USB oscilloscope -  still not worth it? - Page 1
Forum section: electronics / testgear

author: sirvalence
author_rank: Newbie
timestamp: December 25, 2014, 03:31:28 pm
content: hiya,I know this question has been asked before but the last discussion I could find was 3 or 4 years ago, so I thought to ask if the situation is the same.Are USB Oscilloscopes still not worth it? and if not, is this something that is likely to change?to be clear, I don't just mean to compare for an entry level Rigol. I could be ok paying a few hundred more for something that works well.I sometimes switch continents for months at a time so the idea of packing a small usb device instead of one with a screen is very appealing.Thanks for your thoughts!

author: wraper
author_rank: Unknown
timestamp: December 25, 2014, 04:20:11 pm
content: If compared to the same specifications, USB oscilloscopes are not cheaper but actually even more expensive. If you want very cheap, better buy "normal" cheap Chinese oscilloscope. Like Hantek, Atten, whatever, maybe used. As of cheapest decent scope, then look for Rigol DS1054Z, $400 in US.

author: sirvalence
author_rank: Newbie
timestamp: December 25, 2014, 04:31:16 pm
content: thanks for your response!I don't need cheaper. More expensive is ok though I'd like to stay under $1000us. the main attraction for me is the size and portability of a USB device.

author: pickle9000
author_rank: Super Contributor
timestamp: December 25, 2014, 04:34:31 pm
content: Picohttp://www.picotech.com/

author: wn1fju
author_rank: Frequent Contributor
timestamp: December 25, 2014, 05:56:24 pm
content: I second the previous post recommending the PicoScope series. In addition to their included PicoScope oscilloscope software (which also serves as a rudimentary spectrum analyzer), you can get the Software Development Kit which allows you to write your own applications with the Picoscope merely serving as a digitizer. That's what I'm doing with their (higher-end) 6000 series model where I work. And their support (via e-mail) is very good too.

author: Lightages
author_rank: Unknown
timestamp: December 25, 2014, 06:40:47 pm
content: I have a Picoscope 2105. I purchased it to have a portable serial bus decoder and a simple oscilloscope. I have not had much time to check through all of its abilities yet but I am a little disappointed with the software so far.The GUI is something from the 1990s IMHO. There are some glaringly obvious things missing like Y axis cursors, it has very very simple triggering modes, no triggering on any of the serial decoding, and the software has a couple of bugs.The software is extremely important for a USB scope and for such mature products I am very surprised at the lack of some very basic functions in the Picoscope software.

author: HKJ
author_rank: Super Contributor
timestamp: December 25, 2014, 08:29:50 pm
content: Quote from: Lightages on December 25, 2014, 06:40:47 pmI have been using Pico scopes for a couple of years and cannot recognize your description of the software.The software has both X and Y cursors, try reading the manual or watch an instruction video.Triggering depends on oscilloscope model, and can include advanced modes, but not protocols (They are done in software).You do always get all functions with the scope, you do not need extra licenses to decode protocols.The software is frequently updated, i.e. bugs are fixed and you get new functionality on your old scope.Another nice details with USB scopes is that you can run them from a battery powered laptop and avoid all problems with ground loops between equipment.

author: Lightages
author_rank: Unknown
timestamp: December 26, 2014, 01:45:59 am
content: You are correct. I did not notice the small little tiny blue grab handle for the Y axis cursors. I guess I can understand not having a decoded serial trigger in real time when it is over USB. I maybe am expecting too much. They could make it stream and detect the trigger value and then move the cursor to that point and stop the display.The bug I have is with the 2105 there is tip illumination on the probe. If I save a custom user default setup, the tip does not light until I go into power settings, turn it off and then turn it back on, even though it is already set to on by default. This happens on all my computers not just one.I still do contend that the Picoscope software is not the most user friendly but I have seen much worse.Anyway, I do not want to hijack this thread.USB scopes do have their place, but you have to know what you need and if a USB scope will meet those needs. It is a trade off between portability and real world performance.

author: Rubi Han
author_rank: Contributor
timestamp: December 26, 2014, 02:17:28 am
content: Quote from: sirvalence on December 25, 2014, 04:31:16 pmYou may consider Micsig tablet touch oscilloscope TO102 within your buget, with 150,000mAh built-in battery; 100MHz, 18Mpts mermory depth, 1GS/s sampling rate, 2CH, 50,000wfms/s capture rate; You can see the video to learn our touch oscilloscopehttps://www.youtube.com/channel/UCu37SRPI8SaavIhzlXojEnARubi Hanhanzuncheng@micsig.com

author: sirvalence
author_rank: Newbie
timestamp: December 26, 2014, 02:48:03 am
content: Thanks for all the feedback!The pico scopes look like the ticket and I think the 3000, and maybe even the 2000 series will be adequate for my work (analog audio).I agree that the gui leaves something to be desired but I can live without sexy scope software as long as it is functional.The Micsig tablet looks like a really nice solution, however I will benefit from a logic analyzer which doesn't appear to be an option here.

