Show us your square wave

[Electro Fan]

The picture is a 3D color persistence screen, which is essentially a more advanced variant of the common 2D persistence function many scopes have today.

Most scopes have a monochrome persistence function (i.e. intensity grading) where individual waveforms overlap each other on a single "depth" layer (the screen plane) and where the brightness represents the amount of times a waveform has passed through a particular spot on the screen. This can be used (in limits) to see jitter or other signal anomalies. More advanced scopes use color grading,

i.e. the color shows how often a waveform has passed through a particular spot, where red ('hot') shows places of high occurrence, yellow for medium occurrence and blue for low occurrence.

In a 3D persistence screen each waveform is 'stacked' on top of the other, which shows much better how the waveforms change over time. Again, the colors indicate the occurrence of a waveform passing through a certain spot in the horizontal (x/y) plane.

It's a great tool but for this specific exercise I don't think it adds any value, and since the scope was running in RIS (ETS) mode I'm not sure the waveform that is displayed has much to do with the input signal. The picture shows noticeable variations in the waveform, which means RIS is unsuitable here.

Thanks for the color legend and the overall explanation

[joeqsmith]

Hi,

I had a look at this picture:

The FFT shows spectral lines that are 5 GHz apart. This is sampling frequency of the scope 5G samples per second. The Lecroy scope is using RIS acquisition.

Regards,

Jay_Diddy_B

I agree.   

It is amazing how different the results are, between the two devices.....no doubt about that....I would argue that you have the superior scope for this kind of test.....?

I really was not interested in comparing the two setups for the 15MHz squarewave shape.    When I saw your original post with those spurs, it was not at all what I was expecting and I was thinking there was a software problem.   I checked my old LeCroy 7200 and did not see the spurs at the sample rate.    So I attempted to replicate it with my Wavemaster that has the latest version of X Stream loaded on it.   I tried various FFT settings to attempt to replicate those spurs and could not.   

I would have thought they would handle the FFT the same between the two DSOs but it appears they don't.    I assume you were using a boxcar.  What happens if you use a Hamming window?    Some other setting?   

Not useful but I thought it was strange. 

[TunerSandwich]

The RIS sample rate was 200GS, and the non RIS is 10GS (at that timebase), not 5GS......no boxcar on that.....just sin x/x and i believe the settings were power spectrum and flattop.....I can duplicate the result and show the setup screens.....

as you can see in the "broadband" plot the spurs extended out to around 100GHz and then began to roll off up to 200GHz....where there was a dramatic rolloff....pretty close to the way your scope behaved. 

It would be interesting to do a true quantitative comparison.....I will document the EXACT settings, and if you are inclined to spend the time, we could compare again. 

Maybe even load the same waveform into arb?  My signal source and cable were very much inferior to yours. 

The uniformity of the spurs is highly suspicious....in the "1THz" plot you can see the roll-off above 100GHz.....just to confirm you have a 5GHz front end on your WaveMaster?

[joeqsmith]

Yes, I would like to see if I could replicate your results it just because they seemed so strange.   

The data I showed was also sin x/x.  My DSO must also be in sin x/x to get 1THz with the FFT.   I also show the FFT in power spectrum and flat top.   

I don't think the 5G spurs has anything to do with the incoming signal but if you don't mind, try it and let me know.   I can always put it into the ARB if you find its a factor without any problem.   I just need a CSV or something file.   I can always translate it.   Just raw voltage is good enough.   

Yes, my 8500A has a 5GHz front end.   It's pretty old compared to yours but for my home use it is over kill.     

[TunerSandwich]

Yes, I would like to see if I could replicate your results it just because they seemed so strange.   

The data I showed was also sin x/x.  My DSO must also be in sin x/x to get 1THz with the FFT.   I also show the FFT in power spectrum and flat top.   

I don't think the 5G spurs has anything to do with the incoming signal but if you don't mind, try it and let me know.   I can always put it into the ARB if you find its a factor without any problem.   I just need a CSV or something file.   I can always translate it.   Just raw voltage is good enough.   

Yes, my 8500A has a 5GHz front end.   It's pretty old compared to yours but for my home use it is over kill.     

Regardless of age, that is a superior scope....it obviously doesn't have the bells and whistles etc, but 5GHz front end is 5GHz front end....and I believe you can also do 10GS/s interleaved?   I have extended mem on mine plus all options, but I think you essentially have the same, or better "horsepower" in your wavemaster.  I will stay away from "wavestream" view (which I normally do anyhow, because it negates any sinx/x or ERES).  i didn't use ERES for the broadband plots....but did use it on the pulses focusing on the zoomed impulse responses....

I will see if I can load the proper signal into arb (PITA on the ds2000a-s).  if not I will try to get much more specific.  Also there is that cable issue (although I don't see how that should have anything to do with the spurs on my 600MHz front end). 

I will also try the same on CH3....and another option is to use the AP020 probe......do you have one?  That way we can have a more apples to apples comparison (again I doubt the cabling has anything to do with such a dramatic result). 

