Switching from bench to USB scope - bad idea? - Page 1
Forum section: electronics / testgear

author: Hagrid
author_rank: Contributor
timestamp: October 27, 2018, 11:36:28 am
content: Hello folks, a bit ago I started a thread where I have asked for a scope with good analytical features.Some Lecroy devices looked really awesome first, but I now tend to get a Picoscope 5444D.I have a hacked Rigol DS1054Z at the moment (and a crusty analog 20MHz Hameg) and plan to sell the Rigolin order to get the Picoscope.Is this a good Idea? The Rigol device is awesome at this price point and great for general purpose use, to probe around a prototype or when repairing a device. I think this is true in general for most bench scopes since you have great accessibility by a dedicated front panel. On the other hand it is almost limited to the internal features. Exporting data is really slow painful and ugly. This means that I am locked down to the features it offers. For the most part that's more than enough, but when doing more analytical things and statistics its basically useless.It seems that the 5444D with its huge segment able memory is a nice solution here. Even when the memory is full I can just get the data on my computer in a reasonable time via USB 3 and acquire more. For further processing I plan to use Matlab or GNU Octave. The switchable resolution is also a killer feature. The only thing I can't tell is how good it will replace my Rigol when doing general purpose tasks.What do you think, should I sell my Rigol and get the Picoscope? Should I get the cheapest (about 100USD) Picoscope first to check if I like the way it works? Or are these devices completely different meaning I should keep both? I am not really a fan of wasting 100 bucks, but after all its a fraction of the price of the 5444D.Greetings, Hagrid

author: Fungus
author_rank: Super Contributor
timestamp: October 27, 2018, 11:54:03 am
content: a) It depends on your work flow. If your Rigol is always used where there's a powered-on PC then it might work out.b) You can download the sample data from your Rigol to your PC. After that the analysis is up to the software on your PC. Trying a few programs before you make a decision won't cost anything.

author: Hagrid
author_rank: Contributor
timestamp: October 27, 2018, 12:28:36 pm
content: Quote from: Fungus on October 27, 2018, 11:54:03 amI have tried out the python scripts but this is just really slow in general (for example: set single trigger, measure peak after a trigger, transmit data and repeat). Is there a way to download the whole memory when segmenting it? I couldn't find anything.

author: 2N3055
author_rank: Super Contributor
timestamp: October 27, 2018, 12:42:44 pm
content: If you can afford to keep ds1000Z AND get Picoscope would be best option...Little Z machine is excellent for service/ repair scope (like you said), and Picos are great as analytic scopes and protocol decodes.If would have to chose which one to have as a single one, I would choose Pico.I don't care for buttons, GUI is on enough, I always have a PC ready at the desk, and USB3 series from Pico are fast enough to be interactive. Not great but kinda OK. And much better in everything else.But again, best option is to have a standalone interactive scope and Pico. That combination replaces scopes that cost waaay much more than those two combined...

author: MrW0lf
author_rank: Frequent Contributor
timestamp: October 27, 2018, 01:00:51 pm
content: Quote from: Hagrid on October 27, 2018, 11:36:28 amI have 4 USB scopes incl 3 Picos. For brief period had Rigol also. Each scope is different and they form complementary system.Oldest PS 2205 25MHz 2ch (which is similar to 2204A) is still often used. It runs very smooth with PS6 software because it is generation of scopes for which software was originally designed. Also it does all stuff on full memory buffer. I like to use it as V*I integrator.PS 2408B is new gen with large memory. There they are forced to do more onboard processing and in some cases transfer only some tens of kSa worth of snapshots until trigger/zoom whatever. When using automated measurements, roll mode etc you must know thresholds for "snapshot mode" transition.Common issues are lack of good DPO and serial trigger. DPO is separate mode which sort of works but measurements are disabled and memory buffer is tiny.ETS might turn to be useful because it will run full blast on all channels at the same time eg 4x20GSa/s.Full capability of scopes can be unlocked only with SDK because PS6 software is bit overwhelmed by new gen scopes at times. Especially at data transfer rates and wfm/s.Rigol has more-less normal DPO and serial trigger. You can use trigger out help Pico.So all in all if you keep Rigol you wont care for Pico issues because it covers them. Also if you get 2204A it probably wont be left gathering dust in future because you can run 2 PS6 instances to get sort of independent timebase mode with 2 scopes etc. It is sized as probe adapter so will not run of desk space also no matter how much of USB gear you pile up.And when collect little funds can swap Rigol for Siglent X-E to cover DPO type of tasks.

