oscilloscope USB vs. CRT - Page 1
Forum section: electronics / testgear

author: B J
author_rank: Contributor
timestamp: July 02, 2021, 11:22:53 pm
content: Thinking about getting a USB scope and picking up a used lap-top to connect it to. I have two old CRT types that are requiring more time repairing than I like. Is there a good site to go to for pro and cons from people who have made the change? I have found some info., how ever would like to hear from someone who has had experience with both. Looking for a dual channel at about 150 mhz. and nothing fancy, just the basics. Who is selling a good unit? Any thoughts?

author: wizard69
author_rank: Super Contributor
timestamp: July 03, 2021, 12:22:49 am
content: I haven't purchased a USB scope yet but there are several threads on here that go into a lot of detail.As for USB scopes I really believe we have hit an inflection point where, with the advent of USB 3, we now have a common port that is fast enough to do a PC connected scope justice. However not all hardware on the market has caught up, so read the specs carefully. More importantly read about the software and third party support.My interest in USB scopes popped up recently due to the possibility of such a scope being a better device for training. That is having the laptop hooked up to a big screen TV or monitor. Also in the home lab there is a considerable space advantage if you have a PC and a large screen as the central element of the bench. If you are a student the obvious advantage is that you are very portable when moving a USB based scope about with the rest of your gear.Some manufactures:https://www.picotech.com/https://store.digilentinc.com/(sadly owned by national instruments now)https://www.owon.com.hk/list_virtual_oscilloscopeshttps://www.keysight.com/us/en/products/oscilloscopes/handheld-modular-usb-oscilloscopes.htmlOthersThe one thing that surprises me is the lack of effort form the established tech vendors to offer quality PC based instruments. Tektronix and Teledyne for example offer nothing. HP tries but I'm not impressed.So not a lot to say beyond that as I'm looking as much as you are. One big issue for me is software and in that regard I have to dismiss anything that is Windows 10 only and so locked down that nobody bothers with third party software. Which highlights another issue, a used laptop might not be a good idea if it is too limited in performance and will not migrate to Windows 11 well. Performance here means both the USB port and the general system performance. At this point getting to tied to Windows is not a good idea in my opinion either as the transition to Windows 11 may leave a lot of hardware behind.Oh one more thing , you say just the basics but don't highlight expected usage. These days the basics can encompass a lot of non traditional O'scope features. Some of those features can be extremely useful for students and development labs on a tight budget. This is why products from Digilent and other similar platforms, are so popular. Instead of high performance you get a lot of bang for the buck.Quote from: B J on July 02, 2021, 11:22:53 pm

author: bdunham7
author_rank: Super Contributor
timestamp: July 03, 2021, 12:50:29 am
content: Quote from: B J on July 02, 2021, 11:22:53 pmWhy do you want USB vs. a regular DSO?Picoscope makes good units, but they aren't cheap, certainly not cheaper than equivalent full scopes from Siglent or Rigol.

author: B J
author_rank: Contributor
timestamp: July 03, 2021, 02:53:47 am
content: Thanks to both of your replies. You have got me looking into this game from different points and directions. I am just getting in this and have not done as much research as I could. Mainly wondering what others have done and think. As I get deeper into this, I am pleased with some of the pricing I see.My standby (Tektronix RM 546) is really old and quite tired. Now I lost triggering and not sure if I want to put in the time and energy to get her going again. Other than that, and a couple other little things, she still is doing a great job.She is also big and heavy.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: July 03, 2021, 02:59:29 am
content: If you like installing drivers, rolling back windows updates because of compatibility issues, and waiting for CPU microcode firmware patches before you can use the scope for more than 10 consecutive minutes, get a PC-based scope. That goes for the good brands, like Pico, but if you really want to learn the meaning of suffering, get a HanTek. They don't just inherit the PC ecosystem problems, they are also bad at software, and at hardware, and they know that their customers don't read reviews.If you want to push a power button and start probing, get a standalone. Siglent and Rigol make scopes that are cheap, responsive, and have big, bright displays.Just remember, you shouldn't compare the price of a Siglent to the price of a HanTek, you should compare the price of the Siglent to the price of the HanTek that you buy looking for a deal plus the price of the Siglent you buy after you've given up trying to get the HanTek working or return it.

author: Fungus
author_rank: Super Contributor
timestamp: July 03, 2021, 07:17:53 am
content: Quote from: B J on July 02, 2021, 11:22:53 pmWhy? It's going to cost you way more than a standalone and you'll be using a 'scope over slow USB.

author: HKJ
author_rank: Super Contributor
timestamp: July 03, 2021, 07:41:04 am
content: Quote from: jjoonathan on July 03, 2021, 02:59:29 amI have never see that kind of problems and I have been using a couple of Pico scopes for many years and on different computers.Quote from: Fungus on July 03, 2021, 07:17:53 amI have never had any problems with speed on my USB scopes.

author: Andreas
author_rank: Super Contributor
timestamp: July 03, 2021, 08:21:35 am
content: Quote from: B J on July 02, 2021, 11:22:53 pmHello,Guessing that you mean "analog".I have a HAMEG 412-5 as analogand a PicoScope 5444A (up to 200 MHz, up to 16 Bit and with 256 MS sample storage and USB 2.0)Main differences:Hameg5mV/Div up to 20V/Div with 8 divisions (so +/- 800V with 10:1 probe if the probe allows)analog scaling uncalibrated 1-2.5 foldAlternate Triggering + line trigger + LF Triggermax timebase 2 sec / divInvert + Adding channels by knobsno storageno remote operation possiblePicoScope2 mV/Div up to 4V/Div with 10 divisions (so +/-200V with 10:1 probe, plan a isolated 50:1 probe when measuring mains voltages)digital scaling by menueno alternate Trigger / no line trigger / no LF Triggermax timebase 5000 sec / divInvert + Adding channels by math functions256 MS Memoryremote operation with remote desktop and Win Pro version possibleQuote from: Fungus on July 03, 2021, 07:17:53 amIs that only your opinion or do you have experiences with a special model?Of course the screen update speed depends somewhat from the number of aquired points.With 100 kS its faster than with 100 MS.And the Picoscope6 software starts a new aquisition (+ triggering) with each change of the time scale or amplitudeSo the responsiveness is not "immediate".Some points to consider when changing to digital:Often no extra input for external trigger is given. So you might need 1 extra channel for triggering. (my model has external trigger input)Some cheap devices have only 1 or 2 hardware input voltage ranges. The remaining resolutions are calculated by math.Memory depth is essential (but not cheap). I would not go below 10 Megasamples Memory per channel.(so dont consider any PicoScope 2000A devices with only 16/48 kSamples, the B versions have more memory)with best regardsAndreas

author: HKJ
author_rank: Super Contributor
timestamp: July 03, 2021, 09:11:03 am
content: Quote from: Andreas on July 03, 2021, 08:21:35 amYou are underselling the PicoScope a bit, it may miss some trigger modes that are present on analog scopes, but instead it add a selection of advanced trigger mode that no analog scope can do and that cost extra on most other digital scopes.It also includes serial decoding, again something that cost extra on most other digital scopes.It has custom defined math channels, i.e. you can make an expression with advanced functions.

author: 2N3055
author_rank: Super Contributor
timestamp: July 03, 2021, 10:04:08 am
content: Quote from: Fungus on July 03, 2021, 07:17:53 amYes, my Picoscope 3000D is so slow that it can achieve only 170000 triggers per second in normal mode, and has retrigger time of 0.6 usec in sequence mode, 20-30% faster than even Keysight (more than 1.5 Million triggers per second...).Back in the days of USB1.0 I would agree with you, but even USB2.0 is fast enough... They use intelligent data compression.They are excellent devices, but not very inexpensive. But in some regards, they have many high end functions from analytic scopes costing more than 20000€.Mostly people just want knobs to twiddle and they don't like PC or tablet scopes. I connected mine to a 23" touchscreen monitor and they are like huuuuge Micsig :-).I'm certain, you wouldn't have any problems to use them, because you like tablet scopes and are not hung up on a notion "it is not a scope without hundred buttons".

