EEVblog 1632 - WHY sell 2CH Oscilloscopes? + Test Engineering - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: July 28, 2024, 11:09:27 pm
content: Why do companies still sell 2CH oscilloscopes? Plus a massive tangent into test and production engineering. Also showing one of my old test engineering projects.LCR meter and Transmission Line Tester design:Relay Matrix IR Measurement:PC104 Embedded DOS PC:Linus Tech Tips Test Rack:Test rack Part 2:

author: pdenisowski
author_rank: Super Contributor
timestamp: July 29, 2024, 07:46:59 am
content: In my experience there are many scope users who are unaware of how scopes are used in manufacturing / production, and this video is a great explanation - thanks!

author: EEVblog
author_rank: Unknown
timestamp: July 29, 2024, 09:45:54 am
content: Quote from: pdenisowski on July 29, 2024, 07:46:59 amI got hammered in the comments about cheap 2CH scopes!

author: BrianHG
author_rank: Super Contributor
timestamp: July 29, 2024, 11:59:11 am
content: Quote from: EEVblog on July 29, 2024, 09:45:54 amPutting aside that there are valid markets for 2 channel scopes, boy how spoiled we have all become demanding 4 channels. When I grew up, any 2 channel scope was a luxury.

author: Gyro
author_rank: Super Contributor
timestamp: July 29, 2024, 01:23:41 pm
content: Just because cheap 4 channel scopes are on the market, there's no need to question the use of 2 channel scopes, we're not all doing the same stuff. Why stop at 4? Why not insist on an 8 channel scope.- Fundamentally a scope is there to examine the timing relationships and integrity of signals. The minimum you need to do that is... 2 (ok you can look at the integrity with 1). It's an analogue domain tool.- The number of channels needed to do an X-Y phase relationship is... 2.- Everyone knows that any decent 2 channel scope has an external trigger input anyway, so that gives you the timing relationship of 3 signals with intelligent use, and no loss of sample rate.- Screen resolution on DSOs (or minimum analogue spot size, lest we open up that argument!) isverylow - typically 480 pixels vertical on an 8 bit and a whopping 600 pixels on a 12 bit! In the grand scheme of things, that's pathetic!Trying to squeeze 4 traces on a a screen and see any reasonable vertical resolution is a joke.- Just because manufacturers can cheaply stuff in another couple of front-ends is a nice sales feature doesn't make them good. On a typical cheap scope, enable all four channels and the sample rate and buffer size drop through the floor. For example, going back a bit, what was the point of hacking a DS1054Z to 100MHz when the sample rate was only 250Msps with 4 channels enabled.- Protocol decoding on scopes is a cheap (free) S/W gimmick to sell more scopes. Half the time they get it wrong and the display format is typically very basic. If you are working on digital stuff, after verifying signal integrity in the analogue domain, move to a tool suited to the digital domain... a logic analyzer. Singing the praises of the minimal decode facilities of a 4 channel scope is just discouraging the manufacturers from putting decent and affordable digital domain tools on the market.- I wonder how long it will be before you put out a video saying 'geez why would you buy a 4 channel 12 bit scope when you can get a cheap 6 or 8 channel 16 bit'. I bet the vertical resolution will be up to, oh, 1024 pixels by then.Edit: Reading that back after a couple of hours, I sound a bit irate, sorry about that.

author: nctnico
author_rank: Super Contributor
timestamp: July 29, 2024, 07:51:44 pm
content: Quote from: Gyro on July 29, 2024, 01:23:41 pmI guess you never had a DSO with proper protocol decoding in your hands then. R&S pretty much nailed it. And I disagree about getting a logic analyser as in many cases protocol problems stem from problems in the analog domain. If the analog domain works properly then protocol decoding on a large scale using a logic analyser won't do you much good. Higher level tools embedded in the firmware are way more useful as these can produce statistics like number of messages, amount of data, bad messages, etc collected over days, months or even years of runtime. A USB protocol decoder won't do that as it doesn't know the context of the messages it is looking at (for starters). All in all a USB logic analyser is more like an in-between instrument in case you have a DSO with crappy protocol decoding.

