Scope Wars - Page 1
Forum section: electronics / testgear

author: rhb
author_rank: Super Contributor
timestamp: June 23, 2020, 02:20:58 pm
content: EDIT: I have abandoned this project. The level of noise produced by people ignorant of DSP who insist upon pursuing fallacious arguments ad nauseam makes continuing pointless.Have Fun!Reg-------------------------------------------------------------------------------------------------------------------------------------------------I've been kicking the idea of doing this around for quite a while and have decided to go ahead. This will be a long running thread in which I apply a wide variety of tests to DSOs, primarily entry level models.I have acquired a rather substantial set of lab gear so I can perform a lot of rather severe tests. My goal in this is to embarrass the OEMs into improving their products. So I am going to focus on all the things that are wrong of which there are a great many in *all* the DSOs I've tested including a Keysight MSOX3104T and a Rohde & Schwarz RTM3104 both of which are $20K MSRP instruments.I have for signal sources:<40 ps 1 MHz and 10 MHz square wave generators from Leo Bodnar10 MHz 100 ps pulse generator from Leo Bodnar<20 ps rise time 200 kHz pulses from Tektronix 11801 calibrator and SD-24 sampling headdual output frequency GPSDO from Leo BodnarKeysight 120 MHz AWG with <1 ps jitter specFor comparisons of signal sources:Tektronix 7104 1 GHz analog scopeTektronix 485 350 MHz analog scopeTektronix 11801 sampling with 12 GHz SD-22 and 20 GHz SD-24 and SD-26 sampling headsLeCroy DDA-125 1.5 GHz DSOLecroy DDA-120 1 GHz DSOThe current list of "contestants":Rigol DS1102ERigol DS1202Z-EOwon XDS-2102AInstek MSO-2204EAI've not decided on which model Siglent to get. For cost reasons I'm leaning towards the SDS-1202X-E as it is directly comparable to the DS1202Z-E.Have Fun!Reg

author: Grandchuck
author_rank: Super Contributor
timestamp: June 23, 2020, 03:07:45 pm
content: Should be interesting! How about the Siglent SDS2000X Plus? Seems to get a lot of interest here. I don't own one but do have 5 other scopes ... always have been a sucker for scopes

author: SilverSolder
author_rank: Super Contributor
timestamp: June 23, 2020, 03:45:37 pm
content: Sounds like fun! I like it that you have a couple of older scopes in there for comparison, for cases where the "state of the art" is moving backwards...

author: nctnico
author_rank: Super Contributor
timestamp: June 23, 2020, 04:13:59 pm
content: I'd throw in an RF generator as well as a test source. At least it will allow to determine the actual bandwidth. A pulse generator only shows step behaviour.

author: rhb
author_rank: Super Contributor
timestamp: June 23, 2020, 04:21:24 pm
content: I bought the 485 and 7104 precisely because the Keysight and R&S scopes were so bad.This really aimed at helping first time scope buyers understand what they are getting for what is for most a major purchase. So if it's my money, I'm going with the entry level scopes. I'll include other stuff if I get a unit on a 30-60 day loan. And then only after I have worked out the test program.Around 1990 I paid Tucker Electronics in Dallas over $300 for a 20 year old Dumont 1062 dual channel 60 MHz scope. About 5 days after the 30 day warranty expired, the horizontal sweep quit working. I was quite devastated as I'd saved a long time for that. I eventually fixed it. But the trauma was palpable and locating the broken solder joint took every evening for a week plus a good bit of the weekend.@nctnico I've got an 8648C, however, if you know your Fourier transform theory you can determine BW from the step response *very* accurately. Oliver Heaviside pioneered using the step response for frequency domain analysis. The major fault with *all* the DSOs I've tested is attempting to get too much BW for the sample rate and using very steep anti-alias filters. So the step response rings like mad.Have Fun!Reg

author: nctnico
author_rank: Super Contributor
timestamp: June 23, 2020, 04:44:26 pm
content: You are right about the step response. I Pavlov-ed into rise time measurements.