When I did the plot I didn't pay much attention to where the spurs were.....I just zoomed in to the region (roughly) where they had equivalent amplitude and assumed it was harmonic centers.....but now that it has been brought up, and I look closer, that doesn't seem right at all.....that is far too uniform across a bandwidth my front end doesn't even cover, to be signal....*scratches head*

[Jay_Diddy_B]

Hi group,

Here is a little simulation to show what happens with sampling and FFTs. This is to help explain the scope waveform.

I have constructed a model with a square wave with a 66ns period (15.1515 MHz) with a 1ns rise and fall times.

I have also modelled a 100MHz Bessel filter, this will soften the edges without introducing ringing.

And then I constructed a sample and hold to simulate sampling the waveform at 1 Gsps.

Here is the model:



This what the waveforms look like in the time domain:




And this is what the FFT results look like:




The top waveform shows the 1ns rise and fall time square waves. There are spectral lines at 15MHz, 45 MHz, 75 MHz .... There are only even harmonics because the square wave has a 50% duty cycle. There a dips at 1GHz 2GHz etc this comes from the 1ns rise and fall times.

In the second waveform the harmonics are attenuated by the response of the 100 MHz Bessel filter, so no real surprises here.

In the third waveform, we can see the effects of the sampling frequency. We have the baseband spectral lines, then we have components at sampling frequency +/- the baseband components, we also components at 2x sampling frequency +/- the baseband components etc.
This is a form of aliasing because in calculating the FFT we are looking at frequencies greater than half the sampling frequency (Nyquist Theorem) The FFT is only valid up to 500 MHz.



Regards,

Jay_Diddy_B

[joeqsmith]

Regardless of age, that is a superior scope....it obviously doesn't have the bells and whistles etc, but 5GHz front end is 5GHz front end....and I believe you can also do 10GS/s interleaved?   I have extended mem on mine plus all options, but I think you essentially have the same, or better "horsepower" in your wavemaster.  I will stay away from "wavestream" view (which I normally do anyhow, because it negates any sinx/x or ERES).  i didn't use ERES for the broadband plots....but did use it on the pulses focusing on the zoomed impulse responses....

When I did the plot I didn't pay much attention to where the spurs were.....I just zoomed in to the region (roughly) where they had equivalent amplitude and assumed it was harmonic centers.....but now that it has been brought up, and I look closer, that doesn't seem right at all.....that is far too uniform across a bandwidth my front end doesn't even cover, to be signal....*scratches head*

For home, even my old 7200s have way more features than I use. 

My 8500A will do 20Gs/s interleaved, 200Gs/s RIS.    I would expect them to behave the same (for those 5G spurs).   Obviously, I was expecting to see 10G spurs.   I would not have thought to even look at it until you posted.    See, there was a point to this thread after all!   

I don't believe this is caused by the cable or input signal but give it a try.   Those spurs are so nice and flat on yours where mine has nothing. 

AP020 probe......do you have one? 

I only have resistive probes.    I plan to make some low freq buffers at some point to allow me it to work with 10X passive probes as well.   
Best to stick with coax. 

[Rupunzell]

Tektronix 7104, 2x 7A29, 7B10 & S50 pulser with SMA to BNC direct to the 7A29 input (50 ohm).
Base line is trigger channel.




Bernice

[Electro Fan]

Disclaimer:  even though I posted the original question I feel like I'm now posting really dumb commercials inside a seriously good TV program 

That said, I just tripped across the link below - it doesn't address all the end to end system issues (from the generator to the cabling to the scope) but it starts to get at the original question.  I think some of you might have read more into the original post than I intended - but that's A-OK, and I'm very happy to have stimulated the fuller discussion.

In my mind, a "strong" square wave is simply a square wave that looks very "square" - like what you try to get when adjusting a probe on a scope front panel.  And perhaps as many here have pointed out, there might not be a lot of other needs for a very square square wave. 

I don't know to what extent a computing or networking device needs a square square wave but I have to believe that although there are ways to pick out a 1 or a 0 from a relatively weak or poorly formed square wave at some point a very poorly formed square wave might confuse a receiving/decoding device.  No doubt my eyes seem to appreciate a highly square square wave more than most devices and circuits trying interpret square waves as 1s or 0s.  I guess that's a benefit of machines, they put up with workloads and conditions that people might not tolerate

So, again my post was about the simple observation of a square wave in a traditional or human perception/observational sense.  What drove the question was in part the fact that I've seen square waves that look more like sine waves to me from reputable equipment manufacturers who publish a spec for square waves - and at the upper end of the spec the square wave frankly looked kind of (very much) like a sine wave, at least to me.  So, I was just curious to see what people would call a square wave (at various frequencies and at various price points for generators).  Clearly I wasn't giving full consideration to the cabling and scope contributions - but it is great to see the discussion of the wider (and deeper) end to end considerations.

