DS1074Z 4 Channel or DS2072 2 Channel Oscilloscope? - Page 1
Forum section: electronics / testgear

author: Williamscullen818
author_rank: Contributor
timestamp: January 25, 2014, 10:21:24 am
content: Hello, I've been looking into purchasing an oscilloscope recently and thought I had decided on the new Rigol DS1074Z but now I'm questioning my reason.I like the bigger screen, 14 horizontal divisions, dedicated knobs per channel, waveform record knob, and everything else about the DS2072 except the fact that it is only 2 channels.For the most part I'm working with digital electronics, serial decoding, and general purpose analog circuits. I wanted the ability to display all the required signals for SPI on the scope at oncefor debugging, which is why i was leaning towards the DS1074Z originally. Also, I've seen the insides of both scopes now and it seems like you get more scope for your dollar with the DS2072.2072 has the AD Black Fin DSP in it vs. the Freescale version in the 1074. Seems to me like I'll be getting more of a scope for my money with the DS2072My questions is to those of you who are like me and do mostly digital debugging of circuits, and general purpose analog (nothing high bandwidth). Do you find it important and useful to have a4 channel scope over a 2 channel scope? Is it worth missing out on the goodies of the DS2072 for a 4 channel DS1074Z to be able to view all 4 channels of an SPI bus at once? Anything below $1000 for me is doable, I'm not worried about the extra $250 it would cost me to get the DS2072. If I got the DS2072 I would need to switch between MOSI and MISO or not show the CLK/CS when viewing a signal. I would love to get a DS4014, but that guy it out of my price range. Obviously the hack available is a big factor in this as well, tequipment.net no longer sells the DS2072, only the newer version DS2072A. I'm not sure of the differences but I've heard that hack is not yet available for the newer A version yet..? I'd like to hear your input? Anyone with one of these scopes care to share their experiences with them? I heard someone say on another thread that if you need 4 channels you could always buy another DS2072 down the road, but I'm not convinced that is a reasonable option...Thanks,

author: echen1024
author_rank: Super Contributor
timestamp: January 25, 2014, 01:16:50 pm
content: Search is your friend, my friend

author: EEVblog
author_rank: Unknown
timestamp: January 25, 2014, 01:48:39 pm
content: Quote from: Williamscullen818 on January 25, 2014, 10:21:24 amNot really. You can do that with a cheap USB logic analyser. It you need to check serial line signal integrity then you can do that one line at a time usually.Bottom line is I wouldn't make my scope choice based on analog input for digital serial decoding if that's your only reason.YMMV

author: nctnico
author_rank: Super Contributor
timestamp: January 25, 2014, 01:53:44 pm
content: I would never consider buying a scope with less than 4 channels. There are often more than 2 signals which have interesting information.

author: nowlan
author_rank: Frequent Contributor
timestamp: January 25, 2014, 01:54:40 pm
content: I think you will find a lot of people recommend a dedicated logic analyzer for troubleshooting serial protocols.Saleae Logic

author: linux-works
author_rank: Super Contributor
timestamp: January 25, 2014, 03:33:40 pm
content: I'm also looking for a nice 4ch scope (not urgent but if the right one comes along at the right price).I have a 16ch logic analyser (seed studio thing) but I'd still prefer to not use my pc if I don't have to, and instead use the thing with real knobs and a dedicated os/cpu for the task.it could be useful to see the shape and noise levels of the lines you are monitoring, even if digital. rise time and even voltage levels are important and a pure logic sniffer won't show that.so, if I care about the bits only, sniffer it is. if I have to see why things 'mostly work but sometimes dont', then I prefer an analog style display, even if its from a digital scope.I was thinking strongly about the tek 2465b, but its 2nd pair of channels don't have a proper atten knob (they only have a 2 pos switch, which is 'ok' for logic but not nearly good enough for true 4 chan mixed mode operation).if you are going for a scope, I do suggest trying for 4ch.

author: BravoV
author_rank: Super Contributor
timestamp: January 25, 2014, 06:31:21 pm
content: Quote from: linux-works on January 25, 2014, 03:33:40 pmOwn 2465B, channel 3 and 4 of 2465B are basically crippled compared to 1 & 2, I believe they're intended mostly for digital signaling work only.