author: ebastler
author_rank: Super Contributor
timestamp: October 27, 2018, 01:31:41 pm
content: Nobody has mentioned "look and feel" yet, I believe.Personally, I like knobs and buttons on a scope. While measuring something, I often hold a probe in my right hand. I feel comfortable adjusting knobs on the scope with my left, but am really clumsy at moving a mouse pointer left-handed (be it via a mouse or touchpad). Your preferences may be different, of course; but I think it is important to be aware of this aspect.

author: tkamiya
author_rank: Super Contributor
timestamp: October 27, 2018, 05:04:29 pm
content: Unless I have a certain application in mind which PC based product is suitable, I tend to stay away from them. Reason is longevity.For example, TEK 465 is perhaps 35+ years old and still going. I don't recall any product that require a computer to work still used from that period. (yes, they existed) I have one of those "automated" equipment from late 70s. Software is long gone and so as a platform that can run it. It's an automated VNA.PC and particularly OS change so often. Maintaining compatibility with previous releases tend to be hit and miss, and there is no body even remotely concerned about doing anything to maintain Windows 3.1 compatibility. This trend will likely accelerate.Since test equipment for me is a "forever" purchase, I don't want my test gear to depend on a PC.I guess it's different if you are building an assembly line where product cycle is rather short, or money is a prime concern.

author: 2N3055
author_rank: Super Contributor
timestamp: October 27, 2018, 07:20:22 pm
content: Quote from: tkamiya on October 27, 2018, 05:04:29 pmNone of today's standalone scopes will last that long. And no spare parts will be available. And higher end ones are just fancier version of Picoscope (digitizer board) + PC + screen put in a box.I have a Picoscope 212/100 from 2003..Still works, I have old laptop dedicated for it.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: October 27, 2018, 08:41:07 pm
content: Quote from: tkamiya on October 27, 2018, 05:04:29 pmMy 2205 is 8 years old. All new stuff still supported, bugfixes continue etc. How long till typical low end DSO firmware dev drops. completely 3-4 years max? So it's relative. Also I could be possible to run some older opsys as virtual machine depending how well drivers will like it.

author: tkamiya
author_rank: Super Contributor
timestamp: October 27, 2018, 11:16:01 pm
content: Quote from: 2N3055 on October 27, 2018, 07:20:22 pmThat's why I stick with older ones. I can't imagine buying something in excess of ten thousand dollars and not be able to get it repaired.

author: _Wim_
author_rank: Super Contributor
timestamp: October 28, 2018, 08:12:58 am
content: Quote from: 2N3055 on October 27, 2018, 12:42:44 pmI second that. I also have a pico 5000 series scope, and a rigol ds1000z. Both get used quite often. Apart from the physical buttons on the Rigol, I also like the fact that is has a much higher max input voltage, so less likely do damage the front end when probing unknown circuits.

author: VEGETA
author_rank: Super Contributor
timestamp: October 28, 2018, 08:49:34 am
content: I am not an expert but I always find the bench scope a better choice overall, you should find a workaround to get what you want from it if that is your case.However, if you want to sell the analog old scope (provided it is working), then I am interested. Especially if price + shipping is reasonable enough.Good luck!

author: Hagrid
author_rank: Contributor
timestamp: October 28, 2018, 05:34:39 pm
content: Thanks all for the answers. It looks like its mostly personal preference. I think the lower voltage range is a somewhat interesting point, but usually I don't work with line voltage or similar. Maybe I should keep the Rigol first and decide then to sell it or not. I don't want it to sit in a corner and collect dust.Quote from: VEGETA on October 28, 2018, 08:49:34 amSorry, it was my fist scope and I learned so much with it. Selling it would break my heart.If there are any important points about the Picoscope please fell free to share.Greetings, Hagrid

author: james_s
author_rank: Super Contributor
timestamp: October 28, 2018, 05:43:40 pm
content: I don't like PC based instruments, they save very little in cost, the display and controls is no longer a major part of the cost of an instrument. I find that a laptop takes up quite a lot of bench space and it's awkward to find somewhere to balance it. Cables and cords strung around get in the way, usability of scope type controls with a touchpad is tedious, you can have problems with drivers, and if you do need to use a PC say to look at a datasheet or load code into a microcontroller or something like that you either need a large monitor or you're awkwardly flipping between applications. A standalone instrument is just so much nicer to use, I only keep my USB scope around when I think I might want a scope but don't want to drag around a real one.

