Siglent SDS2000X Plus Bandwidth & Aliasing Application Note - Page 1
Forum section: electronics / testgear

author: Performa01
author_rank: Super Contributor
timestamp: January 05, 2022, 12:24:02 pm
content: For those who got unnerved by the fact that, apart from a very few exceptions, the sample rate in modern DSOs barely exceeds the Nyquist requirements for the top model in a product line – and even worse, some models even offer bandwidths so high that the Nyquist criterion can only be met by reducing the number of active channels – I did some research and wrote an application note specifically for the Siglent SDS2354X Plus in order to bring some proven facts into the debate.The SDS2000X Plus is unique within the Siglent product line of DSOs, because it offers a 500 MHz bandwidth option that can only be used in half channel mode, where the sample rate is 2 GSa/s.At this point it should be mentioned that Siglent is not alone with this.Fans of the Rigol MSO5000 often praise the excessive sample rate of 8 GSa/s, which ultimately means 4x2 GSa/s – and this is still more than enough for only 350 MHz bandwidth. I have read statements suggesting that other DSOs have “barely enough” sample rate for their input bandwidth.What about the MSO8000 from the very same brand? Its sample rate would be “barely enough” for 1 GHz with more than 2 channels active, and it can be limited to just 2 channels to still get “barely enough” sample rate for 2 GHz. “Barely enough” in this context means a sample rate to bandwidth ratio of 2.5.This is not limited to the so-called B-brands: the Keysight 4154A has a very similar restriction, although with slightly more margin in half-channel mode:All channels: 1 GHz bandwidth @ 2.5 GSa/s; Ratio = 2.5 (like Keysight 3104T)Half channels: 1.5 GHz bandwidth, 5 GSa/s; Ratio = 3.33By contrast, the summary for the Siglent SDS2354X Plus with 500 MHz option looks like this:All channels: 350 MHz bandwidth @ 1 GSa/s; Ratio = 2.85Half channels: 500 MHz bandwidth, 2 GSa/s; Ratio = 4.0Yes, most entry level DSOs coming from A-brands have a lot more margin, but that’s obviously not because manufacturers all of a sudden worry about aliasing in entry level products of all things, but they don’t want their “cheap” (everything is relative!) 1000 and 2000 product lines to eat into the sales of the much more expensive higher class products with higher bandwidth.Please find the application note attached: SDS2000X Plus Bandwidth.pdfHere is the verdict of the article:QuoteEDIT 20220105: Document revised, corrected some errors and added numbers to the pictures.EDIT2 20220107: Document revised again:Misleading "Safe Signals" and "Conclusion" sections corrected - in half channel mode, the SDS2000X Plus can handle at least the 200 ps rise-time signals without artifacts.Quoted Conclusions in this posting adapted according to the revised document.Artifacts can be Gibbs phenomenon and/or aliasing, both caused by high frequency portions of the input signal that vastly exceed the Nyquist bandwidth of the DSO.Lower bandwidth models most likely do not have a digital filter.Version number added to the title page (V1.02).EDIT2 20230413: Document revised and supplemented (V1.03):Some typos corrected.Quoted Conclusions in this posting adapted according to the revised document."SDS2354X Plus with 500 MHz option" is now called "SDS2504X Plus".The effect of different bandwidths demonstrated by the SDS6204 using digital FIR filters (chapter "How much bandwidth do we need?").

author: tautech
author_rank: Super Contributor
timestamp: January 05, 2022, 03:30:52 pm
content: Nice workhowever some edits are needed in the PDF where on numerous occasions SDS2304X Plus is mentioned where I believe SDS2504X Plus is the intended script.Thread now added into the POI list in the SDS2000X Plus thread OP:https://www.eevblog.com/forum/testgear/siglent-sds2000x-plus-coming/

author: bdunham7
author_rank: Super Contributor
timestamp: January 05, 2022, 03:57:12 pm
content: Very nice article. Two comments:1) The issue of the BW in 350MHz mode being much higher than specified is something they should fix if possible. I understand the idea of maximal leveraging of the sample rate, but having the -3dB point be higher than the Nyquist limit seems to be particularly unhelpful.2) With regard to the usefulness of the scope at varying risetimes, the width of the pulse is just as important a the risetime in how well it triggers, measures times, etc. For typical data signals, I suppose the two are closely related--you won't have signals with long periods and short rise times--but for some other applications you may have just that. The ability of the scope to accurately and reliably trigger, and thus measure fast edges and event timing are actually remarkably good. CH1 is a 33ps rise time 10MHz signal, CH3 is an 8.4ns rise time 10MHz signal.

