Before writing anything else, I'm sorry we got into argument. And what I write further is not a provocation or anything.
Forget it, as far as I am concerned it's history
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I just want to discuss this, fact based, like you (and also me) like it.
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Let me go by the numbers it is easier to be clear and to avoid language barrier.
1. 1 MWfms/sec IS a marketing gimmick, and for more than a few reasons. Most of all, at most timebases it won't be that fast, if you have trigger holdoff it won't be that fast, if you have trigger delay it won't be that fast.
I agree
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2. Short retrigger time IS NOT a gimmick. Short retrigger time is a positive consequence of them chasing 1 MWPS. That is a real benefit they don't market. In interactive, visual mode scope feels analog like. Also in segmented mode, you don't miss sequential events..
I think you said it right, the scope feels analog like
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And for some people that is important because it allows them to use methodology they know. And there's nothing wrong with that
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3. If you are trying to characterise some signal that is well defined as how it should look (serial comm bus, clock etc ), something for what you have a clear specification, then staring in the screen for something to happen is definitely NOT best way to capture anomalies and best use of your time. With that kind of signal and based on specification you can devise set of triggers, searches and stats that you let run for few hours (or days, doesn't matter) and when you come back you get stats and your offenders will wait for you neatly stored in history buffer.
I think this is true for every repetitive signal where the user knows how it's supposed to look like (i.e. it's not probing a completely unknown signal)
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He is SOO right about that. Funny thing is, you can do the same thing on Keysight and all other scopes. Heck, little Rigol 1000Z has so many advanced triggers like many of the midrange scopes of the yore (not very good documentation that will explain how to use it though). That kind of workflow is nothing exclusive to LeCroy. It's just since on LeCroy that is prefered workflow, they explain it and endorse it, because it plays to the strengths of their platform.
He did state that this can be done with many modern scopes, he even mentioned Rigol and Siglent, though
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And Lecroy never talked about WUH in their marketing material. I think the only time I saw a Lecroy sales guy talking about WUR was in an older YT video filmed at a demonstration in a company or at a reseller's place
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But you are right, it works with other scopes, too. And I guess that was the point of his article, i.e. to show people the flaws of an old method born in times when there wasn't anything else and a better alternative more suited to what modern scopes can do
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BUT also, in a pinch you could enable persistence and go to lunch and, when you get back, you take a look at the screen to see if there was a glitch. It will catch it
That's the thing, it *might* catch it if the glitch happens to occur during the 1/10th of the whole acuisition time where the scope can actually see it
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If the glitch is truly rare, it is 9x more likely to show up during blind times and will be missed by the scope
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Only triggers provide absolute certainty for the whole time the scope "looked" at the signal
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but my biggest problem with that is that you won't know when it happened, how it happened and have no way to know that. You will just know something did happen, and now you still have to catch the culprit. So you still have to devise detection protocol, set triggers etc.
That is an additional problem. Even if the scope caught the glitch, you still have to re-acquire in a real-time mode to be able to examine it
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So that is only partially useful. But it does provide differential diagnosis, meaning that if you don't catch anything with persistence, and you didn't catch anything with a protocol of various triggers, it enhances probability you are glitch free. So IT IS useful for that. By itself NOT much.
That is only partial correct. The persistence method is very likely to not show rare events because 9 out of 10 times it is completely blind, so if you don't catch anything with persistence then you still have no idea if your signal is glitch free
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With triggers n the other hand, you'll find a anomaly 100% of the time. So it's the only method to make sure a signal is actually glitch free
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4. If you are working on designs where you are scoping (is that a word?) just some nodes in a circuit, or you are designing something, signal will be nothing like clock or something that can be easily explained with few rules. In that case it is all about you and not the scope. Any scope will at that moment have some good and some bad things. Generally, what is useful is good measurements, history(segmented) buffers, search, stats... Some will LIKE fast interaction, some will NEED deep analysis. I like both, Keysight for interactive, Picoscope to get data on PC and then i can do anything I like. Use of brain is not optional here, no universal answer. Workflow will depend both on problem at hand and every individual skill-set, habits, and how people LIKE to work. Some people have no problem whipping up a custom analysis in Mathlab or Labview in just few minutes, and may actually prefer it that way. Some will insist that scope has to have certain analysis built in so they can just use it. Your mileage can vary.
