Author Topic: Tektronix 1-3 GHz touch screen color DSO back in 1989 !  (Read 17054 times)

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Online David Hess

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #25 on: August 27, 2017, 04:44:50 am »
That is right; the 11403A shown is not a sampling oscilloscope.  Those vertical amplifier plug-ins are not sampling heads; they are an improved version of the 7000 series vertical amplifier plug-ins.

Except for the 11A81 3GHz "presampler" vertical plugin.

I was not aware of the details of this plug-in although I knew it existed.  It is pretty cool but the specifications given in the 1993 catalog on page 79 are not consistent with a sampling plug-in.

What happened is that the mainframe's interface connector cannot handle a 3 GHz bandwidth (1) so Tektronix implemented the attenuators, vertical amplifier, and a sample and hold in the plug-in.  It is not a sampling input in the sense of a sampling oscilloscope and this can be seen in the specifications which show a 10ns overdrive recovery time and a 25 volt peak maximum input voltage.

The older 7854 with the 7T11A sampling timebase works in the same way with the mainframe's digitizer slaved to the sampling plug-in so Tektronix was aware of this possibility.

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(Does anyone know the presampling rate?)

I could not find it in the sparse to non-existant available documentation for the CSA404, 11403A, and 11A81.  It should be only limited by the sampling rate of the plug-in itself because the bandwidth between it and the mainframe is 1 GHz leaving plenty of time for settling between samples.  That would make it 20 MS/s maximum just like any other vertical plug-in.

(1) It was a pretty big deal when Tektronix extended the 7000 series interface to 1 GHz in the 7104 and there were trade articles written at the time about how they did it.

I also has 11801 with SD24 sampling heads. This is 20 GHz bandwidth, but 20 M sps.

The 11K and SD specifications all say 200 kS/s maximum.  I think the chief limit in these single sampling gate designs is the operating life of the avalanche pulse generator.

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If the marketing departments of other companies want to confuse the issue, that is up to them.

It's not confusing the issue, and it's not even driven by marketing.

This is what Keysight has to say:

Oscilloscopes fall into two groups, real-time oscilloscopes and sampling oscilloscopes (also called equivalent-time oscilloscopes) and it is important to understand the difference between the two types. Real-time oscilloscopes digitize a signal in real-time. Imagine a repetitive AC signal - the real-time oscilloscope acts like a camera, taking a series of frames of the signal during each cycle. The amount of frames the real-time oscilloscope captures depends upon the bandwidth, memory depth, and other attributes that we will soon discuss. A sampling oscilloscope, on the other hand, takes only one shot of the signal per cycle. By repeating this one shot, but at slightly different time frames, the sampling oscilloscope can reconstruct the signal with a high degree of accuracy.

It is confusing and here is why.  Sampling oscilloscopes in the sense that I am using the term have three features which are not found in other oscilloscopes:

1. They have zero overload recovery time.  A sampling bridge does not care about what is going on during the time that the sampling gate is not open.  A practical application of this is measuring settling time to high accuracy which is somewhere between difficult to impossible with a normal oscilloscope which otherwise has sufficient bandwidth.

2. They use a sampling efficiency much lower than 100% to exceed the RC bandwidth limitation of a sample or track and hold which uses a sampling gate time greater than its RC time constant to allow full settling.  This results in a huge increase in bandwidth.

3.  2 above produces a non-linear sin(x)/x frequency response do to integration during the sampling gate time.  The effective sampling gate width can be measured by looking for the null in the response.

Both 1 and 2 above lead to sampling oscilloscopes not using linear elements like amplifiers or delay lines before the sampler.  Either would significantly lower the achievable bandwidth and the former would destroy the overload recovery capability.

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Funny you mention PicoScope, as it seems they, too, disagree with your definition of Sampling Scope:

https://www.picotech.com/download/manuals/picoscope-9000-series-questions-and-answers.pdf:

A sampling oscilloscope is a special type of oscilloscope that uses a technique called sequential time sampling.

...


And in the very first sentence, Picoscope gets it wrong.  There is nothing about a sampling oscilloscope which requires sequential sampling.  Indeed, random sampling in a sampling oscilloscope allows viewing the triggering waveform without the use of a delay line or pretrigger.  The only reason they were not more common is that most applications could live with these limitations.