The article below addresses the question of "when is a square wave a square wave" - at least at an intermediate level.  I'll leave the advanced stuff to those here with more system-wide experience not to mention picosecond generators, GHz scopes - and color technologies. 

PS, I really enjoy this forum and I very much appreciate the fact that the pros and other senior members put up with entry level questions and comments.  There is huge amount of knowledge, experience, and good will in this forum and EEVblog overall.  You all rock in my book!  EF

http://mwrf.com/content/when-square-wave-truly-square
- this is a very good article; recommended; comments on it encouraged....

[Wuerstchenhund]

Regardless of age, that is a superior scope....it obviously doesn't have the bells and whistles etc, but 5GHz front end is 5GHz front end....and I believe you can also do 10GS/s interleaved?   I have extended mem on mine plus all options, but I think you essentially have the same, or better "horsepower" in your wavemaster. 

The Wavemaster 8k does 20GSa/s interleaved or 10GSa/s on all channels. However the processing is much slower than on your WRXi even if the latter is equipped with the standard P-M Celeron 1.3GHz only. The WM8k (as the WP7k) came with a first gen P4 Celeron 1.7GHz with 256k cache/400MHz FSB (later scopes came with 2GHz Celeron) which was already a slow processor when these scopes were new, LeCroy was pretty much skimping on the processor power in their older X-Stream scopes (it got better in recent years). Unfortunately there's also a limit on what processor upgrades these scopes can take, although one could replace the mainboard for the one that is used in the WP7kA/WM8kA (later revision of the intel D865GLC) and which can take later revisions P4 processors with 3.2GHz/800MHz and faster. Just never enable Hyperthreading on a WP7k(A) or WM8k(A), ever!

[TunerSandwich]

Regardless of age, that is a superior scope....it obviously doesn't have the bells and whistles etc, but 5GHz front end is 5GHz front end....and I believe you can also do 10GS/s interleaved?   I have extended mem on mine plus all options, but I think you essentially have the same, or better "horsepower" in your wavemaster. 

The Wavemaster 8k does 20GSa/s interleaved or 10GSa/s on all channels. However the processing is much slower than on your WRXi even if the latter is equipped with the standard P-M Celeron 1.3GHz only. The WM8k (as the WP7k) came with a first gen P4 Celeron 1.7GHz with 256k cache/400MHz FSB (later scopes came with 2GHz Celeron) which was already a slow processor when these scopes were new, LeCroy was pretty much skimping on the processor power in their older X-Stream scopes (it got better in recent years). Unfortunately there's also a limit on what processor upgrades these scopes can take, although one could replace the mainboard for the one that is used in the WP7kA/WM8kA (later revision of the intel D865GLC) and which can take later revisions P4 processors with 3.2GHz/800MHz and faster. Just never enable Hyperthreading on a WP7k(A) or WM8k(A), ever!

Although I am VERY pleased with my WR64MXi....the 20GS/s is quite compelling, even by today's standards that is "high end".  Lots of data there....probably grabbing some stuff I am missing, especially at "longer" timebase...do the WM8k's have the "ERES" capability?  I have found that to be EXTREMELY useful for the type of stuff I use my MXi for, day to day.  I can only imagine that the HDO series is a pretty big step above pseudo +3 bits.....I have really been considering getting a demo loan on an HDO8k, but am too afraid I won't be able to send it back. 

[Wuerstchenhund]

Although I am VERY pleased with my WR64MXi....the 20GS/s is quite compelling, even by today's standards that is "high end".  Lots of data there....probably grabbing some stuff I am missing, especially at "longer" timebase...do the WM8k's have the "ERES" capability?

Sure, all 'true' LeCroy scopes¹at least since the early 90's when the 9300 Series came along had ERES, although if I remember right it was a software option back then.

I have found that to be EXTREMELY useful for the type of stuff I use my MXi for, day to day.  I can only imagine that the HDO series is a pretty big step above pseudo +3 bits.....I have really been considering getting a demo loan on an HDO8k, but am too afraid I won't be able to send it back.

The problem with ERES is that it limits the available bandwidth, i.e. my 3GHz WP7300A goes down to 160MHz in 11bit ERES mode. Naturally the HDOs don't suffer from that problem.

But if you can I'd wait a bit as it's very likely that we'll soon see true 12bit scopes at higher bandwidths and sample rates as the HDO Series offers from LeCroy. Especially after Keysight came out with the MSO-S.

Overall I'm extremely happy with my WP7300A which as an every-day scope has now completely replaced my WR64Xi and my LT264M (which I'll probably sell on as I can't see myself really needing to use them in the near future). 20GSa/s and 48M are helpful, and LeCroy's options are really outstanding (although these older scopes lack the SPECTRUM option, but stuff like serial decode for a dozen or so standards incl stuff like USB3 and Fibre Channel, and the Serial Data Analyzer option more than make up for that). I'll guess I'll hang-on to the WP7300A until the WP7zi gets into more sane price regions, and even then very likely keep it.