author: electronics man
author_rank: Frequent Contributor
timestamp: January 25, 2014, 09:01:30 pm
content: I just got the ds1074z and I love it the 4 Channels is great.For the extra $250 you could get the z-s which has a function generator so you get a basic logic analyse and with the 4 chan and and a function generator. I personally think that the ds1074z is the best value for money you won't go wrong its am excellent scope go for that one

author: Williamscullen818
author_rank: Contributor
timestamp: January 25, 2014, 09:58:41 pm
content: Ok, seems like most of you feel that 4 channels is important to have. Now, I could also get a open logic sniffer from dangerous prototypes along with the ds2072 to satisfy my needs for more 2 channel digital work, they are about $50 depending on where you buy it.Can anyone convince me to purchase the DS1074Z over the DS2072A/logic sniffer for digital work when the price point has no significance?

author: electronics man
author_rank: Frequent Contributor
timestamp: January 25, 2014, 10:19:17 pm
content: you coukd get the ds1074z and a much better logic analyser for more + ds074z doesnt have some of the problems as the ds2000 series as it is newer. i feel that you should futureproof yourself whith the 4 channels as you may be stuck in a situation where you need 4 channels such as looking at a sine wave propagating through a circuite although you say you do digital now in a few years you may be interested in analog.

author: linux-works
author_rank: Super Contributor
timestamp: January 25, 2014, 10:32:42 pm
content: just get 2 scopesbased on all the talk, here, a year or two ago, I got the tek 2225 low noise analog scope. its great for audio and times when I need to see the actual look of the waveform. no fan, either, so that's nice.then, due to more talk here, I got the famous 2ch rigol that can be hacked to 100mhz. nice small unit and good price. but if I were deciding now, I would pass on that one and go directly for the 4ch version and still keep the tek analog.when I can justify the money for the 4ch version, I'll probably put my rigol 2ch up for sale. can't see the point of having two rigol scopes.think about a used tek analog scope in addition to your 4ch digital one. as for funct gens, I prefer to have that in its own box, so I can change it or upgrade it as I need.

author: echen1024
author_rank: Super Contributor
timestamp: January 26, 2014, 01:58:56 am
content: I will admit that the DS2072 plus logic sniffer is a more attractive choice over the DS1074Z. Why? First, you are getting a better scope. More memory, more refresh, higher bandwidth, etc. 2, your logic capabilities will be better. Rigol does all software decoding, and that makes it slow as hell. While the same is done on a USB logic sniffer, computers are much faster. Also, you get the capability to monitor multiple serial buses at once, and maybe even 1 parallel in the case of 8 channels, or more for 16.

author: Electro Fan
author_rank: Super Contributor
timestamp: January 26, 2014, 04:04:21 am
content: Quote from: Williamscullen818 on January 25, 2014, 09:58:41 pmI went through some of the same decision-making you are going through. I had a chance to try both the DS1104Z and the DS2072. To me the biggest trade-off was between 4 channels (on the 1000) and the functionality of the Nav knob (on the 2000). In the end I went with the DS2072. I'd like the extra 2 channels but I decided the ability to examine captured signals more easily with the Nav knob and related features was more important than the extra 2 channels. I think many users here would prefer the 4 channels - so it's definitely not a universal opinion. On the other hand lots of users here have a DS2000 - so it just comes down to your specific needs and preferences. I think for SPI having the extra 2 channels would be beneficial but if you are willing/inclined to also purchase a logic analyzer then I think the 2072 will give you a slightly better ability to examine signals than the 1000Z and you can still look at digital signals with the logic analyzer. Ideally we could all afford a MSO with 4 analog channels and 16 digital channels so we could look at plenty of signals and easily correlate them in time but at some point it gets pricey unless you have a pretty compelling need, cost-justification, or healthy budget.You can't go far wrong either way; the 1000Z is an excellent scope and offers a great value for the price and likewise with the 2000. Let us know what you decide. EF