No arguments here, people have their own methods they are familiar with based on their individual backgrounds, and if it works for them more power to them
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The only time I'd draw a line is when it comes passing on personal preference as undeniable facts to less experienced engineers like myself, because learning outdated methodology isn't helping us
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5. Thing about Mr W. is that he doesn't explain why and how he came to the conclusions he proclaims "The Truth". It is not that he's wrong about the topic (he is not right about everything but mostly he makes a good point.), but also didn't provide not even a thought process how he came to his conclusions, much less concrete examples to make his case stick. He just say "this is stupid and waste of time" and "this is solution for all problems". Long time ago when I read his original posts here, I got curious and did a little research. And I realized that he made a lot of good points but his causalities were not always correct. He was basing his assumptions on marketing material and positions of manufacturers. So he concluded that short memory / high WUR scopes (like Keysight) are inferior to long memory / low WUR (like LeCroy) scope, because on LeCroy you CAN use triggers to accomplish so much more than on Keysight with high WUR and persistence. Which was misdirection in terms.
I'm sorry but here I have to disagree. I believe most of the time he explains the reasons very well, based on logic and a solid background of math and physics. In fact, he seems to go to great length to not recommend something because he "feels" its better, but only because there is an objective reason for it
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What I gathered in discussions with him is that many topics he discussed, like the blog post about WURs, is not based on marketing materials but on his own experience and the experience (and frustrations) of the many of the engineers working for him. He once told me that one of his biggest pet peeves is when engineers treat a modern high performance scope like an analog scope, basically foregoing all its capabilities for what essentially is methodology from the electronics dark ages
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Which I think is also why fe often fought so passionately, because he wanted newcomers to learn how to handle a DSO properly and not like a modern version of an analog scope
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And if you look around, finding rare glitches with persistence is still the standard recommendation in this forum
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I can see why he put up some fight, and as a young engineer I'm grateful for that
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After repeatedly reading all he has written in this forum I have to say that, while he certainly was a great source (the only one for a very long time!) about Lecroy scopes, he didn't come across as brand biased to me. In fact, often he recommended something else than Lecroy or advised against a Lecroy because the individual use case was better off with something else
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Correct conclusion is that staring at the screen, looking for a glitch is INFERIOR and LESS productive way of doing it, as opposed to setting triggers, segmented memory and automating search for anomalies. Problem is that Keysight can do that to, the trigger way, for most of the part. Lecroy scopes in that price range and class (Wavesurfers) have none of the advanced features of high end Lecroy machines that makes them so awesome. On lower end Lecroy triggers are not more intelligent than ones on Keysight (or Rigol to that matter), and Wavescan is just fancy name for a search.
I don't know about Wavescan (my scopes are too old for that) but back to the topic of older high end scopes, today I don't believe it matters much if you buy a decent Keysight/Agilent Infinum (not the simpler Infinivision scopes) or a newer Lecroy X-Stream scope (the older ones apparently had poor trigger suites), you will get a fast high performance scope that can do a vast amount of analysis and still makes a great everyday scope
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Fact that Keysight trumpets about WUR and catching glitches with persistence doesn't mean I have to use it that way. So I use Keysight like he uses LeCroy, with prudent choice of triggers and segmented memory, using pretty advanced search capabilities to drill down further. And it works, well.
I know
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He was right about it, thanks a lot for that. But his dogma was you need a LeCroy to do so.
I think you will have a hard time finding something where he said that you need Lecroy to use triggers to find rare occurrences. In fact, he often mentioned that any modern advanced scope can do that
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And there's no word in his blog post saying you can only do that with a Lecroy scope
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You don't. On high end Lecroy with advanced analysis options enabled, you will do it faster, better, easier. But that workflow works well even on lowly Rigol, and it works well.
Which is pretty much what he said
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Actually, exactly that type of workflow enables scope that doesn't have much memory (like Keysight) to not show that. Long memory is not that important in that case because you only capture what is of interest and ignore hours of signal you don't care about. So it actually complements Keysight well, hiding it's imperfections, instead of making it unusable.
It complements any scope that has a good trigger suite (maybe not Tek as I've seen them missing triggers other scopes didn't) but again that's what he was saying
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We could go on for years like this. Everybody will protect their choices, their cognitive biases, their way.
Fact is that a good, working LeCroy Waverunner in a good shape is a hell of a scope. If you can enable advanced analysis options, you will have a scope that you can develop stuff NASA would be proud of. OTOH, some people only need scope for servicing stuff, and they want fast and familiar.
I agree regarding Lecroy waveruner, my LT is a fantastic scope and it's not too big, heavy or loud and makes a great every-day scope. But my new Wavepro 960 is still nicer because of the large screen
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Most of the time though I use my Agilent Infinum 8064 because it's a great scope, too, and has very good triggers
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So it's not just Lecroy who makes great scopes
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But again, you will have a hard time finding anything where Mr WH said otherwise
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