author: _Wim_
author_rank: Super Contributor
timestamp: October 28, 2018, 06:30:35 pm
content: Typically I would agree about the cost of usb instrument vs bench instrument, but:try to find anaffordablescope with:- very high resolution (>12 bit)- lots of decoding options without additional cost- large memory depth (512MS)- built in AWG- possibility to run bode plots- a large display (>10")I think the Picoscope 5000 series are here in a kind of niche, they are not cheap, but nothing else in this price segment (<2000€) has this combination available. I would typically not recommend their offerings below 500€, because in this segment Rigol and Siglent rule.As to the laptop being akward, I would recommend a USB docking station with two monitors attached. I use one monitor for browsing and datasheet, and the other for virtual instruments or devellopment software. This does indeed mean you are kind of fixed to a single location (mostly that does not bother me), but for that reason it can indeed be very handy to keep the Rigol around also.

author: eugenenine
author_rank: Frequent Contributor
timestamp: October 29, 2018, 12:33:12 am
content: Thoughts on the digilent scopes?https://store.digilentinc.com/usb-scopes-instruments-circuits/I don't have a bench so when I want to do anything I have to pull equipment from the shelf in my closet. I have a Tek 2211 but it takes a lot of space.

author: james_s
author_rank: Super Contributor
timestamp: October 29, 2018, 02:34:57 am
content: If those are things you need then a USB scope may be a reasonable option however none of that is something I need. Even older DSOs typically have more than enough memory for typical use, and it's rare that I'd need a built in AWG. Having real knobs and buttons is *so* much nicer from a usability standpoint than clicking virtual controls on a screen. I also very much prefer an all in one unit with a handle on top that I can carry around and position as needed, I hate having to deal with dongles and external devices plugged together.

author: _Wim_
author_rank: Super Contributor
timestamp: October 29, 2018, 08:43:02 pm
content: The built in AWG (signal generator) is only usefull for the bode plotting, because it can be synchonised with the FFT of the input channels. I think I see this kind of scope more as a sort of network/dynamic/spectrum analyzer with the posibility to show scope traces simultaniously. For "pure" scope use, I also would recommend a bench scope.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: October 29, 2018, 09:19:07 pm
content: Quote from: eugenenine on October 29, 2018, 12:33:12 amHere thread with some data:https://www.eevblog.com/forum/testgear/digilent-analog-discovery-2-75742/Strictly as a scope it is quite limited by 100MSa/s sampling rate and 2x16kSa memory. Frontend as such goes to about 50MHz for frequency domain related tasks. Software architecture is innovative because GUI is mostly accessible via scripting and can surgically add DIY functionality w/o need to write all the helper crap you would need with just SDK.Directly from knobbed DSO, for non-programmer - quite steep change. Picos are somewhere in the middle.

author: Hagrid
author_rank: Contributor
timestamp: October 30, 2018, 09:35:42 pm
content: Quote from: MrW0lf on October 27, 2018, 01:00:51 pmI have not dived fully into the sdk capabilities, but do you man that the sdk can also make use of all features which are offered by the picoscope 6 software (like hardware acceleration and so on...)? Would it be able to build a complete custom gui?

author: MrW0lf
author_rank: Frequent Contributor
timestamp: October 30, 2018, 09:56:36 pm
content: Quote from: Hagrid on October 30, 2018, 09:35:42 pmhttps://www.picotech.com/library/documentation"Programmer's Guides"Looking diagonally I can see at least all the main things covered, including downsampling in hardware etc. So dunno if 100% complete but pretty much in the ballpark.Most questionable thing for me in PS6 are various limitations to ensure steady operation. But PCs are not created equal and some limitations seem to be over the top. For example why limit frame rate in main mode to "visually sensible". Ok for visual inspection perhaps no big difference if 25fps or 100fps but huge difference for blind time and measurement stats gathering time.Also streaming (roll) mode speed limitations are quite severe.These problems should be fixable in direct operation via SDK.Edit: Found some numbers (tested on decent laptop):Pico 2408B, all processing OFF, 200ns/div, 125MSa/s ~24wfm/s 0% misses with edge trigger ~32wfm/s no triggerPico 2408B, all processing OFF, 200ns/div, 1GSa/s ~18wfm/s 0% misses with edge trigger ~29wfm/s no triggerAD2 (USB2) all processing OFF, 200ns/div, 100MSa/s ~50wfm/s 0% misses with edge trigger ~100wfm/s no triggerAs can see wfm rate has very little to do with data amount on Pico. Tests were done in main (analytical) mode, not DPO. On AD2 rate also seems throttled but at much more reasonable level. Worst of all Pico USB3 scopes are throttled onsamelevel as USB2. Hope PS6 is EOL because about time for next gen GUI.

