Keysight DSOS204A waveform update rate - Page 1
Forum section: electronics / testgear

author: KrzysztofB
author_rank: Regular Contributor
timestamp: June 10, 2022, 05:37:48 am
content: Yesterday, inspired by Tek2 talking I made a test with still new to me Keysight DSO-S.I donno, maybe doing something wrong, but in Real-time mode I was getting like 700Hz comming out from triggered Out.In segmented mode it went up to 300kHz.Where did I go wrong?

author: Someone
author_rank: Super Contributor
timestamp: June 10, 2022, 08:26:19 am
content: Quote from: KrzysztofB on June 10, 2022, 05:37:48 amProbably nothing wrong, those values are pretty normal for a software renderer, and dumping segments to memory without drawing them respectively. Usual questions, what was the timebase, memory depth, and test stimulus?

author: 2N3055
author_rank: Super Contributor
timestamp: June 10, 2022, 10:48:19 am
content: Waveform update rate is very controversial spec.Using long persistence , very short timebase and a scope that has fast retrigger time is an old technique, dating back to analog persistence scopes.It can detect there is something wrong, and give you clue as to pulse width, rise time or amplitude anomaly in a standardized pulse train (clock or comm channel). You let it run, and com back after few hours, and if there is problem you will see something on the screen.That works but is not useful to figure out when anomaly happened, how often it is or even how it correlates with other parts of the system.So even if you have very fast retrigger rate, it won't speed up the process of actually researching the problem. It will only clue you in how to proceed. So you have to use clues to setup triggers to catch for runts, non monotonic edges, timing violations.. Your time spent will be dominated with this manual process...Clue in long memory scope with tools, like eye diagrams, exclusion triggers etc.Instead of capturing 100ns 10000 times randomly, you capture 200ms (0.2 sec) of data in one go and then unleash software search to search for all and any anomalies inside. With 100% detection rate for multiple anomalies simultaneously. With correlation to outside world, where you can directly correlate that glitch in clock happens exactly at the same time that output relay activates...A good engineer can solve problems in any number of ways... and will adapt to use what he/she has..

author: Someone
author_rank: Super Contributor
timestamp: June 10, 2022, 11:57:11 am
content: Quote from: 2N3055 on June 10, 2022, 10:48:19 amOnly because people like you keep making misleading statements!

author: 2N3055
author_rank: Super Contributor
timestamp: June 10, 2022, 11:57:48 am
content: Quote from: Someone on June 10, 2022, 11:57:11 am

author: Someone
author_rank: Super Contributor
timestamp: June 10, 2022, 11:58:12 am
content: Remembering back to some marketing material from Keysight:

author: KrzysztofB
author_rank: Regular Contributor
timestamp: June 10, 2022, 01:40:53 pm
content: Quote from: Someone on June 10, 2022, 11:58:12 amThat would explain pretty much what I was seeing as it specifies <1000 wfms/sec

author: KrzysztofB
author_rank: Regular Contributor
timestamp: June 10, 2022, 02:32:39 pm
content: Just to clarification, test signal was 10MHz sinus and the point was to see waveform/sec rate. Timebase set to set 2-3 full waves. Can't remember now exactly.Segmented mode riched almost 300kHz on trigger out.And yes, that confirms in this case that for this scope that is not valid way to find problems and needs more approach as 2N3055 said.I'm just trying to get use to it and get to know how to configure it for specific situations. I mean maybe not the most modern one but definately not a bad scope.

author: 2N3055
author_rank: Super Contributor
timestamp: June 10, 2022, 03:51:09 pm
content: Quote from: KrzysztofB on June 10, 2022, 02:32:39 pmIf you have specific analysis packages it is VERY powerful scope..

