Silly question about oscilloscopes - Page 1
Forum section: electronics / testgear

author: lordrafa
author_rank: Newbie
timestamp: September 09, 2021, 03:45:53 pm
content: Hello everyone,I was considering to buy an oscilloscope but it cross my mind a very silly question, what can I use it for?Let me explain myself, I have played with oscilloscopes before and I have a perfect idea what they do but when it came to what can they offer to improve my lab I am not sure what to say.I normally use a logic analyzer, a multimeter, a Usb-UART and a JTAG to debug my hobby projects and to fix random circuits but I am not sure how an oscilloscope could help me with this.For example, nowadays I am trying to fix an old Playstation 2 that doesn't boot, I have use the logic analyzer to watch the buses communication between ROM and CPU, the multimeter to measure the power rails, the UART to check debug messages, and if the specs were available (which I think they are not) I could use a JTAG to see the firmware exec.... but how an oscilloscope could help me fixing this?

author: Kleinstein
author_rank: Super Contributor
timestamp: September 09, 2021, 03:55:47 pm
content: An oscilloscope can give the information about the logic levels. So check if the voltage is right and also the timing can be seen.Checking for ringing (termination working) is another point - way back it was an issue with SCSI interfaces for extrnal and internal hard discs.However for modern relatively fast logig signals it may need a pretty fast scope and good probes to really get relevant timing informatoin.Another point is checking the supply voltages for ripple (e.g. bad caps).

author: Fungus
author_rank: Super Contributor
timestamp: September 09, 2021, 03:58:26 pm
content: Quote from: lordrafa on September 09, 2021, 03:45:53 pmThe logic analyzer won't tell you the voltage levels on those rails, if the signals are nice and square or if there's any noise on them, etc.Oscilloscopes give you more information to work with.

author: Old Printer
author_rank: Frequent Contributor
timestamp: September 09, 2021, 04:17:36 pm
content: One isolated case in point does not give us very much to go on. A detailed description the the types of circuits you use, and expect to use, would be necessary for any useful answer to your question. Pretty much, if you truly understand the oscilloscope, and don't know what use it would be to you, it's unlikely you really need one. Wanting one is another matter entirely, you don't need a reason, just money.

author: lordrafa
author_rank: Newbie
timestamp: September 09, 2021, 04:34:53 pm
content: Thank you guys for your responses.The problems that I see is that even in an old piece of hardware as it is the Playstation 2, some of the buses works at quite high frequency (hundreds), modern signals can work over 1ghz and any oscilloscope that than measure them would be crazy expensive.Of course there still several buses that still working at several tens or less. Check the supply voltages for ripple for bad caps is something that can be interesting too...The kind of projects that I normally work are arduino/esp32 related and from time to time I enjoy tearing a part any victim that comes close to my work desk () to get a better understanding about how it works and "fix" them.....With this in mind now I am a little bit more convinced about what an under 200mhz can offer. I would expect to been able to monitor SPI signals, UART, I2C, PWM and some parallel buses analyzing that they are within it operational ranges but I can forget completely about monitor a RAM bus, any connectivity between GPU/CPU, or try snif a MIPI LCD...This lead me to the question, it is better to have more channels and msps with a 100mhz oscilloscope or have 200mhz oscilloscope with two channels.... I didn't have that much experience with real world projects, what have you found with? do you think that they are worth?PS: Old Printer you perfectly nail it. This is all about money, if I just could spend 20k in a good oscilloscope and forget about cost-utility I would be more than glad

author: Old Printer
author_rank: Frequent Contributor
timestamp: September 09, 2021, 05:20:40 pm
content: There is a series of videos on YT by a retired EE who is evaluating the Rigol MSO5000 for educational purposes on embedded systems. This is a link to the beginning of the series. I think you would come away with a good understanding of the usefulness of a modern scope that is pretty affordable, about $1000 US dollars.

author: xrunner
author_rank: Super Contributor
timestamp: September 09, 2021, 05:25:23 pm
content: Quote from: lordrafa on September 09, 2021, 04:34:53 pmI've used four channels at times, but not often. So me - I'd get the 200 MHz with two channels.