author: thm_w
author_rank: Super Contributor
timestamp: July 29, 2024, 09:42:19 pm
content: Quote from: Gyro on July 29, 2024, 01:23:41 pmI'm not seeing where the logic is going here. More channels adds more cost, while increasing the number of tasks you can complete. Probably 95% of common EE work can be done with 4 channels and adding 4 on top of that adds enough cost to not be worth capturing the final 5%.Quotehdo1000 is 1280x800 which looks ok with 4 channels.You can always overlay traces too, its not like they have to each take up 1/4 of the screen.QuoteLow sample rate is useful to me a lot of the time, eg. monitoring 3V, 5V, 12V at the same time while looking at some input power signal.I'd gladly take a few extra channels that are limited to only 1 or 10MHz bandwidth for rail monitoring.Some of the old Tek stuff had simpler secondary channels, capped at 5V, to reduce the knob space/cost and front end cost, presumably.

author: twospoons
author_rank: Frequent Contributor
timestamp: July 29, 2024, 10:00:26 pm
content: Sometimes budget constraints combine with use cases to make 2-ch the favorable option. When I bought my first scope I could get a 4 ch low bandwidth or a 2ch higher bandwidth scope for about the same money. I chose 2 ch with more bandwidth, based on my expected use cases.

author: EEVblog
author_rank: Unknown
timestamp: July 29, 2024, 11:50:59 pm
content: Quote from: Gyro on July 29, 2024, 01:23:41 pmCopied from my response to the pinned comment on the video:Sure, don't pay for something you don't need. Where did I say a hobbyist should pay for something they know they won't need? Why are people taking this so personally? As always Your Millage May Vary. In this video I was clearly talking about how things typically work ** in the industry **, it was not a treatise on hobby scope selection.As I have discussed in the Rigol 1054Z and DHO800 videos, 4CH scopes have now become very affordable, and they offer great flexibility in usage scenarios and sample rate split, and as ** a general rule ** I advise getting a 4CH scope even if you think you may not need it. But if you want to save every cent, obviously taking my advice would be dumb, just buy a 2CH scope and be happy.QuoteIf 6 or 8 channel scopes become low cost then I'll say that. It won't happen, but that's not the point. The point is that like it or not 4CH has become the new entry level standard at that traditional entry level price.If you want to say every cent, sure buy that 2CH channel scope, it will serve you well.As a leading voice in this community I woud be laughed at if mygeneraladvice to people these days was to buy a 2CH scope. It is very clear that the best "bang per buck" these days is with 4CH scopes. Has been since the Rigol DS1054Z came out.As always, YMMV.

author: Bud
author_rank: Super Contributor
timestamp: July 30, 2024, 01:07:45 am
content: A 4-channel scope in general is a solution looking for a problem. I've been doing RF for 25 years and I needed 4 channels may be 2 or 3 times. People doing digital may need it but there are better tools for that and they likely have such tools already.

author: EEVblog
author_rank: Unknown
timestamp: July 30, 2024, 01:11:51 am
content: Quote from: Bud on July 30, 2024, 01:07:45 amThe market seems to disagree, as practically every entry level scope maker has affordable 4CH scopes now.Sure, in general, most of the time you only need one or two channels, but with the low cost ASIC front ends it's now trivial for makers to include 4 channels at the traditional 2CH price point.

author: Bud
author_rank: Super Contributor
timestamp: July 30, 2024, 01:25:44 am
content: The market these days puts RGB lighting in everything including toilet seats. I am yet to see any useful utility it provides.

author: pdenisowski
author_rank: Super Contributor
timestamp: July 30, 2024, 01:30:43 am
content: Quote from: nctnico on July 29, 2024, 07:51:44 pmIn my experience, it's "most"

