outgrowing 100MHz scopes as a beginner? - Page 1
Forum section: electronics / beginners

author: albatros
author_rank: Newbie
timestamp: October 05, 2020, 03:33:44 pm
content: Hello good people!I've been lurking the forum for a while and I know every couple weeks there's a length discussion on a new topic which is always almost about which oscilloscope to get... and this might hopefully be a bit differentWhat I did not find in either of them is the answer to the question: when would you need a better oscilloscope than a Siglent SDS1104X-E? What type of circuits would a beginner do that this scope would not fit well?Most other topics on this subject have constraints like "I can't spend more than $X" but honestly it does not matter for me if it's $400 or $1000 as long as it does the job. Obviously $4k would be an other topics, but just keeping on reality, spending $1k on a hobby is OK.For comparison sake I can get the 1104X-E for 429 EUR while the 2104X Plus would be 1199 EUR. The former can be hacked up to 200 MHz while the latter can be hacked up to 500 MHz, so it seems like a better buck for the money?Does it make sense, as a beginner, so spend the extra money or I am not gonna run into any type of circuit where I would be like damn, would be great if my scope would do <X>?Thank you!

author: ledtester
author_rank: Super Contributor
timestamp: October 05, 2020, 04:07:27 pm
content: QuoteAs a beginner I'd stick with the 1104 and make sure I had some good multimeters, a good soldering iron, a good power supply (or 2 or 3), maybe a hot air station, a function generator, other tools used in building circuits ... before I spent more money on a higher bandwidth scope.Just pointing out that there's a lot of things to spend money on in this hobby and you'll use some of them -- e.g. the multimeters, power supplies, soldering iron, wire strippers -- a lot more than you'll use the scope.

author: MosherIV
author_rank: Super Contributor
timestamp: October 05, 2020, 05:28:12 pm
content: HiWelcome to the eevblg forum.Measuring signals above 500MHz is really difficult!You pretty much have to design the circuit with measurement in mind with the right pads.So my opinion is that 100MHz is good for 90% of things you want to measure.200MHz if you want to be fancyOnly if you do rf (radio freq) stuff would you need the 500MHz or above

author: HB9EVI
author_rank: Frequent Contributor
timestamp: October 05, 2020, 05:48:43 pm
content: I'd say: it dependsif you are planning getting into hamradio or in general RF technology, I'd go directly for the higher bandwidth scope; otherwise a 100MHz scope is likely to be sufficent.

author: rstofer
author_rank: Super Contributor
timestamp: October 05, 2020, 06:07:01 pm
content: I think you can buy the SDS 1104 X-E and unlock it for 200 MHz, details over in the Test Equipment forum.Four channels is great, for decades all we had was two. Up until I bought the Rigol DS1054Z, all I had was a 2 channel 350 MHz Tek 485 that I bought for about $200 on eBay. This replaced a 2 channel 10 MHz Heathkit scope. The 350 MHz bandwidth was fantastic but it only solves bandwidth. Today we want to talk about decoding, single shot capture, dozens of different measurements and a host of other features that simply can't be provided on an old CRO.I bought 4 channels because I wanted to decode SPI more than I wanted to hold on to the money. Remember, I already had the Tek, I didn't think I needed the features of a DSO. I was wrong! The modern DSO is magic!Unlocking the DS1054Z from 50 MHz to 100 MHz seemed like the thing to do but even the 100 MHz isn't all that much bandwidth if you are interested in square waves. It's fine for sine waves even higher than 100 MHz (real -3dB bandwidth is probably closer to 130 MHz) but for square waves, it might only be good for 10 MHz depending on what you expect to see. Stuff a 100 MHz square wave into a 100 MHz scope and all you get is a sine wave on the screen. The square wave has a lot of harmonics (technically, a 0 ns rise time signal will have all of the odd harmonics from DC to daylight - a really high frequency). With a 100 MHz scope, you can see something that resembles a square wave if you include up to the 9th harmonic (a 10 MHz signal into a 100 MHz scope) so, what you see on the screen is only a figment of your imagination.The real question is: Does it matter? For my projects, I seldom see off-board signals greater than 50 MHz and that is rare. Mostly, I look at signals in the mid to high kHz range and low MHz every once in a while. But that's because I am not testing the signal integrity of the memory bus (or whatever), the development boards I select will already have that stuff squared away and I'm unlikely to design a board from scratch.More often than not, I take a 'stamp' form factor board, like the Teensy 4.1 and plug it into a daughter card. All I have to design is the low frequency peripheral signals. The DS1054Z is more than adequate.You can't argue against bandwidth - more is always better. Two channels versus 4 is equally debatable. We got along without 4 channels for a very long time.Risetime is the real criteria, not bandwidth but they are tied together by a constant: BW = 0.35 / RT where BW is the bandwidth in GHz and RT is the risetime in nanoseconds.Look at the Rigol DS1054Z specs and you will find that the 100 MHz variant has a rise time of 3.5 ns (result is 0.1 GHz or 100 MHz). What's important is that risetime is 'calculated' and 'typical'. They lock in the bandwidth to 100 MHz and then calculate the rise time.