author: Williamscullen818
author_rank: Contributor
timestamp: January 26, 2014, 05:11:08 am
content: Can the DS2072A decode both MOSI and/or MISO without the clock signal on the display, or does the scope require the clock signal for decoding? Maybe this is the wrong place to ask, but does anyone know if a memory dump is required to hack the DS2072A, or does the riglol website keygen work for both DS2072 and DS2072A? Because the DS2072 is no longer available through tequipment.net, only the newer DS2072A.http://www.tequipment.net/RigolDS2072.html

author: Pasky
author_rank: Regular Contributor
timestamp: January 26, 2014, 05:15:22 am
content: There was a neat video showing the serial decoding on a high end Rigol scope vs an Agilent and Tektronix, and the Rigol was missing data every now and then. I'd get the DS2072, and buy a logic analyzer.

author: Williamscullen818
author_rank: Contributor
timestamp: January 26, 2014, 07:04:31 am
content: Was it this video?

author: Pasky
author_rank: Regular Contributor
timestamp: January 26, 2014, 07:07:20 am
content: Yup. That's the one.

author: Mark_O
author_rank: Frequent Contributor
timestamp: January 26, 2014, 08:28:29 pm
content: Quote from: Williamscullen818 on January 26, 2014, 05:11:08 amNo.QuoteYes. One channel must be CLK. The other can be MOSI _or_ MISO. So only one direction can be seen at a time. There's been some discussion on how it would be nice if Rigol made better use of the ExtTrig input, and enabled CLK there. Thus making the full-duplex SPI traffic visible. But that's been owners talking, not Rigol.Also, there's no channel for CS, or Device Select, so if you actually have multiple devices on the multiple device SPI bus, you won't be able to select which one to monitor. Only the DS1000Z or DS4000 series provide full SPI support.QuoteYes, this is the wrong place to ask.

author: Mark_O
author_rank: Frequent Contributor
timestamp: January 26, 2014, 08:45:26 pm
content: Quote from: Pasky on January 26, 2014, 05:15:22 amWhen I saw that video, I was shocked.Shocked I tell you! Who could have imagined that scopes costing "only">$5,000-6,000 USD morethan the MSO4024 would actually perform better, in some ways? That was really damning for the Rigol.I'm curious how many engineers, when debugging serial bus comms traffic, find it effective to monitor the decoded data stream in real-time? Especially when you can't go back and check something that looked interesting? Personally, I find it rather difficult to grok constantly flashing and disappearing byte strings. Even when it's relatively slow (very unusual!) as in the demo setup. I normally like to set up and capturea sequenceof traffic, especially when I have a device with a deep memory capacity. Then go back and step/slide through the exchanges, go backwards if needed, etc. In that mode, the Rigol (like most software-driven decoders) wouldn't have the same difficulty keeping up as shown in the live demo.Lastly, given the $10k+ price tag on the Tek scope demo'ed, I wasn't all that impressed with the display. Yes, it seemed like the decoded info was being updated, but neither the clock trace nor the data trace seemed to be updating properly, as both the Agilent and Rigol were. (The Rigol trace updates seemed about half as fast as the Agilent, but at least they were changing in a visible way. The Tek just seemed to flicker occasionally, and you couldn't even tell there were two different length bursts.)

author: Mark_O
author_rank: Frequent Contributor
timestamp: January 26, 2014, 08:54:43 pm
content: Quote from: Pasky on January 26, 2014, 05:15:22 amWhich logic analyzer would you recommend, that would display decoded serial bus traffic in real-time, as the ~$10,000 Agilent was?

author: echen1024
author_rank: Super Contributor
timestamp: January 27, 2014, 12:01:44 am
content: Try a used Agilent 16700 series, such as the 16702B, or a Tektronix TLA type analyzer.