¹ Doesn't include the WaveAce and WaveJet Series

[EV]

I see Rigol DSO displays are being posted on this thread and comments about overshoot.

Here are pictures you asked:

Generator: Rigol DG4162, sync out, 40 MHz square wave, connected straight to scope with about 1 m RG58 cable.

Scope: Tektronix R7103
1. pic: Timebase 7B15, Vertical amp 7A29, BW 1 GHz
2. pic: Timebase 7T11, Vertical amp 7S11 with sampling head S-2, BW ?
3. pic: Timebase 7T11, Vertical amp 7S11 with sampling head S-4, BW ?

The last picture with S-4 sampling head does not look good. So I connected the RG58 cable with 20 dB attenautor to the S-4 sampling head and here are new pictures with 5 ns and 1 ns timebase.

[joeqsmith]

I tend to use a PC to control a lot of my equipment and then post post process the data with a modern PC.   

I had made a video showing some basic jitter measurements with Labview and had posted it in a LeCroy specific forum. Video can be seen here (WARNING it's pretty long and I am not real good at making videos):     


This spawned  a conversation with I assume a Teledyne sales guy about upgrading the DSOs MB.   The following is just a cut and paste to give some background: 

> Imaged the drive to back it up then started over. Pretty sure anyone playing with this sort of scope
> can handle installing an OS. ha ha

Not necessarily. Not saying this applies to you but I've lost count of the number of EEs I've met that know their field inside out but are complete numbties when it comes to computers.

................

> Yes, it has 256M. Task manager does not show a lot of swapping going on even with the 256. This
> MB supports up to 2G. I added a GB and reran my tests. No gains. You may be using a lot of the > DSOs math.

In fact I do. RAM helps quite a bit (especially since you can get DDR1 sticks for next to nothing these days), but the biggest improvement comes from a faster CPU with larger cache. X-Stream does all its calculations in the CPU cache which speeds up things, but the slow 512k processors LeCroy shipped with these scopes can be a bit of a bottleneck.

> For any post processing I would typically run Labview on a modern PC anyway.

If you have LabView then this is of course an option. But you can't do real-time stuff on LabView the same way you can do on the scope.

> I may install 1Gb Ethernet and see if I can pull the data out any faster.

I doubt that. The scope's mobo has a single 33MHz PCI32 bus which is also used by the aquisition adapter (which converts the 4x Gbit Ethernet links from the acquisition board to PCI). Aside from that the max 133MB/s (theoretical, in reality it's probably closer to around 90MB/s) overall bus bandwidth which is shared across all devices and from which the acquisition system already uses a bulk of, the timing in these scopes is pretty tight so introducing another card might have some side effects.

.....

>> If you have LabView then this is of course an option. But you can't do real-time stuff on LabView
>> the same way you can do on the scope.
>
> Not sure what you mean. Real-time?

LabView needs to gather the data from the scope first, which is awfully slow compared to the X-Stream software which has access to the acquisition data in real-time. If your scope has the XDEV option then you can get around that as it allows you to build your own applications that run on the scope directly.

> > I doubt that. The scope's mobo has a single 33MHz PCI32 bus which is also used by the
> > aquisition adapter (which converts the 4x Gbit Ethernet links from the acquisition board to PCI).
> > Aside from that the max 133MB/s (theoretical, in reality it's probably closer to around 90MB/s)
> > overall bus bandwidth which is shared across all devices and from which the acquisition system
> > already uses a bulk of, the timing in these scopes is pretty tight so introducing another card
> > might have some side effects.
>
> I plan to do some benchmarking on it. Tell me more about this timing problem. Maybe you can
> save me some time.

The acquisition interface acts as a PCI busmaster. The whole processes are very timing critical. The scope is designed so that the acquisition interface has the PCI bus for its own. Introducing a Gbit Ethernet interface which will cause noticable bus loading will probably result in side effects, i.e. lowered acquisition performance, abysmal slow network performance or the scope reacting funny.

I went ahead and ran the tests and made a few videos showing the outcome.

This first video shows the DSO running non-interlaced.   


After making the first video I noticed there was a big hit in download performance when running in interlaced mode.   I played with the DSO for a while then made this second video to show the results.



I had hoped the Teledyne people would jump in to clear up my misconceptions but after making the videos they stopped posting.   

[Wuerstchenhund]

I had hoped the Teledyne people would jump in to clear up my misconceptions but after making the videos they stopped posting.

The Yahoo LeCroy forum is sparsely visited, as the low post count over the years shows (I find myself checking it maybe once a month or less), and most discussions revolve around pre-X-Stream scopes (mostly 9300 and LC Series). Don't forget that even the oldest X-Stream scope (WaveMaster 8000) is still worth some noteworthy amount of money which makes it still prohibitively expensive for most hobbyists.