author: Hagrid
author_rank: Contributor
timestamp: October 31, 2018, 05:26:22 pm
content: Interesting, thanks a lot. This are indeed some points I will have to have a closer look at.

author: David Hess
author_rank: Super Contributor
timestamp: October 31, 2018, 10:30:39 pm
content: Many USB scopes have terrible front ends and rely on "digital" gain for adjusting attenuation factor which is not documented. Also watch out for their overload specifications which may only be 50 volts.I would be most concerned with the lack of galvanic isolation through a USB interface. The right kind of ground loop through the probe ground may not only damage the USB oscilloscope but things connected to it through its USB interface like an attached computer.

author: james_s
author_rank: Super Contributor
timestamp: November 02, 2018, 07:05:02 am
content: I assumed most of them now would be isolated? Maybe not? My USB scope is an older Bitscope which is not isolated. It is very easy for spikes to cause the whole USB bus to lock up, a separate USB isolator solves this but it's clunky.

author: Performa01
author_rank: Super Contributor
timestamp: November 02, 2018, 07:44:05 am
content: Quote from: MrW0lf on October 30, 2018, 09:56:36 pmI wonder if you maybe have accidentally throttled the waveform capture rate in the PS6 preferences?

author: MrW0lf
author_rank: Frequent Contributor
timestamp: November 02, 2018, 10:48:11 am
content: Quote from: Performa01 on November 02, 2018, 07:44:05 amThat's good point to be aware of but highly doubt it. It's just their design philosophy. But these old tests might have been done on slow(er) PC so I can re-check sometime later to be sure.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: November 02, 2018, 02:15:37 pm
content: 1kCycles at 1kHz burst. wfm/s was counted by number of buffers collected during burst.10us/div, Trigger is Repeat, Simple Edge, RisingPicoScope 6404D USB35GSa/s, 500kSa: 32wmf/s1.25GSa/s, 125kSa: 32wmf/s9.766MSa/s, 977Sa: 33wmf/sPicoScope 2408B USB21GSa/s, 100kSa: 34wmf/s125MSa/s, 12.5kSa: 32wfm/s9.615MSa/s, 962Sa: 33wfm/sPicoScope 2205 USB2100MSa/s, 10kSa: 34wfm/s12.5MSa/s, 1250Sa: 33wfm/sAnalog Discovery 2 USB2100MSa/s, 10kSa: 100wfm/s10MSa/s, 1kSa: 100wfm/sTo be fair, 2408B and 6404D will collect 100% no prob with Rapid trigger (segmented mode), but that's besides the point.Edit: To be even more fair looked at DPO mode also, which is also besides to point because it's more like a CRO mode (limited memory, no auto-measurements):PicoScope 6404D12.02MSa/s, 1.202kSa: [170, 450, 350, 490, 400] wfm/sPicoScope 2408B12.5MSa/s, 1.25kSa: [470, 400, 62, 370, 330] wfm/sPicoScope 220512.5MSa/s, 1.25kSa: [190, 200, 190, 180, 490] wfm/sIt would be interesting if some eager person would test something along these lines with SDK. I have no time for that in near future.

author: Performa01
author_rank: Super Contributor
timestamp: November 03, 2018, 01:44:26 pm
content: That's interesting. Had a little play with my old 3206B and got the following:PicoScope 3206B USB210µs/div, 500MSa/s, 50kSa: 41~44 Wfm/s100µs/div, 500MSa/s, 500kSa: 48 Wfm/sDecreasing the buffer length did not change anything.Rapid trigger captured all 1000 events reliably.DPO mode: 12.5MSa/s, 1250Sa, 680~720 Wfm/sA cheap bench scope like the SDS1000X-E manges up to some 1280 Wfm/s for normal acquisition with history in the background and up to 6880 Wfm/s in sequence mode at 10µs/div timebase. In both modes no pulses would be lost due to blind time, yet you'd just get 392 records in the history, even though a total memory of 54.9Mpts is used. At 1GSa/s and with 14 horizontal divisions, the record length is 140kpts.