author: cncjerry
author_rank: Unknown
timestamp: December 26, 2014, 07:16:38 am
content: For high end audio work, I am wondering if a USB scope is desirable due the lack of isolation. It seems to me whenever I attach any computer to my system(s) I pickup buzz. I am running all analog Krell gear. Just attaching a RCA digital spid/f to an outboard DAC generates audible noise. A battery operated, isolated scope would maybe eliminate some of this noise.

author: nctnico
author_rank: Super Contributor
timestamp: December 26, 2014, 05:05:42 pm
content: There are USB isolators available.

author: janoc
author_rank: Super Contributor
timestamp: December 26, 2014, 05:11:43 pm
content: Quote from: nctnico on December 26, 2014, 05:05:42 pmAnd they are usually up to USB 1.1 or USB 2.0 (rarely and expensive). Not exactly great for something like a scope needing a fast USB link.BTW, if the goal is portability and mains is available at the destination (thus not e.g. hacking on a car ECU somewhere in the fields) why not get a normal standalone digital scope? It is certainly more portable than a laptop + USB scope + isolator + mess of cables for everything and the specs are much better, even for the crappiest scopes like low end Attens.Of course, if you need the laptop with you anyway, then the tradeoff may change, but in general USB scopes are really either overpriced toys or something meant for really niche use cases.

author: Mark_O
author_rank: Frequent Contributor
timestamp: December 26, 2014, 05:42:20 pm
content: Quote from: sirvalence on December 26, 2014, 02:48:03 amIn that range, you may want to look at their 3204D. I had been looking at the A/B models, and initially missed the D, which is vastly improved. The 128 MS depth is excellent (gets divided by # of active channels), and it has the logic analyzer capabilities you indicated would be helpful.For audio work, you can oversample to increase the ENOB, and a deep FFT will provide lots of detail with lower noise floors. The 1-million sample FFT capability will reveal far more information than you'll ever see on any of the inexpensive desk scopes, with FFTs limited to a few k-samples. For those, your low-level audio signals will be buried in sampling noise. The log-log display mode will be useful.Lastly, the USB3 interface gets the data from the scope buffer into your PC for analysis and display, very quickly. The advanced triggering capabilities on this model are particularly flexible. It also has a one-channel 12-bit Arb generator built-in, handy for generating test signals.You didn't indicate your location, but here in the US,Saelighas good discounts off the List Price on the Picos. The 3204D is ~$100 off List (under your $1k target), with free shipping (which costs a bit if you have them shipped here direct from the UK).I'd agree with others that if you have to lug a laptop alongjust for your scope use, then a standalone DSO may make more sense. But if you'll already have a laptop with you anyway, for other uses, then packing a compact 1.5x6.5x7.5" ~1 lb. box could be a big win. Other than your probes, the only other cable you'd need would be the USB to laptop link (includes power).

author: TopLoser
author_rank: Unknown
timestamp: December 26, 2014, 05:44:40 pm
content: I've got a box of PicoTech scopes under my desk.They do have their place in a workshop (apart from under my desk), nice to have all the protocols included from the start (and added to) as the PC is updated). Most of them have arbitrary waveform generator built in as well. PM me to get first pick, I'll be listing what's left for sale later this week.

author: jaxbird
author_rank: Frequent Contributor
timestamp: December 26, 2014, 05:49:08 pm
content: Quote from: sirvalence on December 25, 2014, 03:31:28 pmNothing fundamentally wrong with a USB based scope, IMO it's no worse or better than many of the hand held scopes available, except the handhelds are isolated and not GND/Earth referenced. But they are equally frustrating to use when you are debugging a circuit.Proper buttons and knobs just feel so damn nice and intuitive when you are poking around in a circuit.

author: mazurov
author_rank: Frequent Contributor
timestamp: December 26, 2014, 06:59:10 pm
content: Take a look at Agilent U2701A/2702A modular USB scopes. The 100MHz variant might even fit your budget. IIRC the USB interface is isolated internally.

author: nctnico
author_rank: Super Contributor
timestamp: December 26, 2014, 08:35:32 pm
content: IMHO the biggest problem with a USB scope is the lack of dedicated knobs for the controls. I have used Picoscope in the past and found their scale values cumbersome to use. You can choose between 1-2-5 full scale ranges. On a regular oscilloscope you choose volts/div. With the standard 8 divisions in height selecting 1V/div leads to 8V full scale which is just nice to look at a 5V signal or at 0.5V/div 4V full scale for a 3.3V signal. On a Picoscope you'd use 10V full scale for showing one '5V signal' and 20V full scale for 2 traces which leads to signals showing smaller than you are used to even though you have a bigger screen. I guess you could adjust that but it's just fiddly.Another pitfall for USB scopes is that they usually have a much more limited input range than a regular oscilloscope. On the mid-range Picoscope I used the maximum was 5V. And it didn't have 50 Ohm inputs even though it was a 200MHz model.