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As I said, I understand where you're coming from but there's no point to fixate of a some 30 years old definition by a single manufacturer while constantly referring to ancient kit that has long been obsolete when the rest of the world has moved on.

The point is that your definition confuses two different classes of oscilloscope which have distinct properties.  If there is a better and less ambiguous term for sampling oscilloscopes in the older sense, then let us know.

I have posted few 11800/CSA803A frontend photos elsewhere but they are so beautiful they need to be here too. They don't care how they are called.
Leo

2 channel 20GHz sampling head

Note that the coaxial line on the top carries the sampling strobe from the mainframe to the sampling gates and the two coaxial lines on the bottom carry the divided sampling strobes back into the mainframe for timing measurement.  This is required to achieve high horizontal timing accuracy.  None of the coaxial lines carry the sampled signal which is low bandwidth after the sampling gates.

The real advantage of these scopes is in their low price compared to a real-time scope with the same BW.

I like them because they are immune to overload and have a predictable frequency response allowing them to be used to calibrate the transient response of other instruments.  It is even possible to calibrate the transient response of a sampling oscilloscope without an external reference although it takes 3 sampling oscilloscopes to do this.  Maybe I should have included this in my list of features above.
 

Offline MrW0lf

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #26 on: August 27, 2017, 08:22:12 am »
Would add that while RTS scope with ETS feature do not tick all the boxes mentioned it still helps with 2 things:
- no interpolation related artefacts
- very high horizontal accuracy
Weird that many cheap DSOs are dropping support for ETS. Failure to educate end-user of advantages or just cost-cutting? I suppose it needs better trigger system than just RTS / lowish sample rate where users in general seem to expect no better accuracy than +-sample_interval.
 

Offline RoGeorge

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #27 on: August 27, 2017, 08:40:06 am »
I have posted few 11800/CSA803A frontend photos elsewhere but they are so beautiful they need to be here too. They don't care how they are called.
Leo

Beautiful pics, thank you!

Offline Leo Bodnar

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #28 on: August 27, 2017, 08:44:04 am »
I have posted few 11800/CSA803A frontend photos elsewhere but they are so beautiful they need to be here too. They don't care how they are called.
Leo

2 channel 20GHz sampling head

Note that the coaxial line on the top carries the sampling strobe from the mainframe to the sampling gates and the two coaxial lines on the bottom carry the divided sampling strobes back into the mainframe for timing measurement.
No.  The top rigid line is TDR trigger pulse.  It triggers both channels but channel 2 has analogue voltage-controlled delay inserted in line with its trigger.

The middle one is the strobe drive for sampling pulse generator.  Both channels are sampled simultaneously.

Bottom rigid line is the strobe sense for the sampling pulser.  It provides feedback from the output of SRD back to the scope sense strobe driver board.  This feedback has not been used in S-xx series heads.

You probably got confused because Tek uses the same carrier PCB for SD-22/SD-24/SD-26 even though only SD-24 needs TDR section.  It is a low volume product so each head seem to have had some uniqueness to it.  One of my SD-26 heads has provision for loop-through on the sampling hybrid as if it was expected to be used in SD-20.

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  This is required to achieve high horizontal timing accuracy.  None of the coaxial lines carry the sampled signal which is low bandwidth after the sampling gates.
That is true.  The sampled signal outputs travel over two regular pins just like other control voltages and digital data.  It's a low impedance low BW signal so I can see why there was a temptation not to add two more coaxial lines.
However as soon as they enter the scope they are immediately fed into the separate coaxial cables.
Head extender also uses two coax lines for sampled signals. Note two extra coax cables that carry sampled signal.
I have attached a sampling head output for a pulse with 40ps risetime.

CSA8000 head extender before converting to operate on CSA803A:


SD-26 sampled signal output for a 40ps risetime pulse.  Sampling rate is about 115ksps:
« Last Edit: August 27, 2017, 09:04:01 am by Leo Bodnar »
 

Offline Leo Bodnar

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #29 on: August 27, 2017, 09:53:14 am »
There was a relevant post on TekScopes group about 14000 series from someone at Tek. I cross-post for those who are not subscribed:
https://groups.yahoo.com/neo/groups/TekScopes/conversations/messages/96244

John Addis later joins in the discussion which this margin is too small to contain

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At the risk of offending members who may have worked on it, IMO the 11400 was the worst DSO ever put on the market, by any company. It was an embarassment to have a Tektronix name plate on it.