author: Ian.M
author_rank: Super Contributor
timestamp: July 03, 2021, 10:25:34 am
content: IMHO USB scopes are an abomination that should never have made it to the mass market! How long will the current USB 3 standard be stable for, and in ten years time, what are the odds of being able to get signed drivers for current OSes? How many early USB scopes have no software support and application software that has aged so badly it has to be run from a VM or a PC running a legacy OS?Why aren't headless Ethernet interfaced scopes commonly available? Ethernet over UTP with inherent 1KV isolation has been around in one form or another for over 30 years and even 10baseT has enough bandwidth for Youtube SD video, so it shouldn't be a bottleneck if the UI runs on the scope and is accessed via a browser, or VNC or even RDP if its Windows based, which also avoids most of the issues with having to keep application software updated for new consumer PC OS releases.OTOH even if the scope is nominally headless, it would be nice if it has HDMI/DVI + a USB host port on the back panel that will recognize HID keyboards, pointing devices and even game controllers, so it can be run standalone with a monitor if required, with physical UI options to suit all tastes.

author: HKJ
author_rank: Super Contributor
timestamp: July 03, 2021, 11:10:53 am
content: Quote from: Ian.M on July 03, 2021, 10:25:34 amPicoScope has been fairly good at supporting old models. I do not believe 10 year is a problem, but when you get up to and above 20 years it may get problematic.Quote from: Ian.M on July 03, 2021, 10:25:34 amYou mean like this:https://cleverscope.com/products/CS328A-XSE

author: 2N3055
author_rank: Super Contributor
timestamp: July 03, 2021, 11:36:18 am
content: Quote from: Ian.M on July 03, 2021, 10:25:34 amThat is faulty reasoning. What will be support for all in one scope that uses Linux internaly...and cpu and etc..Just put a PC on a side and treat it as a scope, not a PC.Make backup of firmware ( windows and scope sofware) and if some hardware dies I bet a comodity pc hardware will be easier to find than any old scope spare parts. As far as Picotech goes they still support 20 years old hardware..

author: rsjsouza
author_rank: Super Contributor
timestamp: July 03, 2021, 02:29:22 pm
content: Quote from: Ian.M on July 03, 2021, 10:25:34 amQuote from: 2N3055 on July 03, 2021, 11:36:18 amIndeed. The same can be said for standalone scopes: "How many early standalone scopes have no firmware support and parts that had aged so badly it has to be run with limited capabilities or thrown in the trash?"The aged hardware argument was much fairer before the more modern incarnations using USB ports (I have a SCSI-2 Tektronix TWD120 and it works well but it is a dog to setup).Even still, if there are complaints about USB throughput, Ethernet is much worse and much less predictable, especially if used alongside other hosts.To the OP: I have used bad and good USB scopes in the past. I have purchased a very entry-level Owon VDS1022I that I use alongside a standalone Rigol DS4014. The Owon is much simpler and less featured than the Rigol, but it is quite portable and great to look at waveforms in generic scenarios. The presence of a manufacturer-free software also helps a lot (check the end of the thread below)https://eevblog.com/forum/testgear/owon-vds1022i-quick-teardown-(versus-the-hantek-6022be)/

author: Andreas
author_rank: Super Contributor
timestamp: July 03, 2021, 02:46:50 pm
content: Quote from: HKJ on July 03, 2021, 09:11:03 amHello,I only wanted to show that there is a different operating philosophy when changeing from analog to digital.dont mis-understand me. I like my Pico. And the Hameg is rarely in use now.The Pico has much more features including math functions like low pass/high pass and a good FFT.with best regardsAndreas

author: jjoonathan
author_rank: Frequent Contributor
timestamp: July 03, 2021, 03:19:45 pm
content: Quote from: HKJ on July 03, 2021, 07:41:04 amI am glad that your lived experience is different than mine because I wouldn't wish my lived USB instrument experience on anyone. The PC ecosystem has an absurd number of possible hardware and software combinations. That can definitely be a strength, but there are also some real stinkers lurking in the space of possibilities, and you roll the dice every time you touch any part of that combination, even in trivial little ways like flexing a cable!Choosing Pico is a good way to ensure that those dice are weighted in your favor, but still, the last two USB instrument problems I've had were beneath the driver layer (one USB 3 cable issue, one CPU USB stack issue), so general software quality can only go so far.QuoteI disagree. Having a physical box hold the consistent configuration of hardware and software that has been extensively validated beforehand is a very different thing from closing your eyes and drawing an imaginary box around a "USB scope + PC" combination, pretending that you've validated it, and promising to yourself that you'll never separate the two or change the configuration. The former strategy routinely succeeds and the latter strategy routinely fails. Those imaginary boxes just aren't very sturdy: nobody can see them but yourself, so the moment someone else comes into the picture all bets are off, and even if you live your entire life alone on a mountaintop you're going to be tempted and/or forced to play with versions on a regular basis, which will work just fine right up until it doesn't.

author: bdunham7
author_rank: Super Contributor
timestamp: July 03, 2021, 03:57:51 pm
content: Quote from: Ian.M on July 03, 2021, 10:25:34 amI seriously doubt that standard USB-A is going away anytime soon. Apple doesn't rule the whole world and if USB disappeared entirely there would be a lot more issues than just USB scopes. The worst case is you'll need pass-through adapter from Type-C to USB-A.As for support, Picoscope still has nominal support (including modern OS software) for everything going back to their original ADC-10 product of 30 years ago. Granted there are limitations on anything pre-USB, but AFAIK, everything they made with USB 1.0 and up will work fine on a Windows 10 computer. OTOH, my Fluke Scopemeter software uses RS232 and Windows 3.1 running in VirtualBox--or it would if I got it to work.

author: 2N3055
author_rank: Super Contributor
timestamp: July 03, 2021, 04:59:00 pm
content: Quote from: jjoonathan on July 03, 2021, 03:19:45 pmI'm genuinely sorry you had so much problems, but in my life, on all PC and USB instruments combined I never had any. Once Pico had problems that occasionally wouldn't initialize. Then you would have to unplug it and that was it. It was driver problem, and was fixed in few weeks.And all that talk about validation.. PC is most tested, standardized and validated platform in this par of universe. Just get a Lenovo, Hp, Dell or whatever workstation PC and it is guaranteed to work perfectly. Plug in Pico and enjoy. That also applies to Signal Hound USB SA I have. It simply works...I presume your bad experience had more to do with your choices that platform..

author: rsjsouza
author_rank: Super Contributor
timestamp: July 03, 2021, 05:58:40 pm
content: Quote from: jjoonathan on July 03, 2021, 03:19:45 pmAlthough you have a point when mentioning that the long term support of such platforms is very difficult, especially due to the now current trend of SAAS or constant updates, from a pure software standpoint the process of freezing a specific environment in time and be able to restore it in the future is quite attainable - we do this all the time for legacy projects, either by using system image tools such as Norton Ghost or simply creating Virtual Machines (if the hardware allows). From a hardware standpoint, the ability to switch underlying faulty parts carries a level of compatibility unparalleled by custom hardware - anyone that had a fault on any sort of critical system and benefited to have minimal downtime can attest to that. On the other hand, popular standalone brands using custom hardware hinge on the sheer durability of the hardware/software, as repairs can be hard or impossible. A-list brands have additional repair/service options but usually having an unattainable cost to a single user - not to count the downtime.At any rate, both sides of the equation have advantages, but I agree with Sinisa: I imagine your personal experience was indeed terrible but might not be endemic across the board. At any rate, thanks for giving your perspective - all are welcome!

