EEVblog

Why do digital oscilloscopes appear noisier than traditional analog oscilloscopes?
Dave busts the myth that digital scopes are noiser than analog scopes, and demonstrates what inherent advantages digital scopes can have over analog scopes in terms of true waveform capture. And also why your analog scope may be hiding important signal detail from you.
Demonstrations of how memory depth, analog bandwidth, averaging, and intensity graded displays can all effect the signal detail you see on your digital oscilloscope.
And how long exposure camera shots on analog oscilloscopes can reveal detail you can't see with your eyes.
Demonstrations are done on the new Tektronix MDO3000, the Rigol DS1052E, the Tektronix TDS220, and Tektronix 2225 analog oscilloscope.
Previous video on common mode noise measurement: • EEVblog #442 - Analog ...
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[@stevosteve]

This tutorial may be 9yrs old but it still holds up today. Brilliant, just BRILLIANT and informative.

[@compwiz00]

Oh, stay in darkness for half an hour or so, like you would for stargazing. Then look at an analog scope with the brightness juuust high enough to see. It's just amazing how much information you can see. I found it interesting with music on the scope. You could see all sorts of details that are invisible under normal light.

[@DragonDaron]

i'm learning so much with you, things we never do at the university, so thx

[@stuartkerr1012]

+Yacine Wlid Ahlem Yeah, totally. 99% of my knowledge came from this channel and on-the-job trial and error!

[@mdrahman6732]

@@stuartkerr1012 what job do you do/have?

[@TimeWasted8675309]

Dave, you are reading my mind. THANK YOU for this video explanation. I have only used analog scopes and recently bought a new digital one and thought it had a defect because it looked so noisy.

[@DeeegerD]

All of us poor buggers that wish we had a scope look at Dave's bench and think "He has more scopes than a big game hunter!"

[@GoldSrc_]

You can always get a cheap analog scope.

[@DeeegerD]

I finally got a scope (Siglent 1102CML). Dave should do a review on Siglent.

[@GoldSrc_]

Digger D I bought today a Kenwood 20MHz scope, I was going to get a Tektronix 60MHz one but the guy sold it and I only was able to get the Kenwood one xD. There's something about analog scopes that I love.

[@AxelPLasg]

Digger D I got myself SDS1052DL when I had no money, now I'd get 1104 or somethin. It's not that good but enough for me.

[@DeeegerD]

I think most inexpensive 50 and 100 MHz scopes would be fine for most hobbyists. I'd still like to see a Siglent tear down :)

[@petersage5157]

My Rigol 1054Z shows the same consistent noise as the one Dave got a few years after he made this video. I've managed to determine that this "noise" is a 250MHz sawtooth wave about 10mV p-p; it isn't random. I'm not sure if it's sampling noise introduced by the ADC or switching noise from the power supply riding one of the voltage rails; either way, it seems to me this is something that could have been snubbed in hardware or filtered out in software. So high above its specified 50MHz bandwidth; you'd think the designers wouldn't want it showing up on a trace.

[@Foche_T._Schitt]

Your camera set up reminded me of something. >Be at fleamarket. >Pick up CCD camera on table full of junk. >See it's a 55mm f1.2 Nikkor O (oscilloscope lens) >Price 2 dollars. >Know more than enough to know it's a fast lens. >Before I can pull out wallet seller says you can have that for a dollar if you can use it. >Maintaining poker face as hard as possible 😐 >Hand him a dollar and say, "I'm just buying it for the lens, you got anymore of these?" 😐 >"No that's the only one." 😐 >Get home and look up lens. 500-600 dollars. 🤑

[@leecampbell9498]

I've been searching for these answers to why digital scopes do this. This is awesome. One of the simple things I want to use a scope for is just to find clipping of an analog audio frequency waveform.

[@remy-]

You saved my day. Something with a very expensive new scope, high expectations and too less experience (but much motivation to learn)

[@fifteenfootflacid]

I just stumbled upon this universe of oscilloscopes, and as a musician and sound design hobbyist, holy shit if this isn't interesting. I love that there's a universe of people doing the inverse of what I'm doing, and that in this universe and that this universe had their own arguments about analog vs digital, just like in the music universe I reside in. I am going to buy an analog oscilloscope, and I may quite possibly get tangled up in this universe I stumbled upon as well. If so, thank you for being part of my future universe.