The reason for the poor choice in commercial ADCs was the length of the design project - the better part of a decade. Between the time the part was designed in and the scope actually shipped, much better ADCs were available.

The 11k products were totally driven by engineering, with essentially no marketing input. When the project started, 7000 series was the top income producer in the company, and as the replacement, this team was expected to turn out another home run. The problem was that no one was defining what the scope should be or do, or what the minimum deliverables were. There was also a culture problem. Tek unquestionably made the finest analog scopes. There was no need to study the competition, as it was inferior. This carried over to all scopes. But the truth was that for the first couple of generations, the competition was designing much better digital scopes than Tek. But no one took them seriously, or really studied the competitive products.

With no defined product defination or end point, engineering was free to work on (some say "play in the sandbox") it as long as it took to build the digital version of 7k. Don't get me wrong - these truly were some of the best engineers at Tek. The individual circuits they designed and code they wrote for 11400 was great. They just had no direction. The results was what you got, not competitive the day it introduced, with a terrible user interface. Even with Tek's name and recognition in scopes, the series was a business disaster. A high level VP gave a talk at a management training event I attended a few years later, and mentioned the financial details of the 11300-11400 investment and return. I won't repeat them as they are confidential, but suffice to say, incomes did not cover a fraction of the development costs.

For your second question - yes, just about any modern digital scope will perform much better than the 11400 - dollar for dollar with the used prices.

In addition to its performance problems, I would stay away from them for the complexity. The display processor board is pushing 200 ICs, mostly LSTTL. While I don't believe there are prone to reliability problems, the parts count alone will give a stastical poor MTBF. Troubleshooting a state machine this complex can't be any fun.

- Steve
« Last Edit: August 27, 2017, 02:20:01 pm by Leo Bodnar »
 
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Offline Wuerstchenhund

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #30 on: August 27, 2017, 02:14:39 pm »
John Addis later joins in the discussion[/url] which this margin is too small to contain

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[...] There was also a culture problem. Tek unquestionably made the finest analog scopes. There was no need to study the competition, as it was inferior. This carried over to all scopes. But the truth was that for the first couple of generations, the competition was designing much better digital scopes than Tek. But no one took them seriously, or really studied the competitive products.

Unfortunately this wasn't just for the first couple of generations, Tek's overconfidence in its products continued for a very long time, and frankly I'm not sure it's even over yet. The new MDO5 Series, while having some interesting features, looks like another product without a target market.

Tek always treated a DSO as a replacement of an analog scope, without recognizing the power that lies in digitalization, and I'm not sure they ever got it. And even when it comes to making DSOs that behave like analog scopes Tek was left behind by HPAK and its MegaZoom-based scopes.

That's pretty much why Tek's DSO range has been dominated by underwhelming product after product ever since, which is a shame.
 

Offline snoopyTopic starter

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #31 on: August 28, 2017, 02:03:05 am »
John Addis later joins in the discussion[/url] which this margin is too small to contain

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[...] There was also a culture problem. Tek unquestionably made the finest analog scopes. There was no need to study the competition, as it was inferior. This carried over to all scopes. But the truth was that for the first couple of generations, the competition was designing much better digital scopes than Tek. But no one took them seriously, or really studied the competitive products.

Unfortunately this wasn't just for the first couple of generations, Tek's overconfidence in its products continued for a very long time, and frankly I'm not sure it's even over yet. The new MDO5 Series, while having some interesting features, looks like another product without a target market.

Tek always treated a DSO as a replacement of an analog scope, without recognizing the power that lies in digitalization, and I'm not sure they ever got it. And even when it comes to making DSOs that behave like analog scopes Tek was left behind by HPAK and its MegaZoom-based scopes.

That's pretty much why Tek's DSO range has been dominated by underwhelming product after product ever since, which is a shame.