author: nctnico
author_rank: Super Contributor
timestamp: June 10, 2022, 04:03:48 pm
content: Quote from: 2N3055 on June 10, 2022, 10:48:19 amIndeed. Taking a long capture allows to use search for anomalies & statistics. With tracking math you can create a trace which shows variations in period or amplitude. And once the anomaly is found, you can see what happened exactly because the data is there instead of a pile of traces that got stacked on top of eachother.

author: bdunham7
author_rank: Super Contributor
timestamp: June 10, 2022, 04:21:38 pm
content: Quote from: 2N3055 on June 10, 2022, 10:48:19 amThat works for some things, but an anomaly that only happens once in 10 seconds or once in an hour requires something different. That random stack of traces with color grading will tell you what the anomaly looks like so you can then trigger on it and acquire all the surrounding data that way. With this method, the proportion of the overall signal that is captured will determine how long it takes for the event to show up. Take the SDS2104X+ which in normal mode takes about 60µs to retrigger with a 1µs capture (100ns/div) @ 2 kpoints. That means that you will see about 1 in 60 events, so something that happens every 10 seconds will take about 10 minutes on average to show up. Cut that 60µs in half and you cut the 10 minutes in half.

author: 2N3055
author_rank: Super Contributor
timestamp: June 10, 2022, 04:47:51 pm
content: Quote from: bdunham7 on June 10, 2022, 04:21:38 pmIt is not exactly calculated that way..It is statistical game, and there are border cases that are better served by particular scenario.As I said the old school procedure is to use persistence to try to capture a clue if there are anomalies and what they are, and then devising strategy how to catch them red handed... So you get to detect there is anomaly within seconds but your (manual) work just begins then.On the other hand with analytic scope, you might need to let it work for an hour. But when you get back, you will already have a lot of quality information what, when, where, distribution, histogram... A bit more wait but less manual work..There will be certain tasks that will be better served by each approach...

author: Someone
author_rank: Super Contributor
timestamp: June 10, 2022, 11:23:30 pm
content: Quote from: 2N3055 on June 10, 2022, 04:47:51 pmYes, so any claim of 100% capture is misleading unless you explain the unusual situation in which that can happen (glitch must be repetitive/repeatable, multiple times per second for current memory depths), and that doesn't account for the post processing time of a deep capture + analysis, or the blind time of a trigger automation/walk. Making you the one who started with nonsense. Such things can be calculated but you failed to do that and made a ridiculous misleading claim.

author: nctnico
author_rank: Super Contributor
timestamp: June 10, 2022, 11:44:28 pm
content: Quote from: bdunham7 on June 10, 2022, 04:21:38 pmYou can greatly increase the chance of catching something by using a longer record. If you capture 1ms per acquisition, the dead time of the oscilloscope becomes much less significant. If something occurs every 10 seconds, then roll mode (continuous sampling) might even be better to catch something that stands out.

author: bdunham7
author_rank: Super Contributor
timestamp: June 10, 2022, 11:51:49 pm
content: Quote from: nctnico on June 10, 2022, 11:44:28 pmThe test I'm using is a 10 MHz square wave with an additional pulse synced with the signal so that one in every 10 million, 100 million or 1 billion rising edges has a larger-then-normal overshoot. If the additional pulse is 10mHz--every 100 seconds--then it is one-in-a-billion. You can't use roll mode or 1ms/div for a 10MHz signal. You can put as many cycles on the screen as you can see clearly--but that is 10 to 20 at the most. You can try and I'm open to suggestions, but I don't know of a better method than what I'm doing for finding such a glitch.

author: tautech
author_rank: Super Contributor
timestamp: June 10, 2022, 11:55:39 pm
content: Quote from: bdunham7 on June 10, 2022, 11:51:49 pmFinding is just one thing, building a trigger for such rare events is another which is where a Zone trigger can be extremely useful.

author: nctnico
author_rank: Super Contributor
timestamp: June 11, 2022, 12:21:18 am
content: Quote from: bdunham7 on June 10, 2022, 11:51:49 pmLarger than normal overshoot shows up in roll-mode (with peak detect sampling) like a sore thumb. Look at the RTM3004 review I did a couple of years ago. Even with a trigger rate of 115Hz using a worst case scenario it can capture glitches (cycles with a different period) that happen 10 times per second quickly.