author: jjoonathan
author_rank: Frequent Contributor
timestamp: July 03, 2021, 06:34:29 pm
content: QuoteValidation vs combinatorics. The validation is impressive, but the combinatorics are more impressive.EDIT: It's funny that you mention SignalHound and then blame me for bad choices. My last spat of USB 3 issues was on a $10,000 SignalHound USB3 spectrum analyzer. Our SM200B kept dropping its connection (and it has to re-load the firmware every time it connects, so this was especially obnoxious). We were deep in "cannot replicate" support hell until we eventually figured out that it worked fine on one of our older laptops. Since then, AMD USB problems have gone through a press cycle, AMD released an update to their processor microcode, our motherboard manufacturer integrated it into a firmware update that we could actually use, we tested it, and discovered that the firmware update does appear to solve the problem. It also indefinitely stalls during installation and makes all the hard drives disappear, but they come back if you short the CMOS jumper (software clear does not suffice) and after this long exhausting journey our $10,000 USB spectrum analyzer works on all of our PCs, rather than just the crusty Intel laptop. Yay.I'm glad I wasn't the one paying for all that wasted engineer time!

author: james_s
author_rank: Super Contributor
timestamp: July 03, 2021, 06:40:46 pm
content: I have an older USB scope, I never use it anymore since getting a real standalone DSO. The USB scope may have had some advantages at one time when the computer/display part of a DSO was a considerable expense but that stuff is so cheap now that there is no longer any advantage. A USB scope means you've got to carry around multiple devices stuck together with cables and find somewhere to set a laptop or other PC. If you knock loose the USB cable it will often lock up the software and require closing it and reopening and getting everything set up again. Unless you have some specific niche requirement that the USB instrument meets, a standalone scope is vastly superior IMO. The main advantage of PC based instruments in the past was cost but IMO they never really delivered on that promise and today they don't offer any savings at all. Something like a Picoscope costs more than a standalone Rigol or Siglent DSO.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: July 03, 2021, 07:16:27 pm
content: QuoteYes!Before we had the difficulties with our $10,000 USB spectrum analyzer, we had some difficulties with our $1000 USB logic analyzer (Saleae Pro 16). Sometimes the software would lock up, fill the ram, and slog the computer badly enough that you had to restart. For a while we thought it was just a software issue, but our LeCroy revealed that it was losing the high-speed USB channel, falling back to USB 2, and the software was dealing poorly with this. The problem was with the cable. The original cable that came with the thing. A VNA identified the location of the fault, deep within the potted end connector, and an XRay revealed that the shielding slice had severely damaged one of the high speed signal pairs.Obviously buying a standalone scope doesn't guarantee that it will be free from manufacturing defects, but nothing does intermittent behavior quite like commodity cables do intermittent behavior.

author: 2N3055
author_rank: Super Contributor
timestamp: July 03, 2021, 07:31:09 pm
content: Quote from: jjoonathan on July 03, 2021, 06:34:29 pmI certainly didn'tblame you for bad choices. Merely pointed out thatchoices do influence outcomes.SM200B is still rather new product, and Signal Hound always recommended Intel PCs for their software. AMD PC is not something that they will recommend. And as spectacular as new AMD Ryzens are, they are also very new.... So yes that wasn't a safe choice and it was "inviting trouble" of a sort.Also, I don't treat USB T&M devices as a village bicycle, that travels from one PC to another, all of them different types. That is going to be problem. Because you don't know the state of all those PCs. I have a dedicated PC for my USB instruments that is installed, verified and kept stable. Like a PC motherboard inside LeCroy would be left alone and not mistreated by all kinds of stuff people do to their desktop. And it works like charm...Quote from: james_s on July 03, 2021, 06:40:46 pmWell, cheap USB scopes have advantage of being cheap, and by being cheap they won't have spectacular specs or quality.As for "many cables", a scope connected to DUT on your desk is a "mess of cables" anyways, and one, single USB cable is really no problem. If you have cables falling out of instrument you also have problems anyways. They are portable and not really a problem, but a portable scope like Micsig is simpler to use (that is why I do have one). But before buying one, I would carry laptop and Pico and it was not a problem.But I will repeat, Micisg or even Keysight MSOX3000T doesn't have many, many capabilities Picoscope hardware+software has. If you don't need that, than you don't need it. Just buy cheapest thing that is sufficient for your work. But Picoscope saved me many times doing things that I would need to buy a 20000€ LeCroy to have that capability.

author: 2N3055
author_rank: Super Contributor
timestamp: July 03, 2021, 07:43:50 pm
content: Quote from: jjoonathan on July 03, 2021, 07:16:27 pmThat has nothing to do with USB PC instrument concept being bad. It is like saying "Windows is shit, because whenever i put in a dodgy RAM in my PC it throws bluescreens". No, that is defective RAM problem. You had bad cable. That was the problem.I had many problems with all kinds of measurement equipment. Mostly cables, from a IEC power cable arcing inside socket because contacts lost elasticity, to all kinds of passive, active and digital probes doing all kinds of problems. Scope probes would be best if they were cable-less..You could have had an integrated SSA of highest class and have problem with coax cables, connectors, converters, adapters, accessories, cables not screwed in tight enough or too tight....That IEC cable arcing inside socket was lots of fun for me. Not. It took me a while to find out the problem. Of course it would arc only every few hours, randomly...

author: jjoonathan
author_rank: Frequent Contributor
timestamp: July 03, 2021, 07:56:01 pm
content: You can't have it both ways. Either:Quote from: 2N3055Or:Quote from: 2N3055You either have to laboriously reinvent a clumsy, half-baked equivalent of a standalone -- which is the Motte argument you gave in your second post -- or you just have to get a standalone. I agree with the Motte of your argument, but not the Bailey.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: July 03, 2021, 08:11:39 pm
content: Faulty USB 3 cables absolutely do have something to do with the USB PC instrument concept being bad. All cable problems are not equally common or easy to debug and USB 3 cables are especially bad on both counts.

author: james_s
author_rank: Super Contributor
timestamp: July 04, 2021, 01:08:17 am
content: Quote from: 2N3055 on July 03, 2021, 07:31:09 pmMine wasn't cheap, it was just cheaper than a real standalone DSO at the time I bought it, there was nothing like the Rigol, Siglent or other budget scopes on the market. Clearly the USB scope works for you but personally I hate the form factor, the only advantage I see is price, you already had a PC so the idea was you add on the scope stuff and reuse the display and UI of the PC you already have, saving the cost of the computer part, display, buttons/switches, etc. It was arguably a fair trade for the inconvenience of having to deal with separate devices plugged together, having your PC tied up and various software issues given the price was less. With as cheap as some quite good standalone scopes are these days that advantage is gone. You may have a niche where a Picoscope offers some features that are not available elsewhere for the price but for the average person needing a scope it's just less convenient without being any cheaper.

author: HKJ
author_rank: Super Contributor
timestamp: July 04, 2021, 05:13:43 am
content: Quote from: james_s on July 04, 2021, 01:08:17 amFor me the big advantage with a USB scope is space savings on my test bench. Another good detail is the easy way to transfer data to the PC as can be seen in many of my reviews.

