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Let’s Talk About LeCroy Scopes, AKA… the “Wuerstchenhund Holds Court” Thread

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Wuerstchenhund:

--- Quote from: David Hess on September 16, 2016, 09:14:48 am ---What gets stored in the acquisition record has been processed except in trivial cases or apparently if you are LeCroy.
--- End quote ---

That is right, because other scopes use 'destructive' acquisition modes (destructive as in the original sample data is destroyed) when not in normal mode.

It's still only data though  ;)


--- Quote ---
--- Quote from: Wuerstchenhund on September 15, 2016, 12:34:59 pm ---As to my "narrative", all I said was that the tool you clearly know jack shit about should be a sufficient replacement for situations where people tend to use Peak Detect.

--- End quote ---

I am not interesting in "sufficient" replacements; I am interested in superior replacements which if they do not cover all previous applications, at least do not preclude them using the older method.
--- End quote ---

That is fine, but if you follow the discussion then you should realize that it was meant as a "replacement" at a functional sense, not literally, i.e. if you were given the WS3000 you could get the same results as when given a scope with Peak Detect.

It certainly didn't mean people like nctnico should rush out and buy one, besides that I've regularly pointing out that no scope should be bought without a test drive. If you had say a DSOX3000T and it fits your needs then it would be silly to sell it and buy a WS3000 instead. But if you're in the market for a scope in that class then the WS3000 is certainly worth consideration, and while it lacks some features it brings others that, while perhaps using a different approach most EE's would take, can replace many of them plus bring further benefits (you may or may not use, but that's up to you).


--- Quote ---DPO is usually but not always a superior replacement for peak detection so the later is still needed.  I am not sanguine that WaveScan is a superior replacement for either.
--- End quote ---

It isn't, because WaveScan is not meant to replace DPO, a mode Tek had to implement because their scopes architectures suck so badly that they can't get decent update rates in normal mode without using some tricks. Other scopes have had persistence mode for years, and so does the WS3000.


--- Quote ---Marketing said the same thing about large acquisition memories replacing the need for delayed acquisition and peak detect yet the result has been lower performance or outright uselessness in a minority of applications which older DSOs without large acquisition memories have no trouble with;
--- End quote ---

Well, PD is in pretty much any big brand scope aside from LeCroy, so I must have missed when a manufacturer claimed it's no longer needed because of memory lengths. What has happened though is that the need for PD has reduced a lot, simply because of ever increasing sample meory sizes.


--- Quote ---Your comment about LeCroy designs originating with physics applications where all original data is preserved and then analyzed fits with how WaveScan is described as working however I do not think that model is necessary or even suitable for design, development, and troubleshooting.
--- End quote ---

That may be your opinion, but in reality there are many areas where having the original sample data retained so you can run various analysis modes in parallel is a big advantage. You'll find LeCroy scopes in pretty much every segment of high tech, often simply because no other scope including Keysight can offer the same performance or capabilities.  And that has been the case pretty throughout their existence.

If that architecture wouldn't work for their customers then I'm sure LeCroy would have already given up on it because implementing a design as on other scopes where sampling modes can be destructive would make it a lot easier for them.

David Hess:

--- Quote from: Wuerstchenhund on September 16, 2016, 02:34:03 pm ---
--- Quote from: David Hess on September 16, 2016, 09:14:48 am ---DPO is usually but not always a superior replacement for peak detection so the later is still needed.  I am not sanguine that WaveScan is a superior replacement for either.
--- End quote ---

It isn't, because WaveScan is not meant to replace DPO, a mode Tek had to implement because their scopes architectures suck so badly that they can't get decent update rates in normal mode without using some tricks. Other scopes have had persistence mode for years, and so does the WS3000.
--- End quote ---

*All* DSO architectures suck badly if they cannot process the data from the digitizer in real time.  That does not make them useless but it prevents them from replacing an analog oscilloscope like the Tektronix 7834 fast storage oscilloscope.

Persistence has nothing to do with DPO operation.  The earliest non-vector DSOs Tektronix made included it but without DPO operation, it was no faster than non-persistence operation which is to be expected.

If I were designing a DPO mode, I would halve the acquisition memory by dividing it into two banks, fill one bank with the real time histogram, and swap banks allowing the histogram to be processed for display while filling the other bank.  To take maximum advantage of this, the acquisition record length *must* be limited to provide the maximum trigger rate because otherwise multiple triggers will be present in each histogram.  That is not fatal but it effectively creates blind time for data which is not going to be displayed anyway.  It also shows why a short record length may be used in DPO mode without any drawbacks except of course for not being able to see the original data which will be required in specific applications.

If I care about the original data, record it in parallel for display as needed like when a secondary trigger condition is satisfied.  With increasing integration, memory for an extended record is the cheapest thing to add.