author: nctnico
author_rank: Super Contributor
timestamp: January 05, 2022, 04:07:23 pm
content: Quote from: Performa01 on January 05, 2022, 12:24:02 pmOn page 16 you seem to show the difference between sin x/x reconstruction (top) and dot mode (bottom) to show the effect of aliasing. But IMHO this isn't correct. If you have signal distortion due to aliasing, then the dot mode would also show the same signal. The effect you are showing in the top picture looks like the Gibbs effect to me.Edit: it also seems to me that the sin x/x is broken from the picture on page 25 and/or the triggering is wrong. A 200MHz square wave should show as a sine-ish wave. At 1Gs/s the limit for sin x/x to stop working is over 400MHz (1Gs/s / 2.5) and 200MHz is far below that limit. The effect shown has nothing to do with aliasing or rise time!

author: tggzzz
author_rank: Super Contributor
timestamp: January 05, 2022, 04:14:25 pm
content: It would be helpful if each figure was numbered, and the text referred to it like "Figure 123 shows..."

author: Performa01
author_rank: Super Contributor
timestamp: January 05, 2022, 05:59:10 pm
content: Quote from: tautech on January 05, 2022, 03:30:52 pmThere is no such thing as an SDS2504X Plus:https://www.siglenteu.com/digital-oscilloscopes/sds2000xp/What I am referring to is the SDS2304X Plus with the 500 MHz option installed, that is sitting on my desk.

author: Performa01
author_rank: Super Contributor
timestamp: January 05, 2022, 06:22:13 pm
content: Quote from: bdunham7 on January 05, 2022, 03:57:12 pmYes, of course it would be nice to have more margin in this case. As stated in the article, the high tolerances of the PGA-integrated bandwidth limit will most likely prevent any improvements in this regard.The -3dB point is at 460 Mhz. This is not higher than the Nyquist frequency at 500 MHz. But I agree - it makes no difference.Quote from: bdunham7 on January 05, 2022, 03:57:12 pmI did not consider these other aspects an issue, hence I did not see any need to cover them in my document.Triggering will always work the same, regardless of the timebase or the pulse width - as long as it doesn't get too narrow, that is. The trigger signal is always derived directly from the ADC at the full channel sample rate and sin(x)/x is always applied to find the exact trigger point.As discussed earlier in another thread, time measurements can only have the resolution of the sample rate as soon as the record length is greater or equal to the screen width. For 1000 points or longer records, the resolution of time measurements in general will be limited to 500 ps or 1 ns, depending on the sample rate. At faster timebase settings, when less than 1000 points per record are acquired, the reconstruction generates additional data points, thus enabling a better resolution. If you need to see a long record but still want more accurate rise-time measurements, just use the zoom window and set this as the source for the respective automatic measurements.

author: bdunham7
author_rank: Super Contributor
timestamp: January 05, 2022, 06:24:47 pm
content: Quote from: Performa01 on January 05, 2022, 05:59:10 pmWhat does your scope identify itself as in the system menu?

author: 2N3055
author_rank: Super Contributor
timestamp: January 05, 2022, 06:43:39 pm
content: Quote from: nctnico on January 05, 2022, 04:07:23 pmpg 16.Yes they are Gibbs artefacts, because there are no sufficient harmonics available, because of sinc working with not enough data. Dot mode works like RIS and builds the image in repetitive triggers. It will have much higher apparent sampling rate and not use sinc interpolation. Hence no Gibbs.pg 25.3rd harmonic is 600MHz, and 5th one is 1 GHz. Way over any sampling limit. But it will still place at least some points of sampled signal somewhere on those fast edges. And every sampling period it will be somewhere else. And it will draw different wrong sinc reconstruction every time. With trigger point being estimated from that. So you get this wobbling sinewave.