author: 2N3055
author_rank: Super Contributor
timestamp: July 04, 2021, 09:48:34 am
content: Quote from: james_s on July 04, 2021, 01:08:17 amPicoscope 3406D MSO is a 2500 USD device. I already had both small Rigol DS1104Z and Keysight MSOX3103T (full bundle).. Because Picoscope has many features they don't have.If I would buy 2500 USD Siglent today, I would do it to replace Keysight 3000T, but would still keep the Pico. FFT and math on Pico is almost in class of 25000 USD LeCroys compared what you can do with it.Form factor? On a desk, form factor of a Picoscope is that youdon't use any space.. It is miniature compared to anything else. You have to have PC at your work desk. For datasheets, documentation, BOM when assembling, instrument control (other instruments controlled with SCPI)... Mount monitor off the desk (on a wall, articulated stand...).There are no inconveniences. You plug standalone scope to power and network, you plug Picoscope to power and USB. Or only USB if they don't need more power. Both 3406D and 4262 can work from normal USB3 (and USB2 with slower update rate) without external PSU. 4262 doesn't have power supply at all and 3406D has it if your USB port (or hub) has problem supplying power.I really don't understand all the talk of PC problems. I have none. Maybe I'm lucky, or maybe I tend to run conservative hardware and am being conservative with what I do to PC. I don't know. But I have no problems with what you are mentioning. I'm sorry you do have them.Niche? Lets see:1. Do you do protocol decoding?2. Do you do documentation? That is so beautiful on Pico.3. Do you need to do capture, save it for later and then analyse it for days. Meaning creating math channels, decodes, comparisons for days trying to figure out what is going on?4. Do you need to capture something remotely? And then download capture and analyse it at your lab?5. Do you like to be able to simply copy capture to your laptop and carry it with you and analyse it later (software works without scope). Scope offline software from Keysight and LeCroy exist but are very expensive, and you need their scopes too...6. Do you ever use custom probes, that can have not only custom attenuation factor, but can have full linearization tables for the sensor/probe?7. Would you like to have scope with 24" screen in full HD resolution?8. Would you like to be able to set multiple widows on screen (or multiple monitors maybe?) that show you multiple measurements, math, FFT, X-Y plot all at the same time ..etc etc..Picoscope is not meant to be digital emulation of analog scope on a PC. It is deliberately different, new, concept of signal analysis device. We call it scope, but really these devices are signal analysers. That is also true for LeCroy and now new Siglent devices. Partially that also applies to new gen of Rigol, Micsig and similar, to a limited extent.If a person only uses scope as they would use and "analog storage scope" then all this is a moot point.I would actually reverse your statement a offer a hypothesis that many people have a niche where they don't need advanced stuff. Or versatility. They do what they do and, they do it certain way and it works for them. And frankly that is perfect.But I'm telling you, and I stand by it, if a magical force took from you all the scopes and gave you only Picoscope, in a short time, you would be able to do everything you do now and more, if you wished to.. Fact that you don't like it and have a choice and prefer other things is fine.I'm not trying to convince you to get Pico or anything like that. Have no affiliation with them, just a happy customer.But I like to set the record straight and to speak out when I see facts that are not really correct.Take care!

author: tttonyyy
author_rank: Regular Contributor
timestamp: July 05, 2021, 02:09:54 am
content: This is conflating analogue analysis with digital. The complexity of protocol decoding (and stacked protocol decoding) is better handle by a PC. Setting up complex triggers is more intuitive with a PC GUI, mouse and keyboard. But analogue domain, setting trigger levels and timings, it's hard to beat some twiddly knobs on an actual scope. Modern scopes use a conservative amount of desk space as well.I know that if I need to look at some analogue signals the scope will "just work" but the same may not be true of the logic analyser if I move on to Windows 11. The key is really just understanding what the potential consequences are of your choices and balancing them against the way you want to use the equipment.USB Vs standalone both have their merits but in my view tip different ways between logic analyser and analogue.

author: Fungus
author_rank: Super Contributor
timestamp: July 05, 2021, 05:15:31 am
content: Quote from: HKJ on July 03, 2021, 07:41:04 amWhat's the cheapest USB 'scope that can record ("stream") to your PC RAM in real time? What version of USB does it need?

author: 2N3055
author_rank: Super Contributor
timestamp: July 05, 2021, 06:44:11 am
content: Quote from: tttonyyy on July 05, 2021, 02:09:54 amAnd your statement might be conflating "analogue analysis" with "I need to look at some analogue signals". As I said, if you use scope like "digital emulation of analog scope" and simply look at the squiggly lines on screen most of the time, then by all means, buy something that is best emulation of that. Or use CRT scope if you have a good working one..You probably concluded this because I didn't go to length explaining any analog examples. Like fact that you can have arbitrary number of zoom windows, that you have phase cursors, arbitrary number of math or reference channels, Deep Measure that will analyze millions of periods inside sampled window and give you table of all measurements that you can analyze further. When I said analysis, I wasn't referring to user thought process, but part where you tell scope to do the heavy lifting for you.Arbitrary probes (with lookup table linearization) alone saved the day many times... Math with filtering, arbitrary math..You can also decode from math channel, there iscombinedanalog (filter noise) and digital (decode) processing and analysis.As for timebase and channel sensitivity operation, that is easy enough. With buttonsandscreen youselectfunction (choice of knob, or graphic element ) andselect value(rotate knob, or click on timebase from a popup, click on a up/down, or rotate mouse wheel). I tell you ( i grew up on analog scope too ), after few hours you wouldn't notice "something wrong" or would fight with it because "that's not how it's supposed to be", but would do it naturally, like you type this text on a keyboard. And it is equally fast, even faster for some things that you have on screen right there as opposed to some scopes that you have to go 3 levels deep in a menu, with a rotating knob.I, personally, always found classic digital scope U/I (without touch screen, one that you have to go trough all the menus, choices, numbers and alphabet by twiddling the knobs and few buttons around the screen) quite annoying. They remind me of arcade machines when I was a kid, where you had to enter your name for High score by clicking through the alphabet letter by letter... Simple things like timebase, trig level, ch atten is Ok, anything else not so much... Just changing trigger type is menu diving..New generation of touch screen scopes is much more logical and easier to use. Having so many options and functions, computer like GUI is better way to organize that complexity. Fact that it might not look and feel like classic scope, doesn't mean it's not better.. Butit is different.But first time I could type in values (with unit) for parameters and file name directly from a onscreen keyboard was a point of no return for me.I also run my Picoscopes ( I have two, 3406D MSO and a 4262 16 Bit scope) from a PC that I have 23" touchscreen on. So I use it as a huge tablet scope. You tap on timebase up or down, or you drop menu an directly choose. Same with attenuation. A bit of trivia: Picos have Auto mode for channel atten, where they autorange same as multimeters do. When you're just poking around looking what is there I sometimes use that....

author: rsjsouza
author_rank: Super Contributor
timestamp: July 05, 2021, 10:57:37 am
content: Quote from: Fungus on July 05, 2021, 05:15:31 amOwon VDS1022I, USB2.0 (roll mode)

author: voltsandjolts
author_rank: Unknown
timestamp: July 05, 2021, 11:30:06 am
content: Quote from: 2N3055 on July 04, 2021, 09:48:34 am9. Would you like 8, 12, 14, 15 or 16 bit scope? Or all of these in one?10. Would you like superb FFT that comes with aforementioned increased sampling resolution?11. Would you like it in nice portable format so your employer can pay for it then you can easily transport it home for the weekend?I have Picoscope 5K and a Micsig STO. Both are great scopes but the Pico is my go-to at the bench.

author: Fungus
author_rank: Super Contributor
timestamp: July 05, 2021, 12:21:56 pm
content: Quote from: rsjsouza on July 05, 2021, 10:57:37 amAt 100MS/sec? That's gonna be difficult on USB 2.0...More likely it's just updating the 5k internal sample memory and sendingthatto the PC.

author: HKJ
author_rank: Super Contributor
timestamp: July 05, 2021, 12:30:11 pm
content: Quote from: Fungus on July 05, 2021, 12:21:56 pmThat is how all good USB scopes works. For PicoScope check the SDK maybe you can send directly to PC at slower sample rates.https://www.picotech.com/library/oscilloscopes/picoscope-software-development-kit-sdk

author: Fungus
author_rank: Super Contributor
timestamp: July 05, 2021, 12:50:19 pm
content: Quote from: HKJ on July 05, 2021, 12:30:11 pmIknowthat, but that's not what I was asking.Quote from: HKJ on July 05, 2021, 12:30:11 pmHence the "real time" thing.Also: Not much point when there's only 5k of sample memory.(Yes, Ialsoknow you can pay for Picoscopes with more sample memory but the price of a decent Picoscope is way more than a similar spec standalone 'scope). There's no way the OP should be considering a Picoscope+used laptop instead of a standalone Rigol/Siglent.