author: Electro Fan
author_rank: Super Contributor
timestamp: January 27, 2014, 12:53:29 am
content: Quote from: Mark_O on January 26, 2014, 08:45:26 pmIf I understand this correctly it is the reason that tipped me from the Rigol DS1000Z to the Rigol DS2000. The ability to fairly quickly and easily navigate during the review process (with the big Nav knob and related features/buttons/controls on the DS2000) is IMO a pretty valuable advantage of the DS2000 vs. the DS1000Z. (This is not intended to start a big battle about the value of 4 channels - all other things being the same, 4 channels is better than 2 channels, especially if you need 4 channels).No doubt the Rigol DS4000 is a great choice as it brings 4 channels and the Nav functionality. And no doubt it would be nice to have the speed of hardware rather than software enabled performance (as offered by Agilent)- so there are some great choices beyond both the DS1000Z and the DS2000 if you have the budget.If the next version of the DS1000Z was a MSO1000Z with 4 analog channels, 8-16 digital channels, and the big Nav knob functionality... now that would be cool.

author: Pasky
author_rank: Regular Contributor
timestamp: January 27, 2014, 01:33:44 am
content: Quote from: Mark_O on January 26, 2014, 08:45:26 pmI don't understand your point other than you want to be condescending towards me. Regardless of the price of those scopes, you're talking about a $4000 Rigol scope that's isn't recording (at least I think it wasn't recording, maybe it just wasn't displaying it all but still captured it? I'm unsure, it doesn't really explain it, but that's what I assume, If I'm wrong, then well, I'm wrong) all the serial data coming from an Arduino, yes, an Arduino...... It's well known that the Rigol's use software for signal decoding that video is an excellent example of how slow it really is. If you're considering purchasing an even lower model, expect THAT kind of performance or worse from it was my point, it's better to just get a dedicated logic analyzer if that's the case.

author: RRobot
author_rank: Regular Contributor
timestamp: January 27, 2014, 01:45:04 am
content: If I had to diagnose a I2C communication issue, and I spent an afternoon trying to diagnose why bytes were missing on the I2C bus. Then later found out that they were not missing but that the scope simply lost them ( and I2C none the less), I would throw that scope right out of a window.

author: linux-works
author_rank: Super Contributor
timestamp: January 27, 2014, 03:23:14 am
content: if the scope really could not keep up with 'simple' i2c, yes, I agree, it would be frustrating beyond belief.you need to trust your tools. digital capture (unless you agree you are ok with simple 'sampling') should be lossless and reliable. if its not, its less than useless.

author: Williamscullen818
author_rank: Contributor
timestamp: January 27, 2014, 04:46:05 am
content: Is the DS1074Z any less useful for most applications? What I mean is, do you think the slight boost in specs on the DS2072A warrant loosing the 4 channel option? I know in terms of useability, the DS2072A is a better choice, but for instance if I was looking at 2 traces (input and output of something) will the DS2072A give me anything other then useability improvements or is there a serious improvement in performance? I seems like it when you look at the insides of the 2 scopes, seems like there is much more stuff inside the DS2072A, not to mention better quality.On the other hand, The price point of the DS1074Z is about the same as the price of an option of other more expensive models. If I decide I really needed a 4 channel scope, and logic analyzer won't do the trick I could spend another $600 to get a DS1074Z. It's like purchasing an option for the DS2072A down the road, but you get a whole new scope...

author: leppie
author_rank: Frequent Contributor
timestamp: January 27, 2014, 04:55:51 am
content: Quote from: Williamscullen818 on January 27, 2014, 04:46:05 amI am in the same 'dilemma', but it seems pretty easy to get an extra 2 channels by using another scope, say a cheap analog one using the the trigger out from the Rigol and the ext trigger in on the analog. Sure you will lose the memory aspect on the extra 2 channels, but not a biggie IMO.I have an Open Workbench Logic Sniffer and it works well enough. Not realtime, but not really an issue either.This thread and the slowness I have seen from the DS1000Z has made me choose the DS2000 instead. Now just to save some money for it.

