Hi. Now there's a myth regarding oscilloscopes that simply will not go away. and that is that. Digital Scopes Be they ancient like this? Uh, Tectronics TDS 210 Sort of a bit more modern like this Ryo 1000 E Series Or something like this, you know, really? Kick-Ass High-end Uh Tectronics 3000 Series Just released.

And the myth is that your old traditional analog oscilloscopes like this Tectronics, Triple 25, or any analog oscilloscope is in quote marks lower noise than a digital scope. and well, that's not actually true. And I want to explain it to you today. So let's start off by: take a look at this: Uh, Tectronics Triple 25 Nice Analog Oscilloscope 50 MHz Bandwidth Fairly typical analog scope.

and look at that. Trace Look at it. It's just beautiful. Look how fine that is.

I've got no input connected to these Scopes or any of these Scopes as we see and they're all going to be by the way, set to the same volts per division, one volt per division in this case, and 1 millisecond time base just so that we're consistent across all. Scopes But look at that. You might think how beautiful is that? There's no noise on that whatsoever. These analog Scopes are so massively low, they practically don't have any noise at all.

They're brilliant. And then you go to something like this: uh, Ancient TDS 220 100 MHz bandwidth Analog scope One of the first realtime bandwidth scopes on the market. and well take a look at the waveform. It's you know it's a bit fuzzy.

Look at the noise on there. Eh you? You know anyone would say that is noisier than that? Tech than that analog Tetronics Triple 25 we saw before and then we've got this 6 seven year old old Ry Gold Ds1052e It's still sold. It's almost obsolete. but once again, it's A.

Even though it's a 50 MHz bandwidth, the firmware has been hacked. It is actually 100 MHz bandwidth front end. and this is a pretty, um, you know, a good example of a modern lowcost. you know, bottom of the range DSO And well, look at the waveform once again.

all these time bases are identical. The vaults per division are all identical. And look. and we get in.

See, see those little occasional blips in there? Look at that. that's you know, a good four pixels high or something. All that noise. You would think, well, that one's actually slightly worse than the Tetronics TDS 220 And then we'll have a look at this brand spanking new Tectronics 3000 Series scope.

Very expensive scope. You know, over $10,000 worth. Just released. It's a quality Tectronics brand.

You'd expect this to have, you know, be a really well-designed scope. and well, once again, same time base and same voltage setting. No input. Look at the waveform.

it's all over the shop, right? That is the worst of these four. Scopes It looks like they got progressively worse or digital Scopes have got progressively worse as time has gone on. Well, is that fact or fiction? So clearly I know what you're thinking Dave You're talking rubbish I Can see it with my own eyes. This one analog scope traditional analog scope is definitely the lowest noise scope.

This one is the uh, next best. The ancient digital then the slightly more modern digital is probably better again, and this latest modern one is just absolutely hopeless. I Can see it with my own eyes. Well, I'm here to tell you that your eyes aren't deceiving you.

Yes, this is better, but you're not seeing the whole picture. You're not thinking fourth dimensionally. Now, the thing you must remember with a traditional analog scope is obviously it has no storage capability and the brightness of the image on the screen is going to be determined by how long the trace spends in that position. So if we just had a little tiny run pulse that went boom up there like that and it happened one in a million times, you're never going to see it on an analog scope because in each sweep, assuming that the trigger actually uh, you know it was actually able to be displayed.

it only be displayed one in those million sweeps or whatever, so you wouldn't see it. It wouldn't be there long enough to produce a bright image on the screen like we're seeing with that Trace there. And yes, I can make that Trace fatter by turning up the brightness. Now that is like a blooming effect on the scope.

but it's not just that, it's also displaying more information when you make it brighter. And I've shown that in my previous video as I mentioned. which I'll link him down below how your analog oscilloscope can be hiding the true signal. So in this respect, analog Scopes aren't nearly as good as digital scopes for capturing the actual hidden data in there.

The hidden signal in there? So somewhat confusing, but a lot of people make that mistake thinking: analog Scopes display the signal better. not necessarily. So watch the other video and you'll find out why. So the bottom line is any noise on the analog amplifier input down here, or on the signal that you're feeding in.

Any noise which is uncorrelated to your sweep speed or your trigger. I.E is just randomly appears, it's not synchronized with the sweep. Then it's going to appear quite dim or non-existent because it's not going to show up all the time. And that is why an analog scope will always show this beautiful, clean signal like that effectively.