author: nctnico
author_rank: Super Contributor
timestamp: November 03, 2018, 03:13:12 pm
content: Quote from: Hagrid on October 27, 2018, 11:36:28 amI have used a Picoscope as a bench scope a few times but I found the operation by using a mouse very cumbersome. If the software for Picoscope has good support for touch screen operation I'd consider it a solution in combination with a PC with a touch screen. If you are only after a remote operated data acquisition unit then any Picoscope will probably do. Another option is to look for an oscilloscope with faster data transfer. The recent oscilloscopes from GW Instek (1000B and 2000E series for example) have really fast data transfer rates because they have a lot of processing power. Somewhere in an old thread various forum members compared download speeds over the network and the GW Insteks came out on top.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: November 03, 2018, 03:20:10 pm
content: Bit more toying with 2408B:50ns/div, 1GSa/s, 500Sa:850kHz in 10kCycle burst:Scope (collecting buffers): 1Rapid (collecting buffers): 10000 (100% capture) => 850 kwfm/sPersistence/*: >1850kHz steady signal:Scope (collecting buffers): 34 wmf/sPersistence/Fast: ~31 kwmf/sPersistence/Advanced/Scatter/Frequency: ~4 kwmf/sSo that Rapid/segmented thing is quite serious business. Persistence somewhat works depending on mode. But normal mode (Scope) is clearly crippled on purpose, and quite surely on the PC software end.

author: Performa01
author_rank: Super Contributor
timestamp: November 03, 2018, 10:59:09 pm
content: My results for the 3206B:50ns/div, 500MSa/s, 250Sa:850kHz in one 10k cycles burstScope (collecting buffers): 1Rapid (collecting buffers): 10000 (100% capture) => 850 kWfm/sPersistence/*: >0 -> rather weird…850kHz steady signal:Scope (collecting buffers): 35.7 Wfm/sPersistence/Fast: ~62 kWfm/sPersistence/Advanced/Scatter/Frequency: ~6 kWfm/sYes, I have figured that a PicoScope should be able to compare with (or even beat) a MegaZoom scope with regard to acquisition rate - only in sequence (rapid trigger) mode, that is.Old 3206B again:10ns/div, 500MSa/s, 50 (216)Sa5MHz in one 10k cycles burstRapid Trigger: 10000 (100% capture) => 5 million waveforms per second!5MHz -> 200ns period, x 10000 = 2ms total burst length.10ns/div x 10 divisions x 10000 buffers = 1ms acquired data. => blind time = 50%Re-arm time < 200ns.That competes with analog scopes at similar timebase settings – sadly just for 2ms…At even higher rates the Pico starts missing triggers, but hey, that is a pretty darn decent result.For the true applications of sequence mode, this means we can be almost 100% sure to not miss any event, no matter how random their timing might be.Speaking of real applications for sequence mode - if only Pico Tech would have realized after all that time that we need time stamps (with µs resolution) for that to be actually useful!

author: 2N3055
author_rank: Super Contributor
timestamp: November 03, 2018, 11:43:26 pm
content: Quote from: Performa01 on November 03, 2018, 10:59:09 pmYes, that old chestnut...Cast a vote here :https://www.picotech.com/support/topic17321.html?&start=15#p140390Maybe if more people create fuss...I plan to have discussion with them at Electronica. I'm not holding my breath, but man has to try... :-)Regards,Sinisa

author: MrW0lf
author_rank: Frequent Contributor
timestamp: November 04, 2018, 10:45:50 am
content: @Performa01: About that 10k buffers thing. It is not listed for 2408B but for 6404D 10k is again PS6 limitation. Also total capture by method is limited to meager 100M. And you'd better insure that 3206B because seems after that they limited Rapid to ~1Mwfm/s because neither of mine will go much over that with 100% capture rate.BTW SDK spec for 6404D it is max 2M buffers and of course ~2G memory: "something useful could be done".@2N3055: I have dumped about 5 A4 worth of illustrated suggestions on them about true potential of Rapid trigger, DeepMeasure etc over a year ago. They said many viable and got green light. As of today - yes there have been some improvements with DM but nowhere near the potential.As for proper timestamps they do not like them because even new version of PicoLog dumped time values rounded to seconds into CSV, which was also reported:https://www.picotech.com/support/topic38461.htmlEdit: Did poke PS6 a little on hope to eliminate speed limit but instead did manage to make it slower & more accurate:https://www.eevblog.com/forum/testgear/picoscope-2000/msg1940467/#msg1940467

author: MrW0lf
author_rank: Frequent Contributor
timestamp: November 08, 2018, 10:07:24 pm
content: Quote from: MrW0lf on November 02, 2018, 02:15:37 pmFound the setting. InOptionsbelowTime. Need to setUpdateas 1ms, it was on 10ms. New numbers:100MSa/s, 10kSa: 125wfm/s10MSa/s, 1kSa: 135wfm/sTried other settings, smaller memory etc but this seems to be about the top speed in any case.