--- Quote ---
--- Quote ---Your comment about LeCroy designs originating with physics applications where all original data is preserved and then analyzed fits with how WaveScan is described as working however I do not think that model is necessary or even suitable for design, development, and troubleshooting.
--- End quote ---

That may be your opinion, but in reality there are many areas where having the original sample data retained so you can run various analysis modes in parallel is a big advantage. You'll find LeCroy scopes in pretty much every segment of high tech, often simply because no other scope including Keysight can offer the same performance or capabilities.  And that has been the case pretty throughout their existence.
--- End quote ---

Many areas like physics?

Apparently then LeCroy oscilloscopes are found in every segment of high tech except those I have worked in.  When evaluating equipment, LeCroy has always been close to the bottom for me.  These days based on historic reputation which may or may not be deserved, I would group them with the likes of Rigol.  Pointing out other manufacturer's flaws does not make them better; just because I am not a fan of current Tektronix designs does not lead me to default to LeCroy.


--- Quote ---If that architecture wouldn't work for their customers then I'm sure LeCroy would have already given up on it because implementing a design as on other scopes where sampling modes can be destructive would make it a lot easier for them.
--- End quote ---

I do not believe this at all.  LeCroy has specialized in a specific DSO design to the exclusion of markets where their reputation is poor anyway.  It is easier for them to accept the status quo than to pursue those markets.  I am sure they also had patent conflicts with other manufacturers which made certain designs more attractive than others and marketing is going to push what you have.

Wuerstchenhund:

--- Quote from: David Hess on September 17, 2016, 05:43:40 pm ---
--- Quote ---
--- Quote ---Your comment about LeCroy designs originating with physics applications where all original data is preserved and then analyzed fits with how WaveScan is described as working however I do not think that model is necessary or even suitable for design, development, and troubleshooting.
--- End quote ---

That may be your opinion, but in reality there are many areas where having the original sample data retained so you can run various analysis modes in parallel is a big advantage. You'll find LeCroy scopes in pretty much every segment of high tech, often simply because no other scope including Keysight can offer the same performance or capabilities.  And that has been the case pretty throughout their existence.
--- End quote ---

Many areas like physics?
--- End quote ---

That was where they started decades ago. It's hardly their main market.

Today this are areas like storage technologies (LeCroy scopes were and still are standard in the labs of most hard disk and other storage manufacturers), and high speed communications/networking (guess what one of the target market for the 100Ghz scope is) or aerospace/defense (for example, LeCroy is the *only* scope manufacturer that even offers procotol support for standards like SpaceWire or EFABus/STANAG3910). They have "scopes" with up to 80 channels, sampling rates of 240GSa/s and inter-channel jitter of less than 130fs. You think this is for physics when the majority of options are for communications, Vector Signal Analysis and other EE related stuff?


--- Quote ---Apparently then LeCroy oscilloscopes are found in every segment of high tech except those I have worked in.
--- End quote ---

Well, then I guess that was either in different fields which didn't require as cutting edge in a scope. Or maybe it wasn't as high tech as you think it was.


--- Quote ---When evaluating equipment, LeCroy has always been close to the bottom for me.  These days based on historic reputation
--- End quote ---

"Historic reputation"? Which was what exactly?


--- Quote ---which may or may not be deserved, I would group them with the likes of Rigol.
--- End quote ---

Really? Rigol which really has nohing that isn't bottom-of-the-barrel? You compare the company that makes the fastest, most advanced scopes you can find, and which supports their scope longer than any other manufacturer with a CHinese B-brand that required Agilent to teach them so that they come up with the bug-ridden products they offer today?   :palm:

If that isn't a stupid statement then I don't know what is.


--- Quote --- Pointing out other manufacturer's flaws does not make them better; just because I am not a fan of current Tektronix designs
--- End quote ---

And still that's the vendor you seem to go to for new scopes, which i guess is because you trust them based on the great analog scopes they had.

It's no secret that Tektronix scopes are crap. That's why pretty much no-one who knows a bit about the T&M market buys them unless they have no choice.


--- Quote ---does not lead me to default to LeCroy.
--- End quote ---

So what, I never expected it did, nor do I care. Why should I, it's your business what you buy and what not, not mine. I obviously don't even know what you work on so I couldn't even recommend something even if you asked (although my gut feeling is that whatever it is it should be as close to an analog scope as possible).

Juts to be clear, I don't want to "convert" anyone, and as stated nor do I suggest that if you have a decent scope already to dump that and buy a LeCroy. All I do is show some alternative about scopes not too many people here know much about, so people know there are alternatives to the trotten path of pretty much only Keysight. You're completely free to ignore that of course and consider only those manufacturers that you trust personally, even if it's what today is pretty much the bottom scrape of all the big brands.