author: pdenisowski
author_rank: Super Contributor
timestamp: July 30, 2024, 01:47:50 am
content: Quote from: Gyro on July 29, 2024, 01:23:41 pmSpeaking as someone whose company just released its first 8 channel scopes (MXO5 and MXO5C): there are a lot of cases, e.g. power sequencing (i.e. timing between power rails), when 8 channels is useful / necessary.Believe me, we wouldn't have developed (two models of) an eight-channel oscilloscope if we didn't have a really strong business caseAnd speaking of power: one thing that people often overlook when it comes to channel counts is power measurements: generally speaking, if you want to measure power, you're going to need two channels: one for voltage and one for current. A basic power efficiency measurement (Pout/Pin) requires 4 channels all by itself.But speaking as a hobbyist (spending my own money), I think it depends entirely on one's needs / budget, so IMO it's good to have a choice between two and four channels - there was a time when that wasn't really a choice (see attached)

author: EEVblog
author_rank: Unknown
timestamp: July 30, 2024, 02:26:04 am
content: Quote from: pdenisowski on July 30, 2024, 01:30:43 amAnd that's the problem with logic analysers, they can't show that. They only work on electrically robust systems. The first thing I do when troubleshooting a digital system is to use a scope to eliminate any signal integrity issues.

author: EEVblog
author_rank: Unknown
timestamp: July 30, 2024, 02:30:46 am
content: Quote from: pdenisowski on July 30, 2024, 01:47:50 amAnd that's the point I'm making. In general, scope choice has always been about the best "bang-per-buck", and 4CH has never offered that in the past, so it usually wasn't a viable choice. Now it's clear that best bang-per-buck option is the 4Ch domain.My first >2CH scope was a used Kikusui COS6100M, and even then I didn't have 4 full channels.

author: Peabody
author_rank: Super Contributor
timestamp: July 30, 2024, 03:58:02 am
content: Your original question was not whether someone should buy a two-channel scope, but why manufacturers even bother to offer them anymore, the implication being that they shouldn't, which would be bad news for hobbyists. And haven't we been down this road with you before? "Is an $800 scope overkill for a hobbyist?" What do you think electronics hobbyists do?One of my other hobbies is photography. Ask any professional photographer what kind of tripod you should buy, and he will answer a carbon-fiber model costing about $400. It will be very light, amazingly sturdy, and will last a lifetime. And that's the right answer for a professional, but clearly the wrong answer for an amateur. If you buy a $50 aluminum tripod instead, or even an aluminium tripod, the remaining $350 will get you two complete flash light stands, including the stands, the flashes, the umbrella adapters, the umbrellas, and the radio triggers. And the tripod will work well enough. When it comes to buying gear, the professional can be the amateur's worst enemy. The needs and requirements are often just completely different. And you know, people do have budgets, and the amateur may have no revenue from his hobby to pay for all this fancy stuff.Well, I guess for an EE a 4-channel scope is the right choice. But if there is any difference in price, a 2-channel scope might well be the better choice for a hobbyist. I could even make a case for getting a two-channel, battery-powered, hand-held "toy" scope of the type you've summarily dismissed. They are pretty good now, and cost $100 or less. That's what I use (but very rarely both channels).

author: Kleinstein
author_rank: Super Contributor
timestamp: July 30, 2024, 06:34:24 am
content: With more channels there is a chance that one runs in the ground loop problems, at least for small signals.With 2 channels one often has an extra trigger input, as a very limited 3rd input. So the step from 2 to 3 is not that large. Granted that a real input channel makes triggering easier with adjustable attenuation / gain.With a dedicated 2 channel design (not just cut back from 4) one is more likely to have seprate knobs for the vertical range and thus a more intuitive UI - at least for those who where used to analog.The power sequencing case is indeed one where many channels really help and even more than 4 may be ideal. One can however still use a master for the trigger and than do it with a few channels at a time.Of cause it gets nasty when one is looking for glitches in the power on sequence (e.g. depending on mains phase).Quite a few of the features of a scope are rarely used, but it is still nice to have them. The 3rd / 4th channel can also act as spares - in case one gets damaged.With some scopes the step from 2 to 4 channels also comes with a 2nd ADC and thus more sampling rate when using 2 channels.If a $800 scope is overkill for hobby use really depends on the income situation. If you have the money this may be no issue at all - in countries like India or China this may very well be an issue. DSOs got really affordable - they were pretty expensive only some 30 years ago.