author: edigi
author_rank: Regular Contributor
timestamp: June 23, 2020, 05:17:45 pm
content: The SDS-1202XE is a nice fit to this contest list (SDS2000X Plus is already in a different class among others due to FFT), although it makes me wonder what's the point of this test?Entry level DSOs are not about BW or step response right?Nevertheless if that's the focus I don't see how rolloff will be characterized with the listed equipments.This kind of DSOs are frequently used to check non repetitive signals (like not so fast buses, transients) and for that they are pretty OK.With modern higher BW DSOs you get not just BW but a bunch of other tools, like decent FFT (Siglent is pretty good in this; but this is not the only math) or plenty of protocol decoding options plus there are fancy triggers (to name a few: runt, pattern, zone; not all of them are in entry level though). Another story is measurements (with histograms but this is also not entry level) and cursors (on math like FFT).

author: tautech
author_rank: Super Contributor
timestamp: June 23, 2020, 05:30:51 pm
content: Quote from: rhb on June 23, 2020, 02:20:58 pmFair enough, although for a fair comparison covering many models their respective sampling rate specs should be considered.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: June 23, 2020, 06:46:37 pm
content: when does this war begin? I just have to take my first entry level oscilloscope; my choice will be between siglent1202 and rigol1202, I don't know the other two brands

author: rhb
author_rank: Super Contributor
timestamp: June 23, 2020, 07:18:23 pm
content: Quote from: CharlotteSwiss on June 23, 2020, 06:46:37 pmI don't yet have a Siglent. The DS1202Z-E came yesterday. I've had the others for quite a while. The Owon is *not* usable as a DSO, but it will acquire 20 Mpts of 12 bit data in a single shot. So unless you need that don't consider it. The Instek GDS-2000E is quite good and as an all around scope is the best I've tried so far. But the GDS-2072E is twice the price of the SDS1202X-E or DS1202Z-E.So I'll get started with some basic stuff this evening if all goes well.Have Fun!Reg

author: rhb
author_rank: Super Contributor
timestamp: June 23, 2020, 07:21:05 pm
content: Quote from: tautech on June 23, 2020, 05:30:51 pmNot only am I working for free, I'm paying for the scopes. So I'm not about to do a comprehensive review of everything even if I got loaners for all of them.This is to help people like CharlotteSwiss.Reg

author: Bud
author_rank: Super Contributor
timestamp: June 23, 2020, 08:18:48 pm
content: Can you make up your mind if you are trying to help CharlotteSwiss or embarrass the OEMs?

author: tautech
author_rank: Super Contributor
timestamp: June 23, 2020, 08:31:36 pm
content: Quote from: tv84 on June 23, 2020, 07:56:52 pmReg has already stated (maybe in another thread) step response performance is one of the reasons for venturing down this road yet at fast timebases for fast edges sufficient sampling rate comes into play.Single shot captures will need interpolation to show meaningful results and the more samples it has to work with will influence reproduction.What's under the hood will matter !

author: Bud
author_rank: Super Contributor
timestamp: June 23, 2020, 09:00:00 pm
content: Dont you guys understand this gibberish talks make no sense to the beginners you are "trying to help". You will need to first educate them on what that technical terms all mean.

author: nctnico
author_rank: Super Contributor
timestamp: June 23, 2020, 09:23:17 pm
content: Quote from: Bud on June 23, 2020, 09:00:00 pmFound the thread. I agree. Step response is the last thing a beginner will worry about. For most measurements I do it doesn't even matter.

author: stafil
author_rank: Regular Contributor
timestamp: June 23, 2020, 09:34:57 pm
content: Accompanying videos would be cool