author: rstofer
author_rank: Super Contributor
timestamp: October 05, 2020, 06:37:35 pm
content: Despite the wall of text I posted above, I think that the SDS 1204X-E would be my choice. At the time I bought the DS1054Z, it didn't exist. More likely, I would buy the SDS 1104X-E and unlock the 200 MHz bandwidth. I would still want 4 channels and 200 MHz is always better than 100 MHz (unlocked DS1054Z). I don't know anything about the X Plus models but by the time you have the required options, that SDS 2104 X Plus is VERY expensive.At the entry level, there is a tendency by the manufacturers to unlock most of the options (other than bandwidth) for free. If you want to unlock bandwidth, you need to do some homework. First, see if it is even possible.Dave did a video about MSOs and he is not convinced, at least for the entry level scopes. I suspect a decent logic analyzer is a better way to go but, again, it depends on what you want to do. At 8:30, Dave talks about the lack of a state clock input on MSOs and this seems to be fatal for my purposes. I work with FPGAs and I often send the state number and state clock to the logic analyzer.The DS1054Z is now selling for $349 at Amazon. That's a pretty spectacular price for a 100 MHz 4 channel scope (after unlocking) even if the user interface is a little slow. People bitch about it and they're right, it is slow, but the real question should be: "What percent of the time are you twiddling knobs compared to viewing the result?". What difference does it make when you probably spend less than 1% of the time with the knobs and it's increased to 2%.Yes, the Siglent is reported to have a much better user interface and it would be my choice today.

author: bdunham7
author_rank: Super Contributor
timestamp: October 05, 2020, 10:13:02 pm
content: Quote from: albatros on October 05, 2020, 03:33:44 pmYou are more likely to run into a situation where you know your scope can do whatever you are trying to do but the UI makes it difficult to find. The 1104X-E does everything I can ask of a basic scope and more, although I cannot comment on any decoding or logic analysis functions. I would say buy that and spend some money on probes, adapters and maybe even a differential probe or Siglent's IFE (Isolated Front End). And if you already don't have a function generator, the matching SDG2042X will bring your bill to about $1000 USD (sorry, I know the CAD exchange rate sucks). And you can entertain yourself by hacking both.As far as a situation where your scope can't do something, what other equipment do you already have? And what do you intend to do? You will probably run into situations where you need other things many, many times before you get to the point where a better scope is what you need--again, unless you are looking at decoding or logic, in which case I have no idea.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: October 05, 2020, 11:48:21 pm
content: I have owned maybe 20 scopes.In today's world, I think a good used 500 MHz scope with the correct probes is probably the standard for advanced users. You really need the proper probes. Very important.On the other hand, I have used old grossly uncalibrated analog scopes with good results, i.e.I got the job done.However, more and more I rely on spectrum analyzers using the scope probes....About the comment about measuring anything over say 500 MHz is difficult with a scope, I would say he has an excellent point.I think a good rule is to buy something that has near twice the bandwidth you need, the scope will have an easier time making a picture on the screen. The probes will be better...Look at what you are going to work on, HAM HF equipment?? Microwave?? Then make a judgement. 100 MHz is OK for HF radio equipment.If you are into GHz stuff, get a good Spectrum Analyzer.If you plan on doing audio stuff, I think a lot of audiopholes use old analog scopes maybe even down to 10 MHz units. They prefer them.For $1K you can get a good used scope and a good used spectrum Analyzer and maybe some more stuff.The new scopes have a spectrum analyzer built in Fourier Analyzer, not as good as a Spectrum but quite useful.Mixed signal scopes are OK for logic circuits, but you can probably get a separate ( computer based ?) better logic analyzer much more cheaply.A regular scope will show you as many logic outputs as there are channels.If you are a beginner... I tell people who have some financial resources that they should buy a good used scope with probes cheap, even a 30 or 60 MHz scope, even an analog scope. If you buy one for say$200 (probably a lot less) and want something else, you can most likely get most of your investment back.. pretty cheap education, less than an hour of university credit. If you buy a new one and do not like it,you are probably out half the money.A scope is a really fun thing to have when learning. When most of us here started, these things were as much as a used car.Watch the for sale listings on this site.