[@dave-d]

Excellent work Dave. Really appreciated.

[@neptunevibe]

8:07 "you gonna be able to see it! watch!" .... yeeeeeep... I've seen it very very clear!

[@jotaemebee]

There are lots of ways to explain something, and after all those ways, there is the Dave-Way to explain things which of course, is the best of all... Bravo!

[@mikemullenix6956]

Excellent explanation of digital vs analog. You hit a home run with this one !! Thank you

[@johnfranks]

This has driven me bananas on my Rigol for years. I had a basic idea of what was going on since turning on BW limit and shortening the memory depth cleaned up the trace, but I never knew why noise was ALWAYS present. Thanks.

[@Conenion]

Thanks for explaining this. Well done!

[@famossfla]

Great explanation Dave. Thanks for sharing....

[@VK5ZSH]

Nice, thanks for sharing Dave

[@ObligedTester]

Thank you for these great videos!

[@channelengineer]

great vid, just back from national electronics week here in uk and while I was there over heard some old guys raving over how analogue scopes are much better, man just cant see it myself and this is just more proof why, sometime I think they get stuck in the past

[@RyanJensenEE]

This is awesome. Thanks for educating me!

[@TheDyingFox]

I've always thought about it in this way: The more "noise", the more sensitive the equipment is at picking up data... (Camera, Audio recorders etc...)

[@mpag6195]

Thank you. I did not know this. been using an analog scope my whole life and never wanted to switch to digital before this.

[@DIYerGuy]

Absolutely Brilliant Dave ! You're the Best !

[@jeanious2009]

Nice, thanks for sharing Dave,

[@SomeGuyInSandy]

Very cool video Dave!

[@PeteSnipe]

I was thrown by the 'noise' on a new Rigol . That was overshadowed by two probes that created large glitches when the leads were moved. Telonic (UK) listened and replaced the probes under warranty. I'm now very happy with the scope and have accepted this facet of digital scope use. Nice vid explaining this non issue,

[@SaeligCoInc]

Good stuff, Dave!

[@dennis2494]

Thanks for the explanation, with a good demonstration.

[@davidgoadby]

Brilliant! As a recent buyer of a digital 'scope I was ready to send it back to the supplier because of the noisy traces. Now I understand what is really going on, the analogue 'scope will go into the skip - well eventually ;-)

[@erikbruus]

Great video. I am very impressed. Best regards Erik.

[@michaelhawthorne8696]

Nice video Dave. As someone who has been brought up on Analogue scopes, Gould, Hameg, Tektronix, etc....having to use a Tektronix 720 Portable Digital was quite worrying. I have been fooled into thinking my circuit I was fault finding on was worse than it was. I saw many times on your videos, the apparent noisy waveforms you seemed not to be worried about and thought why was this.... This video has helped enormously. Thanks again Dave.

[@hairypaulmm7wab195]

Good demo and excellent explanation. Nice one Sir :-)

[@SlyPearTree]

I have a Tektronix TDS 210 that I bought brand new way back then, weirdly enough it's about at the time I stopped doing electronic. Now that I'm back in the Hobby I'm very glad to have it. It still works great.

[@crohkorthreetoes3821]

Super useful information, thanks a bunch!

[@bflmpsvz870]

Dave you saved my day. I thought my new MSO1104 was faulty. I know now it is only more sensitive and just found High Res Acquire mode that shows graphs I expected. Thanks!

[@PafiTheOne]

Actual AC RMS input noises I've just measured @ 5, 10, and 20 mV/div: - Tektronix 454 (150 MHz, on Ch1 output): 60, 80, and 110 uV - Keysight DSOX1102G (2 GS/s, 70 MHz) : 120, 180, and 400 uV - Siglent SDS1204X-E (1 GS/s, 200 MHz) : 120, 50, and 400 uV The strange (and strongly varying) result on Siglent at 10 mV/div is the result of quantization error. The thermal noise rarely reached the threshold of 1 LSB, therefore it was truncated to 0 too often to get a correct measurement. And this is exactly the reason why noise of a digital oscilloscope must be higher than one of an analog equivalent.