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: June 23, 2020, 09:44:20 pm
content: I am a beginner squared in the field of oscilloscopes; I certainly don't look for the little things of you experts from the oscilloscope, but ease of use and software stability (no bugs).but fate seems already (almost) sealed for me: reg he ruled out for me Owon, rigol1102 it seems old of hardware, rigol 1202 they say out there that it's based on z old platform, instek is prohibited price... on the square he remains alone siglent 1202thanks for warsCharlotte

author: tv84
author_rank: Super Contributor
timestamp: June 23, 2020, 09:47:10 pm
content: Quote from: CharlotteSwiss on June 23, 2020, 09:44:20 pmI think Charlotte is the one teaching many here...Edit: I removed all my previous BS to not clutter Reg's thread.

author: rhb
author_rank: Super Contributor
timestamp: June 23, 2020, 10:38:05 pm
content: In many respects, the DS1102E looks better to me than DS1202Z-E. So don't jump to conclusions. The point of this is to apply exactly the same tests to a series of instruments and show what they do well and what they do badly. My observation of Keysight and Rohde & Schwarz new $20k instruments is they are buggy as all hell. I'm told that the Tektronix 3 series crashed during a demo for a friend. It seems that for $20k you get the privilege of being a beta tester for the top tier OEMs.The DS1202Z-E has a bigger screen, but it is permanently cluttered by menus, so the trace display area is about the same as the DS1102E.Sorry, but I am *not* doing videos. Not no, but hell no!Step response *is* the last thing that a novice will think about. It's also the single best test of the performance of the AFE and the DSP design. With 30+ years of DSP experience in the oil industry, I can look at the step response and draw the AFE filter profile on a cocktail napkin. TANSTAFL You cannot have a DSO BW which is more than 50-70% of Nyquist and have the traditional analog Tek <3% overshoot.If you need to test signal integrity for things like ringing on a data line, how do you do that if the step response has a 7% overshoot such as the Keysight MSOX3104T I bought and returned? I suspect that the MSOX3054T is actually a decent scope as it *should* be able to provide a decent step response, though the FFT is still crap.I shall explain very thoroughly the tests and what they mean. However, this is an evening entertainment, not a job. I have other things I have to do. So it will not be quick. And I still need to get an SDS-1202X-E or similar.Have Fun!Reg

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: June 23, 2020, 11:12:34 pm
content: Quote from: rhb on June 23, 2020, 10:38:05 pmin fact, old scilloscope does not necessarily mean that it is scarcer; hope you also get siglent1202x-e

author: rhb
author_rank: Super Contributor
timestamp: June 24, 2020, 12:02:32 am
content: I have sent requests to my contacts at Siglent, Rigol, Owon and Good Will (Instek) informing them of this effort and asking that they facilitate responses to the issues that are raised.I also stated that I shall be reporting on how responsive OEMs are.Have Fun!Reg

author: james_s
author_rank: Super Contributor
timestamp: June 24, 2020, 02:00:18 am
content: Quote from: rhb on June 23, 2020, 04:21:24 pmAh, Tucker, I remember drooling over scopes in their catalog around that time. I was not even a teenager yet so they were all WAY beyond what I could afford, though I did pick up a Tek 531A for $40 at a garage sale somewhere in that era.

author: rhb
author_rank: Super Contributor
timestamp: June 24, 2020, 02:14:22 am
content: I was 36 and had spent 24 years in school. So most of the stuff was way beyond what I could afford also. And Tucker was not cheap. I did a lot better at First Saturday before they kicked out the RF guys and made it just computers.Reg

author: med6753
author_rank: Super Contributor
timestamp: June 24, 2020, 08:11:31 am
content: For some reason the theme "Junkyard Wars" comes to mind.

author: Fungus
author_rank: Super Contributor
timestamp: June 24, 2020, 12:41:33 pm
content: Quote from: CharlotteSwiss on June 23, 2020, 09:44:20 pmInstek can be had real cheap right now:https://www.tequipment.net/Instek/GDS-1054B/Digital-Oscilloscopes/?search=true