Don't get me wrong, the LeCroy Yahoo forum has been a great help in the past and this on several occasions, but it's not really the place for long-winded discussions like this thread, simply because there aren't enough people spending sufficient time in it.

[joeqsmith]

I had hoped the Teledyne people would jump in to clear up my misconceptions but after making the videos they stopped posting.

The Yahoo LeCroy forum is sparsely visited, as the low post count over the years shows (I find myself checking it maybe once a month or less), and most discussions revolve around pre-X-Stream scopes (mostly 9300 and LC Series).

Maybe the videos had nothing to do with sudden drop in responses.   If I were in sales and made a bold statement how I lost count of the number of EE's who are noobs when it comes to PCs and how making such a change was going to cause all sorts of problems, and then have a customer call me out,  I would not handle it by going silent.   

Honestly, I never did figure out what they were talking about.  I've had no problems with the 1Gb interface to date and never saw a down side to it.   

[TunerSandwich]

The problem with ERES is that it limits the available bandwidth, i.e. my 3GHz WP7300A goes down to 160MHz in 11bit ERES mode. Naturally the HDOs don't suffer from that problem.

Yes, but that is not a problem for the very specific things I use it for.  I.E. checking control signal in SMPS and other (various) low frequency DC-DC applications.  However, I would much rather see a true 12bit vertical reading, as I am not 100% sure on what levels of interpolation the ERES might be using....which obviously skews things to some degree or another. 

It has been an invaluable tool in catching over/under shoot, that normally would be missed.  I would love to see a true 12bit capture, along with a higher sample rate and some reasonable mem depth, for longer power quality captures.  That is probably my biggest complaint about the MXi I have.  It starts to lose a lot of performance and resolution/fidelity 2 long capture windows.  Obviously the PMA and other such utilities suffer because of that. 

If I expand the scope of my work (which is happening) the need for higher bandwidth, bit depth and sample-rate (plus mem) is there.  I did notice there were some trade-offs in the HDO series.  Would be nice to see LeCroy roll some technology into a single package.

I.E.
3GHz
12 bit
deep memory
industry leading sample rate
their excellent Ui/MAUI
bundle some spectral tools (with a dedicated FFT/spectrum button)
all packaged in nice form factor (which I think LeCroy does quite well) for a market leading cost
AND expand their current probe options.....
and update Wave studio (not a fan of it's interface, speed, etc...)

[Wuerstchenhund]

Maybe the videos had nothing to do with sudden drop in responses.   If I were in sales and made a bold statement how I lost count of the number of EE's who are noobs when it comes to PCs and how making such a change was going to cause all sorts of problems, and then have a customer call me out,  I would not handle it by going silent.   

Honestly, I never did figure out what they were talking about.  I've had no problems with the 1Gb interface to date and never saw a down side to it.   

Just because you were lucky doesn't mean that such mods are always troublefree. In fact, it might well be that your mod has other side effects you just didn't notice (yet). Just because something looks ok doesn't necessarily mean it is. Also, do you know how many different PCI 1Gbps network adapters exist? And just because you didn't see side effects with one makes you think it will always be allright? Hopefully not.

The simple fact is that these scopes are not designed as expandable systems, and just because you can plug in some PCI card doesn't mean it can be expanded like a standard PC. The scope as sold is the only supported (i.e. guranteed to work) configuration, aside from a few upgrades offered by LeCroy like CPU and RAM (which even if done with generic parts should be pretty painless). And really, it should be pretty obvious to an EE why on a single PCI bus with a theoretical max transfer rate of 133MB/s a 1Gbps network adapter (which in a good environment transfers between 90-100MB/s) doesn't leave much room for anything else. And something like 33MB/s isn't much for an acquisition system which captures over 20GB data per second, and while not everything in the sample memory goes to the CPU, everything that you want to see on the screen or that you want to process in any way does. Well, you do the math.

In addition, the acquisition system in these LeCroy scopes definitely *is* timing sensitive. I've been bitten by this myself when I upgraded my CPU (hint: never enable Hyperthreading on a WP7k(A) or WM8k(A), unless you want to reinstall your OS).

This aside, "just works" isn't really good enough if you want to use your test kit professionally, where people generally want to have something that is supported by the manufacturer and where problems are solved by their support. If you modded your scope most manufacturers simply tell you to piss off, and rightfully so.

Maybe these EE's you were talking about weren't such 'noobs' at all.

I'm not going to ask why you need a 1Gbps network adapter in your scope. The standard intel 100Mbps Ethernet port should be more than enough for transferring data or remote controlling it.

BTW, the Yahoo LeCroy forum is operated by a guy who has nothing to do with LeCroy other than using their scopes (and helping members). In fact, there are only two LeCroy affiliated member I know of, and they certainly don't use the forum as a marketing vehicle. But generally you can expect that the familiars there pretty well know know what they're talking about.

