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New Tektronix 3 Series MDO

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Someone:

--- Quote from: Wuerstchenhund on April 29, 2020, 10:53:52 am ---
--- Quote from: james_s on April 28, 2020, 05:05:02 pm ---I don't really grasp what you mean by it being slow. I have a TDS3054 and a TDS784C and the only time I've ever noticed any kind of slowness in either one is using deep memory on the TDS784. The TDS3000 feels very snappy to me, what do I need to do to see this "painfully slow" lag you refer to? I'm genuinely curious and don't know what you're talking about.
--- End quote ---

It's not about 'lag' or general controls. There isn't any input lag when operating the scope. But unfortunately the user interface isn't everything.

For example, try mask testing on the TDS3000. Or FFT. The TDS3000 is also slow when it comes to waveform rates, as in normal mode it's trigger rate is some 450 wfms/sec. This raises to 3k wfms/s or so in Fast trigger mode but then the sample memory (with 10kpts not exactly large) is limited to a measly 500pts. It's not a big problem if you can make it with the available trigger suite (which is quite good if the advanced trigger option is installed) but that doesn't change the fact that the scope *is* slow, and when used in an 'analog scope' manner (like searching for glitches through trace persistence) then it will perform poorly.
--- End quote ---
Slow waveform update rates make it bad, got it...

--- Quote from: Wuerstchenhund on April 29, 2020, 11:37:57 am ---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
--- End quote ---
Wait, waveform update rates are useless? (others will disagree on this point). Wash my fur but don't get me wet?

The reality is there is a balance, triggers can find some sorts of problems, and realtime viewing others, its all application specific and neither is better than the other for everything. You've been consistently coy about highlighting example applications or methods to enlighten us readers as to specific advantages. Ideally a scope would be capable in both areas, luckily those exist too.


--- Quote from: snoopy on April 29, 2020, 02:44:02 am ---The TDS700 becomes very sluggish as you increase the memory depth unfortunately but I occasionally find its InstaVu, high-res mode and equivalent time sampling features very useful that are missed on other scopes even today ! Tek did equivalent time sampling better than anyone else ;)
--- End quote ---
Equivalent time sampling is a great way to capture high speed signals with a slow ADC, but all the big manufacturers have ADCs fast enough at prices that it makes little sense anymore (the cost of front end and sampling needed would be close enough to cost of a full realtime sampling system). Instavu is an oddball, possibly more comparable to modern eye-diagram 2d histogram modes which are often a separate acquisition mode with limitations etc, but similarly aimed at collecting statistical measures and outliers as quickly as possible.

snoopy:

--- Quote from: Wuerstchenhund on April 29, 2020, 11:37:57 am ---

--- 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.


--- End quote ---

Yes but you have to know what kind of glitch to trigger on otherwise you are poking around in the dark and that's if you even have the ability to trigger on it ! But you still didn't answer my question about the original megazoom acquisition rate ? Be interested to know ;) Here is a comparison between an early Tek scope and apparently still current model Keysight scope ! Not bad for a mid 90's Tek scope ;)

https://youtu.be/uUM7UDWifWw?t=1809

snoopy:

--- Quote from: Eric_S on April 29, 2020, 06:37:11 pm ---
--- 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.

--- End quote ---

More correctly it's about dynamic range. If you have to cram 4 waveforms stacked on the screen at the one time you have to attenuate the signals to the ADC's to make them fit on the screen. So because of this you are using less dynamic range of the ADC and adding more quantization noise, thus effectively reducing the bit depth or effective number of bits ! Apparently the new Tek MSO's don't suffer from this scaling issue. Not sure about the other scope offerings. Maybe some others can enlighten us ;)

cheers

nctnico:

--- Quote from: snoopy on April 30, 2020, 02:11:56 am ---
--- Quote from: Eric_S on April 29, 2020, 06:37:11 pm ---
--- 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.

--- End quote ---
More correctly it's about dynamic range. If you have to cram 4 waveforms stacked on the screen at the one time you have to attenuate the signals to the ADC's to make them fit on the screen. So because of this you are using less dynamic range of the ADC and adding more quantization noise, thus effectively reducing the bit depth or effective number of bits ! Apparently the new Tek MSO's don't suffer from this scaling issue. Not sure about the other scope offerings. Maybe some others can enlighten us ;)

--- End quote ---
IMHO you are trying to spread FUD here. I already explained how it works by using seperate grids (which has been around for decades).

2N3055:

--- Quote from: snoopy on April 30, 2020, 02:03:22 am ---
--- Quote from: Wuerstchenhund on April 29, 2020, 11:37:57 am ---

--- 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.


--- End quote ---

Yes but you have to know what kind of glitch to trigger on otherwise you are poking around in the dark and that's if you even have the ability to trigger on it ! But you still didn't answer my question about the original megazoom acquisition rate ? Be interested to know ;) Here is a comparison between an early Tek scope and apparently still current model Keysight scope ! Not bad for a mid 90's Tek scope ;)

https://youtu.be/uUM7UDWifWw?t=1809

--- End quote ---

What "apparently still current model Keysight scope !", Agilent MSO6104A ?
That thing is dead and gone, replaced by MSOX3000 series many moons ago...

And what "magical glitches" are everybody talking about? Runts, too short pulses, dropouts, rise time anomalies ? What?
All of those are well covered by triggers. 
This was discussed ad nauseam many times, like Someone nicely said.
Using on screen persistence to capture signal anomalies can be used but has limited usability.
Only information you get is that you caught something, but not when and in correlation to what.
It can be used only as a proof that there are some anomalies, and hopefully give enough information for operator to devise triggering scenario to reliably capture such anomalies every time. So you can count how many are there, what is distribution and try to correlate with system state and other signals to try to find a source.
Also, if you don't catch anything on screen, it is NOT a proof all is well, because you maybe didn't wait long enough...

I personally use screen persistence, but first go through a set of well known triggers (rise time, pulse width, runt), that is really quick thing to do,  and if those don't catch anything, i might let it run in infinite persistence mode for few hours just to be sure...
You can also set mask mode, and use that too. Nobody mentions this in this context. But it is probably best way to do it. It is a built in anomaly detector, that will detect any deviation of the signal.  And it will give you much more info than display persistence, because it will give you stats and confidence interval...


 


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