author: EEVblog
author_rank: Unknown
timestamp: July 30, 2024, 08:49:48 am
content: Quote from: Peabody on July 30, 2024, 03:58:02 amThat was not my intention at all. It was to explain why 2CH is still needed and requested by the industry. As discussed in a recent forum thread on the Keysight scope which provided the inspriration, I thought a lot of people my not know about the educational market and the industrial test markets.QuoteI will repeat a response I put on the video comments:I was talking about how some people seemingly can't understand what *general advice* is. As if this video was specific advice *for them* and *their situtation*. I literally said it's best to get a 4CH "unless you need to save every last cent". As a leading voice in this field I would be a laughing stock if my *general advice* was to get a 2CH scope when a 4CH scope today is *clearly* better bang-per-buck. As always, YMMV. As a creator I can't possibly make a video that takes everyone's personal financial and requirements situations into account.It is literally impossible for me to make an advice video that cater to every need an requirement, that's just silly. Not that this was an "advice" video anyway, it was nothing of the sort!As for "summarily dismissed", rubbish, have you actually watched some of my pocket scope reviews? Unless it's absolute garbage, my general advice has been along the lines of "this is ok and can be useful for certain requirements".I don't know how many times I have to say it, YMMV.

author: EEVblog
author_rank: Unknown
timestamp: July 30, 2024, 08:52:55 am
content: Quote from: Kleinstein on July 30, 2024, 06:34:24 amYes, handy.But 2CH scope usually has only one ADC, so you get half the sample rate for two cahnnel.A 4CH scope usually has two ADC's and you can get the full sample rate on two channel by using 1/3 or 2/4.Handy benefit.

author: EEVblog
author_rank: Unknown
timestamp: July 30, 2024, 08:55:39 am
content: Quote from: Kleinstein on July 30, 2024, 06:34:24 amIME, the $800 price point has always been about what you pay for a decent entry level scope.Back in my day it was a 20MHz dual channel analog.Then you'd get progressively better bang-per-buck over the years.It wasn't until the DS1052E did you get a digital for that $800 price point.Then that price actually started to drop where "entry level" is around the $400-$500 price point now.

author: Gyro
author_rank: Super Contributor
timestamp: July 30, 2024, 09:44:30 am
content: Quote from: EEVblog on July 30, 2024, 02:26:04 amThis is where there is a disconnect. A scope is fine for the 'basic' slow interfaces - I2C, SPI, serial etc. (although as I said the decoders can be buggy, for instance the Siglent SDS1202X-E doesn't get the stop bit settings right on simple async serial - unless they've fixed that with an update by now). To be fair, these are the ones that are more likely to be 'casually' implemented and so suffer more signal integrity issues.There's a difference between these types of interfaces and 'big boy' interfaces like high speed parallel video busses, DDR3 etc. where you have to pretty much guarantee signal integrity by design. It's one thing to 'coo' over the cute length matched traces, it's quite another to actually have to design that stuff. Both ends disappear under BGA packages, and you can't afford the stubs caused by test headers, you have to align traces, leave a rectangular solder mask window and use Mictor probes. My personal logic analyser is a 34 channel Agilent, 250MHz timing, with 100k 1.5pF probes - and that's nowhere near current crop, it's around 25 years old. Try putting your x10 passive scope probes on those signals and see what happens - at very best, you'll be looking at the signal integrity that you just trashed. Of course you can buy 4 very expensive active probes, but they will cost more than the scope. With luck, youmightget away with custom Z0 probes (effectively what the LA probes are). The best you can do in signal integrity terms (apart from designing it right in the first place) is to wind down the thresholds to below the IC worst case input specs and look for reflections.Anyway, leaving aside logic analysers, it's the effect of "WHY sell 2CH Oscilloscopes?" type videos that worries me. The very obvious answer is that there is a market for them. Looking around, I can get a Rigol DS1102Z-E for reasonable £250 in the UK, a pretty good deal compared to a short buffer buggy Hantek. A DS1054Z on the other hand can be had for about £350 - now that's not just £100 difference, it's also a 40% more. You can go on more or less indefinitely, adding £50-100 more to get this or that model with a 'must have' fancy feature. It's a honey trap for beginners [Edit: "best bang-per-buck" doesn't cover it, it should be 'how many bucks do theyneedto spend'].It's probably fair to say that the viewership of your videos is heavily slewed towards beginners (not your fault). It worries me when, particularly over recent months, I've seen a number of beginner scope threads where the OP's 'entry level' shopping list consists of various 2Gsample and/or 12 bit (and yes, 4 channel) models, because that's all they see you getting excited about in recent videos. I wonder how many of them will spend £500 on a scope, play around unsuccessfully with some 555s and opamps on a breadboard, get disillusioned and stuff it in a cupboard, together with their fancy AWG and other stuff. Maybe the 20MHz bandwidth filters should be enabled by factory default.Bottom line, maybe it's time to start putting out some videos on bargain scopes and equipment that will suit beginners, get them through the first couple of years of learning, playing with basic stuff, Arduinos etc. (maybe a lot of them will never need to go past that stage), and see if they're actually going to stick with the hobby. Either that, or start putting a 'parental warning' saying that beginners really don't need this level of stuff, save your money. I think there's a danger of disconnect with your actual (versus target) audience.