author: bdunham7
author_rank: Super Contributor
timestamp: June 11, 2022, 12:42:38 am
content: Quote from: tautech on June 10, 2022, 11:55:39 pmYes, first you find, then you trigger. The presumption of this test is that you can't trigger on it because you don't know what it is. My simple example is trivially easy to trigger on, but if my 'anomaly' were a slow rising edge, or example, it would be a bit more of a challenge. But as nice as the zone trigger is, I really haven't yet run into anything that was impossible without it.

author: free_electron
author_rank: Super Contributor
timestamp: June 11, 2022, 01:04:56 am
content: Quote from: 2N3055 on June 10, 2022, 04:47:51 pmthat is why you need fast acquisition rate. if you can stream continuously without deadtime the chances of seeing it in persistence mode are 100%. if i can overlay every sample taken in one hour i will know if there are glitches or not. if i can only do one sample out of every 100... i have 1% chance of catching the glitch. if it can only grab 1 every thousand and then have random idle times between bursts ... i can't do the math but your chances are next to nothing.Sample fast , collect everything.First see if there are anomalies BEFORE you start fishing for them by doing data analysis.

author: tautech
author_rank: Super Contributor
timestamp: June 11, 2022, 01:20:24 am
content: Quote from: bdunham7 on June 11, 2022, 12:42:38 amLikewise however with a zone trigger on a touch or mouse capable scope is quick to setup and a breeze to use.This zone is triggering on a signal from a STB3 that I later tweaked for nicer round numbers but initially setup with just a a mouse.....draw around the area of interest and kick it into life.Here the rising edge 0s trigger dominates and the set zone complements and we have a 2nd unused zone trigger if we need it.

author: bdunham7
author_rank: Super Contributor
timestamp: June 11, 2022, 02:24:46 am
content: Quote from: free_electron on June 11, 2022, 01:04:56 amThere are going to be limitations. In my example with a 10MHz signal and a 10mHz anomaly, at a bare minimum you'd need 100MSa/s which for 100s is 10 billion samples--and typically you'd want 10X that many samples for a 10Mhz square wave. So 100 billion samples is a bit more memory than is commonly available, so your alternative is to acquire and process (for display) all that data in real time--and that just takes a lot more FPGA horsepower than your typical budget scope has. So yes, more faster is better, but you aren't going to eliminate retrigger and blind time over the scale of my test in anything I can afford.

author: KrzysztofB
author_rank: Regular Contributor
timestamp: June 11, 2022, 07:33:12 pm
content: I'm starting to have very mixed feelings about this scope.I setup a test: 10kHz sin waveform with a small glitch every second. Made a mask test on both RTB2004 and DSOS. Similar settings, 5MSa/s, 10kPoints.During 60 sec test:RTB did 21k tests and failed 26DSOS did 2.4 ktests and failed 3Pretty disappointing to be honest.

author: bdunham7
author_rank: Super Contributor
timestamp: June 11, 2022, 08:19:02 pm
content: Quote from: KrzysztofB on June 11, 2022, 07:33:12 pmThat's an interesting slower-speed test. Just for comparison I did the same-ish thing with a Siglent SDS2354X+. I had 200µs/div and 20 cycles per screen--does that match?@ 20kpts/10MSa/s (the closest I could get to yours with one channel) on I got 23.9K tests with 50 fails.@ 10kpts/5MSA/s (switching on CH2 to halve the sample rate) it was 20.3k tests and 41 fails.Yet in segmented mode, depending on the exact settings, I get 330k plus wfms/s similar to yours. So the DSOS204A seems to be powerful enough in the acquisition department and very sophisticated in its analysis software, but just not quick about doing certain things. I don't usually get to play with such nice things, but I suspect that this sort of tradeoff is common. It's why a $100K scope may not make a good daily driver.