[Wuerstchenhund]

Yes, but that is not a problem for the very specific things I use it for.  I.E. checking control signal in SMPS and other (various) low frequency DC-DC applications.  However, I would much rather see a true 12bit vertical reading, as I am not 100% sure on what levels of interpolation the ERES might be using....which obviously skews things to some degree or another. 

There's no interpolation in ERES. You are getting the full 11bit resolution, at the cost of bandwidth. Here's a LeCroy document explaining ERES in more detail (it's from 1999 but still remains valid):
http://teledynelecroy.com/doc/digital-oscilloscopes-enhanced-resolution

It has been an invaluable tool in catching over/under shoot, that normally would be missed.  I would love to see a true 12bit capture, along with a higher sample rate and some reasonable mem depth, for longer power quality captures.  That is probably my biggest complaint about the MXi I have.  It starts to lose a lot of performance and resolution/fidelity 2 long capture windows.  Obviously the PMA and other such utilities suffer because of that. 

I know that they're working on expanding their High Definition 12bit technology into higher end scopes, I guess eventually all their mid-range and high-end scopes will be 12bit, aside from the LabMaster maybe (which is a different beast anyways). The HDOs are nice but they're essentially WaveSurfers on steroids only. There's also of course the WaveRunner HRO but again 2GSa/s only, and very likely one of the next models to go.

If I expand the scope of my work (which is happening) the need for higher bandwidth, bit depth and sample-rate (plus mem) is there.  I did notice there were some trade-offs in the HDO series.  Would be nice to see LeCroy roll some technology into a single package.

I.E.
3GHz
12 bit
deep memory
industry leading sample rate
their excellent Ui/MAUI
bundle some spectral tools (with a dedicated FFT/spectrum button)

The button already exist on the WaveRunner 6zi/HDO. But I think that the SPECTRUM option should be standard for WaveRunner and higher models, really.

all packaged in nice form factor (which I think LeCroy does quite well) for a market leading cost

Indeed, LeCroy does the packaging quite well, and often does have some things (i.e. an adjustable widescreen display with pivot mode on the WR6zi/HDO, or the detachable control panel and the dual BNC/SMA inputs on the WP7zi) you just can't find anywhere else.

Cost-wise I don't think they have a problem. LeCroy has been cheaper than Agilent/Keysight and Tek pretty much forever when comparing comparable scopes, and unlike Tek they are very flexible in their pricing.

AND expand their current probe options.....

What do you miss?

and update Wave studio (not a fan of it's interface, speed, etc...)

Well, it's ok for a free program, and while it's slow it still much better than the equivalents from Keysight and Tek. The update rate is difficult to increase as the program captures individual screenshots and not a video stream. If you want faster then just login via RDP. Works like a charm even on XP, and even better on Windows 7 scopes.

[TunerSandwich]

What I would like to see them do, is sort of a "best of" from all of their current lines....

screen and interface options from the units you mentioned....12 bit, big mem, high sample rate....keep it in line with the general LeCroy "value model".

would like to see a current probe with more sensitivity and bandwidth at higher current (don't mind paying for that).....or at least update the AP015 to take just a bit more current for that 10 second window and give me 100MHz (and update the deskew process, to be a bit less "clunky").  They just seem to take a big jump from the CP031 to the CP150, with nothing really in between...

on the wave studio front...I would like to see them take a more direct approach, as opposed to screen capture (the current trace tools aren't at all good IMO)....maybe just use a template that looks like the scope Ui and stream data into the waveform and measurement sections (might not be possible, from a processing perspective).....also give us the ability to create new Ui building blocks in WS would be nice.  Think of it as just a "customizable skin/bounding boxes" approach, with some blocks that contain a live update on statistics/waveforms.....and the ability to include markers/tags....that would be very useful for reporting.....also a direct "video capture" would be nice and maybe throw in some simple "one click" encoding and uploading buttons, for example a quick HD capture/encode/upload to a vimeo pro account, for sharing etc....obviously all of that can be done to some extent now, with discreet software packages and a lot of hassle....but a "one click" approach would be nice.....

maybe I am expecting/asking too much....

i would like to see all of those features, plus what we already discussed....in an 8 channel scope (modular front end would be awesome....like labmaster....especially external clock gen/sync)....for somewhere under $40k (with some options) maybe under $45k.  In this day and age charging what they charge for PMA and spectrum, seems a bit out of line with others....

It would be very cool if someone came up with a more modular way of displaying data....tab view, and the ability to move statistics and waveform windows independently to various screens......AND allow users who have external touch screen monitors to retain the touch capability when splitting out to ext monitor.....and give me 2 ext monitor outs...

[joeqsmith]

Just because you were lucky doesn't mean that such mods are always troublefree. In fact, it might well be that your mod has other side effects you just didn't notice (yet). Just because something looks ok doesn't necessarily mean it is. Also, do you know how many different PCI 1Gbps network adapters exist? And just because you didn't see side effects with one makes you think it will always be allright? Hopefully not.

