SDS800x HD vs DHO800x FFT - Page 1
Forum section: electronics / testgear

author: cyo3fff
author_rank: Contributor
timestamp: July 12, 2024, 01:46:22 pm
content: Hello,I had a DHO804 scope and I give it away thinking to replace it with something "better".SDS824x HD seems to be the right choice but I have at least one question not answered.It is about FFT refresh rate.On DHO804, the FFT refresh rate was "real time" updated like a real time spectrum analyzer for at least 100MHz span with narrow RBW (1kHz or less).Up to know I did not found a youtube or something similar to show the refresh rate of the SDS800x FFT.Could someone having both scopes to do a demo on this topic please? Or one with SDS824x HD at least because I know what DHO804 is capable of.Thank you.BR,Cristian

author: Martin72
author_rank: Super Contributor
timestamp: July 12, 2024, 03:00:38 pm
content: Hi and welcome to the forum.QuoteAnd how is this measured or is it more of a belly feeling:QuoteYou can also get the DHO800 to "stand still" at FFT, believe me.As always, this depends on the settings, no matter which scope you have.That's why I don't think the question can be answered in general terms; you can rather "pick out" a specific situation and then compare it - with a sense of proportion....

author: cyo3fff
author_rank: Contributor
timestamp: July 12, 2024, 03:33:59 pm
content: Hi Martin72,Thank you for welcoming me."And how is this measured or is it more of a belly feeling:"Is more of a "feeling".A test case would be:FFT on an arbitrary signal (could be a wire as an antenna close to a dc-dc convertor or from a wave generator) with the following parameters:start/stop frequency: 1MHz/200MHzRBW: 10kHz (or 1kHz)Max sample rate and number of points available for the kind of measurementsWindowing: Flattop (or else)----------But I prefer to see a movie not a still picture or, mathematically, how many frames/seconds the scope could achieved on this test case.To "pass" the test (on my "feeling" criteria), the scope should have at least 30fps (just to give a "real time feeling" - like in a movie with 30fps or better).Could you do this for me Martin72 please? It will help me a lot.Thank you.BR,Cristian

author: TomKatt
author_rank: Frequent Contributor
timestamp: July 12, 2024, 03:58:50 pm
content: If you gave away a DHO804 because you wanted something better, I'd be thinking you're aiming higher than an SDS824X HD... This Siglent is a good scope (I have one myself), but this seems like a lot of fuss to basically just change team brands. If FFT is that important and the DHO804 wasn't good enough, perhaps you ought to be aiming higher?

author: Martin72
author_rank: Super Contributor
timestamp: July 12, 2024, 04:15:51 pm
content: QuoteI no longer have an SDS800X HD.QuoteThe FFT function in particular is something that has been solved much better in the SDS800X HD than in the DHO800.

author: cyo3fff
author_rank: Contributor
timestamp: July 12, 2024, 04:44:43 pm
content: Quote from: TomKatt on July 12, 2024, 03:58:50 pmHi TomKatt,Thank you for your comment. Believe it or not, one of the main reason I give DHO804 away was...it smell! It has a very steep plastic smell and I think I'm a bit allergic to that cause if I leave it in the lab for few days, I can't stay there...so it was something serious for me.By the way, do you (others) know if SDS800x smells like a plastic? I mean very bad not just as a "new plastic box"...I remember that smell was reported early after DHO800x was launched, here on this forum.Coming back to the upgrade, I want something around 1000EUR +/- and yes, I'm interested to hear your (or other's) proposals so please do.Thank you.BR,Cristian

author: cyo3fff
author_rank: Contributor
timestamp: July 12, 2024, 04:51:43 pm
content: Hi Martin72,"The FFT function in particular is something that has been solved much better in the SDS800X HD than in the DHO800."As I started, first I'm interested how many frame per seconds can give SDS824x HD for say the above test case in comparison with DHO804.So first I want to find the answer to that.Second, can you detailed a bit your thought (above)? What is better on SDS800x than in DHO800?On the other hand, maybe there is someone else on the list who can help me with FFT on SDS800x HD please.Thank you.BR,Cristian

author: KungFuJosh
author_rank: Super Contributor
timestamp: July 12, 2024, 04:54:56 pm
content: Siglent's FFT execution is well known to be superior.However, with your budget, I would look at the 1000X HD series.