That is simply not true. The older Tek TDS744A DSO catches glitches just as well if not better than a later Agilent MSO6104 scope with Megazoom !! Tektronix were way ahead of their time with their patented digital phosphor technology !





« Last Edit: August 28, 2017, 02:17:38 am by snoopy »
 

Offline Wuerstchenhund

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #32 on: August 28, 2017, 08:09:21 am »
That's pretty much why Tek's DSO range has been dominated by underwhelming product after product ever since, which is a shame.

That is simply not true. The older Tek TDS744A DSO catches glitches just as well if not better than a later Agilent MSO6104 scope with Megazoom !!

And you gather that from a single Youtube video (where the narrator even says towards the end that the Agilent is the better scope)? :palm:

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Tektronix were way ahead of their time with their patented digital phosphor technology !

No, they weren't 'way ahead of their time'. For a start, try to do some math on a signal when the TDS744A is in InstaVu mode. Oops, you can't, because InstaVu works by data reduction (it drops the sample rate and the sample memory) and writing the data directly into the video buffer. Which is why a lot of the scope's features (Auto Trigger, Zoom, limit testing, FastFrame, Math, X/Y, Envelope mode, Average mode, HiRes mode, no single-shot capture, and no interpolation in real-time mode) are unavailable in InstaVu. Needless to say that HPAK's MegaZoom doesn't suffer from these limitations.

Tek's idea was to re-create the display of an analog scope (because their basic assumption was that DSOs should just be a modern form of analog scopes), and that's exactly what InstaVu does. You get high waveform rates at the price of being able to do nothing with the sampled data other than look at it. If you want to do something with the data (i.e. use the very basic set of math and analysis tools the TDS offers) then you have to go back to the TDS' 50 updates/s normal acquisition mode.

HP on the other side didn't believe that digital scopes should replicate analog scopes, and didn't give up on the advantage of digital signal processing just for high waveform rates (and actually managed to deliver both as an 'always on' solution which back in 1995 was quite a feat, even more so considering that the 54600 Series were on the lower end of the price scale). HP knoew that engineers would want to make use of the benefits of digitalization, but back then a standard scope like the 54600 would still often be used in places where it replaced an analog scope, and where the high waveform rate was useful.

LeCroy did go a different way than Tek and HP, not offering high update rates but instead providing a very sophisticated trigger suite which would allow to trigger and capture pretty much any signal devication on its first occurrance, after which it could be analyzed further with the advanced math/statistics and analysis tools their scopes offered. LeCroy didn't build entry-level scopes (they were always bought in from other vendors like Iwatsu), and they figured that their advanced toolsets will more than compensate for the lack of superfast waveform rates.

Looking at the market some 23 years later, it turned out that HPAK and LeCroy were right in their  assumptions. Keysight is the largest T&M vendor, and of the three big names sells the highest number of scopes. LeCroy is doesn't have the numbers as they can't really compete in the entry-level (for which they offer rebadged versions of old Siglent scopes) but they pretty much lead in the high-end segment (where for some products there simply is no other vendor). Tek however has been on a constant decline pretty much since the end of the analog scope era, and have been for a reason. It would be nice if they finally woke up and smelled the coffee, and started turning the ship around, but all signs indicate that after the separation from Danaher they just continue in their old ways.
 

Offline snoopyTopic starter

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #33 on: August 28, 2017, 09:22:44 am »
That's pretty much why Tek's DSO range has been dominated by underwhelming product after product ever since, which is a shame.

That is simply not true. The older Tek TDS744A DSO catches glitches just as well if not better than a later Agilent MSO6104 scope with Megazoom !!

And you gather that from a single Youtube video (where the narrator even says towards the end that the Agilent is the better scope)? :palm:

Quote
Tektronix were way ahead of their time with their patented digital phosphor technology !

No, they weren't 'way ahead of their time'. For a start, try to do some math on a signal when the TDS744A is in InstaVu mode. Oops, you can't, because InstaVu works by data reduction (it drops the sample rate and the sample memory) and writing the data directly into the video buffer. Which is why a lot of the scope's features (Auto Trigger, Zoom, limit testing, FastFrame, Math, X/Y, Envelope mode, Average mode, HiRes mode, no single-shot capture, and no interpolation in real-time mode) are unavailable in InstaVu. Needless to say that HPAK's MegaZoom doesn't suffer from these limitations.