author: bdunham7
author_rank: Super Contributor
timestamp: January 05, 2022, 06:53:21 pm
content: And to add to 2N3055's second point, I'd like to see the signal on p26 with the settings the same except the trigger slope set to falling or alternate.

author: Performa01
author_rank: Super Contributor
timestamp: January 05, 2022, 07:01:28 pm
content: Quote from: nctnico on January 05, 2022, 04:07:23 pmYes, you are right. Aliasing should be barely visible, because the strongest signal components above Nyquist around 540 MHz should already be 33 dB down.Quote from: nctnico on January 05, 2022, 04:07:23 pmI’ve only touched it in my article, maybe I should have been more clear. The DSO shows a signal that cannot exist in the real world. This is because with this particular signal that has a strong -10 dBc spectral component at 600 MHz, the aliasing is so strong that also the internal trigger signal path is affected, as can be clearly seen in the vector display mode screenshot on page 25. Consequently, the trigger point itself gets jittery and the individual samples are misaligned. In other words, the samples have lost their common reference on the time axis.So yes, triggering is “wrong” – and this can happen whenever the input bandwidth is too wide for the sample rate and the input signal has transition times that generate strong harmonics above Nyquist, even when the fundamental frequency is well within the nominal bandwidth.

author: Performa01
author_rank: Super Contributor
timestamp: January 05, 2022, 07:08:11 pm
content: Quote from: bdunham7 on January 05, 2022, 06:24:47 pmUnsurprisingly it says: "SDS2354X Plus". The model name in the screenshots also comes from the scope itself.

author: Performa01
author_rank: Super Contributor
timestamp: January 05, 2022, 07:31:28 pm
content: Quote from: bdunham7 on January 05, 2022, 06:53:21 pmClever thinking!

author: knudch
author_rank: Regular Contributor
timestamp: January 05, 2022, 08:18:37 pm
content: Quote from: Performa01 on January 05, 2022, 07:08:11 pmMy SDS2104X+ with "features" say SDS2504X plus in system menu

author: Performa01
author_rank: Super Contributor
timestamp: January 05, 2022, 08:48:30 pm
content: Quote from: knudch on January 05, 2022, 08:18:37 pmWell, quite obviously mine is not an SDS2104X Plus. it says "SDS2354 X Plus" on the front cover.An SDS2504X might exist in China, but in the rest of the world it is just a hint that the user might be an EEVblog member

author: knudch
author_rank: Regular Contributor
timestamp: January 05, 2022, 08:52:27 pm
content: The naming scheme:2104 = 100MHz2204 = 200MHz2354 = 350MHz2504 = 500MhzGive sense...So far as I remember it changes type each time I applied the BW options 100=>200=>350=>500

author: tautech
author_rank: Super Contributor
timestamp: January 05, 2022, 08:54:56 pm
content: Quote from: knudch on January 05, 2022, 08:18:37 pmYes, AFAIK SDS2354X+ with the 500 MHz BW SDS2000XP-4BW05 option applied should display SDS2504X+ in the system menu.Maybe other members need also confirm this.

author: Performa01
author_rank: Super Contributor
timestamp: January 05, 2022, 09:00:01 pm
content: Quote from: tautech on January 05, 2022, 08:54:56 pmDo these scopes display the 500 MHz option in the options menu?