author: radiolistener
author_rank: Super Contributor
timestamp: July 05, 2021, 12:56:59 pm
content: The problem with USB oscilloscope is a speed limitation.If you perform all processing on RF frontend unit and send the video picture through USB interface, it require about 800x600x3 x 60 fps = 86.4 MB/sec = 691.2 MBit/sec.USB 2.0 is not enough to handle such stream. USB 3.0 can transfer it, but USB 3 chips are expensive. Also so high speed stream make very heavy load on the PC, so you will needs PC with a very good performance, something like i7 level CPU.Another way (which is often used) is to transfer RAW data from ADC to the PC and perform all signal processing on PC. It also requires PC with very good performance and such processing will leads to a heavy load of the main CPU and GPU on your PC which is not convenient.Existing solutions for USB just reduce data flow to fit into USB 2 interface or reduce CPU load for USB 3 interface. This is why USB solutions almost always much worse than dedicated oscilloscope.And another issue is that USB is not a good solution for a high speed transfer. The better way is to use PCI Express bus.Such PCI Express oscilloscopes very expensive and needs expensive PC with top performance to handle high speed data stream which consume a lot of electricity and needs full tower case for a good cooling. So this is very expensive and inconvenient solution.For example:http://acqiris.com/wp-content/uploads/2017/11/Datasheet_U5309A.pdfIf you want more cheap solution. There is a nice option for home: Digilent Analog Discovery Pro 3000https://eu.mouser.com/new/digilent/digilent-analog-discovery-pro-3000

author: HKJ
author_rank: Super Contributor
timestamp: July 05, 2021, 01:05:51 pm
content: Quote from: radiolistener on July 05, 2021, 12:56:59 pmThat would be a silly way to do it, you could perform the processing in the front end and then just send the curve, i.e. 800x1 or 800x2 bytes for each channel to show.

author: Fungus
author_rank: Super Contributor
timestamp: July 05, 2021, 01:08:35 pm
content: Quote from: radiolistener on July 05, 2021, 12:56:59 pmYou don't need to send the whole screen, just the Y-coordinates of the visible samples.ie. If the screen is 800 pixels across then it's 800 bytes of information per channel, that's 600x3 = 1800 times less than your calculation.Edit: 1800 times less when there's a single channel. Two channels needs twice as much data, etc.

author: radiolistener
author_rank: Super Contributor
timestamp: July 05, 2021, 01:15:57 pm
content: Quote from: HKJ on July 05, 2021, 01:05:51 pmIt cannot help much, because it will reduce memory depth. Oscilloscope with memory depth 800 points is a crap... For example 800x1 is not enough to represent video signal on the oscilloscope (note such signal will cover almost entire display surface, not just one pixel per X axis)If you want memory depth 28 megapoints, then you're needs to transfer 28 MB * 60 fps = 1680 MB/sec = 13440 MBit/sec = 13.44 Gigabit/sec. This is too much traffic for PC, I'm even not sure if top rated PC can handle such stream in realtimeIf you transfer just 800 points per frame, you will get cheap Chinese crap instead of oscilloscopeAnd this is why USB oscilloscopes have much reduced frame rate, slow response and worse display quality in comparison with dedicated oscilloscope. Just because they reduce data flow to fit into USB 2 and PC performance.Also there are another issues with USB oscilloscope, for example galvanic isolation from the mains ground, unpredictable noise interferences, etc...Quote from: Fungus on July 05, 2021, 01:08:35 pmNo. Such way cannot work properly. See example above.When you transfer just 800 points per frame, it means that you limit memory depth to 800 points. As result you will catch aliases and cannot see digital phosphor...800 points memory depth is not enough for a modern digital oscilloscope. It's just a crap... May be it can be usable for a simple high frequency sine. But you will catch a problem for a low speed horizontal resolution and will be unable to see low frequency signal changes properly.

author: HKJ
author_rank: Super Contributor
timestamp: July 05, 2021, 01:48:20 pm
content: Quote from: radiolistener on July 05, 2021, 01:15:57 pmYou do not know anything about programming, the idea was to let the scope do the data reduction, no screen can show 28 megapoints.Quote from: radiolistener on July 05, 2021, 01:15:57 pmAnd I have not seen any slow performance with my USB scopes, maybe you ought to try some good USB scopes before writing about them.Quote from: radiolistener on July 05, 2021, 01:15:57 pmThat is an issue with stand alone scopes, but with USB scopes you can use a laptop and avoid it.Quote from: radiolistener on July 05, 2021, 01:15:57 pmIt can, it is a question about splitting the task correctly between the scope hardware and the PC.

author: radiolistener
author_rank: Super Contributor
timestamp: July 05, 2021, 02:57:45 pm
content: Quote from: HKJ on July 05, 2021, 01:48:20 pmJust FYI, I'm Senior Software Engineer with more than 15 years of commercial software development in a medical devices industry. Include RTOS, graphics programming, signal processing, database, network communications, client and server side applications for a known company.As a hobby project I'm implemented my own software oscilloscope on PC. It is based on a high speed 14-bit ADC working at 100 MHz sample rate, FPGA for a stream processing and Gigabit Ethernet PHY to transfer data into PC.Since gigabit ethernet is unable to handle 1.6 Gigabit stream from ADC directly, I capture sample into FIFO buffer and then transfer it through GMII PHY into PC at about 600-800 MBit/sec. On PC side I perform software processing of the captured data almost in the same way as a usual digital oscilloscope. I spent some time in order to investigate how digital oscilloscopes doing things in order to done it, so I know what I'm talking about.Quote from: HKJ on July 05, 2021, 01:48:20 pmYou're just don't realize that data reduction which you're talking about is just memory depth limit. And when you transfer just 800 points to the PC you will get exactly the same result as you will get on a dedicated oscilloscope with memory depth limited to a 800 points.Just FYI, with a low memory depth you will get aliasing issue for a slow horizontal scale.There is a trick which is used on oscilloscopes with a low memory depth, the name of this feature is "Peak Detect" mode. In such mode you can transfer 2 points per X coordinate - min and max value. But such approach cannot allow you to reconstruct image in the same way as it works in "digital phosphor" feature on a dedicated oscilloscope.In order to implement "digital phosphor" you will needs to transfer all 28 megapoints per frame, or to transfer entire image of oscilloscope display image with already processed data.There is no way to reduce 28 megapoints to 800 and then reconstruct it with no loss and no aliasing. This is mathematically and physically impossible.So, you will be unable to see the same image quality at the same update rate through USB as you have on a dedicated oscilloscope.You can use approach with FIFO buffer as I used in my software oscilloscope, but in such case you will needs to process all data on PC side and it needs to transfer data at very high speed rate. As a side effect, you will have long gaps between frames, just because you will be unable to transfer ADC data at full speed through USB interface due to USB bottle neck. Longer memory depth will leads to a low frame rate, because it will needs more time to transfer FIFO buffer into PC.For 1 GS/sec oscilloscope you will need to transfer 8 Gigabit/sec into PC. Not all USB 3 ports can transfer 8 Gbit/sec, and it will be hard to process so fast stream on PC in realtime.In theory PC can process 1 GS/sec in realtime, but in reality there are too many bottlenecks and problems. This is not so easy and not cheap task to attach gigabit realtime stream to PC.Quote from: HKJ on July 05, 2021, 01:48:20 pmYou're just didnt notice image quality and update rate speed.Actually these things are not obvious and many users just don't know about specific issues with digital oscilloscopes and thus very often don't realize what is going on under the hood.Quote from: HKJ on July 05, 2021, 01:48:20 pmThat's not a problem to find issue of some oscilloscope. They all have some issues. I never seen oscilloscope which works ideally with no simplifications. And since USB 2 has serious bottleneck it will be not a problem to find issue on USB 2 oscilloscope.With USB 3 there is less transfer speed limit, but I'm sure I can find limitations in comparison with a dedicated oscilloscope.Quote from: HKJ on July 05, 2021, 01:48:20 pmNo, it cannot. For each X coordinate it needs to transfer entire Y row of pixels in order to represent proper color gradients in a vertical pixels row. When you transfer just one pixel instead of pixels row, you will loss a key information and will be unable to restore it.Technically you will catch aliasing issue at low speed horizontal scale due to Nyquist limit which is shifted down due to sample rate reduction. And there is no way to restore information which already lost when you decimate your signal.As I said above, you can bypass it with a "Peak Detect" mode. But it cannot allow you to restore original signal waveform with "digital phosphor" (with original pixel intensity integration), it just show you diagram with min/max values.