Instavu and DPO is not an underwhelming product enhancement by any stretch of the imagination. No other scope at the time had the ability to catch glitches at the same rate as these Tek scopes. I have measured the trigger rate on these scopes and yes they do deliver on the vendors claims of up to nearly 400,000 waveforms per second capture rate.

And yes the sample memory is dropped and yet it still catches the glitches that other scopes miss. And yes a lot of features are disabled with Instavu mode enabled but you are missing the point of this feature. You enable this feature to determine whether or not your circuit has glitches and you don't want to wait days glued to the screen to find out. Who cares about the measurements if you are trying to chase down an intermittent and illusive problem in the design missed by other scopes ! Once you have determined the nature of the problem then you can setup a trigger to catch the glitch in action in normal DSO mode. Also that Megazoom feature on Agilents scopes has that pesky limitation of only providing measurements on the screen data and no more .

And comparing a 1995 scope with a 2015 scope that costs megabucks is not a fair comparison when you can pick the Tek scopes up pretty cheap in comparison to this 2015 Agilent model !
 

Offline Wuerstchenhund

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #34 on: August 28, 2017, 10:26:53 am »
Instavu and DPO is not an underwhelming product enhancement by any stretch of the imagination. No other scope at the time had the ability to catch glitches at the same rate as these Tek scopes.

That's nonsense, a scope that uses dedicated triggers will if setup correctly find always a glitch on its first occurrrence, as it doesn't have to rely on failure-prone human eyes to identify the glitch.

Also, seeing all these glitches fly by in InstaVu mode only shows you that there are glitches, which is great if you're the 'stare-on-the-screen-until-you-see-something-abnormal' type of guy, but usually finding out that there are glitches is only 1/3rd of the work, the other two are analyzing the anomaly (to find out where in your UUT the problem is) and then fixing it.

Step 2 already fails in InstaVu so you have to re-acquire in normal mode, which on the TDS700A is dog slow (Tek specifies an update rate of 50 per second). And if you can't trigger on the anomaly because your TDS700A lacks the advanced triggers then you have to rely on the 50 updates/s and the resulting large blind time to capture the glitch so you can do some analysis of it. Great  :--

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And yes the sample memory is dropped and yet it still catches the glitches that other scopes miss.

No, it doesn't :palm: That's just your imagination. And like an analog scope, the TDS isn't really 'catching' glitches, all it does is displaying them. Same as an analog scope.

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And yes a lot of features are disabled with Instavu mode enabled but you are missing the point of this feature. You enable this feature to determine whether or not your circuit has glitches and you don't want to wait days glued to the screen to find out.

Seriously, if your glitch hunting technique is limited to looking at a screen until you see a glitch then either you're using poor equipment or you have a lot to learn about how to use a scope properly. Especially with very rarely occurring glitches (i.e. say every 10 minutes) there's a very good chance you miss the glitch, because your eyes get fatigued from staring at the screen, you blink, or become otherwise distracted. That's why better scopes come with a set of advanced triggers so you can setup the scope and do something else while the scope will 'see', capture and if necessary process (i.e. build a histogram, which can be tremendously helpful in finding out what's causing the glitch) the data and present you with the results on your return.

The reality is that InstaVu is unlikely to show you any glitches that you can't see on a similar old MegaZoom scope, and neither of those can capture glitches better than a scope using a suitable trigger. If you think otherwise you're just deluding yourself.

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And comparing a 1995 scope with a 2015 scope that costs megabucks is not a fair comparison when you can pick the Tek scopes up pretty cheap in comparison to this 2015 Agilent model !

WTF are you talking about? What comparison?
« Last Edit: August 28, 2017, 10:29:55 am by Wuerstchenhund »
 

Offline snoopyTopic starter

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #35 on: August 28, 2017, 11:06:31 am »
Instavu and DPO is not an underwhelming product enhancement by any stretch of the imagination. No other scope at the time had the ability to catch glitches at the same rate as these Tek scopes.

That's nonsense, a scope that uses dedicated triggers will if setup correctly find always a glitch on its first occurrrence, as it doesn't have to rely on failure-prone human eyes to identify the glitch.