[@Jonathan-xe4ec]

"There's a myth about oscilloscopes that will not go AWAAAAIIIIII!!!"

[@g0fvt]

Great video, makes the point well.

[@mixolydian2010]

Thanks Dave, point taken. Cheers

[@helifynoe9930]

Thanks bro. I am an old timer who has used nothing but analog scopes, so I had no idea that square noise ever existed. LOL

[@davidwoodbridge862]

Analogue grey beard here. Just bought a DSO because the old 20MHz unit lacks bandwidth. So, now I know why it appears to be noisy, thanks!

[@jusb1066]

very nice work dave

[@JustinAlexanderBell]

Thanks for the great video, learning all sorts of things.

[@redtails]

8:38 very nice way of showing your point

[@TechTins_Projects]

Fantastic video!

[@TheWeepingCorpse]

I'm a software guy these days but I never knew about the camera hoods for scopes, very interesting video mate.

[@snaprollinpitts]

thanks Dave, I learned something, great video!!!

[@ohaya1]

Very helpful, thank you. I was interested in this as I am a 'young player' and recently purchased a Hantek DSO 2D15 which seems noisy.

[@johngarret9215]

Could have been a great video but those no signal tests should have been done with terminated inputs on the scopes aka grounding caps. Is the noise we see being picked up by the little BNC stub in the female socket on the scope? It's high enough frequency noise that the connector probably makes a good antenna. Or is the noise from the A/D converters or numerous processors in the digital scope. Without grounding the inputs all the data is invalid.

[@RetroSwim]

Makes me kinda sad to hear the DS1052E being called a "cheap old" scope. It still does alright!

[@EEVblog]

Yeah, but it's around 7 years old or so, that's more than a lifetime in this market.

[@M6MDR]

I purchased a Hantek 100MHz scope about a year ago and I honestly have to say that it's the best piece of kit I've ever spent money on. While it isn't super top of the range, it's certainly more than adequate for my needs at the moment. I would really love to get a network anayliser next but sadly, I couldn't even afford the dust cover for one lol.

[@mikemullenix6956]

Its interesting that digital osc's have done exactly what digital cameras have done. As time passes they get higher and higher resolution and now have extremely high resolution. I come from the old school of film and large format. Digital is the only way to go now.! The difference however, is that film started with higher resolution and digital cameras had to catch up. Additionally, osc' s try to emulate there analog counterparts. The same thing happened to digital cameras emulating film.

[@bsodmike]

I just realised that Dave took his shirt off to capture the analogue scope. Haha...

[@vehasmaa]

Nice explanation of "noise" on scopes

[@FurkanBahadr]

wow this one is super helpful for engineering students like me :D now the errors are more explainable to instructors :D

[@micaiaskauss]

Very informative, Dave. Thank you.

[@Razor2048]

With the money they charge for modern scopes, why cant they put a 2560x1600 display on them and get closer to around 260-300ppi? I high pixel density display on a smartphone of around 5 inches, is often around $50 With oscilloscope companies getting number happy and charging nation state bankrupting prices for their scopes, they should at least be including a high resolution display.

[@redtails]

The asic doing all the signal processing from memory is in essence also producing the waveform display. The asic is the limiting factor for display resolution. Accommodating a larger resolution would mean the entire asic would need to be an order of magnitude more powerful. Besides, if the ADC is doing 8bit conversion, you'll only get 256 lines of vertical position. Increasing the resolution does not increase the adc bitrate

[@Razor2048]

But it will allow for less graphical aliasing of the lines. Think of it like when you move from a 1920x1080 display to a display that may be only 1-2 inches larger but the resolution is 2560x1600, and you suddenly don't need enable antialiasing, (or at most, only need around 2X antialiasing in order to make things smooth. The points of data making up the waveform or anything else being displayed may not increase, but things will look smoother. It will also make the text and other GUI elements look much better, or allow for more efficient use of the screen space, by making smaller GPU elements that are still easily readable. For the prices these companies charge for high end scopes, they should throw in a R9 290x while they are at it, just so it can drive the display a little better, and also mine bitcoin while you are while you are using the scope.