author: Andrew_Debbie
author_rank: Frequent Contributor
timestamp: July 05, 2021, 03:13:39 pm
content: Quote from: HKJ on July 04, 2021, 05:13:43 amExactly -- We have a 76m2 (820 sq. ft) house. Space is at a premium. There isn't room for a large workbench. I don't have a USB scope at the moment, but is tempting.

author: HKJ
author_rank: Super Contributor
timestamp: July 05, 2021, 03:45:25 pm
content: Quote from: radiolistener on July 05, 2021, 02:57:45 pmIt really doesn't matter, both PicoScope and CleverScope makes fairly advanced USB scopes and I have not seen people using them complain about update speed, i.e. they now how to make it work.

author: radiolistener
author_rank: Super Contributor
timestamp: July 05, 2021, 04:00:00 pm
content: Quote from: HKJ on July 05, 2021, 03:45:25 pmI know PicoScope, they looks like really good devices but they are expensive, you can buy dedicated oscilloscope with similar specs cheaper than their price.It looks like they using USB 3, so their speed can be pretty good. Does it supports digital phosphor?Can you please record screenshot or video with some complex signal on the input (such as PAL or NTSC signal at slow horizontal scale to see several frames on the screen)?Just interesting how they implemented data transfer and drawing.Window video capture with a complex signal like PAL/NTSC will be great to see artifacts and analyze how they implemented it.Quote from: HKJ on July 05, 2021, 03:45:25 pmI see a lot of peoples using pretty buggy Chinese devices and they almost don't see pretty obvious issues (and critical from my point of view) that catch on my eye just at first look. So, I don't rely on people's opinions and check things out myself

author: HKJ
author_rank: Super Contributor
timestamp: July 05, 2021, 04:12:35 pm
content: Quote from: radiolistener on July 05, 2021, 04:00:00 pmNot really, you always get all triggers and serial decoders with PicoScope, it is never extra.Quote from: radiolistener on July 05, 2021, 04:00:00 pmNewer is probably USB 3, older USB 2.Quote from: radiolistener on July 05, 2021, 04:00:00 pmCheck their website, I am sure there is some video clips.

author: radiolistener
author_rank: Super Contributor
timestamp: July 05, 2021, 04:20:23 pm
content: Quote from: HKJ on July 05, 2021, 04:12:35 pmI don't expect serial decoders and analyzer features from any kind of oscilloscope. It's better to use dedicated signal analyzer for such functions. They have more convenient controls and more interesting features than oscilloscope. I think such function is useless for oscilloscope.The possible extra with PicoScope is a vector network analyzer by using it's signal generator and SDK to control and sample data. Such feature can be interesting for me.Quote from: HKJ on July 05, 2021, 04:12:35 pmUnfortunately there are only simple waveforms example on their site which don't shows processing artifacts.At a glance it looks that they just decimate sample to about 2500-7000 points. If this is true, then it don't have digital phosphor and can have aliasing issues. Then this is major con in comparison with dedicated oscilloscope.Just watched some videos and I almost sure that PicoScope just apply decimation to the signal with no integration for the pixels intensity (the same as you said when you told about 1x800 points). If this is true, then PicoScope cannot show the true picture of the signal, like dedicated oscilloscope can do...So this is the answer how it works on USB 2, it just didn't show a true picture and show you aliased picture after decimation.For comparison, a cheap Siglent SDS1102X shows 14 million points on the screen.That's the difference with USB PicoScope. USB PicoScope shows 800 points, and dedicated Siglent shows 14 million points

author: james_s
author_rank: Super Contributor
timestamp: July 05, 2021, 06:25:06 pm
content: Quote from: Andrew_Debbie on July 05, 2021, 03:13:39 pmMy laptop takes up more square footage of bench space than my scope does, and that's not even including the external box. This may not be an issue if you always work at your bench and already have a PC set up there all the time but I often work on things on the coffee table in my living room or elsewhere. USB scope means dragging around my laptop + an external device and cables, connecting it together and finding space to set it all. Once I got a lunchbox DSO I found I never used the USB scope anymore, the standalone unit is just so much more convenient and works better. Another issue is the USB scope never worked quite right once I moved to a 64 bit OS, I kept an older laptop around specifically for it. You never know when you may have to upgrade your PC or OS and whether the scope will still work with the new one. The transfer to a PC thing is a moot point, you can do that with a standalone DSO too. Maybe it will work better for you, I'm just stating that in my actual experience, PC based test equipment has never really delivered the advantages it promised and I have thus abandoned mine in favor of standalone instruments which I find work much better in practice.

author: Fungus
author_rank: Super Contributor
timestamp: July 05, 2021, 06:35:36 pm
content: Quote from: james_s on July 05, 2021, 06:25:06 pmWait 'til you get a Micsig, you won't use the lunchbox DSO any more.(tablet form factor, runs on battery, use it anywhere...!)

author: james_s
author_rank: Super Contributor
timestamp: July 05, 2021, 06:39:22 pm
content: I really don't like the tablet form factor in general, I hate touchscreens and only tolerate them when there is no alternative. I have several tablets and find them to generally be an inconvenient form factor, I always have to find a way to prop it up so it doesn't slide flat on its back and the various kickstand gadgets always leave something to be desired. Having tried for several years to find a good use case for a tablet I have mostly failed and do not really understand why they're so popular. I suppose a scope in that form factor could be handy for automotive work but I certainly would not choose it over a lunchbox form factor for the stuff I most often use a scope for.

author: voltsandjolts
author_rank: Unknown
timestamp: July 05, 2021, 07:38:29 pm
content: Quote from: radiolistener on July 05, 2021, 04:20:23 pmMSO scopes are quite popular, and are particularly useful when correlating between analog and digital signals. Correlating between separate instruments is of course a PITA.Quote from: radiolistener on July 05, 2021, 04:20:23 pmNot decimation per se, which loses information, but aggregation.Min/max values are calculated for each block, either in hardware or software depending on the model.Intensity grading on the Picoscopes is not great but that's something I'm very happy to trade for the huge versatility they provide.

author: Fungus
author_rank: Super Contributor
timestamp: July 05, 2021, 08:51:42 pm
content: Quote from: james_s on July 05, 2021, 06:39:22 pmMicsigs have a really good built-in stand. And knobs, if you don't want to touch the screen.You can even use a mouse if you want. It's not as fast as the touchscreen but it's still way faster than using the knobs. You can also put the mouse in your working area to avoid reaching over to the 'scope.