What it's doing is averaging your signal by way of brightness. But let's take a look at the first example of our digital scope here: Ancient Tectronics TDS 220. But as you should know, a digital scope actually samples the signal, then displays it, so any noise or anything else in there is going to get captured in that data acquisition and displayed. Now in this case, this signal looks relatively clean.

You can see little noise artifacts on there. You can see it right, but it's not that bad. You would think that's not too bad at all, especially compared to the Ryo one above it. But here's the first fact you need to know about Digital Scopes The amount of information you're seeing displayed on that screen.

there is going to be determined by the sample memory depth. and with this ancient scope here the 200 Uh series TDS it's only got 2.5k of sample memory. Practically buger. All and that is why we're getting a nice clean signal there.

So that's fact. Number One and I can demonstrate that on this. Ry Go here now. You can see that it looks a little bit worse than the Tectronics one.

Okay, 100 MHz band with same time base, same voltage, no input, all those spikes. But this uh, Ryol DS 1052 has 1 Meg of sample memory. So for any given time base in this case, 1 millisecond uh per division, then it can capture much more high frequency noise and actually display it on the screen. And that's exactly what it's doing.

And I'll show you that if we go into the acquire menu here. if I it's on long memory at the moment, so it's got that one uh Meg points. it's using that one one Meg points of memory. but watch what happens to this signal if I Uh, drop it down to short memory I Think it's only a couple of K or it might be 10K on this scope.

But we'll see a difference. It's going to clean it up. not by a huge amount, but it will. You'll be able to see it.

watch. See it dropped. Oh theel scope's memory depth is 8k or 16k in normal mode and with 512 or 1 Meg in long memory. By there you go.

It answered that for us. So you can see that difference. there. it's going.

It's dropping at least a whole line of pixels there. It's thinner by at least one pixel. one least significant bit if it's displaying 256, for example. That's because in log memory mode, it is capturing more of that high frequency B that high frequency noise.

And it's and it's putting it on the screen. so it's showing you more of a true representation of the signal than the analog scope is because this data this that high frequency data in long memory mode wouldn't be displayed on an analog scope. because it wouldn't be. uh, it wouldn't be visible.

It wouldn't be on the screen long enough to light up those phosphors. And that's why an analog scope appears to have less noise. but it actually doesn't. And fact number two that you should know about digital Scopes or any scope, even analog ones.

the higher the bandwidth, the greater the inherent noise of the amplifier and other front end circuitry. So in this case, we can see this by turning our bandwidth limit off and on. At the moment, this Rol Scope is 100 MHz bandwidth. but I if I turn this bandwidth limit on, it'll drop down to 20 MHz bandwidth and we should see this noise drop a little bit more.

You won't see it a huge amount on this. We'll be able to see it on our high-end tectronics in a second. but I'll show you there we go. There's slightly less you can see just on the bottom of the waveform.

There there's little pixel chunks taken out, so it's slightly less noise. Look at that. hey fact. Number two.

Now on our brand new Tectronics Mdo 3000, we'll be able to see both of these things much better than we could on the previous one. Now, as before, exactly the same time base, exactly the same voltage input and the noise looks pretty horrible. Look at that. But if I call up Channel One here.

Look, the bandwidth is full and the bandwidth of this scope is 1. Gz Got a massive bandwidth so the first thing we can do is change this. 250 m hurts. We'll see the noise.

maybe dropped by a smidgen. It might be hard, but we'll give it a go. Here we go: 250. Yep, slightly, you can see that grow just a little bit there.

and 250 we drop it down to 20 same as we did on the Ryo. It's less noise Again, look at That So I put that back to its full 1 GHz bandwidth. We'll go to the Acire menu and we'll now marck around with the record length. Look, it's 10K at the moment.

Okay, so not a huge amount. Okay, now if we vary this, let's drop it down to a th000 just like we had on that Ancient Tectronics TDS 200 series. Watch the noise on the waveform Bingo Look at that. it's dropped significantly and once again, if we, uh, drop the bandwidth down to 20 MHz look at that.

Our line is exactly almost exactly identical to what we were getting on the ancient TDS 220 because our, uh, those two rules. the bandwidth makes a difference and also the amount the sample rate showing that high frequency content. But we've dropped both of those down and bingo, our noise has magically vanished. Look at that.

I'll turn it back now. Watch this so we're back to our 1 gig bandwidth. so we're now on. 10K Let's go up to 100K Look at that.

the line gets thicker. One Meg line gets thicker again. Five Meg Oh, you probably? yeah, you won't see. might not see much difference there, but 10 Meg that is as thick as it's going to get.