[@BDBK666]

***** Is there a good reason why they can't make that a 12 or 16bit ADC, or is it just not needed?

[@redtails]

Razor2048 It's not aliasing, the asic displays only absolute data points (data events that it registered and stored). Each pixel on the display is an actual data point (or combination thereof). Interpolating your data is the same as data manipulation.. You use an oscilloscope to get answers, not to get pretty interpolated lines. You can compare this to upscaling photos from a 1.2mpixel webcam to 5mpixel. With some smart algorithms and aliasing, you can probably get the image to look nicer, but it's not giving you more information

[@redtails]

Kevo F I think Tektronix has a couple of 12 bit oscilloscopes, maybe also 16 bit but I'm not sure. They're not really necessary, thus not very popular. With increased bit depth, you lower your noise floor, but decrease sampling speed (and probably increase costs). With increased bit depth, you also make quantification a bit better. It's not very common that the noise floor interfered with what you use the scope for. And an oscilloscope is by nature not a quantification platform, even if it is possible to do that

[@bakupcpu]

Awesome video! I didn't know that. Although I prefer and use digital scope all over my lab and chop :) Cheers and thanks for sharing!

[@dorbie]

Brilliant video.

[@pexoto5093]

18:09 - "Huh?" 18:12 - "No way..." 18:21 - "oh my that has to be the most beautiful thing i've ever seen"

[@whitcwa]

For my first digital scope I bought a Tek 2232 which had analog and digital modes. For some measurements with noisy signals, analog was better. One analog technology not mentioned is CRT storage. I have a Tek 7834 which can capture single shot waveforms at high sweep speeds, but its best use is as a long persistence display for a spectrum analyzer plug-in.

[@Roxor128]

When I spotted this I wondered "Is it because the digital scopes are more sensitive than the old analogue ones?" Seems I was on the right track.

[@GiNodrog]

Just as an extra and I belive worth a mention ! My ex students had problems with digital oscilloscopes with digital aliasing ! "The wrong time base setting would sample incorectly and would look like the wrong frequency on the display" where as good old analogue scopes wouldn't do this!

[@listerdave1240]

Funny coincidence looking at the stack of equipment, I have a Rigol DS sitting on top of of a Tektronix analog scope sitting on top of a Tektronix TDS. Not the exact same model numbers but close enough to catch my attention - 1052E, 2215 and TDS 784C.

[@runforitman]

that temperature waveform palette mode is incredibly useful seeming instead of losing the noise information to gain the average information, you can see both

[@Thanson199415]

Nice you got nearly the same analog Tektronix oscilloscope like mine, but mine's 2205

[@binaryglitch64]

It's not the analog oscilloscope that 'hides' the actual noise that IS in your signal, nor is it your eye, it's your how your brain processes images that's 'hiding' the noise. Actually the analog scope seems to be representing the noise much more accurately, it just doesn't bother to fake that noise into appearing longer than it actually does in an attempt to give your brain's slow image processing a chance to catch up, the digits that light up around the line in the digital scopes stay there for 10s to 100s of milliseconds even though that anomaly it's representing is long gone, so if you really want to get down to it, the digital scope lies to you about the signal more than the analog scope, but it does so in order for you to be able to see the truth or rather a closer representation of the truth than your actually capable of seeing... so in the digital scopes defense I'd say it's not the scopes fault your slow, but at least it tries to compensate. And in the analog scopes defense, I'd say it's not the scopes fault your too slow to see it, at least I showed you the noise for the tiny fraction of time it was there, but I'm busy capturing tons of info, I don't have time to make up for the fact that you can't see something that was only there for like a millisecond or two. Also I think the time lapsed analog was way more beautiful to look at than the digital scopes representation of the actual noise that does exist... now I want to design an analog scope that has a time lapsed display feature, that would be awesome. Granted I'm speculating a lot here but I feel it's mostly common sense concluded/drawn from the evidence you are providing.

[@crasbee]

Looking at the time on the oscilloscope is kinda weired. In Germany, it's now 13:21 and the oscilloscope shows 18:13. The same day :D

[@RyanVasquez6089]

This is excellent @_@ i learned so much today

[@886014]

Thanks very much, that was absolutely brilliant. My old Tek 'scope just blew up and I'm trying to get my head around the new entry level digitals So if a manufacturer offers 3 oscilloscopes in the same series, let's say Hantek 5000 series, the only difference is the memory depth, the DSO 5102P is 40K, the 5102M is 1 M, and the 5102BM is 2 M but they should otherwise be identical. If they were all lined up in a row, the 5102BM would appear "noisier" than the M, and the M would appear "noisier" than the P?

