EEVblog 1632 - WHY sell 2CH Oscilloscopes? + Test Engineering

[EEVblog]

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.

You'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.

[EEVblog]

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.

Yes, 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.

[David Hess]

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.

Yes, 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.

I 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.

[SIBtronics]

You'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.

Thing 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.

[thm_w]

Thing 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.

In 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.

[Geoff-AU]

That 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.

Still 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.

[pdenisowski]

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.

We (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.html

Since 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.

[EEVblog]

That 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.

Still 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.

Education, and test systems that don't need it but you still want a scope in the rack.
In both cases the reason can be price and/or simplicity.

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.

AFAIK 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 the OR I bolded above.

[EEVblog]

You'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.

Thing 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.

I'ts not just students, everyone loves cheap shit and bang-per-buck. It's inherent in the nature of engineers.

[Xena E]

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.

[ftg]

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.

Four 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.

[coppice]

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.

[McBryce]

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.

[thm_w]

Yes he did acknowledge in the youtube comments, doesn't really affect the explanation of a test rack in this context though.

[Doctorandus_P]

Why do companies still sell 2CH oscilloscopes?

This 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.

[David Hess]

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.

Having 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.

[EEVblog]

But 2CH scope usually has only one ADC, so you get half the sample rate for two channel.

That is implementation dependent.

Yes, 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.