author: tautech
author_rank: Super Contributor
timestamp: January 05, 2022, 09:13:55 pm
content: Quote from: Performa01 on January 05, 2022, 09:00:01 pmAvailable BW options are only applicable to the model the scope already is. As BW lifts from option installation the next BW upgrade option becomes visible.See last screenshot here:https://www.eevblog.com/forum/testgear/siglent-sds2000x-plus-hack/msg3822731/#msg3822731

author: Solacity
author_rank: Newbie
timestamp: January 05, 2022, 09:32:25 pm
content: Quote from: tautech on January 05, 2022, 08:54:56 pmMy 'upgraded' SDS2104X Plus identifies as "SDS2504X Plus" in the 'Utility | Menu | System Settings | System Status' screen.The options menu no longer shows the 500 Mhz or any other bandwidth option.FYI...Performa, very nice work! Following it with great interest.-Rob-

author: knudch
author_rank: Regular Contributor
timestamp: January 05, 2022, 09:33:06 pm
content: @Performa01Does your scope have the 500ps/div setting ?It might be you "only" have the 350MHzIf that the case...then 500MHz BW option only gives the 500ps/div settingAccording to your results

author: Performa01
author_rank: Super Contributor
timestamp: January 06, 2022, 04:31:29 am
content: Thanks for all the hints regarding the model name miracle.Given the fact, that I certainly know what I have and in this very thread of all things, where I clearly demonstrated the 580 MHz bandwidth in half channel mode, any speculations that I might "only have 350 Mhz" sound a bit strange.To sum it up one last time:My instrument is an SDS2354X Plus. It says so on the front cover, it says so in the System Info box and it puts this model name in the file names of the screenshots.My instrument has the 500 MHz option. It has a measured 580 MHz bandwidth, it has the 500 ps/div timebase setting and it shows no bandwidth option in the Options dialog.I have a very early version of this instrument and I got it long before its official release date. My early hardware is version 2.00 and I still have the blinking power button, yet I wouldn't expect this to have any impact on the model name, as this should be a software thing.Now I would like to leave it at that and get back on topic, which is bandwidth and aliasing.I have updated my initial posting yesterday to provide a corrected version of the document.

author: bdunham7
author_rank: Super Contributor
timestamp: January 06, 2022, 04:46:22 am
content: Quote from: Performa01 on January 06, 2022, 04:31:29 amIt might seem a strange question until you consider that my scope also says SDS2354X+, does show a 500M optional upgrade and does not have the 500ps/div setting, yet still has 540MHz + BW. We didn't know you had the 500ps/div.QuoteOK! On that topic (I think) can you tell me how the 20M, 200M and to the extent it does or doesn't exist, the 350M BW limiters are implemented? The 200M BW limiter only appears on the 2354X+ and 2504X+ models, the 350MHz BW is not manually selectable. Are these done in software or hardware and are they the exact same BW limiter that would be used to define a lower model? IOW, does a 2204X+ behave exactly like a 2354X+ with the 200M BW limit on?

author: Performa01
author_rank: Super Contributor
timestamp: January 06, 2022, 06:19:54 am
content: Quote from: bdunham7 on January 06, 2022, 04:46:22 amAh okay, 540 MHz is not that much different from 580 MHz. Well, it all comes down to the fact that manufacturers cannot define a precise bandwidth limit in hardware, because:The low order gaussian or Bessel filters don’t have a flat passband, so the corner frequency has to be placed high in order to get e.g. less than 2 dB amplitude drop at the specified bandwidth.It doesn’t pay off to implement a discrete filter (and maybe an additional buffer) in the high speed signal path right before the ADC. In practice, the integrated bandwidth limiter of the PGA gets normally used for this - and this has high tolerances which must be allowed for. Consequently, the actual bandwidth limit might be at nominal 650 MHz +/-25 %.Quote from: bdunham7 on January 06, 2022, 04:46:22 amWell, at least a part of this question has been dealt with in my document already, e.g. page 8:QuoteFirst of all, Siglent have indeed considered a more effective AA-filter already for the SDS2000X-E. The idea had been dropped as there just is no good compromise between bearable effort, effectiveness, and still good pulse response.I do not know about all the details. Many of them are obvious anyway. What do we have:The manually selectable bandwidth limits are the ones in the PGA. They have a typical tolerance of 20 to 25 % (mind you, “typical” does not mean guaranteed), hence also the 185 MHz for my 200 MHz bandwidth limit.The 350 MHz bandwidth limit should be there, but we cannot be sure because 460 MHz is so close to Nyquist and this “bandwidth limit” might just be the natural aperture error. a typical PGA might have 20 MHz, 100 MHz, 200 MHz, 350 MHz, 650 MHz and 750 MHz bandwidth limits with typically(!) 20-25 % tolerance. What to choose for 350 MHz? 350 MHz might fall into the -25 % category and users will complain if their individual scope has a measured bandwidth of only 270 MHz. So, 650 MHz it has to be. Yes, this is just an example, maybe the PGA used in the SDS2000X Plus has some different bandwidth options, but at 25 % tolerance, it would have to be at the very least 470 MHz. So, you can just as well forget about it.An SDS1104X-E is different from the SDS1204X-E in that it has a digital 18 dB/octave filter, limiting its bandwidth to precisely 110 MHz. I do not know if lower bandwidth versions of the SDS2000X Plus have something comparable, but it doesn’t seem to be the case.