author: cidcorp
author_rank: Unknown
timestamp: January 27, 2014, 06:24:47 am
content: Well I do own both a DS2102 and a DS1047-S as well as a Logic 16 from Saleae. When the DS2000 came out, I really wanted the scope but was disappointed thatthere we no options to purchase with 4 channels. After waiting it out for a while I needed to get a replacement for an aging digital scope I had from GW-Instek, I wentahead and bought the DS2102 (with the knowledge that the scope *might* be hacked in the upcoming months like the older 1000 series), I went with the mid range onejust in case the hacks never materialized. I was still regretting that the scope didn't have the 4 channels.I bought the Logic 16 cause I knew most things wouldn't cut it on the 2 channels scope - and I do like this product. The Logic software is well written and features have beenadded over time so it feels like it was a good investment.The DS1047-S is new, just got it and I have to say it's like the 'mini-me' version of the DS2000,withthe 2 extra channels the DS2000 should have got.Haven't done any decoding with it yet so the conclusion is out for now on that, but I can say it is much slower feeling and I HATE that you cannot hide unused menusfrom the right and left of the screen, you lose sooooo much real estate.As for the options: DS2072 (hack it to 200Mhz) will run you about $839, plus the logic 16 another $299 = $1138 for the two, versus the DS1047Z (hack it to 100Mhz) at $585 or $818 if you want to add the built in 2 Channel 25Mhz Waveform Generator, add the Logic or Logic 16 if you need it down the line and the scopes not cutting it - you'll save the $299 for now.I figure eventually down the line we'll be seeing a MSO2072 or a MSO2074, cause we've already seen the unpopulated sections on the PCBs from Rigol. If you go DS1074Z and wait you can sell the DS1074Z and buy up to the Mixed Signal version when it comes out.OR as someone else joked, Buy both (and the Logic 16)... works for me.Chris

author: Williamscullen818
author_rank: Contributor
timestamp: January 27, 2014, 07:50:01 am
content: There really should be a 4 channel DS2000 option, I would have paid triple what I'd pay for the DS1074Z for one of those. You would think they would be working on one, I'm sure they know they would sell many of them. Does anyone know if the display in the DS1074Z is driven via an FPGA or from the freescale chip? I'm not so sure it is, cause I only see 1 fpga in the device which is doing acquisition with the ADC, but maybe they are driving the lcd in there as well.I've got a opportunity to get an Agilent DSOX2004A for $1500 cause of a student discount, only think holding me back is the cost of the options and no hacks right now. The Embedded serial option alone is $500, which is about the cost of a DS1074Z. I could probably strech my budget to get that scope, but no sure if it's worth it. Anyone think I should do that over one off the Rigol scopes? That is a price point question tho.

author: Williamscullen818
author_rank: Contributor
timestamp: January 27, 2014, 08:01:40 am
content: Another question about decoding on DS2072A... can the scope use the ref waveform as the clock in spi decode mode? I was thinking I could capture one cycle of the clock then put it on a ref channel, then I can use both 2 channels for data +/-.

author: Williamscullen818
author_rank: Contributor
timestamp: January 27, 2014, 08:11:46 am
content: cidcorp,If you had to do some spi debugging, would you grab your DS1074Z, or would you use your DS2000, even though you would have to switch between mosi and miso to decode the data/verify the waveform? What would be your go to scope for something like that?I'm not taking about the logic analyzer, I'll be getting one of those anyways I think for on the go with the laptop.

author: Mark_O
author_rank: Frequent Contributor
timestamp: January 27, 2014, 04:21:14 pm
content: Quote from: Pasky on January 27, 2014, 01:33:44 amOh, no, you've got it all wrong. It's not just you... I like to be condescending towards everyone . J/KActually, what I was trying to do wasmockyou. Because you were being ridiculous, and arriving at bogus conclusions.Quote(highlights added by me)And there's the rub. Youwerewrong. Totally and completely wrong. And the problem from that is evident... (some) others will read that, take it at face value, and promulgate it as gospel. You don't have to wait for it, or look far. The follow up comments are right below your own."its less than useless.""I would throw that scope right out of a window.""frustrating beyond belief."And yes, I know these were all conditional comments. IF, then. Yet they were all speculative commentary, generated from your own, uninformed and incorrect conclusions. The Rigol doesnotdrop the actual communications stream. That's all captured intact, and at speeds far beyond anything an Arduino normally generates. But it's too slow (pig slow, from that video) to keep up with display of the decoded version. In fact, from the very slow speed of that I2C bus traffic, I'd say it's embarrassing. But that's why I tried to point out that this isn't necessarily the way one would spend most of their time examining such comms traffic. (If it was, you'd be silly to buy anything less than the Agilent.)People will read and pass on what they see posted here. So the word will be that the Rigol is a POS for serial data analysis and protocol decoding, that can't even keep up with an Arduino!, for god's sake, and will drop comms data left and right. And that's what they'll remember, and repeat to others. "Didn't you hear? The Rigol is crap...". When you don't know WTF you're talking about, it's not reasonable to post conclusions, then say, "I think" and "I assume". That's just irresponsible.Which is why I was trying to make fun of your comments, in a light-hearted way. If you chose to take umbrage, be my guest.