author: egonotto
author_rank: Super Contributor
timestamp: July 05, 2021, 11:38:53 pm
content: Hello,Quote from: radiolistener on July 05, 2021, 04:20:23 pmreally with a screen of 800 x 480?If someone give me a complex waveform, that I can load in my Siglent SDG6022X, than I can show the pictures with several USB scopes.Best regardsegonotto

author: radiolistener
author_rank: Super Contributor
timestamp: July 06, 2021, 07:07:03 am
content: Quote from: voltsandjolts on July 05, 2021, 07:38:29 pmThis is fake waveform. Actually this is min/max chart, but not waveform. You can't see waveform details between min and max value on such min/max chart. Such mode is named Peak Detect and was used in old digital oscilloscope as a workaround to avoid aliasing due to low memory depth limitation.Quote from: egonotto on July 05, 2021, 11:38:53 pmyesQuote from: egonotto on July 05, 2021, 11:38:53 pmyou can try the following simple sanity test for oscilloscope. Use AM modulation with 10 MHz ladder waveform as a carrier and 10 kHz square or triangle wave as a message. Modulation depth 100%.You should get something like that (see pictures). The line count inside a filled area of the waveform should be equals to the ladder step count - 1.If your scope shows these lines with proper count, then it shows waveform properly. If you don't see these lines, then your scope show you fake waveform. If you can see proper wave envelope without lines, then your scope use Peak Detect mode, it's better than nothing. If you don't see envelope at all and see some garbage, then your scope showing you incorrect waveform.In my case I was used ladder waveform with 5 steps, so you can see 5 regions separated with 4 lines. Amplitude of the carrier is 4 Vpp with no termination on oscilloscope side, cable length 1 meter.

author: voltsandjolts
author_rank: Unknown
timestamp: July 06, 2021, 09:41:34 am
content: Quote from: radiolistener on July 06, 2021, 07:07:03 amFake waveform? Eh, no, it's an aggregated waveform, which contains range information. Peak detect as you say. You can then zoom in to areas of interest to see all data points. Number of datapoints available depend on hardware memory depth etc. - something which those old digital oscilloscopes you mention did not have of course. 512MS is enough for me. Also on Picoscope, it has always-on waveform buffer / segmented memory which makes full use of this memory depth, such that you can view every detail of previous waveforms.You prefer the 'aggregated waveform' to be presented as waveform intensity, and you are determined that is the only correct way.For some applications that may be true, but in the varied domains I work in the Picoscope does a fine job as a general purpose scope.Horses for courses, as they say. Or perhaps, horses for jockeys in this case

author: egonotto
author_rank: Super Contributor
timestamp: July 06, 2021, 03:27:03 pm
content: Hello,I made a try with a 10 MHZ ladder wave form and AM with 10kHz triangle.Test with:R&S RTA4000PicoScope 5243A with older software (6.12.7.2687) under VISTACleverscope CS328A (10 bit)Voltcraft DSO-2074G which is a Hantek DSO3064ABest regardsegonotto

author: Fungus
author_rank: Super Contributor
timestamp: July 06, 2021, 04:54:16 pm
content: Quote from: egonotto on July 06, 2021, 03:27:03 pmUSB's Achilles Heel revealed nicely.

author: radiolistener
author_rank: Super Contributor
timestamp: July 06, 2021, 05:25:38 pm
content: Quote from: voltsandjolts on July 06, 2021, 09:41:34 amNo, the trick is to see details with no zoom in. It should be seen on a slow horizontal scale.Quote from: voltsandjolts on July 06, 2021, 09:41:34 amI just expect to see full waveform with no simplification and no kludges and workarounds. Not min/max diagram, but a full waveform, the same as it will be shown on analog oscilloscope.Quote from: egonotto on July 06, 2021, 03:27:03 pmR&S RTA4000 has passed the test, it shows good waveform as expected.All other has failed. They show simplified min/max diagram instead of full waveform.It looks that Voltcraft DSO-2074G has issue with linearity.And Cleverscope CS328A has some strange distortion, I have no idea what is the root of cause.I wonder why your ladder waveform is a little bit noisy? What kind of signal generator did you used?

author: Fungus
author_rank: Super Contributor
timestamp: July 06, 2021, 05:41:21 pm
content: Quote from: radiolistener on July 06, 2021, 05:25:38 pmI'd sure hope so at that price.I suspect even a Rigol DS1054Z could do a decent job on that signal though.

author: egonotto
author_rank: Super Contributor
timestamp: July 06, 2021, 08:00:19 pm
content: Hello,Quote from: radiolistener on July 06, 2021, 05:25:38 pmI used a Siglent SDG6022X. In Arb function the first function is the ladder wave form.It is not only noise as the 10MHz_Ladder_1.png shows.Best regardsegonotto

author: egonotto
author_rank: Super Contributor
timestamp: July 06, 2021, 08:16:52 pm
content: Hello,Quote from: Fungus on July 06, 2021, 05:41:21 pmIn the eyes of R&S it is a cheap scope:Mathematics: basic (math on math)Trigger oprions: comprehensive (10 trigger types)Mask test: elementary (tolerance mask around the signal)Best regardsegonotto

author: kcbrown
author_rank: Frequent Contributor
timestamp: July 08, 2021, 06:33:25 pm
content: Quote from: radiolistener on July 05, 2021, 02:57:45 pmThe purpose here is display only, though. The variable in the equation is the target display resolution. You might need as much as the entire window's number of pixels per refresh, of course, since you're having to display the decimation of what could well be multiple trigger events which would yield overlapping pixels after decimation.Then it's a question of the refresh rate. I'd argue that you really only need 24 frames per second. That's the frame rate of a motion picture.Now, seeing how the use case here is a USB scope, I'd argue that you want to be able to resize the display window to something larger than a mere 800 pixels across. You might set a maximum on that to, say, 2560x1440, but in reality it should probably be capped based on whatever data rate the USB connection is capable of.What it's capable of transporting is much greater than it appears at first glance.Firstly, the vertical position data is actually whatever the scope's bit resolution is, or the vertical resolution of the screen,whichever is smaller. So there's a hard upper bound on the resolution of the vertical axis. It might be simpler to just use the scope's bit resolution to define the vertical axis of any given point.But secondly, and more importantly, what we're talking about here is very similar to a video stream, which ishighlycompressible. A 4K (3840x2160) video needs about 20 megabits per second bandwidth in order to play seamlessly at 60 frames per second. But that's when video is optimally compressed. Live streaming bandwidth requirements are going to be a better indicator of the actual bandwidth you'll need, and it seems that for 4K 60 FPS, you'll need about 50 megabits per second.Despite the vertical resolution limits, it might be simplest just to treat the waveform display as something to be streamed as a video. Of course, you'd have to compress the data in real time on the scope, but chipsets that make that possible are now widely available from what I can tell.50 megabits per second iseasilyachievable with USB 2. And this will get you the "digital phosphor" effect, or really any effect you want for that matter.

author: radiolistener
author_rank: Super Contributor
timestamp: July 08, 2021, 09:51:09 pm
content: Quote from: kcbrown on July 08, 2021, 06:33:25 pmNo. As shown above, with 800 points (actually 1600, because it require min and max value for every point) you will get the following picture.With 280000 points you will get the following picture:As you can see the difference is obvious, despite the fact that display size is about the same ~800 points width. 280000 points shows picture with detailed structure. You can see a high frequency components details on a slow time scale. The same as you can see it on analog oscilloscope.While 800 points didn't show all these details. And this is not acceptable for a full-fledged oscilloscope.Quote from: kcbrown on July 08, 2021, 06:33:25 pmYes, you can compress it. But there are two issues. First, it should be no loss compression, because some artifacts on the image is not acceptable for oscilloscope. With no loss compression you cannot obtain good compression ratio. The second issue is that compression needs additional performance and resources for both - PC and for FPGA. Since stream is pretty fast, the realtime compression can eat significant amount of CPU time. So what is better - compressed stream or a raw stream with no compression is not obvious question. In some cases the compressed stream can allocate even more wide bandwidth than a raw stream with no compression. And you cannot use some kind of MP4 with losses and good compression here, because an artifact can be interpreted as a signal glitch which is not acceptable. Also compression needs a lot of additional resources on FPGA. So it will cost more money.25 fps can be acceptable, but this is too low update rate to get "live effect". 60 fps will be a good choice. I tested it and can say that 75 fps for oscilloscope looks much more smooth and more "live" than 30 fps.