author: KrzysztofB
author_rank: Regular Contributor
timestamp: June 11, 2022, 09:43:28 pm
content: Totally can accept that in real-time, waveform update rate is not great, but ok, something to accept.In segmented mode it has absolutely no problem grabbing so much frames that would be enough to find all of those anomalies.But one thing I absolutely cannot understand, is WHY you can't run mask test on the data that are already sitting in segments previously captured?I dont mind if that test would run for a while, but it's absolutely not possible?WHAT?Also after capturing segmented data, I can't make it to work to Search for specific events, which ie. in RTB is easy, you just go to Search.If you set triggers right it has absolutely no problem capturing every single glitch, but to set the trigger you have to have at least little idea what are you dealing with.I'm very confused, especially that we are talking kHz signals. Why it even has that mask test if it works so poorely?

author: Someone
author_rank: Super Contributor
timestamp: June 12, 2022, 12:06:26 am
content: Quote from: KrzysztofB on June 11, 2022, 09:43:28 pmYou come at the problem with fixated mind on the "one" way to solve it. The deep memory offline analysis scopes work very differently and use different approaches for the "same" problem.Quote from: KrzysztofB on June 11, 2022, 09:43:28 pmNot sure if that scope has hunting tools for segmented mode, but you didn't use that scopes headline/flagship tool for that sort of problem: InfiniiScan (requires license?) which takes a deep memory capture and then searches back through it with complex or multiple different triggers.If that is faster or not, you can measure!

author: KrzysztofB
author_rank: Regular Contributor
timestamp: June 12, 2022, 09:04:31 am
content: Quote from: Someone on June 12, 2022, 12:06:26 amWhat I just said is completly the opposite. I get that doing it in realtime is not gonna work (as MXR probably would). So yes, running segmented mode to capture as much as I can and search it.But at least so far I did'n found any way how to analize data that has been captured and sits in segments.Mask testing / Limit testing works in other modes not in segmented.Quote from: Someone on June 12, 2022, 12:06:26 amFaultHunt is new feature in newer scopes.One i have has InfiniiScan active, however the only thing it does, it works as a secondary more advanced trigger in Real-time, as Zone triggers etc. Not as post aquisition analysis tool.As long as you are aware that "something" is there, and you build right trigger for that event, scope is great.So yeah, I agree withbdunham7. Not always buying something more expensive is the right tool for the job and it's possible that something with less bandwidth, but more modern would suit my needs better.So what I'm I doing here is getting to know tool I've got, knowing it strengths / weaknesses and expected behavior. To know what I can and cannot. Because some you only get one chance to capture something, that one and only chance, that should not be wasted by not knowing how you tool will behave.When I was picking up this one, i thought that is gonna be the last scope i'm getting, but looks like it's not the end

author: Someone
author_rank: Super Contributor
timestamp: June 12, 2022, 12:38:03 pm
content: Quote from: KrzysztofB on June 12, 2022, 09:04:31 amSegmenting the caputres is usually for reasons other than fast visualisation (what you were trying to benchmark). Only other thing I can think of to get more edges to the screen would be the real time eye unfolding (time to setup, may not work on very slow/sparse signals, needs license).

author: Bud
author_rank: Super Contributor
timestamp: June 12, 2022, 01:27:06 pm
content: Segmented mode is not good for capturing "as much as you can". There may be lost information at the segments boundaries because of re-trigger time if you capturing a continious signal. Segmented mode is best for capturing burst of a signal where memory is not used in pauses between bursts.