Look at that. we're on 1 V per division with no input whatsoever and a 1 GHz bandwidth. You would think this is the worst scope in history, but it's not. It's actually showing you real data.

So there you go. There's nothing inherently wrong with Digital Scopes You've just got to understand those two reasons why: they can show uh, more noise in quote marks. It's not really noise, it's actually real data that's there, which is ordinarily being hidden on an analog scope because that analog scope just averages out over its screen. So in that respect, digital can actually be better.

CU You can easily capture that high frequency data that's really there. Now, if we go into the acquire menu again, I Can demonstrate that let's go into highres mode, which puts on Box Car average in. so it's averaging out some of that high frequency content. Boom.

Look at that and then if we go into normal, uh, average Mo we can do that as well. but that is what happens when it averages out that content. and then we can, of course, uh, combine our memory depth so we can do our Box Car Averaging our memory depth go right down to 1,000 points. Oh, let's be reasonable.

Let's go down to 10K get a decent amount of memory. but look at how thin that line is now because we've turned on that box car, averaging over time to filter out effectively that high frequency content almost exactly like the analog scope does, except the analog scope does it using Persistence of Vision on your phosphor based screen. And then of course you have other modes like your Peak detect mode which can show uh, which captures those Peaks and stores them better than your full memory depth. Even with a th a record length of a th000 here, we can still get it to display all of that high frequency data cuz it captures it.

It's got that Peak detect mode in the ADC and likewise envelope mode. Of course you can with infinite persistence. you can capture that and it just fills it up. fills up the screen like that.

There something you can't get on an analog scope, but that's real information there over time you'll never see on an analog. Now there are two types of digital Scopes and this will make a difference. Uh. One is like your Riyo 1000 series scope without what's called an intensity graded display or variable persistence display goes under all sorts of uh names like that or analog like display.

but something like this Uh, Tectronics 3000 Series does have that and that's what this intensity button over here actually does. If we hit that, it's at 100% at the moment. That's why this wave form looks exactly like it will on a Ryo 1000 series. It's all chunky, you know, and there's there's no sort of variable intensity in that at all.

But but if we drop that down, you'll notice that the real signal going down, going down, going down. Look the real signal. The real line in there is actually thinner than that. and there's high frequency noise superimposed on top of that which you which you'll see clearly.

If you have a an oscilloscope like the RAR 1000 that doesn't have this intensity grer display, you always see all of that high frequency noise. There is no way for the oscilloscope to tell you the difference between ones that are uh that appear there all the time and just noise that just appears there periodically. And that's one of the advantages of the analog oscilloscope. Of course because it shows you that intensity graded Uh display just like these modern scope modern digital Scopes and that's what these modern digital Scopes try to do.

They try try to replicate that sort of thing. So if I show you that waveform with 100% waveform intensity operates just like that. uh, cheap low-end Rgo one or any of those low-end Scopes without this intensity grader display, look if I turn it down, then it operates more like an analog one and you can see I've got one Mega Sample memory now so it's showing lots of high frequency detail in that waveform, but you turn it down, you turn it down and you start to see that the true line actually gets thinner and thinner. Take a look at that because that high frequency information isn't displayed or captured nearly as often.

and that's why the um, that's why these digital Scopes offer this intensity grader display cuz it tries to simulate the analog scope in that respect. But in my opinion, they're actually better. Digital scope is better than analog scope because you can actually pick up that information, especially one with these intensity graded displays. Really fantastic.

Look at that see, it's almost all gone. and there's the tiny amount, the tiny waveform. that's the one that's there all the time. and the rest of that information is just more uncorrelated noise around that.

and you'll really see that here because I've added 30% noise to this signal. So if we turn it right up to 100% there we go. Look at that right. There's a ton of noise that is deliberately added on that waveform cuz this scope allows me to do that.

You can see if I turn that intensity right down because that noise is effectively uncorrelated. It goes away like that and you can see that the noise is uncorrelated. cuz if I go into my choir mode and choose average down here. Bam, it disappears so that noise was actually superimposed on that signal.

Now if I turn on the fast acquisition mode which this Tectronic 3000 has I can select different variable intensity display modes. Now the normal one we uh, had before down here was showing up yellow, but if I set it to temperature mode here, check this out, we'll see what it does change the waveform intensity. got it set to 100% so it looks just like it would on that. uh you know cheap low-end Rle without any waveform intensity.