Well if you can't identify what the glitch is then how can you ever setup the trigger to catch them ? Just try every possible permutation or combination of triggers ? A normal scope may never show the glitches for days and one may assume that there is nothing wrong with the circuit at hand. Later Tek scopes had the ability to set off an audible alert and freeze the display when a glitch occurred ! You talk like Instavu has no value at all in diagnosing a problem with a circuit !! Perhaps you've never done any fault finding and this feature would not be of any use to you ?



« Last Edit: August 28, 2017, 12:02:00 pm by snoopy »
 

Offline Wuerstchenhund

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #36 on: August 28, 2017, 01:12:29 pm »
Well if you can't identify what the glitch is then how can you ever setup the trigger to catch them ? Just try every possible permutation or combination of triggers ?

No, of course you're not trying every permutation. On older scopes (like some of the ones from the mid-'90s) you just setup an exclusion trigger with the parameters of the signal, and wait for the glitch to appear. Chain it with statistics and you can get a nice histogram of when each glitch occurred, which in a complex circuit should usually gives you an idea to narrow the cause of the glitch down.

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A normal scope may never show the glitches for days

Yes, for glitches that have periods of 10's of minutes or even hours, in which case sitting in front of an InstaVu screen would be equally silly because all it does is showing that there's a glitch, and that only if you happen to see it (sometimes glitches can even be small enough for them to remain unrecognized by the operator), and if you see it you then have to re-capture again in snail mode and hope your slow Tek scope will capture it with its now vastly extended blind time.

Also, in your rabid praise of InstaVu you completely ignore that even this mode has a blind time, and is likely to miss the occurrence of a glitch. Which means that even if you spend half an hour looking at your signal in InstaVu without seeing a glitch doesn't mean there is none, it just means you can't say with certainty that there are glitches.

The only way to be sure are advanced triggers.

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Later Tek scopes had the ability to set off an audible alert and freeze the display when a glitch occurred

Yes, in DPO mode, which is just a slightly improved version of InstaVu.

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You talk like Instavu has no value at all in diagnosing a problem with a circuit !! Perhaps you've never done any fault finding and this feature would not be of any use to you ?

I never said InstaVu has no value, I said it provides the same value like an analog scope which even back in 1995 was pretty limited. It's all great that InstaVu and DPO can achieve high waveform rates but the point you (and Tek, obviously) miss is that for a digital scope just emulating an analog scope isn't enough.

Ever wondered why even modern high-end scopes often only have waveform update rates in the thousands or 10k's per second? Exactly, because high update rates become pretty meaningless when you have a set of advanced triggers and analysis functions that can find pretty much any problem in any signal you want. Even on non-repetitive signals (try to find glitches on a non-repetitive signal with InstaVu, good luck!).

The point I was making (and on which you jumped off with your InstaVu fanboisim) is the same as the one the former Tek guy John Addis Steve Ditter was making, which is that Tek has been (and still is) living in their own world without considering what the competition does and what customers actually want. Again, if the aim was to make a digital scope that feels and can be used exactly like an analog scope then Tek was indeed very successful. But that's not what customers wanted, which was taking advantage of the possibilities that digitizing an analog signal brings, and which have been offered by HPAK and especially LeCroy (which for DSOs is pretty much what Tek has been for analog scopes). And this mindset can still be seen in Tek's latest products, which I find very unfortunate as I'd really like to see them stepping up and becoming a noteworthy competitor once again.
« Last Edit: August 28, 2017, 03:00:20 pm by Wuerstchenhund »
 

Offline Leo Bodnar

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #37 on: August 28, 2017, 01:30:22 pm »
The 11K and SD specifications all say 200 kS/s maximum.  I think the chief limit in these single sampling gate designs is the operating life of the avalanche pulse generator.
I came to conclusion that SD sampler heads don't use avalanche effect generators.
They do have SRD and clipping line sampling setup carried over from S series but SRD is excited by complimentary BJT pair in an arrangement that looks like a multivibrator.
I am not certain if SRD has stress limit when it reverse-conducts but it is certainly not well thermally connected to anything - it just hangs on its beam leads between two capacitors.
Perhaps, the sampling rate limit is enforced by maximum rate of TDR pulsers or some recovery processes in the mainframe.  11700 is so complex, it's hard to say for certain.

