 is one more example how Tek missed the mark by ignoring analysis capabilities for a focus on update rates. And then dragged it along for way too many years.


--- Quote ---Regarding ADC resolution if you scale the display to fit two or more channels stacked on the screen at the same time don't you automatically lose ADC resolution ? Apparently it is not an issue with the new Tek MSO scopes ;)
--- End quote ---

It's not an issue with *any* DSO! ADC resolution is completely independet on what is shown on the screen. It doesn't matter if you have one, two, three, four or eight traces, the ADC resolution doesn't change. Why should it?

But it's a perfect example of Tek's misleading marketing.

nctnico:

--- Quote from: Wuerstchenhund on April 29, 2020, 11:37:57 am ---It's not an issue with *any* DSO! ADC resolution is completely independet on what is shown on the screen. It doesn't matter if you have one, two, three, four or eight traces, the ADC resolution doesn't change. Why should it?

--- End quote ---
It depends on how the traces are shown. If you take one grid and change the v/div so you can fit 4 traces you'll lose ADC resolution (and thus math precission). An alternative is to have multiple grids (split display) in which each trace can be shown at full height (IOW: using a lower v/div setting); in this case you won't lose ADC resolution. But this isn't a modern feature.

Eric_S:

--- Quote from: nctnico on April 29, 2020, 04:47:42 pm ---
It depends on how the traces are shown. If you take one grid and change the v/div so you can fit 4 traces you'll lose ADC resolution (and thus math precission). An alternative is to have multiple grids (split display) in which each trace can be shown at full height (IOW: using a lower v/div setting); in this case you won't lose ADC resolution. But this isn't a modern feature.

--- End quote ---


When people talk about the resolution of the ADC, why would they mean something to the tune of "ADC input voltage range utilization"? The concept can be important, but that is not really what I think people are talking about when they say that an Arduino Uno's got a 10bit ADC.

jjoonathan:
I'm pretty sure he's talking about vertical interleaving in the Infiniium S. According to: https://www.arbenelux.com/wp-content/uploads/2018/08/comparing-high-resolution-oscilloscope-design-approaches-wp-1.pdf

2 Channels: 10bit 8GHz 20GS/s
4 Channels: 8bit 2.5GHz 5GS/s

Which is odd, because as phrased it looks like one configuration is strictly worse, rather than each configuration trading channels / bandwidth / resolution through vertical and horizontal interleaving. My best guess is that "10bit 20GS/s" only applies to a reduced bandwidth/channel configuration, the 8bit 5GS/s mode is a Keysight typo, and the Lecroy analysis is trying to maximize FUD by stirring the two together.

I don't really care who is right, I just enjoy watching monkeys throw poo at each other  :popcorn:

Someone:

--- Quote from: nctnico on April 29, 2020, 04:47:42 pm ---
--- Quote from: Wuerstchenhund on April 29, 2020, 11:37:57 am ---It's not an issue with *any* DSO! ADC resolution is completely independet on what is shown on the screen. It doesn't matter if you have one, two, three, four or eight traces, the ADC resolution doesn't change. Why should it?

--- End quote ---
It depends on how the traces are shown. If you take one grid and change the v/div so you can fit 4 traces you'll lose ADC resolution (and thus math precission). An alternative is to have multiple grids (split display) in which each trace can be shown at full height (IOW: using a lower v/div setting); in this case you won't lose ADC resolution. But this isn't a modern feature.

--- End quote ---
Indeed, not a modern feature, but a useful one that is only just starting to become commonly available (possibly related to the increase in display resolutions making the problem more obvious).

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