author: Fungus
author_rank: Super Contributor
timestamp: September 09, 2021, 07:15:02 pm
content: Quote from: lordrafa on September 09, 2021, 04:34:53 pmSo will a logic analyzer.Quote from: lordrafa on September 09, 2021, 04:34:53 pmThere you go! You answered your own question.Quote from: lordrafa on September 09, 2021, 04:34:53 pmFor "Arduino"? Definitely 4 channels minimum, 100Mhz is enough.

author: Trader
author_rank: Frequent Contributor
timestamp: September 09, 2021, 09:07:30 pm
content: Rigol DS1054Z has several serial communications protocols, is better an 4ch 100MHz scope than a 200Mhz because the bandwidth is not so significant (and the Rigol DS1054Z can do well up +150MHz), the 4ch is very useful.

author: james_s
author_rank: Super Contributor
timestamp: September 09, 2021, 09:21:32 pm
content: Generally you should buy a tool when you have a need for it, not buy a tool and then go searching for a need, that is the tail wagging the dog. My scope is my second most used instrument behind my multimeter, I have a logic analyzer but I only rarely use that.

author: kcbrown
author_rank: Frequent Contributor
timestamp: September 09, 2021, 10:09:01 pm
content: Quote from: Trader on September 09, 2021, 09:07:30 pmThese days, for an entry level scope, I'd go straight for the Instek GDS-1054B. It's way more responsive in its UI, its decoding capability is implemented properly (it decodes everything in memory, not just what is on the screen, and that can be important for protocols that have start indicators), its FFT is excellent, it does arbitrary math, etc. Costs the same as the Rigol DS1054Z nowadays as well. For a time, it was possible to get one for less than $300, but not currently (that I've found).To the OP, you will know when you'll want a scope. It'll be when you've got a time-varying signal that is misbehaving and is either analog (such as when you're attempting repair of an audio device) or is behaving strangely in a way that can't be explained by a logic analyzer. Admittedly, scopes are very cool devices, though, so if you've got the money and want a cool piece of test equipment to play with, an inexpensive but highly capable one (like the Instek above) is certainly a good way to go. But if you're on a budget, then I'd refrain until the need presents itself.

author: lordrafa
author_rank: Newbie
timestamp: September 10, 2021, 12:01:41 am
content: Thanks for all your responses actually I found really useful Old Printer link to the MSO5000 series. Now I have a much better understating about what an oscilloscope can offer.Also I have discover that surprisingly many oscilloscopes can be "hack" to get better version. i.e. the "MSO5072" can be updated to the "MSO5374". With this in mind is there any 350mhz (or 300) hackeable oscilloscope with 4 chanels for around 500€?The GDS-1054B looks hackeable and the DS1054Z too but which oscilloscope give you the best for 500€ (or less)I agree with many of you that first is the need and after the tool but if I don't know how the tool can be used to solve problems, how can I know if the tool can satisfy a need... after your answers now I am sure that it would be really useful in many situations but still I need to get the best tool for my budget...

author: David Hess
author_rank: Super Contributor
timestamp: September 10, 2021, 12:10:04 am
content: The most common things I use an oscilloscope for are digital signal integrity, digital signal levels, frequency compensation including regulator stability, glitch hunting, gated measurements, noise measurements, and timing measurements including jitter.

author: Trader
author_rank: Frequent Contributor
timestamp: September 10, 2021, 12:20:20 am
content: Quote from: james_s on September 09, 2021, 09:21:32 pmI think he wants to buy an instrument to anticipate future hobbyists projects.Quote from: kcbrown on September 09, 2021, 10:09:01 pmhttps://www.eevblog.com/forum/testgear/instek-gds-1054b-vs-rigol-ds1054z/msg732890/#msg732890

author: tautech
author_rank: Super Contributor
timestamp: September 10, 2021, 12:46:07 am
content: Quote from: Trader on September 10, 2021, 12:20:20 amYep seems so however a 300+ MHz design with 4 channels under 500 Euro just won't happen.Beyond ~200 MHz requires 2 GSa/s ADC's and that bumps pricing up some.Eg. The 2ch 200 MHz SDS2202X-E is a 350 MHz design is $619 getting on for double the price of a SDS1202X-E.