author: madires
author_rank: Super Contributor
timestamp: July 30, 2024, 09:57:10 am
content: When repairing stuff I very rarely need more than two channels. And dedicated knobs for the second channel are quite handy.

author: nctnico
author_rank: Super Contributor
timestamp: July 30, 2024, 10:50:18 am
content: Quote from: Bud on July 30, 2024, 01:07:45 amMy rule of thumb:For doing repairs a two channel oscilloscope is typically more than enough. And 100MHz bandwidth is plenty. 4 channels is something you need if you are working on digital microcontroller circuits and more complex circuit development in general.

author: David Hess
author_rank: Super Contributor
timestamp: July 30, 2024, 07:42:50 pm
content: Quote from: EEVblog on July 30, 2024, 08:52:55 amThat is implementation dependent.Increasing integration made digital triggering less expensive than analog triggering, so if digital triggering and all of the built in trigger modes apply to the external trigger input, then the external input has to go through the same digitizing process into the FPGA as the vertical inputs. What is not required is the sample memory.So in this case, the only difference between an external trigger input and a vertical input is the lack of sample memory and analog signal conditioning like attenuators. The digitizer is still shared, or duplicated.The cost difference could be just sample memory and analog signal conditioning. I suspect the most important reason to provide two channel DSOs is price discrimination through product versioning. They can charge more for their 4 channel "premium" DSOs by offering 2 channel "economy" models while the costs are practically identical.

author: EEVblog
author_rank: Unknown
timestamp: July 31, 2024, 12:10:09 am
content: Quote from: Gyro on July 30, 2024, 09:44:30 amYou're going to hate the review of the $5k Uni-T function gen and the new Keysight scope then I guess...FYI, according to my last viewer poll, my audience is mostly professionals and students. Hobbyists run a distant third.BUT it does seem true that low cost review videos get more views.

author: EEVblog
author_rank: Unknown
timestamp: July 31, 2024, 12:12:32 am
content: Quote from: David Hess on July 30, 2024, 07:42:50 pmYes, just go look at the teardown of a moden scope. There is very little in the front end now. This is why some manufactuers have been able to sell cheap 4CH scopes in the last 4-5 years. Front ends used to cost money.

author: David Hess
author_rank: Super Contributor
timestamp: July 31, 2024, 03:55:01 pm
content: Quote from: EEVblog on July 31, 2024, 12:12:32 amI think the difference comes down to integration, with greater integration reducing cost and also the space requirements. Old true 4 channel oscilloscopes were almost always larger laboratory instruments because the hardware for attenuation and switching took so much space. (1) Old true 4 channel portable oscilloscopes were very rare, and offhand the oldest one I can think of is the Tektronix 2214 from 1991 (!), shown below; behind each of those vertical controls is an equally large attenuation assembly with a cam switch for the many connections taking up most of the volume. (2) Older 4 channel portable oscilloscopes used a 2 + 2 channel configuration with external trigger inputs used as auxiliary vertical inputs having limited capabilities, like 1 attenuator stage and DC coupling at most.Now all of the signal conditioning, including attenuation and coupling, can fit on less than 10 square inches of board space, and controls can be digitally multiplexed to minimize the space required on the front panel.(1) Just the volume required for the signal conditioning of 4 channels on my old laboratory oscilloscopes is larger than an entire modern 4 channel DSO.(2) Before they standardized on their custom cam switches, Tektronix had relay switched attenuators in 1969, but they were not really any smaller, and I suspect they were more expensive, less reliable, and limited to perhaps 200 MHz.