author: hpw
author_rank: Frequent Contributor
timestamp: January 06, 2022, 08:26:37 am
content: Nice measurements...Well, may show the HW setup as may you simple measure a 50E chain using a given cable...As looking for overshoots in real gear (as LVHC logic) things fails soon by the used probe..This means using a 300Mhz probe witch has a to high cap as ~20pF will draw more overshoots as using a FET/1GHz as ~1pF.Not only the BW is important, the phase shifts will cause or show the overshoots. So phase is currently neglected.Attached a Spectrum of a 10MHz clock up to 1.5GHz using as SSA juts to see that we get or have a large fourier content.

author: 2N3055
author_rank: Super Contributor
timestamp: January 06, 2022, 09:00:09 am
content: Quote from: hpw on January 06, 2022, 08:26:37 am50Ohm source impedance and 20pF would form additional RC filter with -3dB point at cca. 160MHz. Good 10x probes at 300MHz and up would be more in a 12-14pF range. Good 500 MHz ones maybe even 10-11 pF.I again fail to see your point. What are you trying to say: that manufacturers should stop making any scopes with less than 2 GHz bandwidth and that passive probes shouldn't be made and used anymore and we should be allowed only to use active probes..Or are you complaining about phase response of the scope (i.e. overshoots) when using a 200 MHz scope to look at signal that has 1.5GHz content?Or you are complaining that BW measurement of scope at 50 Ohm with coax directly from signal generator is not representative of using a scope with passive probe?It is representative of 50 Ohm signal path that has to be measured also. And that is how scopes are specified and measured. So we can compare with other manufacturers on equal footing.There are several topics where Performa did detailed characterization of how this scope behaves with several passive probes, done to industry standard too..

author: hpw
author_rank: Frequent Contributor
timestamp: January 06, 2022, 09:24:48 am
content: @2n3055: My point is, as it shows using the given probes (using shortest connections) gives false results (overshoots) for fast clocks.So using a 1GHz FET probe using shortest connection trusted me. Also the phase behavior about is an opened task. IMHO.50E basic measurement is one task, using probes the second task... and so on.As the Topic on the given PDF: "Siglent SDS2000X Plus Bandwidth Discussion"... is IMHO a starting point.Home workers may have a limited/reduced requirements, so to deal on real digital world required BW and Phase behavior to consider.Even Siglent with the new DSO 6K model and 1..2 GHz FET probes does not provide the required information how the probes performs.While currently I am missing a clear advice about required DSO BW & probes to measure more or less exact overshoots.