Leo
« Last Edit: August 28, 2017, 02:23:52 pm by Leo Bodnar »
 

Offline edavid

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #38 on: August 28, 2017, 02:43:40 pm »
The point I was making (and on which you jumped off with your InstaVu fanboisim) is the same as the one the former Tek guy John Addis was making, which is that Tek has been (and still is) living in their own world without considering what the competition does and what customers actually want.

You misread that, it's Steve Ditter who is the 11K series hater.  John Addis is more positive.
 

Offline Wuerstchenhund

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #39 on: August 28, 2017, 03:15:55 pm »
The point I was making (and on which you jumped off with your InstaVu fanboisim) is the same as the one the former Tek guy John Addis was making, which is that Tek has been (and still is) living in their own world without considering what the competition does and what customers actually want.

You misread that, it's Steve Ditter who is the 11K series hater.  John Addis is more positive.

My bad, thanks for the correction. Posting updated.
 

Offline snoopyTopic starter

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #40 on: August 31, 2017, 01:30:13 pm »

Yes, for glitches that have periods of 10's of minutes or even hours, in which case sitting in front of an InstaVu screen would be equally silly because all it does is showing that there's a glitch, and that only if you happen to see it (sometimes glitches can even be small enough for them to remain unrecognized by the operator), and if you see it you then have to re-capture again in snail mode and hope your slow Tek scope will capture it with its now vastly extended blind time.

Also, in your rabid praise of InstaVu you completely ignore that even this mode has a blind time, and is likely to miss the occurrence of a glitch. Which means that even if you spend half an hour looking at your signal in InstaVu without seeing a glitch doesn't mean there is none, it just means you can't say with certainty that there are glitches.

The only way to be sure are advanced triggers.


Yes it is blind for small amount of time but it all comes down to probabilities.  Even if a glitch has an average rate of one per hour you just set Instavu mode with infinite persistence so you are likely to capture the glitch in an hours time or there abouts without having to stare at the screen to wait for it. Whereas your traditional 1% acquisition time scope would take 100 hours on average at the very least to reproduce the glitch ! Also with Instavu mode switched on, measurement are still available as well so not everything is disabled. I think these scopes were way ahead of the competition at the time ;)

cheers
 

Offline smaultre

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #41 on: June 16, 2024, 07:42:22 am »
Hello guys, is it actual to buy nowdays HP 54120B with the 54124A, which could go up to 50Ghz?
Or Tek stuff like 11700 or 8000 series are better?
I would like to measure up 40-50GHz division.
Start a new life here!!!
 

Offline tggzzz

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #42 on: June 16, 2024, 08:28:49 am »
And Philips had the PM3340 2GHz 10bit 50kSa/s sampling scope back in 1988:

Philips had the PM3400 1.7GHz "11/12 bit" sampling scope back in 1971. It could resolve ~200µV in 3V, hence "11/12 bit" :)

IIRC there are three transistors with fT exceeding 500MHz; the rest are BC107 class with an fT around 200MHz.

https://www.radiomuseum.org/r/philips_sampling_oscilloscope_pm3400.html
https://www.eevblog.com/forum/testgear/tektronix-scope-with-sampling-plug-in/msg468702/#msg468702

Quote
Quote
Anyone still using one of these old war horses ?

I doubt it. Sampling scopes are useful only in very few situations.

Some of them are prized by their owners, e.g. for TDR assessments of PCB tracks+components, or examining the last 0.1% of an amplifier's risetime.

General purpose? No. But that's not necessarily the point.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Online David Hess

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #43 on: June 16, 2024, 02:57:51 pm »
Quote
Quote
Anyone still using one of these old war horses ?

I doubt it. Sampling scopes are useful only in very few situations.

Some of them are prized by their owners, e.g. for TDR assessments of PCB tracks+components, or examining the last 0.1% of an amplifier's risetime.

General purpose? No. But that's not necessarily the point.

Sampling oscilloscope are almost uniquely useful for doing transient response calibration.

The input stage of a sampling oscilloscope is immune to overload, so they are also very good for making settling time measurements at high sensitivities that other oscilloscopes simply cannot do.
 