author: SIBtronics
author_rank: Contributor
timestamp: July 31, 2024, 07:43:43 pm
content: Quote from: EEVblog on July 31, 2024, 12:10:09 amThing is students often dont have a lot of money, hence also why the low cost videos get more views. It appeals to that part of your viewers. and that leads us to the main use for 2CH scopes, a 4 channel might only be 100$ more, but thats like 40% more and for a student that just wants to experiment around thats a lot.

author: thm_w
author_rank: Super Contributor
timestamp: July 31, 2024, 10:09:35 pm
content: Quote from: SIBtronics on July 31, 2024, 07:43:43 pmIn the grand scheme of things, $100 is less than one textbook. If you plan on becoming a serious EE, and using the equipment going forward, its worth it. If you are just trying to get through classes, or are struggling to pay rent sure. Though student loans are always an option.When I was in school a 2 vs 4 channel DSO was $500+ difference in price so it made sense to save. If I take into account inflation, a 4 channel DHO800 would cost only ~$250. I sure as hell would have saved up that $250.

author: Geoff-AU
author_rank: Frequent Contributor
timestamp: August 01, 2024, 02:49:00 am
content: Quote from: EEVblog on July 30, 2024, 08:49:48 amStill wondering what the answer to the question is. I might have missed the point by skimming the 28 minute video and the subsequent cross-purposes discussions... all of the images of test engineering scopes seemed to have several channels too.I can see that educational use may prefer 2-channel for simplicity when teaching newcomers.Is there anyone in industry specifically demanding 2 channels? As in, if you offered them a 4CH for basically the same price they'd still pick the 2CH one? Niche space constraints seems to be the only reason I can think of, if a headless 4CH is still too big.

author: pdenisowski
author_rank: Super Contributor
timestamp: August 01, 2024, 03:25:15 am
content: Quote from: Geoff-AU on August 01, 2024, 02:49:00 amWe (R&S) offer two channel scopes because we do have customers who ask for them and who don't want to pay extra for scope channels they don't need. The difference in list prices for the RTB2000 2- and 4-channel versions is about 1000 USD.https://www.rohde-schwarz.com/us/products/test-and-measurement/oscilloscopes/rs-rtb2000-oscilloscope_63493-266306.htmlSince the scopes are the same size (just 2 fewer BNC connectors on the front), there's not really a size difference between 2- and 4-channel models. This is true for all scope models that come in 2- and 4-channel versions.

author: EEVblog
author_rank: Unknown
timestamp: August 01, 2024, 03:39:27 am
content: Quote from: Geoff-AU on August 01, 2024, 02:49:00 amEducation, and test systems that don't need it but you still want a scope in the rack.In both cases the reason can be priceand/orsimplicity.QuoteAFAIK there is no maker that doesn't sell the 2CH at least a bit cheaper. It's basic market segmentation.In the vidoe i did speculate that even if they did, some would still pick 2CH because of theORI bolded above.

author: EEVblog
author_rank: Unknown
timestamp: August 01, 2024, 03:42:38 am
content: Quote from: SIBtronics on July 31, 2024, 07:43:43 pmI'ts not just students,everyoneloves cheap shit and bang-per-buck. It's inherent in the nature of engineers.

author: Xena E
author_rank: Frequent Contributor
timestamp: August 01, 2024, 11:54:05 am
content: As an answer to the title of the thread, I'd say if you ever had to teach an unskilled assembly "technician" how to set up an oscilloscope for the umpteenth time, (wheres the trace gone?!) You thank your personal diety that simple(r) equipment is still being offered, the cost incentive is secondary.And who hasn't got the convenience of little scope/meter/gen/ component check gizmo lurking on the bench next to their big bucks DSO?Horses for courses people.