[@williamhayden7711]

I like the fact the digital scopes are so much smaller and lighter. As Dave can attest work benches get crowded and having a few extra inches on your bench is a huge help.

[@KrotowX]

That is. I like analog scopes. But have no room for them at my home workbench which even almost have no space for digital scope.

[@MyCrazyGarage]

Interesting Video!

[@petersage5157]

Any application I would have for an oscilloscope would only involve audio frequencies perceptible by chordates. Within this frequency spectrum, what advantages do DSOs offer over analog CROs?

The best thing with the Tektronix 2225 ,50MHz is that is has no fan, -perfect for does late night operations.

[@howitzerm777]

this is so cool!!!

[@redtails]

20:35 oh god lol, I was really hoping you weren't going to tell me those ridges were for long exposures

[@laernulienlaernulienlaernu8953]

But depending on what you are probing and if you know roughly what you’re expecting, could the analog scope be more easy to read coz it’s kind of filtered out the noise?

[@knottreel]

That's my feeling as well. It's kind of like seeing too much detail in a photo, so photographers sometimes add a little blur to make the photos more readable.

[@basspig]

So given all the visible noise on digital Scylla scopes, how does one differentiate between a noisy audio amplifier stage and the noise in the aucilla scope? With my analogue 20 to 65B, I can see if an amplifier stages putting out a pure sine wave or has some noise on it. But these scopes have noise on the sine wave no matter how clean they are. And the other problem is the low resolution of these displays exacerbates the noise I think that's the real reason why these scopes look noisier. These displays in 2020 should be able to show 300 points per inch Just like our smartphones do. It's ridiculous that and over $10000 instrument is stuck in 1990 as far as display resolution.

[@junkerzn7312]

Oh neat. On my Siglent 1202X-E I got a variable result. The color grading worked as expected, but the intensity really did not. It just uniformly dropped the intensity of the waveform on the display... made the whole thing uniformly more or less bright but didn't make the waveform look any thicker or thinner. Averaging mode worked quite well on its own but didn't change how intensity worked. -Matt

[@Robbie1949]

I bought a Hantek digital DSO5202B 100 Mhz scope some years (9) ago when Silicon Chip paid me for an article. I find I still prefer my many Tektronix analogue CRO's to do most servicing work and it's not about the perceived noise. I am in general not looking for a random event but signals that are repetitive so a digital storage scope does not usually help me. I bought the instrument in order to capture pictures of waveforms to include with electronics articles. I believe in some procedures the analogue scope does a better job.

[@reotrb]

This was a brilliant video Dave. Thanks!

[@marvinmoss8127]

Why does my digital scope shift the trace when I increase the sensitivity of the input channel with no input? My old Tek scope has a DC Balance adjust so the trace is at the same place no matter what the vertical sensitivity is set at.

[@fichambawelby2632]

As ever, excellent demonstration, Dave. I also have both analog and digital scopes (mainly from Tektronix), and I always thought that another huge difference besides to the screens; phosphor ones -no "squares"-, and LCDs -a matrix of squares. In fact, I love the old CRT tubes for this matter. The new scopes didn't have a "super-retina" display, so we will see squares in the round parts of a waveform.

[@MinhTran-wn1ri]

@9:11 The wider the scope bandwidth, the more noise you'll see. Analog scopes don't have as wide a bandwidth so higher frequency components (such as noise can't be recorded)

[@MichaelSchwagerPlace]

Wow. Super interesting! Thanks. I was just wondering today why my ds1052e had such a fat ugly line. Now I know it's my fat ugly circuit. :-)

[@ilia-ned]

Thanks from 2020!

[@dakata2416]

The thing I don't like on the digital scopes is the slow refresh time & resolution of the display.

[@skoronesa1]

Short answer is, the noise was always there, your "ear" just wasn't sensitive enough to hear it. Modern scopes aren't noisier, they are just better at picking up and displaying more of the signals floating around. Basically, they're doing exactly what you want them to, show you what's going on.