Data is data.  Better than dealing with how someone feels it's going to work.  I provided info on the board I am currently using.  Also tested with a bottom end Star tech card.  Saw no problems with it. 

The simple fact is that these scopes are not designed as expandable systems, and just because you can plug in some PCI card doesn't mean it can be expanded like a standard PC. The scope as sold is the only supported (i.e. guranteed to work) configuration, aside from a few upgrades offered by LeCroy like CPU and RAM (which even if done with generic parts should be pretty painless). And really, it should be pretty obvious to an EE why on a single PCI bus with a theoretical max transfer rate of 133MB/s a 1Gbps network adapter (which in a good environment transfers between 90-100MB/s) doesn't leave much room for anything else. And something like 33MB/s isn't much for an acquisition system which captures over 20GB data per second, and while not everything in the sample memory goes to the CPU, everything that you want to see on the screen or that you want to process in any way does. Well, you do the math.

In addition, the acquisition system in these LeCroy scopes definitely *is* timing sensitive. I've been bitten by this myself when I upgraded my CPU (hint: never enable Hyperthreading on a WP7k(A) or WM8k(A), unless you want to reinstall your OS).

This aside, "just works" isn't really good enough if you want to use your test kit professionally, where people generally want to have something that is supported by the manufacturer and where problems are solved by their support. If you modded your scope most manufacturers simply tell you to piss off, and rightfully so.

Maybe these EE's you were talking about weren't such 'noobs' at all.

I'm not going to ask why you need a 1Gbps network adapter in your scope. The standard intel 100Mbps Ethernet port should be more than enough for transferring data or remote controlling it.

Certainly if I worked for Teledyne, I would see making a general statement about EE's in this manner in a public forum as pissing my job down the toilet. 


I data I presented in the video shows a point to point running 400Mb, no problem.   Not sure why your thinking 100Mb on a Gig connection. 

Looking at this particular DSO's dead time:

10GS/s, collecting 5Ms requires 640ms.   If the PCI bus could handle 60MB sustained, it would require 83ms to move the data or about 13% of the bus BW.   Say the Ethernet can move the data at 50Mb/s which is about what I was getting with the built in board.   So about 6.25MB/second.   Moving 5Ms will require about 800ms.     

If we want to handle the data and not miss any of the little data the DSO does happen to collect, the 100Mb won't cut it.     At 400Mb/s with the 1G Ethernet, this time drops to 100mS.  Maybe enough time to move the data to the modern PC, post process and display it.   

At 10GS/s and collecting 200Ks requires 35ms.   Staying with 60MB on the PCI bus, it would require 3.33ms or about 9.5% of the bus.  The Ethernet transfer would be about 32ms using 100Gb. 

The one video I posted showed some of the longer collections.  Dead times were several seconds.   It's not a bad DSO but you can miss a lot of information with it.   It's a pretty common complaint.   I have no idea if their new products are better.  Where I work we switched to Agilent. 

I suspect there are other bottlenecks in this system causing the poor dead times beyond the PCI bus.   May put a probe on it at some point to see what is going on.   

I can't see calling Teledyne and ask for support on a 14 year old  system.   I bought this one for home use, not for anything "professional"  but I appreciate your concerns.     

BTW, the Yahoo LeCroy forum is operated by a guy who has nothing to do with LeCroy other than using their scopes (and helping members). In fact, there are only two LeCroy affiliated member I know of, and they certainly don't use the forum as a marketing vehicle. But generally you can expect that the familiars there pretty well know know what they're talking about.

After posting about the VNA in that forum, I had Teledyne sales contact me using my work email wanting to know who he could contact.    Don't kid yourself.  They use it for marketing.  No big deal.  I would expect them to. 

[TunerSandwich]

I data I presented in the video shows a point to point running 400Mb, no problem.   Not sure why your thinking 100Mb on a Gig connection. 

That is not possible.  There is an error in the data/math there.  1Gb = 125MB, with NO protocol overhead....ethernet protocols are going to slash at least some margin off that....if you see 90-100MB full duplex you are lucky, and have a top NiC/cabling etc etc etc....

I have some fancy NAS/SAN devices here at work, running LACP (802.3ad) link aggregations, and top tier controllers, drives, cabling etc....and we are lucky to see a sustained 130-150 MB rate, on large blocks....forget small blocks of non contiguous file headers....that has generally mirrored my experiences in that realm for the last couple decades....

are you confusing MB and Mb?  As you can see below Wuer is talking MB and above you are talking Mb....big difference there

Just to clarify are you saying 400Mb on 1Gb ethernet?  If that is the case, sure....0.4Gb....but Wuer said 100MB, which is generally accurate on 1Gb ethernet, provided everything is going well and you have large contiguous blocks, with no dropped packets....

And really, it should be pretty obvious to an EE why on a single PCI bus with a theoretical max transfer rate of 133MB/s a 1Gbps network adapter (which in a good environment transfers between 90-100MB/s) doesn't leave much room for anything else. And something like 33MB/s isn't much for an acquisition system which captures over 20GB data per second, and while not everything in the sample memory goes to the CPU, everything that you want to see on the screen or that you want to process in any way does. Well, you do the math.