author: aat24
author_rank: Contributor
timestamp: January 22, 2015, 02:58:08 pm
content: A product overview covering USB oscilloscopes in the price range of 100 to 500 USD and with minimum 50 MHz bandwidth was recently published here:http://oscopes.info/market/2256-usb-oscilloscopes-product-overview-low-end

author: rx8pilot
author_rank: Super Contributor
timestamp: January 22, 2015, 08:20:41 pm
content: Quote from: nctnico on December 26, 2014, 08:35:32 pmIn the high-end world of audio recording, all the knobs and buttons have become encoders for some remote rack of I/O. Long ago the audio running through the pot on the console disappeared and it is for the better. There is no reason that a USB interface of knobs could not be coupled to a a USB acquisition device to make a very usable high-end scope solution. The high-end Agisight and LeCroy scopes do all of the heavy lifting on the acquistion board and the display is all handled by a PC of limited power. I would love to see this concept on my bench. If the acquisition board is doing its job, the USB bandwidth needed is not over the top since it only has to transfer the data to be displayed.

author: Pjotr
author_rank: Frequent Contributor
timestamp: January 22, 2015, 09:06:35 pm
content: I see sometimes audio studios too on the inside. A DAW speeds up work flow a lot with a skilled operator. However the way of working is and set up is quite different there than at an EE lab. The set up is fixed for the most of the part. And one of the complains of musicians nowadays is the lack of direct interaction with the equipment: They love to turn knobs

author: zapta
author_rank: Super Contributor
timestamp: January 22, 2015, 09:09:31 pm
content: Quote from: pickle9000 on December 25, 2014, 04:34:31 pmI see that they also support Max OSX. That's nice.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: January 22, 2015, 09:40:12 pm
content: Quote from: rx8pilot on January 22, 2015, 08:20:41 pmWell, no. The acquisition board does what the name says - acquiring the analog signals, converting it to digital and feeding it to the PC part via fast PCIe interconnects. But all the heavy stuff (i.e. the processing of maths and signal analysis) is done in the PC part, with a power that isn't that limited btw (unless you call highend multicore processors and tons of RAM 'limited).

author: rx8pilot
author_rank: Super Contributor
timestamp: January 22, 2015, 09:52:06 pm
content: Quote from: Pjotr on January 22, 2015, 09:06:35 pmMy point is that the 'creatives' have plenty of knobs to fiddle with, they are just sfot knobs that have a software determined function. There are still linear faders, buttons, and everything.Quote from: Wuerstchenhund on January 22, 2015, 09:40:12 pmI am not a scope designer by any means, but the Agisight S series seems to have the majority of the challenges dealt with in the acquisition stage including waveform memory and DSP needed for FFT and other heavy math. The PC side seems to handle post acquisition signal processing as well as display, knobs, keyboard and mouse. That appears to be how it can layer many functions without slowing down. There is not much reason to send 1 million waveforms per second to the PC when you only need a fraction of that for display.Do the LeCroy's rely on the PC and Windows OS to to process all that data?

author: HKJ
author_rank: Super Contributor
timestamp: January 22, 2015, 10:56:41 pm
content: Quote from: mojo-chan on January 22, 2015, 10:31:16 pmI have been using Picoscope for some years and have only had minor problems with buggy software.For me the design works very well, it is not packed with "smart" design, but is very functional and easy to use. I do not like PC scopes designed with virtual knobs on the screen, it is a waste of screen space and more difficult to use than real windows controls.It is easy to try the software, it is possible to download for free and it will work in a demo mode when no scope is connected.

author: manzini
author_rank: Regular Contributor
timestamp: January 23, 2015, 07:27:41 am
content: Quote from: HKJ on January 22, 2015, 10:56:41 pmthen I think an oscilloscope with thunderbolt (sorry I hate usb on windows due latency issues), combined with an external controller like a DAW with "real" push&pots that would be nice. Maybe the best of two worlds ?dreaming is free, I just settle, if instrumentation software developers could implement a usb midi interface and allow mackie control protocol.