author: cyo3fff
author_rank: Contributor
timestamp: July 14, 2024, 09:11:28 pm
content: Hello KungFuJosh,Thank you for advice. SDS1000x HD with 4ch/200MHz is higher than 1000EUR. I don't need 10' screen, neither 50ohm input.One of the main feature of the scope should be good and fast FFT cause I need to use it as a kind of spectrum analyzer for EMC debugging.Coming back to my question, is there anybody with a SDS800x HD (particularly SDS824x HD) who can help me with FFT refresh rate (how many fps it has for the above test case)?Thank you.BR,Cristian

author: KungFuJosh
author_rank: Super Contributor
timestamp: July 14, 2024, 09:44:05 pm
content: There's no difference in hardware between the 800 series models. There's also no difference in hardware with the 1000 series models.The SDS804X HD FFT is the same as the SDS824X HD.

author: tautech
author_rank: Super Contributor
timestamp: July 14, 2024, 10:00:18 pm
content: Quote from: cyo3fff on July 14, 2024, 09:11:28 pmLake a proper analyzer, sweep speed is related to the settingsyoumake.Points, Span and Averaging settings provide speed or precision, pick your poison.There are many examples of FFT use here:https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/However these low cost DSO's don't provide a proper EMI mode like for example the SSA3000X Plus range which have preinstalled the many EMI standards and their respective level limits.SSA3015X Plus is a good model for these LF analyser needs.

author: Martin72
author_rank: Super Contributor
timestamp: July 14, 2024, 10:10:15 pm
content: Quote from: cyo3fff on July 12, 2024, 04:51:43 pmFirst would be the partially faulty windows of the FFT function, here a user had proven that they could be easily corrected, but actually this is Rigol's job to do this.Secondly, the Rigol, like all Rigol models, lacks useful additional functions such as average and peak detect.At least average should be "mandatory".This would also be easy to solve if rigol were to attach importance to it.Let's get back to your main concern, the measurement of "speed", the FPS.I still don't quite know what you mean by that, as you mentioned realtime spectrum analyzers as a comparison.This is a different technique behind it, the FFT function in a scope is, as the name suggests, a function, calculated mathematically.This cannot be done/displayed in real time per se.The "speed" then stands and falls with the number of points, the time base and the memory.Just as an example, if the time base is set to 100ms/div in order to keep the RBW small, for example, an acquisition takes at least 1 second.Then there is the calculation and finally the display of the function, i.e. either way you would be miles away from your 60fps.If I were you, I wouldn't get stuck on that, instead I would focus on other qualities.Nevertheless, I can make an FFT according to your specifications.

author: Fungus
author_rank: Super Contributor
timestamp: July 15, 2024, 06:17:46 am
content: Quote from: cyo3fff on July 12, 2024, 04:44:43 pmThat completely goes away after a week or so.(OKl, I left mine powered on for a week in a spare room so it was warm so YMMV but the smell definitely goes away)No idea why they chose that plastic. Is it still the same in new ones...?

author: Fungus
author_rank: Super Contributor
timestamp: July 15, 2024, 06:21:12 am
content: Quote from: Martin72 on July 14, 2024, 10:10:15 pmThere's a big difference between doing the math 60 times a second and doing it 6 times per second.The Rigol may have a simplified FFT but itisfast.

author: cyo3fff
author_rank: Contributor
timestamp: July 15, 2024, 04:50:46 pm
content: Quote from: Fungus on July 15, 2024, 06:21:12 amHello Fungus,Thank you for answering to my question or at least to try to answer briefly.What I liked much to Rigol (DHO804) was its FFT speed and could compare it with the old 1054z which has a"joke" FFT in terms of speed! It take a loooot of time to do even a "few points" FFT therefore I cannot call it even close to "real time".Just to align with everybody here, particularly in this case, by "real time" I mean at least 25fps or if you like, FFT calculations/second.I know that this not "real time" such it is with a real time spectrum analyzer which can do a full span measurement in 1us or so but it is all right for my particular needs.So, one conclusion is that for the same FFT settings, DHO804 (Rigol) is "way faster" than SDS824x HD.Am I getting right? Because this is one of my main concern.Thank you.BR,Cristian