author: 2N3055
author_rank: Super Contributor
timestamp: January 06, 2022, 10:00:55 am
content: Quote from: hpw on January 06, 2022, 09:24:48 amOk thank you for clarifications..It seems that you have missed previous few topics (they were some time ago) where it was discussed exactly that.If you want to look at signals that have 200 ps edges you need 4 GHz scope and corresponding active probe. That is only way you will get what you want: a pristine pulse response. PeriodAny time signal has edge that is faster than the risetime of the scope one of two things will happen:1.) if scope has strong AA filters and aggressively cuts of (lowpass filters) any frequency that is above Nyquist by 40 dB or more (for a 8 bit scope) and it will show perfectly shaped squarewave with no overshoots but completely wrong, without any high frequency content and edges that will be as fast as a scope and not in any relation to what signal edges are. It will be complete lie, but it will look pleasing because it will look perfect. Which is complete bullshit because original signal is not perfect and 1/3 of energy content from that signal is missing.2.) You can have response like most modern digital scopes have. That one will try to show as much of frequency content they can. If you feed that one with a signal that has slower edge than scope has, it will show it nicely without overshoots. It will show the same as scope from 1. point. But if you feed it signal that has very fast edge (like here where we feed signal with 40ps risetime to scopes with nominal risetimes from 500-800ps, 10-15 times faster), scope will show overshoots. You say that is bad. I say it is not. It's great. Scope is having problems and is not hiding the fact.Those peaks areinformationthat my edge is too fast for my scope and that I know scope is lying to me. Scope in point 1. will show clean edges without overshoot all the time, when I have nice signal and when I have too fast signal with many thing hidden inside. I wont know a difference ..So with my digital scope, if I see that a signal has an edge that is 400 something ps (edge of what my 1GHz scopes can do) and I see overshoots, I know signal is too fast for my scope. If I see the signal has an edge that is 400 something ps and there are no overshoots, I know it is right there at the edge. And what I see is true. And if I see 500-600 ps edge and overshoots I know it is DUT, not a scope.If I routinely want to look at 100 ps edges I need to buy 4GHz+ scope...So much about that.As for probing, that has been discussed even more times.That is something that we all agree is a most important and most misunderstood topic in using scopes.Most of the times quality of measurements is directly related to probing issues. And realities of it.Many users don't understand that when you connect probe it becomes part of the circuit and changes it. Even active probes, just to a bit smaller extent (if you chose right probe for the job). As frequencies go up, it gets much, much worse.There is no perfect probe or a scope. It is all about education and knowing your instrument. Both weak and strong points. And working around those.

author: hpw
author_rank: Frequent Contributor
timestamp: January 06, 2022, 10:23:43 am
content: Quote from: 2N3055 on January 06, 2022, 10:00:55 amThank you for repeating the old good stuffmay your given content should be added to the PDF??!!While was about an 20G/s Keysight DSO but the support question made theend

author: 2N3055
author_rank: Super Contributor
timestamp: January 06, 2022, 10:43:09 am
content: Quote from: hpw on January 06, 2022, 10:23:43 amThanks!Yes unfortunately Keysight seems to have gone the way of IBM. Instead of greatest T&M company in the world, they are now cloud/synergy/solution partner for emerging synergistic 5G solution providing electronics synergy solution T&M workflow optimizing profit solutions something....T&M instruments are not a focus anymore, they are made just to enable consulting and support sales.Basically, you used to buy a scope from them ( a primary product) and if you wanted some support you got some for free and extended support you had to pay for (additional revenue).Now support, services and consulting is the primary product. Equipment is only there so they have an object as an anchor to sell you the services for it.That will (and already has) mean that they will ignore all market segments (customers and products) that does not have potential for large volume of services and paid support.That means all low and mid range equipment, small business etc etc..