Offline tggzzz

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #44 on: June 16, 2024, 03:09:43 pm »
Quote
Quote
Anyone still using one of these old war horses ?

I doubt it. Sampling scopes are useful only in very few situations.

Some of them are prized by their owners, e.g. for TDR assessments of PCB tracks+components, or examining the last 0.1% of an amplifier's risetime.

General purpose? No. But that's not necessarily the point.

Sampling oscilloscope are almost uniquely useful for doing transient response calibration.

The input stage of a sampling oscilloscope is immune to overload, so they are also very good for making settling time measurements at high sensitivities that other oscilloscopes simply cannot do.

Just so.

Unfortunately that doesn't stop some salesmen claiming otherwise.
https://www.eevblog.com/forum/testgear/choosing-between-entry-level-12-bit-dsos/msg5433389/#msg5433389

But advances in ADC and front ends are continuing to eroding that advantage.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Online David Hess

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #45 on: June 16, 2024, 06:00:21 pm »
Sampling oscilloscope are almost uniquely useful for doing transient response calibration.

The input stage of a sampling oscilloscope is immune to overload, so they are also very good for making settling time measurements at high sensitivities that other oscilloscopes simply cannot do.

Just so.

Unfortunately that doesn't stop some salesmen claiming otherwise.
https://www.eevblog.com/forum/testgear/choosing-between-entry-level-12-bit-dsos/msg5433389/#msg5433389

But advances in ADC and front ends are continuing to eroding that advantage.

ADCs and front ends have been trying to solve the overload problem for decades, (1) and greater sensitivity makes it worse.  It along with the settling time problem are hard problems, which a sampling input completely solves.  Jim Williams wrote about these two problems, which are linked.  He spent a lot of effort designing a circuit to prevent oscilloscope overload and then used a sampling oscilloscope to verify its performance.

Oscilloscopes that have input offset controls may make an attempt to solve this.  The Tektronix 7A13 differential comparator uses feedback to clamp the input, so does better than most oscilloscope inputs.  I think this was also a feature of the differential comparator Tektronix made for their 11k series of mainframe oscilloscopes, which includes DSOs.

Jim Williams talked about the issues here:

https://www.analog.com/media/en/technical-documentation/application-notes/an47fa.pdf

(1) Not really - hardly anybody cares about overload performance.
« Last Edit: June 16, 2024, 06:04:11 pm by David Hess »
 
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Offline tggzzz

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Re: Tektronix 1-3 GHz touch screen color DSO back in 1989 !
« Reply #46 on: June 16, 2024, 07:18:48 pm »
Sampling oscilloscope are almost uniquely useful for doing transient response calibration.

The input stage of a sampling oscilloscope is immune to overload, so they are also very good for making settling time measurements at high sensitivities that other oscilloscopes simply cannot do.

Just so.

Unfortunately that doesn't stop some salesmen claiming otherwise.
https://www.eevblog.com/forum/testgear/choosing-between-entry-level-12-bit-dsos/msg5433389/#msg5433389

But advances in ADC and front ends are continuing to eroding that advantage.

ADCs and front ends have been trying to solve the overload problem for decades, (1) and greater sensitivity makes it worse.  It along with the settling time problem are hard problems, which a sampling input completely solves.  Jim Williams wrote about these two problems, which are linked.  He spent a lot of effort designing a circuit to prevent oscilloscope overload and then used a sampling oscilloscope to verify its performance.

Oscilloscopes that have input offset controls may make an attempt to solve this.  The Tektronix 7A13 differential comparator uses feedback to clamp the input, so does better than most oscilloscope inputs.  I think this was also a feature of the differential comparator Tektronix made for their 11k series of mainframe oscilloscopes, which includes DSOs.

Jim Williams talked about the issues here:

https://www.analog.com/media/en/technical-documentation/application-notes/an47fa.pdf

(1) Not really - hardly anybody cares about overload performance.

Yes.

The improvements in ADC and front ends appears to be just an increased number of bits (effective or otherwise) at high sampling rates. That enables software "select rectangle and zoom in" functions, i.e. without hardware fiddling with large DC offsets.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 
The following users thanked this post: egonotto


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