author: lordrafa
author_rank: Newbie
timestamp: September 10, 2021, 03:38:23 pm
content: Thank you everyone with all this information now I have a better understanding about what can I expect from an oscilloscope and price ranges. Now is up to me decide if I should go for a 962€ oscilloscope as the MSO5072 or buy something under 500€ 4channels 100/200

author: james_s
author_rank: Super Contributor
timestamp: September 10, 2021, 06:58:31 pm
content: Quote from: tautech on September 10, 2021, 12:46:07 amThat depends. I paid less than 500 Euro for my 1GHz 4 channel TDS784C, had to do a minor repair on it but it's been a great scope since then. It's a boatanchor but it offers a ton of bandwidth at a price I could afford for a toy.

author: Fungus
author_rank: Super Contributor
timestamp: September 11, 2021, 02:32:41 am
content: Quote from: Trader on September 10, 2021, 12:20:20 amThat link is completely obsolete. The Instek now comes with a complete set of serial decoders, etc.The Instek is a lot more expensive than in the EU. Here the choice is really Rigol or Siglent.Rigol doesn't have a nice 500 Euro 'scope so tor 500 Euros get a Siglent.Siglent doesn't have a nice 1000 Euro 'scope so for 1000 Euros get a Rigol.

author: Trader
author_rank: Frequent Contributor
timestamp: September 11, 2021, 06:31:27 pm
content: Quote from: Fungus on September 11, 2021, 02:32:41 amSiglent SDS2000X Plus

author: marcus h
author_rank: Contributor
timestamp: September 11, 2021, 09:53:06 pm
content: Quote from: Trader on September 11, 2021, 06:31:27 pmI Europe we have way higher sales taxes than you lucky ones in the USA: Germany = 19%, Spain = 21%So all prices I mention here are for Germany with taxes included.Taxes included, paying 1000 Euros gets you the two channel model (SDS2102X Plus).But you have to plunk down a bit more than 1.400 Euros for the 4-channel model (SDS2104X Plus).At these prices I'd rather have a look at the four channel Rigol MSO5074 (a bit over 1.000 Euros).And in no way would I get a scope with only two channels, especially not at 1000+ Euros.

author: kcbrown
author_rank: Frequent Contributor
timestamp: September 11, 2021, 11:03:02 pm
content: Quote from: Trader on September 10, 2021, 12:20:20 amThat's a difficult thing to do. Such projects can cover a wide range of needs. Without some idea of what those projects will look like, then all you can do is point at the most capable and versatile scope available, and that has a substantial price tag attached to it. The alternative is the least expensive scope with reasonable capabilities, which are already under discussion.QuoteThe Instek is hackable. The author of that message doesn't elaborate on what the Instek in its fully-hacked form is missing that the Rigol has.The Instek is the same price (from Sealig or Tequipment, at least. Don't know what prices are like outside the U.S.), is faster, is more responsive, has a better UI (individual channel controls, a separate button to activate selections, etc.) anddefinitelyhassubstantiallysuperior decoding (because it decodes the entire buffer, not just what's on the screen).The Rigol has 2.4x the samples at most. Instek has a consistent 10M samples per channel, while the Rigol can be 12M or 24M depending on which channels are active. Hard to say how much of a difference that really makes. I'd say the Instek's memory is adequate, at least, especially for a beginner scope.The Instek's FFT makes the Rigol's look like a joke. It's one of the best.All these factors combined are why I recommend the Instek over the Rigol.If someone can show a substantial advantage of the Rigol over the Instek, I'm all ears. I know of none. At least some of the advantages the Instek has are considerable.I have both. I definitely prefer the Instek over the Rigol, as if you couldn't tell.

author: Fungus
author_rank: Super Contributor
timestamp: September 12, 2021, 06:51:07 am
content: Quote from: marcus h on September 11, 2021, 09:53:06 pmYou can actually buy the Rigol MSO5072 for less money and unlock the other two channels.The downside is you only get two probes with it so the savings aren't much after you go shopping for two more.

author: Fungus
author_rank: Super Contributor
timestamp: September 12, 2021, 06:55:08 am
content: Quote from: kcbrown on September 11, 2021, 11:03:02 pmThe Instek is definitely the one to get in the USA. $300 is a complete bargain.In Europe it's much more expensive so it's not so clear-cut.