When we turn it down, you'll notice that the waveform changes color and outside there the ones on the outside. like the little hints of blue and green out in there. they they signal anomalies or noise or whatever it is on your signal that is occurring less frequently than that red line in the middle. just like the color temperature gradient in light.

uh, for example, same sort of thing. So it's that red part in the middle there which is your main signal which is showing up all the time. That's your baseband signal with all the less frequent noise or it could be. You know some other part of your signal can? It's real information there that's ordinarily hidden on an analog scope.

It shows up here as you know infrequent blue and green data. This is really handy. Very powerful feature of digital Scopes and especially this one with that uh, color temperature graded display. and it also has an inverted mode here which actually does exactly as the name says.

It actually inverts the waveform so the list frequency stuff, the Glitchy stuff or that noise shows up brighter than your main waveform so we go up to 100% Oh, it's all there and your May waveform in the middle vanishes. That's just a neat little uh, different way to view your data on this Mdo 3000. but that's the same noisy signal 30% noise added and can we see it on our analog scope? Well, not really. It's very difficult.

look. it looks like a very clean sign w W but there's actually I've added all that noise to it. You can't see it because it's uncorrelated to the sweep signal and it's only showing up very briefly there. but we should be able to capture that with the camera now.

I'll attempt to demonstrate that this analog scope can actually display that high frequency content because it's so short, it doesn't light up the phosphors much and your eyes can't see it well. We can try and attempt to capture that by using a long exposure on our camera here. so that's what I've got here here. I'll put what they used to use back in the old days as camera hoods.

You could buy. That's what these ridges around here were for on these analog. Scopes You buy these hoods, you hook your film camera back then up to it and you can get long exposures. Well, I'm going to do that.

I'm going to whack some t-shirt over the top like that and I'll turn out the lights here. try and get as dark as possible and I'll see if I can capture the noise on a couple of typical signals. first a flatline with no input and then a to be the control so there shouldn't be much noise on that, and then a 1 khz analog signal that will have noise on a digital scope, but you won't see it on the analog unless we do this. And here's what: I Shot with the camera at different shutter speeds.

Now the signal was barely visible. that's 125 of a second and you'll notice that it does get a little bit thicker there and now it's sort of pretty much stopped. So that is the real signal. there bit of Bloom in.

But basically there was a difference between the signal as originally that I could see with the eye and then what we recorded with the camera got a little bit thicker. And here's that noisy signal as you can see barely visible at the low shutter speed and that's what it looked like to my eye. But as you increase that shutter speed, you start seeing all that dim phosphor you couldn't see with your eye and you can now see the noise superimposed on the waveform. Brilliant! So there you go I Hope that's cleared up the myth that digital Scopes are noisier than analog Scopes Because they're not.

They're just better and they work differently. And hence they're showing up all that high frequency stuff that your analog scope has pretty much been hiding from you all these decades by way of the uh, the phosphor persistence on there and having that uncorrelated noise or signal uh, just not being bright enough back in the old days when we didn't have digital Scopes You had to, uh, turn the brightness right up on this sucker to sort of. You know, see all that? Oh I Think there's something hidden in there, is it? Oh I Don't know. Sometimes you might have to get your camera and hook it up to actually SAR it as I uh demonstrated there.

It wasn't a totally thorough uh demonstration for the camera, but it did at least show the difference that when I've got at low intensity like that, there is actually more information there that my eyes just aren't picking up because they aren't AR displayed as frequently. but the exact same signal on a digital scope, especially one that doesn't have variable persistence like this Rgo or this ancient Uh Tectronics one. It shows up, and that's why the waveform looks thick or noisy, but it's not. Yeah, there might be subtle differences between analog front ends, but it's not like this modern Uh Tectronics 3000 Series scope just released is going to have a noisier analog front end than this ancient analog tectronic scope.

No, it's not the case and is a little bit involved in terms of the 8bit digital sampling and things like that. But in the end, what it comes down to is as I said: the memory depth of the scope. the more memory depth. the more you're going to pick up all that high frequency content.

The greater your bandwidth, the more noise you're going to see. and that's inherent in analog. Uh Scopes as well. not just, uh, digital.

And of course, your variable intensity displays. If you got something like the old R, go all the old tectronics here that doesn't have variable intensity. Well, you're just got to capture everything. And sometimes as I showed in the previous video, that can be a good thing.

So there you go. Don't rag on digital. Scopes They're not that bad. They can actually be better.

Sorry for all you analog gray beards out there. Catch you next time and.