author: Performa01
author_rank: Super Contributor
timestamp: January 06, 2022, 02:33:39 pm
content: I've only very lightly touched the topic of probing in my document:QuoteThe article was not intended as a tutorial for high-speed probing, but to show the capabilities as well as the limits of a modern upper entry level instrument like the Siglent SDS2000X Plus series. We need to know what our tools can do for us in the first place, then we can look into a proper probing solution.For me personally the 50 ohms probing is quite a natural thing. It is far better to design some 50 ohms test ports into the prototype in order to get easy access to the strategic important signals and limit the fiddling with probes to the less important signals that need not be accessed that often.One goal was to establish some basic understanding what really dictates the required bandwidth – after all I've experienced "professionals”, also here in the forum, who seriously claimed that digital oscilloscopes are crap, because a 50 MHz square wave didn’t look square at all on a 100 MHz DSO…(…and then there’s also the fact that this of all things would not be any different on their beloved old CRO)Taking this one step further, the fundamental frequency is almost completely irrelevant if a close representation of the real signal is of any importance. This has been demonstrated by using a 10 MHz pulse, which requires at least 1 GHz bandwidth (a hundred times the fundamental frequency!), just because it has fast 500 ps edges. Of course, the spectrum extends to even higher frequencies, but everything below some -40 dBc becomes irrelevant – at least for an 8-bit DSO.In the vast majority of applications, it should not matter whether a pulse overshoot is measured as 2 % or 1.5 % - or even 3 % for that matter, so the -40 dBc figure should give plenty of margin, even on a 12-bit DSO. We just don’t want to see a significant overshoot from the scope itself when fed with a signal spectrum within its bandwidth. Regarding my 500 ps tests, other than for 1 ns and above, I do not have a perfect signal available; all overshooting came from the signal source, as is confirmed by the reference measurement on the 2 GHz scope.

author: mawyatt
author_rank: Super Contributor
timestamp: January 06, 2022, 03:55:04 pm
content: Something useful for those without a proper fast edge sub-nanosecond pulse generator is the inexpensive RF Signal Source based upon the ADF4351 chip. This is much better than the kludge avalanche transistor junction we were using before!! Someone else posted this on another thread which I can't locate, so maybe they'll spot this post and take credit. These are handy little sources than operate from USB, shown below being USB battery powered.Here's the response of an "Enhanced" SDS2104X+, enhanced to 500MHz which also has the 500ps/div sweep extension. Note the screen capture is shown as SDS2504X Plus.Best,

author: blurpy
author_rank: Regular Contributor
timestamp: January 06, 2022, 08:07:45 pm
content: Since there is some confusion about the model name, it's been discussed before:https://www.eevblog.com/forum/testgear/siglent-sds2000x-plus-coming/msg3088181/#msg3088181Performa01 likely has an old configuration file from before Siglent officially added 500MHz model name.

author: trp806mo
author_rank: Regular Contributor
timestamp: January 06, 2022, 09:34:22 pm
content: Quote from: 2N3055 on January 06, 2022, 10:43:09 am+1 and more when you read the topichttps://www.eevblog.com/forum/testgear/keysight-officially-lost-the-plot-dont-buy-if-youre-a-hobbyist/msg3865562/#msg3865562Currently if I'm not able to spend at least 50K€ of"service/hardware" every year I have the same service as 10 years ago when I were a private person with a 1K€ old stuff.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: January 06, 2022, 10:07:52 pm
content: Quote from: tautech on January 05, 2022, 08:54:56 pmI upgraded my SDS2104X+ to the 500MHz BW option over a year ago (mid 2020), initially landing up with the serial number showing a series of xs in place of the original and I think the displayed model number showed as SDS2354X+ (I'd done the upgrade in steps) until a couple of the forum members provided the required keycode to restore my 'scope's original serial number which also changed the displayed model number to correctly reflect the 500MHz BW upgrade (or not - see edit below).The xxxxx serial number was, iirc, a Siglent testing mode. If you've upgraded to the 500MHz BW but the model number isn't being displayed as SDS2504X+, I'd expect your 'scope would be displaying a series of xs in place of the original SN (or not - see below). I may be conflating the destroyed SN issue with a different issue to the one relating to the failure of the 500MHz BW update to correctly update the model number. This was seemingly a typographical error in a cfg file which Siglent corrected in a later version as reported by tv84 here:https://www.eevblog.com/forum/testgear/siglent-sds2000x-plus-coming/msg3088181/#msg3088181

author: Performa01
author_rank: Super Contributor
timestamp: January 07, 2022, 09:46:58 pm
content: I had to replace the document one more time, see changelog below:Quote from: Performa01 on January 05, 2022, 12:24:02 pm