author: marcus h
author_rank: Contributor
timestamp: September 12, 2021, 09:08:46 pm
content: Quote from: Fungus on September 12, 2021, 06:55:08 amThat's unfortunately right: The GW Instek can be had for a bit more than 500 Euros in Germany.For that price I would probably rather get a Siglent SDS1104X-E if I were to buy a new scope in that range.The FFT may be not as good as with the GW Instek but it has other advantages:- It can be hacked to 200 MHz (but AFAIK it would need better probes?)- Optional 16 channel logic analyser- Optional function generator

author: 2N3055
author_rank: Super Contributor
timestamp: September 12, 2021, 09:26:16 pm
content: Quote from: marcus h on September 12, 2021, 09:08:46 pmMore importantly:segmented mode2x1GS/s ADCtrue 500uV inputscolor persistenceBode plot (FRA) with compatible AWG.

author: eloso
author_rank: Regular Contributor
timestamp: September 12, 2021, 09:36:31 pm
content: Not a silly question !Neither is it one that really anyone is really qualified to advise on apart from the OP himself who knows what he wants to do - it really is such an individual thing. But what we can do perhaps is just describe our own reasoning for owning our own scopes and which kind of scope suits us.I would be lost without my Rigol DSO2072A (upgraded to DSO2302A). I do lots of digital, general analogue and RF circuitry. I design my own and am often fixing other peoples designs, be they consumer items or more specialist.I would prefer a good fast 2 channel scope over a more mediocre 4 channel scope anytime, despite digital being my thing. Memory depth is crucial to me too.When I want to analyse lots of digital signals all together at the same time I rarely am doing it from the point of view of the examining quality of the waveform - usually its a digital encoding thing and for those jobs I use my cheap and cheerful logic analyser with 16 inputs it usually covers my needs.On the other hand to examine the qualitative characteristics of digital signals I never need more than two channels. Occasionally I use one for triggering and am looking at the other trace to look for abnormalities. Following that I may stick with the same trigger config but probe a different line alongside the previous. And then I might do this again. i.e. my 2 channel scope is being used as say a four channel scope but not all channels simultaneously if you know what I mean.The beauty of modern scopes unlike the behemoths of my youth is the ability to look back in time, not just in the here and now. It is also to freeze the moment in a single shot or to average a signal to get rid of noise. Nowadays we can set triggers and examine the waveform as it was prior to the trigger event. Wow – really useful.We all have different needs but just in case it helps, here are the things I have used a scope for recently listed in no particular order. Some of them you could do with a multimeter, or a logic analyser, some of them only a ‘scope.1. Check for the presence of the right kind of signals on SPI, I2C and UARTs. Quick and dirty just to make sure the software is driving the lines that I think it should be, and that it is doing so at more or less the right times/intervals and that the signals have all the appearance of reasonable quality and proper polarity ones.2. Check polarity of GPIO inputs and outputs.3. Measure RF power output accurately of a commercial transceiver.4. Measure overshoot of RF being fed into an amplifier that was tripping out with an overload indication.5. Look at and measure signals on an RF mixer circuit as part of a fault finding process.6. Set up a mechanical bug key so that its relative timings (mark space ratio of the dots for example) are correct. Very, very slow timebase.7. Check voltage transients on power supply that kept tripping.8. Using a current sense resistor and a differential probe measure inrush current accurately for a device that was tripping its power supply.9. Monitor output from an optical sensor.10 Check the level of back-emf from a relay coil to ensure it doesn’t exceed safe limits.10. Look at key clicks on TX output.11. Quick and dirty frequency counter to ensure xtal oscillator is running on its fundamental.12. Do quick and dirty FFT to check the level of the third harmonic (not a strong point of most scopes but it can be useful)13. Determine the precise trigger point of some comparators14. Design and debug some op amp circuits being used to generate +- 40V ramp testing signals for another circuit under test.15. check for clipping on some AF signals.16 Set audio levels precisely to match an amplifier's input range.And more of the above that I have forgotton about.One important thing to note is that a modern oscilloscope is a fun instrument and to me has always had a kind of magic about it. (Mind you, so easily pleased am I that even a humble DMM has a magic about also!) You don't need to have one - but if you want one and have the cash then get one and have a play.Careful though, this might be the start of the slippery slope leading to Test Equipment Anonymous....Eloso