[Rupunzell]

Could this measurement be run without the RG58 coax, connectors and related adapters? Use only a single adapter if possible between the S4 head and generator output as there appears to be a reflection from the RG58 coax/connectors/adapters.

See circled areas in this altered image:



Bernice

Here are pictures you asked:

Generator: Rigol DG4162, sync out, 40 MHz square wave, connected straight to scope with about 1 m RG58 cable.

Scope: Tektronix R7103
1. pic: Timebase 7B15, Vertical amp 7A29, BW 1 GHz
2. pic: Timebase 7T11, Vertical amp 7S11 with sampling head S-2, BW ?
3. pic: Timebase 7T11, Vertical amp 7S11 with sampling head S-4, BW ?

The last picture with S-4 sampling head does not look good. So I connected the RG58 cable with 20 dB attenautor to the S-4 sampling head and here are new pictures with 5 ns and 1 ns timebase.
[/quote]

[TunerSandwich]

I data I presented in the video shows a point to point running 400Mb, no problem.   Not sure why your thinking 100Mb on a Gig connection. 

That is not possible.  There is an error in the data/math there.  1Gb = 125MB, with NO protocol overhead....ethernet protocols are going to slash at least some margin off that....if you see 90-100MB full duplex you are lucky, and have a top NiC/cabling etc etc etc....

I have some fancy NAS/SAN devices here at work, running LACP (802.3ad) link aggregations, and top tier controllers, drives, cabling etc....and we are lucky to see a sustained 130-150 MB rate, on large blocks....forget small blocks of non contiguous file headers....that has generally mirrored my experiences in that realm for the last couple decades....

are you confusing MB and Mb?

1000Mbit connection or yes 125MByte.  Getting 400Mbit or 50Mbyte data rates.   Project I am working on will run at 500Mbit sustained until I fill a TB drive and not miss a beat.   No problem.     In the case of the DSO, I tried a direct link then ran it through the old crappy Cisco.  No performance hit.     Keep in mind that the overall average data rate for the DSO will be much much lower.  This is a burst.  Then we wait for the DSO to collect it thoughts.
 

Ok, that is fine...but Wuer said 100MB and you retyped it as 100Mb and said you didn't understand why he said that was impossible.....he didn't say 100Mb.....you misread or misquoted that....50MB on 1Gb ethernet is no problem....even on small blocks you should get somewhere around 47MB, so 50MB is totally in the realm....but 400MB on 1Gb, no way.....

I see a misquote on your end....that's why it's not adding up.  Wuer is bang on with his statement of 100MB on 1Gb ethernet....and he is being generous there. 

When you showed your data on the LeCroy forum, did you mistakenly flip those MB vs Mb figures?  If so I can see why no one responded....not trying to be rude at all, just trying to point out that those bits of terminology are pretty damn critical in making any realistic assessments

Another issue there is "burst" rates typically apply to contiguous streams of data....small files, with small byte/sector allocations on drives are going to put those theoretical rates in the dumpster....

Big files, going between magnetic drives, with 4k byte sectors....over ethernet MIGHT get 100-110(ish) MB/sec....SSD is no help there either as the reduced (non existent really) seek times aren't very relevant.....ethernet is still dealing with packets snd, rec, ack etc....there is much more latency there than the drives....

How is the LeCroy provisioning this data?  I don't mean internally, I mean off through the PCi bus, into the NiC and on down the line....there is going to be far more complexity, overhead etc, over ethernet than any potential latencies across PCi bus or associated mem controllers etc.....

Even the most arcane SATA drive is going to get limited by the network overhead.....If I recall correctly, most OTS/modern magnetic drives have a seek time of around 3-20ms. 

Maybe we are talking apples an oranges here and I need to go back and read what you posted prior, but in terms of Wuer being wrong about 1Gb ethernet being capped @ 100MB/s, he isn't.....that is how it goes.  Again he didn't say 100Mb/s as you re-wrote it....key key point there....

[joeqsmith]

are you confusing MB and Mb?  As you can see below Wuer is talking MB and above you are talking Mb....big difference there

 

Quote from: Wuerstchenhund on Today at 06:04:46 AM

And really, it should be pretty obvious to an EE why on a single PCI bus with a theoretical max transfer rate of 133MB/s a 1Gbps network adapter (which in a good environment transfers between 90-100MB/s) doesn't leave much room for anything else. And something like 33MB/s isn't much for an acquisition system which captures over 20GB data per second, and while not everything in the sample memory goes to the CPU, everything that you want to see on the screen or that you want to process in any way does. Well, you do the math.

Right a 1Gbps adapter in a good environment transfers between 90-100MB/s.   Again, I am getting around 400Mb or 50MB.  Around 50%.   I must  be missing the question.