author: cyo3fff
author_rank: Contributor
timestamp: July 15, 2024, 04:56:59 pm
content: Quote from: Fungus on July 15, 2024, 06:17:46 amIn my case the smell was there, very intense (especially when the scope was turned on) after 6 month or so!I've kept it in the solar light on a balcony with 30 degrees or higher temperature. Also I kept it running in a free space for few days in a row without luck.So I've tried what I could to get rid of that but no luck at all.The trouble with the smell is there is no way to know about it in advance. Simply there are no specifications for it. And if does exist, nobody can guarantee it will gone after a while.Coming back to SDS824x HD, do you (or others) know if this scope has a similar smell (if you smell DHO804 you know what I mean by "similar smell")?Thank you.BR,Cristian

author: cyo3fff
author_rank: Contributor
timestamp: July 15, 2024, 05:05:43 pm
content: Quote from: Martin72 on July 14, 2024, 10:10:15 pmHi Martin72,Forget about real time or however we call it.Let focus on what I want to find out by this post.Say you have a certain FFT settings (you name it).I want to know how long it will take to solve and display that FFT on both scopes (same settings), SDS824x HD and DHO804.I hope now it is much more clear what I need.Can you (or others) answer to this question please? If possible without arguments from theoretical point of view (no need for theme).Thank you.BR,Cristian

author: cyo3fff
author_rank: Contributor
timestamp: July 15, 2024, 05:11:19 pm
content: Quote from: tautech on July 14, 2024, 10:00:18 pmHello Tautech,Thank you for the answer.I know the above thread. I could not see a speed comparison (how long it takes to compute and display the results) for a given FFT settings between SDS824x HD and DHO804.If you find such post, please point me to it but please, if it is possible directly to the message, not the whole thread (with tens or hundreds of messages!)It could be useful.Thank you.BR,Cristian

author: TomKatt
author_rank: Frequent Contributor
timestamp: July 15, 2024, 06:20:58 pm
content: It seems like FFT is the primary goal here - perhaps the solution is to purchase the appropriate test gear ie an actual Spectrum Analyzer ?As others have pointed out, the FFT feature on entry level scopes is more of a math channel operation on the acquired signal.

author: cyo3fff
author_rank: Contributor
timestamp: July 15, 2024, 08:38:08 pm
content: Quote from: TomKatt on July 12, 2024, 03:58:50 pmI'm not saying DHO804 was not good.In fact I have pleased with its FFT speed (update speed on the screen) and I simply want to know if I can expect the same speed from SDS824x HD.That is all.Can you answer to this question please? You have the scope, that I want to buy it and I'm in stand by after this FFT clarification.Thanks for help.

author: tautech
author_rank: Super Contributor
timestamp: July 15, 2024, 08:49:12 pm
content: Quote from: cyo3fff on July 15, 2024, 04:56:59 pmSDS800X HD units I have unpacked (~12 now) have no strong lingering smell other that what you get from new electronic devices.Certainly nothing I consider offensive.Quote from: cyo3fff on July 15, 2024, 05:11:19 pmAs I have mentioned before, FFT sweep speed is related to the settings you use, just as they are for an analyzer.Speed vs accuracy < pick your poison !Today I may have a chance to do some tests.

author: tautech
author_rank: Super Contributor
timestamp: July 16, 2024, 04:38:59 am
content: SDS814X HD FFTA few assorted screenshots, all showing a 400 MHz span representative of you might use for EMI work.Signal from SDG6022X, dual tone with the principle @100 MHz.These results are only applicable to the scope settings in use. FFT 2Mpts remained unchanged although it's auto managed by the scope. Memory depth is just what it was, didn't check.Higher FFT sweep speeds are likely possible if one takes the trouble to optimize them.At 200us/div and max 2Mpts FFT a sweep speed of ~1/s is obtained.100us/div = ~2/s50us/div = ~4/sAs we increaseonlytimebase the sweep gets faster where at 10us/div its speed is indiscernible and at 500ns/div detail is starting to be lost without changing other settings.Max hold and Average screenshots thrown in for good measure.All other settings should be plain to see in screenshots.