author: Mark_O
author_rank: Frequent Contributor
timestamp: January 27, 2014, 04:40:25 pm
content: Quote from: Electro Fan on January 27, 2014, 12:53:29 amI'd definitely agree with that!Even better would be if Rigol would add some Search and Marker capabilities to the DS2000. When you've got the exceptional memory depth capabilities of such units, having a way to find a few "needles in the haystack", and do so quickly, would bephenomenally powerful. IMO (and others may disagree), this might even be MORE useful than having exceptionally high wfms/sec refresh rates, which only increase theprobabilityof seeing an abnormality in real-time.They've already got all the selective Event/Trigger Defining capabilities in place. They just need to let you use them in a post-process, to tag & flag all the "interesting" occurrences in the current sample set, already in memory. Then let you step forward and back through them. Wow, the timethatcould save!Tektronix has been doing this for years. Agilent does it. Hameg does it too, even on their HMO units costing less than the DS4000. It would be nice to see Rigol catch up.QuoteSadly, I don't think there's any way they could/would add any different knobs to the 1000Z-series.

author: Mark_O
author_rank: Frequent Contributor
timestamp: January 27, 2014, 05:01:36 pm
content: Quote from: Williamscullen818 on January 27, 2014, 07:50:01 amAMEN to that!QuoteLook around the Forum here a bit more.QuoteUnfortunately, no. Besides, the whole thing with SPI is that interpretation of the MOSI/MISO transitions is totally dependent on the synchronous phase relationship to the Clock (read on rising/falling edges). Just having "a" REF Clock isn't going to help you out at all.

author: Mark_O
author_rank: Frequent Contributor
timestamp: January 27, 2014, 05:09:48 pm
content: I had asked, "Which logic analyzer would you recommend, that would display decoded serial bus traffic in real-time...?"Quote from: echen1024 on January 27, 2014, 12:01:44 amThanks! Could you give me a pointer to where I'd find the software for CAN decoding for my Tek TLA704? Either for the 4 analog channels (TLA-7E2) or 136 digitals (TLA-7M4, or -7N?). That would be great.

author: Williamscullen818
author_rank: Contributor
timestamp: January 27, 2014, 06:49:40 pm
content: So I ended up purchasing the DS1074Z, tequipment.net told me I could return it within 30 days, so if I find that some features of the scope warrant a change to the DS2072A I can do that. I found that the 4 channel option was extremely difficult for me to give up compared to the DS2072A.Anyone think that was a mistake?

author: Mark_O
author_rank: Frequent Contributor
timestamp: January 27, 2014, 07:12:18 pm
content: Quote from: Williamscullen818 on January 27, 2014, 06:49:40 pmI don't. I think you'll probably be very happy with it. It wasn't long ago thatany4-chan scope at this price was unbelievable. Much less one with all the capabilities the 1000Z has, and the deep sample capacity.Folks that need and can make use of a 4-chan scope will notice the lack of 2 full channelswayfaster than somewhat reduced performance specs and a few features. However, thosewithoutmuch need for more than 2-chans (or having gotten by for so long with only 2, can no longer remember them), will be much happier with the extra specs and features of the DS2000.Luckily, there's an option for both camps.When evaluating what limitations you might find along the way, refer back to Electro Fan's posted experiences. See if you share any of them, and whether they turn the tide for you or not. Some complaints folks have about the 1000Z are shared by the DS2000. While others are unique to it. However, neither is perfect (but then, neither is the DS4000!).QuoteOh, did you order one of their custom $25 cases for it? Unless you never move the scope off the bench (always possible), they're a very nice accessory to have. And they're a perfect fit for the 1000Z.