[@RFC3514]

21:40 - "Low shutter speed" should actually be "high(her) shutter speed". And "as you increase" should be "as you decrease". A 1-second shutter is (fifty times) slower than 1/50th of a second shutter, so you're decreasing the shutter speed (or increasing the exposure time).

[@thomasmaughan4798]

It is likely (hopefully) the case that a tiny signal averaging 1/2 least significant bit is added to the input to "dither" around the LSB. Without it, you get a huge step increase going from zero to 1 but your signal might have only gone from 0.99 to 1.01 So a non-harmonically related sawtooth, or just thermal noise, (random but at least non-harmonic) noise will, for instance, at one moment in time be 0.95 and now your tiny signal is enough to push it over the threshold from a zero to a 1. But a moment later it doesn't. The *average* of these sometimes-0 and sometimes-1 will converge on the actual value. Let's say three measurements of 0, and one measurement of 1, repeat. The average becomes 0.75 and can be displayed as 0.75 which is accurate. This is why (probably) choosing less memory depth on the Tek scope reduces noise; under the hood the sampler is going full speed, and with some dithering noise added to average out the quantizing error, then subtracted. So you might take a thousand noisy samples in extremely rapid succession but store the average as a single sample. The effective ADC bits is increased by doing this; a Keysight DSOX1202 can deliver up to 12 bits of effective vertical resolution even though its ADC is only 8 bits. You get this effect more or less automatically on a Keysight (unless you tell it not to); it optimizes memory depth based on sweep speed and probable zoom setting. If you want maximum zoom then you'll have to run the ADC at maximum speed and now you're back to 8 bits per sample.

[@gglovato]

when is that Tek 3000 review coming? ;)

[@GeorgeGraves]

What if I don't want to see all the noise? If I pretend it doesn't exist...it just might go away? Right? ;)

[@EEVblog]

Just like on your analog scope, yes, you can make it go away!

[@SantaClaw]

I recommend using black insulating tape, to narrow down the line so it's REALLY thin... Noise is a thing of the past..

[@GeorgeGraves]

***** Will blue painter tape do in a pinch? Oh look...NO NOISE on my 1052e.

[@SantaClaw]

I don't know GeorgeGraves I simply don't know. I've found my scope is compatible with 3m black insulating tape, but 3m "invisible" brand tape had very little noise reducing effect on my scope.

[@matawin2]

Photonicinduction told me to smash the screen with a hammer, it just might help.

[@runforitman]

I'm surprised people jumped to "analogue is less noisy", and not "analogue cant display this noise"

[@mnovo]

Very err, enlightening.

[@johndude70]

Very useful video, I have forgiven my digital scope and we are friends again!

[@Mr2Xri]

Hi Dave, the intensity button that has the RIGOL on top right of the screen it is like a fake intensity adjust?

[@jacks5kids]

This video very misleading. Since he used the 1Mohm input setting, the waveforms shown do not represent the noise floor of the scope, not even close. The noise you see on an unconnected scope is the combination of the the Johnson noise of the input impedance and the random component of the ADC's conversion. If you use a low gain setting (e.g. 1V/div) you mostly see ADC noise. If you use a high gain setting on the scope (e.g. 1mV/div) you mostly see the Johnson noise of the scope's input impedance. To estimate this correctly you cannot just use a the 1Meg input resistance, since this has a shunt capacitance, limiting the effective bandwidth. For example, a 1 Meg resistor with a 1GHz bandwidth, has a Johnson noise (=sqrt(4kTRB)) of about 4mV rms, or more than 30mV p-p for most settings that he used. But since the input capacitance is about 10pF, then the effective Johnson noise is sqrt (kT/C) = 20 microvolts. For any serious look at the noise level of an unconnected scope you must therefore use the 50 ohm input option, and Dave did not do this for this video, resulting in conclusions that are both misleading and irrelevant.

[@CraigOverend]

Would be nice to see a comparison with an analog MCP (microchannel plate) CRT scope like the Tek 7104 or 2467 series.

[@user-dn9tb3ol8f]

It is not a mif, it is reality! Dave, you're wrong. DSO noise has two components - analog and digital. Analog oscilloscope has only one component - noise of analog tract. It's very simple.