--- Quote ---
--- Quote ---If that architecture wouldn't work for their customers then I'm sure LeCroy would have already given up on it because implementing a design as on other scopes where sampling modes can be destructive would make it a lot easier for them.
--- End quote ---

I do not believe this at all.  LeCroy has specialized in a specific DSO design to the exclusion of markets where their reputation is poor anyway.
--- End quote ---

Which are? You already stated something about "poor reputation" so it would be helpful if you could provide some details.

It's clearly not digital storage, communications and aerospace/defense, so what are these markets where they have a poor reputation?


--- Quote ---It is easier for them to accept the status quo than to pursue those markets.
--- End quote ---

Again, what are these markets?


--- Quote ---I am sure they also had patent conflicts with other manufacturers which made certain designs more attractive than others and marketing is going to push what you have.
--- End quote ---

What "patent conflicts" are these? Can you provide some links please?

Someone:

--- Quote from: Wuerstchenhund on September 17, 2016, 06:38:50 pm ---Juts to be clear, I don't want to "convert" anyone, and as stated nor do I suggest that if you have a decent scope already to dump that and buy a LeCroy. All I do is show some alternative about scopes not too many people here know much about
--- End quote ---
Then how about instead of using one sided feature comparisons you show some of these unique features and how they're used. Telling everyone you have a secret technique/feature that makes all other scopes pointless while failing to tell anyone else either how it solves problems better or even what that feature or technique is just makes you look like a you're here to be intentionally obtuse and blustery.

Even when presented with well described examples of how people use peak detect to learn about signals, you immediately dismiss them without capturing all the requirements:

--- Quote from: Wuerstchenhund on September 14, 2016, 10:13:21 am ---
--- Quote from: nctnico on September 14, 2016, 09:44:36 am ---Even with long memory I use peak detect often at low sweep rates to make sure I don't miss a narrow pulse c.q. see a trace which has all the expected elements and nothing missing or malformed due to aliasing. It is true that timing information is lost but when looking at (for example) video signals it is nice to see the hsync and vsync pulses are all there. To me having no peak detect is a show stopper.

--- End quote ---

I understand. Well, on a LeCroy scope I would rather use WaveScan for that.

Your scenario is actually not too unsimilar to a pet project of mine, where one element relies on a set of (unevenly spaced) sync pulses. To find out if pulses are missing or out of spec I just throw WaveScan at it and let it run for a while, it then tells me any pulses were missing/out of spec, and if so presents me with a nice histogram showing when exactly that happened. If I wanted I could even set it up to do specific measurements on malformed pulses, or just let it do some screen shots everytime a deviation occurs, or do a range of other stuff.

It's pretty handy, and helped me to identify a problem where the sync generating unit producted malformed pulses in varying periods. It also helped me finding the source of a problem where the sync providing element occasionally threw out malformed pulses. With WaveScan and the statistics function I found out that the timing depended on the operating mode of that unit, i.e. power load, and that it was a flaw in the PSU which caused it.

Granted, on a entry-level scope which doesn't have any advanced functionality, PD is probably the best (only?) way to do that.

--- End quote ---
Peak detect runs at the acquisition sample rate, and as discussed can have zero blind time. This can be very important to quickly assess the signal especially in something as complex as video. But without any examples or evidence you claim that a technique with substantial blind time (still unquantified) would be a much better way to do it, and then continue to argue on and on about it. The simple answer is to provide some figures of the blind time and the capabilities of the wavescan triggers then we can see what applications it might be superior for. But until then you're just broadcasting your unsubstantiated view and we're all sceptical.

Analog (even some digital) video signals are good candidates for visual assessment or mask testing due to their structured frames which are complex enough to only be decoded by specialist signal analysers (from Tek). We know of two tools which work for this, a fast realtime scope, or the video analysers.

heavenfish:
There're two primary usecases for oscilloscopes. First it's a validation tool that people use it to view the waveform or make measurements to see whether your circuits work as expected; second it's a troubleshooting tool that people use it to find bugs by looking for a abnormal signal or incorrect cmd being sent through serial buses. Though the later seems need more advanced features sets in oscilloscopes, an oscilloscope still needs some basic things to do what it was invented for: waveform visualization.

Wavescan can help to debug and find any glitches from video waveforms or any other waveforms. But if a student or technician wants to show an entire frame of video signal on the screen, just show, there's no better way than simply using peak detect mode.

This doesn't mean Lecroy did anything wrong. In the end, no product can meet everybody's need and make them all happy. It's about the choice of the company and the product manager. Which features are more important for the applications and customers they focus, or easier to implement with their technology.

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