author: Williamscullen818
author_rank: Contributor
timestamp: January 28, 2014, 06:11:43 am
content: No, didn't get a case for it. I won't be taking it out often at all. Thanks for the recommendations everyone, this is my first oscilloscope so hopefully in the future I'll be purchasing something that doesn't require as much compromise.

author: Mark_O
author_rank: Frequent Contributor
timestamp: January 29, 2014, 01:00:53 am
content: Quote from: Pasky on January 26, 2014, 05:15:22 amI do agree that that was an interesting video. Interesting enough that I decided to go back, and take another look. Initially I had been focusing on the price differential between the 3 scopes. Which made it seem like a somewhat unfair comparison, to me. This time I noticed it was Part 1, so I went looking for Part 2, which turned out to be even more informative. Part 2 did some closeup shots, which made it possible to ramp up to 1080P, and see what modes the various scopes were running in. All were set for 100us/div, butthat was the only thing they had in common.It's important to remember that these modern DSOs are powerful and complicated devices, and it's easy to overlook important details that have a large impact on their operation. And hence the results obtained, and the conclusions that one draws can easily be compromised. Here's how they were configured and operating*:Code:ScopeSampleSamples RelativeModelRateDisplayed "Work"Agilent500MSa/s500K 5xMSO-X4154ATekMSO3054100MSa/s100K 1xRigolMSO40542000MSa/s 2800K 28xSo not only are the 3 scopes sampling at radically different rates, they're also capturing significantly different amounts of data**. Then they have to process all that data down, to create the 600-700 points actually displayed. And finally that data is processed through a decoder, to generate the protocol stream. The other 'disadvantage' the Rigol is subject to is that it provides 40% more display area, with 14 horizontal divisions, vs. 10 for the other two. Something that would certainly come in handy for displaying protocol streams.In light of the above information, the fact that the Rigol is processing28 times as much dataas the Tek may help explain its "slowness". And not only does the Agilent have hardware decode that the others lack, it also has another5.6x advantageover the Rigol, due to the smaller amount of data it's processing for display.Lastly, I found several things from the YouTube reviewer rather odd:1) he emphasized that the Tek was keeping up with the decoded data, but made no mention that its display of the SCL and SDA analog traces were not collapsing and expanding, between Write and Read modes, as the Agilent and Rigol were. Basically both traces were nearly worthless.2) he stated that the Rigol was notcapturingall the data, which was untrue, when it was actually only notdisplayingall the decoded data. Those are two quite different things.3) after already pointing out how slow the Rigol was, he then went on to comment on how it could be made even slower, by turning an additional decoder channel on? I fail to see what the point was in that, since he didn't turn additional decoders on either of the other scopes, to see what impact that may have had.4) he finished by pointing out how unresponsive the user menus were, while the Rigol was busy processing gigasamples of data. An implementer has to decide, when there's too much going on to keep up with all of it, whether to give priority to data acquisition, display, or interactive user feedback. Rigol certainly could have decided to make the menu selection buttery smooth, at the expense of the other functions. Instead, it appears they've tried to strike a balance. Which, IMO, is the proper approach.5) he concluded that the Rigol was underpowered, and needed a faster processor. That may be true, but his demo did not validate that claim.Conclusion: don't take at face value everything you see on YouTube.--*NB: I was checking this on a small screen, and if I had scrolled down, I would have seen in the Comments section that Martin Zuber already noticed some of the same anomalies, and commented on the sampling rates and extra points the Rigol was processing.[** One other thing to note is that while the Rigol (and the Tek) continuously capture their full sample set while in Run Mode, the Agilent doesn't necessarily do so. This is a clever 'trick' they devised, which actually makes a fair amount of sense. Let's say they had a 4M sample deep buffer. Rather than capture all that on every cycle, they only capture as much data as is being displayed. In this case 500K. Then, when you hit Stop, the scope actually continues running, and captures the remaining 7/8 of it's buffer, so it can be examined afterwards.]

author: Mark_O
author_rank: Frequent Contributor
timestamp: January 29, 2014, 01:05:42 am
content: Oh, I should probably provide a pointer tovideo.