author: Fungus
author_rank: Super Contributor
timestamp: July 16, 2024, 06:35:20 am
content: Quote from: tautech on July 15, 2024, 08:49:12 pmYes, but one can still be slower than another.

author: Fungus
author_rank: Super Contributor
timestamp: July 16, 2024, 06:46:08 am
content: Quote from: tautech on July 16, 2024, 04:38:59 amRigol is three or four times faster than that.

author: tautech
author_rank: Super Contributor
timestamp: July 16, 2024, 06:59:12 am
content: Quote from: Fungus on July 16, 2024, 06:35:20 amWhich one wise guy ?

author: tautech
author_rank: Super Contributor
timestamp: July 16, 2024, 07:18:54 am
content: Quote from: Fungus on July 16, 2024, 06:46:08 amQuote from: tautech on July 16, 2024, 04:38:59 amPick your poison, speed or accuracy.

author: 2N3055
author_rank: Super Contributor
timestamp: July 16, 2024, 08:03:15 am
content: To be honest, only scope in less than 7000-8000 € range that has something resembling realtime SA is GW-Instek MDO-2000A series.And that is because it literally has realtime SA mode implemented. It works well but it's ADC are only 8 bit so limited dynamic range. Also scopes are in 1500€ ranges, a bit old fashioned by now etc.....All other scopes in that price range will have only FFT as a math function, with implementation variations.Short version for the two scopes mentioned:- if you want just something bouncing on the screen to see if there is something happening at some frequency, DHO800 will have faster refresh at some settings.- if you want control of what are you measuring, accurate windows, accurate level measurements, Peak Hold and Averaging, various markers and peek markers and control of them, then SDS800xHD is the one.If you want SA display on your scope that resembles R&S MXO4 or MXO5 or Tektronix MSO 6 digital down conversion tech, you will have to pay for those...

author: tautech
author_rank: Super Contributor
timestamp: July 16, 2024, 08:10:08 am
content: Quote from: 2N3055 on July 16, 2024, 08:03:15 amWhich buys a SSA3021X Plus with dedicated EMI mode.See Reply #8

author: Fungus
author_rank: Super Contributor
timestamp: July 16, 2024, 09:31:05 am
content: Quote from: tautech on July 16, 2024, 06:59:12 amThat's what we're trying to establish here, not just to sell Siglents.

author: Fungus
author_rank: Super Contributor
timestamp: July 16, 2024, 09:32:21 am
content: Quote from: 2N3055 on July 16, 2024, 08:03:15 amThe Rigol shows peaks, etc.

author: 2N3055
author_rank: Super Contributor
timestamp: July 16, 2024, 12:12:31 pm
content: Quote from: Fungus on July 16, 2024, 09:32:21 amDon't start with this. You know well how little capabilities DHO800 has in that regard, compared to SDS800XHD.Rigol only shows peaks. And that is it. No manual control of markers, harmonic markers, delta, etc. etc..It does not even have Peak hold mode or average mode.All it does is show jumpy waveform and jumpy peak markers on waveform and ever changing list in a table. That is it.It is useful only for static signals, which is irony, because OP wants it for fast changing signals.Fact is that using SD800xHD in peak detect mode will let you detect (and measure) where some fast frequency peaks, while Rigol will blink something on screen for a moment and if it was too fast to read you will lose it...

author: Fungus
author_rank: Super Contributor
timestamp: July 16, 2024, 12:33:12 pm
content: Quote from: 2N3055 on July 16, 2024, 12:12:31 pmI'm notstartinganything, just correcting a factual error.

author: 2N3055
author_rank: Super Contributor
timestamp: July 16, 2024, 01:53:14 pm
content: Quote from: Fungus on July 16, 2024, 12:33:12 pmNo you are not. You are INSINUATING capabilities Rigol does not have.I didn't say Rigol has no Peak markers at all. I said SDS800xHD has order of magnitude better capabilities in that regard..I also explained additionally factually what it has.Rigol shows realtime peaks. Full stop. There is no etc.There is nothing else there as you would insinuate...So yes, please don't start with this.