author: ftg
author_rank: Frequent Contributor
timestamp: August 01, 2024, 12:51:22 pm
content: Quote from: Bud on July 30, 2024, 01:07:45 amFour channes is excellent for doing things like monitoring an SPI bus and feeding the 4th port with RF powermeter output while searching for glitches.Been there, done that, found fun things.That can also be done with the fancier logic analyzers that have some analog inputs.One of those + JTAG allows for monitoring the DUT state quite well.

author: coppice
author_rank: Super Contributor
timestamp: August 01, 2024, 02:53:53 pm
content: Nobody has mentioned the elephant in the room. In many companies its relatively easy to get a scope, but really hard to get accessories like probes. You probably never use more than 2 channels on a 4 channel scope, but it comes with enough probes to be keep you going when you break a couple. A very powerfui advantage over a 2 channel scope.

author: McBryce
author_rank: Super Contributor
timestamp: August 07, 2024, 08:45:24 pm
content: Am I the only one who was screaming "They're programmable loads, not power-supplies!!!" at the screen every time you spoke about the test rack in the Linus video??McBryce.

author: thm_w
author_rank: Super Contributor
timestamp: August 07, 2024, 09:30:18 pm
content: Yes he did acknowledge in the youtube comments, doesn't really affect the explanation of a test rack in this context though.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: August 10, 2024, 04:07:45 pm
content: Quote from: EEVblog on July 28, 2024, 11:09:27 pmThis really is the wrong question, and the answer is very simple. Companies make 2 channel scopes because people (or companies) buy 2 channel scopes. If people stopped buying them, they would stop making them very quickly.Two channel scopes are quite often also plenty. You can look at the input and the output of a "box" at the same time. Old analog scopes also rarely had more then two channels, so many people are still just "used to 2 channels". The analog scopes did have an advantage here, as they often had a separate trigger input. Digital scopes generally don't have that, but you can use a 3rd channel for the triggering.I was in doubt when buying a new scope last year. Two channels would have been enough for almost anything I do, so (for the same price) it was a tradeoff between more channels or more bandwidth. 100MHz of bandwidth is already plenty for me, and accurate probing for higher bandwidth is nearly impossible anyway (Just have a look at how signal ringing changes when you move or touch the GND connection). So in the end I did go for a 4 channel Siglent SDS1104X-E Part of the reason is also interest in 3-phase motors and motor drivers.Built in logic analyzer functions are also a motivation for more channels, so you can keep an eye on uC communication while probing other things. or synchronization between those things.LA's for the Siglent scopes are completely bonkers though. Extreme prices, and on top of that you have to buy a license for the software too??? Instead, I also bought an Kingst LA2016 for around EUR100. Plenty of inputs, and a PC with keyboard + mouse is also a better user interface then a scope screen for an LA. (higher resolution screen, pan/zoom/ scroll works faster, input for channel names, saving samples). And the LA2016 works with Sigrok, so I can write my own protocol decoders if I want to. Sure, the LA2016 does not synchronize with the scope, but If I need synchronization with analog, signals I still have the 4 scope channels.

author: David Hess
author_rank: Super Contributor
timestamp: August 10, 2024, 09:59:50 pm
content: Quote from: Doctorandus_P on August 10, 2024, 04:07:45 pmHaving an external trigger input is important enough for 2-channel oscilloscopes, whether analog or digital, that 2-channel oscilloscopes lacking an external trigger input are either rare or toys. 2-channels are only acceptable if an external trigger is present. Some 2-channel oscilloscopes, both analog and digital, had 2 or even more external trigger inputs.There were plenty of 4-channel analog oscilloscopes in the form of 2+2 channels where the extra 2 channels were primarily external trigger inputs, which could also be used as limited vertical inputs. These evolved from earlier models which had some type of "trigger view" capability.

author: EEVblog
author_rank: Unknown
timestamp: August 11, 2024, 10:13:42 pm
content: Quote from: David Hess on July 30, 2024, 07:42:50 pmYes, but I can't recall the last time I tore down a 2CH scope and found dual ADC's.If you know of a modern example, please name it.