author: tv84
author_rank: Super Contributor
timestamp: January 07, 2022, 11:06:39 pm
content: Quote from: Performa01 on January 05, 2022, 09:00:01 pmAs I've described in the scope's thread awhile ago:It seems there was an initial batch of SDS2000X+ that contained an "incorrect" .cfg file (maybe on purpose, at the time...).I find it no surprise that, as some other members here, Performa01 has got one of those. When this was discovered, some members corrected the thing by replacing the .cfg file with the newer one (or simply upgrading the FW with the recent .cfg file).So, although Siglent doesn't show in its site the model SDS2504X+, the fact is Siglent from long ago started including that designation in the scope's config files (which is what most of the EEVBLOG users see in their system menu). Nitpicking: for me it would be clearer/simpler if the document stated SDS2504X+ instead of SDS2354X+ with 500 Mhz option.Attached are the 2 .cfg files (one from the old batch and the newer one) and their respective parsing so that you see their content's little difference.BTW, nice document!

author: hpw
author_rank: Frequent Contributor
timestamp: January 09, 2022, 02:03:44 pm
content: @Performa01Lets do an "HpW G/s Equation" to calculate the required DSO BW so handy for the sales teamDSO BW as : 20..50 / (5 x of fastest rise of a single slope 10..90%) [1/s]this will shows more IMHO or less the findings within the document...as 500ps = 20 / (5 * 500ps) = 8 G/sas 1ns = 20 / (5 * 1ns) = 4 G/sas 50ps = 20 / (5 * 50ps) = 80 G/sFor the probes to use, may 1/2 of the DSO BWAbout why 5 times:1. the fastest slope2. repeat 1 as second slope3. & 4 as the top & bottom level time equal to 1 & 25. to compensate the other 0..10% and 90..100% timeso to get more or less 5 times the fastest slope as our signal frequencySo lets

author: Performa01
author_rank: Super Contributor
timestamp: January 09, 2022, 07:43:49 pm
content: Yes, scope manufacturers tend to recommend the use of an instrument that has only one tenth of the signal rise time.Of course they do, because it will increase their income, as engineers will approach their bosses and say: "look, what Tek specifies here in this application note! So we need to buy a 100 GHz highest end DSO in order to properly look at our signals with 50 ps rise time".This could easily backfire though, because bosses might reply: "ooops, do they even have such a beast? If not, we need to look elsewhere! Can you bring the LeCroy and Keysight catalogs?"Of course, it is the same thing everywhere. Buy a measurement solution that is ten times faster and/or ten times more accurate than what your DUT can deliver, and you should be able to trust all your measurements blindingly ... if you know what you're doing and how to avoid systematic errors due to probing or environmental effects, that is.Yet there are situations, where we need to leave that comfort zone and make do with an instrument, that is only little faster and/or little more accurate than our DUT, or not even that – it is also an art to determine whether an instrument is up to the task. In any case we need to use a calculator (or even spreadsheet) in such cases.We can calculate the rise time of e.g. the 500 ps pulse that is measured as 540 ps on the SDS6204 by taking the 230 ps rise time specification of the scope and do the math: the result is roundabout 490 ps. Close enough?Even the result for the 200 ps signal, which is already faster than the scope itself, is still pretty close.And with regard to the bandwidth, I guess no one can argue against the practice to check the spectrum and then decide that a scope covering all signals down to a certain level is sufficient for a certain application. Of course, if we want the maximum fidelity, we need to cover the dynamic range defined by the ENOB, which might be more than 45 dB on an excellent 8-bit system - and not that much more even in 12-bit high bandwidth systems.

author: Performa01
author_rank: Super Contributor
timestamp: April 13, 2023, 01:55:20 pm
content: Only now I have found a supplemented version of my document, which for some reason didn't make it to the public back in January 2022. I have now updated the initial posting and the attachment.

author: BillyO
author_rank: Super Contributor
timestamp: April 13, 2023, 02:42:29 pm
content: Nice document!There are (quite) a few places where you refer to the SDS2504X-P as the SDS2304X-P, but otherwise I found it informative.Thanks!