author: Pjotr
author_rank: Frequent Contributor
timestamp: January 23, 2015, 02:19:56 pm
content: I have used a Picoscope for trouble shooting on location. Main reason was its size and I had to carry my laptop anyway. Had some issues with the software. It is always luck if the software finds the scope, kind of a lotto machineI cannot say it is a productive solution either, controlling a scope with a mouse and small on-screen buttons.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: January 23, 2015, 02:34:16 pm
content: Quote from: rx8pilot on January 22, 2015, 09:52:06 pmThe sample memory is indeed with the acquisition system (only the revelant data is recalled and pushed to the PC part), but modern high end scopes in general do a lot (Agilent, Tek) to most (LeCroy) of the processing on the PC part. Which is understandable since developing individual DSPs for every function doesn't make much sense and is less flexible.In terms of Agilent/Keysight, it's true that older Agilent Windows scopes (i.e. the dreadful 54800 Infiniiums running Win9x) did not make much use of the PC part other than using it for displaying information, but all newer Agilent high-end scopes push most of the processing to the PC side.QuoteYes, mostly. LeCroy X-Stream uses the (very fast) CPU cache for all their calculations, which is one reason why these scopes are usually pretty fast and flexible when it comes to processing. In fact, even their pre-Windows scopes (i.e. the WaveRunner LT/WavePro 900 Series) did almost all maths and calculations in the "PC side" (which in these scopes was a PowerPC "PC" like found in older Apple Macintosh computers, just running VxWorks instead of Mac OS), and their scopes before that did that with 68k processors. LeCroy pretty much settled on more or less standard computer technology when others were still baking their own DSPs for most of their scope's functionality, which allowed LeCroy scopes to do things that other scopes couldn't because of their inflexible architecture.

author: manzini
author_rank: Regular Contributor
timestamp: January 23, 2015, 03:23:26 pm
content: Quote from: mojo-chan on January 23, 2015, 11:57:23 amThanks for the warning. I am completely ignorant about TB. To me it was a hope, tired of latency issues with USB audio on windows or any attempt at RT. I will research for my curiosity about what you have shown me.A core Rigol DS2000-TB without display (computer for this) with third party diy/usb/midi/ipad controls supported, seemed like a good idea.Thanks a lot.

author: nfmax
author_rank: Super Contributor
timestamp: January 23, 2015, 03:40:57 pm
content: Well duh! Thunderbolt is insecure in much the same way that PCIe is insecure: it's a direct connection to the system bus. Presumably you would never plug any third-party card into your PC?

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: January 23, 2015, 03:49:19 pm
content: Quote from: nfmax on January 23, 2015, 03:40:57 pmIt's somewhat difficult to attack a bus which is predominantly located *inside* some kind of enclosure. It gets a lot easier once the bus is available externallyThe Thunderbolt vulnerability is actually rather stupid, considering that Firewire suffered from a similar issue.

author: janoc
author_rank: Super Contributor
timestamp: January 23, 2015, 03:50:56 pm
content: Quote from: mojo-chan on January 23, 2015, 11:57:23 amEhm and USB 3 (or USB in general) is secure by a virtue of what, exactly?Also we are talking about an interconnect to attach a peripheral to a general purpose computer. I thought that the security is determined by how the data are secured, what the OS allows to do with them and various organizational measures (such as who is allowed to approach and use the machine), not by which connector is something plugged in.Well, that is unless you are talking about "security" a-la Apple orLextronicLexmark with peripheral authentication (forms of DRM). But that has nothing to do with the security of your design documents stored on that machine.

author: nfmax
author_rank: Super Contributor
timestamp: January 23, 2015, 03:57:38 pm
content: If an attacker has physical access to the machine - inside or out - it's game over. The 'vulnerability'http://en.wikipedia.org/wiki/DMA_attackarises because a Thunderbolt device, like many others, can transfer data by DMA transfer into main memory. That's what makes for a usable, responsive PC oscilloscope. Can you imagine what it would be like if every waveform had to be scanned for viruses before being shown on the screen?

author: janoc
author_rank: Super Contributor
timestamp: January 23, 2015, 04:00:39 pm
content: Quote from: nfmax on January 23, 2015, 03:57:38 pmDon't USB 3.0 interfaces also use DMA? I cannot imagine it being implemented differently, except maybe on standalone phy chips (if there are any), considering how high-speed interface it is.

author: elgonzo
author_rank: Unknown
timestamp: January 23, 2015, 04:31:43 pm
content: Quote from: janoc on January 23, 2015, 04:00:39 pmImplementation is quite differently. TB extends the PCIe bus, and a TB device can initiate DMA transfers from/to main memory - underneath the OS so to speak. USB 3.x does not have the ability to let USB devices initiate such a low-level access to main memory by themselves. USB DMA is initiated and controlled by the respective drivers, not by the USB device hardware.However, such a threat can be addressed by placing a kind of gatekeeper (IOMMU) between the host's TB controller and the memory controller. Both Intel CPUs with VT-d and AMD CPUs with Hypertransport have integrated IOMMUs, and it is up to the respective BIOS and/or OS to utilize this IOMMU to protect against TB DMA attacks.

author: rx8pilot
author_rank: Super Contributor
timestamp: January 23, 2015, 09:22:38 pm
content: I can't believe the thread is discussing the security merits of TB and USB.