author: kcbrown
author_rank: Frequent Contributor
timestamp: July 08, 2021, 11:55:39 pm
content: Quote from: radiolistener on July 08, 2021, 09:51:09 pmYes, I realize that. I wasn't arguing for a mere 800 points worth of transmitted data.QuoteThat's fair, but that only constrains the degree or kinds of of loss that would be acceptable.QuoteThat depends on the amount of difference between frames. If the amount of frame-to-frame difference is consistently substantial (like it would be when you're looking at random noise) then you won't get good compression, but at 24 frames per second or higher, the end result will be so much of a mess that accurate representation won't matter anymore anyway. The entire point of being lossless is so that you can see transients easily and so that you'll have correct gradients when the display is reasonably stable. Both of those situations are ones for which compression will be high.So I expect that the amount of compression is actually likely to beveryhigh, even if you make it lossless.Remember, too, that the vertical resolution is constrained by the sample resolution. If you're talking about 10 bits of resolution thenat mostyou're talking about 1024 values worth of vertical resolution. Oh, and the values themselves arenotRGB values. They're just intensity values.The worst possible case here is a very wide window (e.g., 3840 pixels) being used to display noise that fills all of the vertical values. But for a 10 bit sample resolution, that's 3840 x 1024 x 8 bits per frame, or 31 megabits per frame, uncompressed. At 24 frames per second that's 754 megabits per second. If you could cut that in half somehow then you could just squeak it under the USB 2 bandwidth limit. Or you could drop to 12 frames per second for random noise, or something.QuoteOf course. But as I said, the chipsets for this type of work are readily available and, as far as I know, relatively inexpensive (though I haven't done the research on that, and in any case, what we're talking about might well be a custom implementation anyway).QuoteYou either pay for it with a higher bandwidth link or you pay for it with compression hardware. There ain't no such thing as a free lunch. But remember that the original claim is that this kind of displaycan'tbe done over USB 2, and that's clearly not true.QuoteThat's true, but those are pathological cases, for which you'd want to do something else anyway.QuotePerhaps. Perhaps not. It depends entirely on the nature of the artifacts and how they show up in the first place. I don't know enough about how the compression works to make any kind of reasonable guess as to how well it'll work, but I fully expect that it involves frame difference encoding among other things. Icansay that in videos of people using their scopes, I've not seen anything to make me believe that it'll be a real problem.But it should be easy enough to test this. Take a video of your scope's screen, then compare the resulting video against what you originally saw on the scope, and see if there are any obvious artifacts that would somehow cause you to change your assessment of what the scope was telling you.QuoteOf course. There ain't no such thing as a free lunch.QuoteI certainly agree that 60 FPS would be better, but if a tradeoff has to be made, a drop in FPS is the logical first step.The real question is why you want a higher frame rate in the first place. This is a test instrument, not a video game. Interactive responsiveness is likely to be limited more by the other processing that happens within the scope than by the frame rate. And one can easily argue that a lower frame rate isbetterfor seeing transient glitches because it allows a glitch to remain on screen for longer.

author: rsjsouza
author_rank: Super Contributor
timestamp: July 09, 2021, 01:45:13 am
content: Interesting that Picoscope website shows some heat mapped waveforms which precludes applying weights to specific pixels on the frame buffer to display their relative frequency of occurence.https://www.picotech.com/library/oscilloscopes/digital-persistence-modesI obviously don't know Pico's implementation, but I imagine the hard work of calculating and formatting the framebuffer with the proper weights to the pixels is done in the custom hardware - especially also because of the very high waveforms per second count.If I haven't missed any details, there's not much difference than a standalone oscilloscope, since the only difference would be the speed of transmitting all the data via the wire - USB2.0 and the newer implementations have an excellent link budget (unless perhaps if you are doing high speed transfers in the same USB chain).

author: 2N3055
author_rank: Super Contributor
timestamp: July 09, 2021, 06:22:28 am
content: Maybe instead of wild speculation and funny numbers pulled out of the hat some real data might be interesting.Unlike many, Picotech exactly documents what is being transferred and how. In their API manual.And it's not compressed or 800 points. (why 800 points).Also Pico has (Tektronix like) two display modes, a standard and persistence mode. In persistence mode it can have classic intensity grading, or color grading with several strategies and phosphor emulation. Palette is also adjustable. You would use that for that type of work. It's not very good, because of short sample lengths used ( to maximize wfms/sec), despite persistence algorithms being excellent. It will work great for signals that don't have too heterogenous frequency content (widely scatered frequencies from low to high), because sample rate drops quickly like in Keysights in that mode..In standard mode it has flat pixel rendering without intensity. In that mode it simply plots data points and not emulating phosphor. And won't be of much use for looking at intensity gradients of AM modulated signals. But it will calculate measurements over full 100MS buffer.... In that mode it plots on screen similar to old Teks without intensity...So yeah, as I said many times before, every instrument won't be brilliant at everything. 20000 USD Keysight MSOX4100 cannot capture PSU startup sequence 100 msec long at 1 GS/sec because you need 100MS for that and it has 1 or 2 or 4 based on settings. At those high lengths it will drop sampling rate to 10 MS/sec and still keep 1 GHZ input filter and will heavy allias with anything going over 5 MHz.Fact that it has brilliant phosphor emulation won't help you there.And also nice intensity plot is only a visual aid. If you're going to inspect that signal, you will still need to zoom in and look at the signal at a carrier and modulation friendly timebases...There are many combinations different carriers and modulation waveforms that will produce same visual effect, including artefacts from aliasing at unlucky timebase/mem depth combinations and interaction with scope refresh rates.If you work on a known signal and know what exactly to expect, you can just look at shapes in a manner of a signature analyser.If you are analyzing signal, then, well you analyze it...Fact is, you can confuse any instrument if you try. Or if you know your instrument, you can avoid problems, by knowing it's limitations.Otoh, it's fun to see a little Siglent is shown as a reference example of a well made implementation. It is amazing how much of the useful instrument you can get these days for not much money, compared to only 10 years ago...

author: Andrew_Debbie
author_rank: Frequent Contributor
timestamp: July 09, 2021, 07:02:08 am
content: Everytime I look at getting a Picoscope, I end up back at a Siglent SDS-1000X-x series.UK prices from UK distributor. Prices include tax.SDS1202X-E 2CH 200MHz 1GS 14Mpts, ? A/D £360SDS1104X-U 4CH 100MHz 1GS 14Mpts, 1 A/D £391.20 - reduced feature setSDS1104X-E 4CH 100MHz 1GS 14Mpts 2 A/D £454.8Pico2207B 2CH 70MHz 1GS 64Ms £3792208B 2CH 100MHz 1GS 128Ms £4792407B 4Ch 70MHz £579I belive the Picoscopes all have per channel A/D but I'm not certain.It is hard to justify paying more for a Picoscope than a Siglent SDS-1000X-x series.

author: tautech
author_rank: Super Contributor
timestamp: July 09, 2021, 08:03:42 am
content: Quote from: 2N3055 on July 09, 2021, 06:22:28 amThat little Siglent is a some years old SDS1000X model and their first compact using what is now a much further developed GUI with 8” display and 50 ohm inputs.Later X-E and the new X-U have the more powerful Xilinx processors but otherwise owe their parentage to SDS1000X models.

author: tautech
author_rank: Super Contributor
timestamp: July 09, 2021, 08:11:13 am
content: Quote from: Andrew_Debbie on July 09, 2021, 07:02:08 am4ch X-E are the pick of that bunch if you’re looking for the fullest featured scope.