author: KrzysztofB
author_rank: Regular Contributor
timestamp: June 12, 2022, 02:23:58 pm
content: Quote from: Bud on June 12, 2022, 01:27:06 pmLoosing in betweens or not, I would expect to have a possibility to search through acquired segmented waveforms.Problem is, those scopes are not that common and I can't figure out how that is suppose to be done. Or if i need some extra package of software for that, which is not present at the moment.That video explains a bit, of what would be nice to have:But I can't afford buying EXR or MXR. Got my S series for 10K and that was absolute maximum i would ever pay for a scope.Would be nice if someone using Infiniium software said something about how and how? Is it possible to search through waveforms / segmented?

author: Bud
author_rank: Super Contributor
timestamp: June 12, 2022, 04:59:54 pm
content: This video is about speed of acquisition, but you want to "search through acquired waveforms". Not sure how they relate....

author: KrzysztofB
author_rank: Regular Contributor
timestamp: June 12, 2022, 06:06:41 pm
content: Whole thread started with low waveforms/second and video is related to that.But yes, what worries me more than low w/s is that, it can acquire a lot of data, but I can't find any good way of searching defects in those other clicking Play on segmented view and staring at playback

author: Bud
author_rank: Super Contributor
timestamp: June 12, 2022, 06:43:06 pm
content: QuoteThis is because in real time mode they are real time processed inhardware. But you are looking for post-processing insoftware. I dont think you can do it on the scope, but may be possible in GPIB/SCPI connected software.

author: Someone
author_rank: Super Contributor
timestamp: June 13, 2022, 01:03:34 am
content: Quote from: Bud on June 12, 2022, 06:43:06 pmOn the Agilent/Keysight 9000/9000H/S platform? pretty sure mask testing is software based processing on those (otherwise they would have listed it in the hardware accelerated features).The OP purchased a deep memory offline analysis scope, without realising its drawbacks. Tek, Lercroy, also offered comparable models. They are fundamentally different in their capabilities and were never great at realtime captures.Its only recently that scopes started to blur that boundary with deep memory, GHz bandwidth, and fast waveform rates: Keysight EXR/MXR, R&S RTO/RTP, Tek 5/6 series, Siglent 6000, Rigol 8000/70000.

author: KrzysztofB
author_rank: Regular Contributor
timestamp: June 13, 2022, 05:06:44 am
content: Quote from: Someone on June 13, 2022, 01:03:34 amAgree. If it was hardware based, wouldn't be that slow.QuoteThat is true, different way to do stuff.However if we agree that process is: First grab then analize, my question is, how to analize?Because as I mentioned I already found out how to capture the data, and to get a lot of them and not miss much it has to land in segmented memory.Question is how to Search through it?Noone using Infiniium here to give me a hint?

author: Someone
author_rank: Super Contributor
timestamp: June 13, 2022, 07:39:58 am
content: Quote from: KrzysztofB on June 13, 2022, 05:06:44 amSegmented data is the wrong way to start with.InfiniiScan (a name that is a catch-all for several features including software triggers, and ) includes the tools to hunt through long captures and find additions things, including more complex details than triggers. Its right there in the marketing copy:"Manually inspecting waveforms is impractical, as 1 M point of memory represents 10,000 screens of waveforms. [with InfiniiScan] Scope scans the waveform so you don’t have to, and no programming is required"Pull up the help/documentation loaded on the scope if you don't understand it.

author: KrzysztofB
author_rank: Regular Contributor
timestamp: June 13, 2022, 08:12:33 am
content: I get that, Infiniiscan is there and it works. I did set it up, 1MHz sin with small glitch every second.And yes, Edge trigger + Infiniiscan as a zone trigger at some point captured it. It took ages but it did. Probably with EXR it would be way faster cause of way better update rate.But that is not what I'm asking at the moment.If as you say it's deep memory scope it can store a lot of date.Doing the same test, within one second I captured every single glitch happening in that time. Great.My question is: Is there a way to do postprocessing analyze like Infiniiscan would? Or even simple like finding places in waveform where voltage crosses specific level. Even RTB2004 can do it with Search function.Cause I don't see a benefit of deep memory if I can't analyze signal after capturing it.