author: rpro
author_rank: Regular Contributor
timestamp: July 16, 2024, 02:26:08 pm
content: Quote from: Martin72 on July 14, 2024, 10:10:15 pmI agree, I would guess it would probably take their SA software people a few hours (not even a day) to implement and test standard avg. and peak-hold in their DHO and MSO series.On the positive side I have found their color heat map scheme useful to see/measure FFT peaks, etc., e.g., see attached.

author: cyo3fff
author_rank: Contributor
timestamp: July 16, 2024, 04:08:26 pm
content: Quote from: tautech on July 16, 2024, 04:38:59 amDear Tautech,Thank you very much to be the first to broke the ice with real facts!This is the information I was expected from my post.I will not answer to all of your messages but will try to summarize theme up to now. Please correct me if I'm wrong or add more if I miss something!===========Rigol DHO800x vs Siglent SDS800x HD- FFT speed:Rigol is 4 times (average) faster than Siglent- FFT accuracy:Siglentis better but slower than Rigol- FFT features (Peak, Avg, Max Hold, customize parameters of the FFT such RBW, manual markers, Log scale, etc.):Siglentis better than Rigol- FFT color heat map:Rigolis the only one with this feature (useful too)- Balance between speed and accuracy: NONE of the scopes have such thing; you can chose only one of this features like speed=Rigol OR accuracy (and FFT better features)=Siglent (4 times slower)Abot smell, Rigol have "annoying" smell, not Siglent.=============I hope this summary will be helpful also for the future reader in need to find an answer to those questions.I will not conclude which one is better because it would be a false answer. Best is to say NONE of theme are good for this task or "it depends".Quote from: 2N3055 on July 16, 2024, 08:03:15 am2N3055 (I'd liked that transistor anyways) thank you for this answer. I have no experience with GW-Instek scopes therefore I cannot judge your statement.On the other hand (I'm an EMC engineer) I have experience with Keysight 20GB/s scopes used with FFT for EMC troubeshooting and they are good...in their price range.One advantage of a scope vs RTSA is the dual more (time/frequency domain) and very wide real time bandwidth on the scope side (professional scopes I mean).Not to mention the trigger functions that can correlate aggressor with observed emission, things that cannot be achievable with a simple SA.A lats word about Rigol DHO804. The reason I'm stick to its FFT speed performance is that I've used it for the EMC tasks and it was enough for basic investigation but yes, in terms of markers and SA management is not very useful. The reason I've stopped to SDS824x HD is its better implementation of the FFT Math function and much closer look to a SA. Unfortunately its speed is not that good and I have no idea why they failed on that. I guess is due to the processing power available on the HW. Who knows.Thank you very much to all of your for help.Cristian

author: 2N3055
author_rank: Super Contributor
timestamp: July 16, 2024, 05:47:18 pm
content: About "heatmap", Siglent also (and many other) support color grading.. I have no idea why people think it is something "only Rigol has".As for speed, Siglent didn't fail on it. Rigol is faster because it does a fraction of things, with much less points. Basically Rigol optimized for speed at the expense of everything else. Siglent chose to make full implementation.I did "have a feeling" that you are talking about FFT (or spectrum mode) on higher end devices as a reference.On Siglent SDS7000A FFT is also very fast.Anyways, I don't know if Rigol have fixed wrong windowing, and if they did and if all other shortcomings are not important to you maybe for you Rigol will do..

author: Martin72
author_rank: Super Contributor
timestamp: July 16, 2024, 09:34:44 pm
content: Quote from: 2N3055 on July 16, 2024, 08:03:15 amI had a look at it earlier, the built-in SA has a bandwidth of DC-500Mhz.I find that interesting, other SAs only start at 9kHz (why actually, because of possible interference on the mains voltage?), much to my regret.I find it “stupid” to add a (software) analyzer for the LF range.

author: tautech
author_rank: Super Contributor
timestamp: July 16, 2024, 10:43:07 pm
content: cyo3fffAs I have said numerous times and you as a EMC engineer should know only too well, sweep speed is directly related to settings in use.Speed vs accuracy, pick your poison.Before I need setup gear for other tasks, some closing screenshots.