Rohde & Schwarz RTB2000 Scope Pulse Response

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  • Опубліковано 29 січ 2025

КОМЕНТАРІ • 65

  • @Alamagosa
    @Alamagosa 2 роки тому +9

    I saw a couple of different problems. The slope of the pulse top on the RTB2000 looked like printed circuit board hook in the high impedance attenuator. The reverse of the top on the Tektronix looked like a mismatch in medium frequency compensation of the two path front end.
    However I would not rely on the flatness from your AWG without verifying it using a sampling oscilloscope. A reference level pulse generator is normally required for these sorts of measurements.

  • @shazam6274
    @shazam6274 2 роки тому +4

    Dave, tell us again why those "Super Precision" Big $$ scopes are soooo much better, more accurate, etc. etc..... 😂

  • @jenniferwhitewolf3784
    @jenniferwhitewolf3784 2 роки тому +10

    I have recently been corresponding with
    John Addis, the designer of the Tektronix 7A29 1 GigHz vertical amplifier, and principle engineer of the 7104 1 GigHz mainframe... which I own. Those guys had all these problems solved 50 years ago. The attenuator in the 7A29 actually works to 5 Gigs... the guys making this stuff today have no clue about how it was done, and are doomed to create glitchy stuff. My other scopes are:
    Tek R7844 400MHz dual beam rack mount
    Tek 7834 400MHz storage scope.
    Tek 2247A 100MHz portable with integrated digital co-processor.
    Non of these exhibit any of these issues.
    I use a Siglent SDS 2202X-E but mostly in FFT driven by residual out of a distortion analyzer, the Tek AA501. The degree of real science and engineering in the post 1970 to pre 1990 Tek products is unparalleled. No finer analog engineering exists.

    • @Alamagosa
      @Alamagosa 2 роки тому +1

      For a good design the only residual pulse distortion will be from the calibration of the frequency compensation and calibration of the thermal balance. The specifications usually require aberrations to be within 0.2 divisions but performance is commonly much better than this. The results Dave got are probably considered within their specifications, but I sure would not put up with some of them.
      I have:
      2 x 2230
      2 X 2232 which are my most used DSOs
      2247A
      2246
      7904A which is my favorite analog oscilloscope
      7603
      2 x 7834
      7854
      2440

  • @robinsattahip2376
    @robinsattahip2376 2 роки тому +8

    Insult my wife or religion but not my dog or oscilloscope. Wish you had tried one of those old analog scopes you've repaired over the years, that would be interesting.

  • @laser-sj
    @laser-sj 2 роки тому +8

    Dave you fool !!!
    Its schroedingers signal.
    Its perfect until observed. 🤣

    • @Alamagosa
      @Alamagosa 2 роки тому +4

      A man with one oscilloscope knows the pulse shape. A man with two or more oscilloscopes is never sure.

    • @SystemX1983
      @SystemX1983 2 роки тому

      😂 was searching for that comment
      "It's schroedingers squarewave"
      But as others mentioned, how can we be sure the signal is generated totally perfect unless we measure?
      If we measure the exact same signal with several scopes and get a similar result, we might need to change the source, to check if the quirks come from there, right? 😯

  • @miqueles5783
    @miqueles5783 2 роки тому

    what if when using the same signal at the same time observed by an other scope for comparison (I would say a propper termination is not needed for this test)

  • @israeldlr4365
    @israeldlr4365 2 роки тому +1

    why is this on channel 2

  • @WizardTim
    @WizardTim 2 роки тому

    If that slope error is a result of error in the compensation network do you think some freezer spray would worsen it or is this more of a compensation network design/topology limitation?

    • @Alamagosa
      @Alamagosa 2 роки тому +1

      That slope is more typical of circuit board hook in a high impedance attenuator and is not really suitable for compensation using a network. A measurement over a longer time period would make this more certain.
      The circuit board might have absorbed humidity after being manufactured causing this. Many differential high voltage probes suffer from this as well after months to years. Early oscilloscopes used plastic substrates (Polysulfone?) for their high impedance attenuators to avoid this problem before it was understood. It is not a mistake I would expect Rohde & Schwarz to make.

  • @JFirn86Q
    @JFirn86Q 2 роки тому

    Thanks for showing it on all the different brands, really interesting. Too bad no Lecroy one there :)

  • @vincei4252
    @vincei4252 2 роки тому +1

    I have the Rohde & Schwarz HMO3004 500Mhz scope. It would be interesting to see if it exhibits the same thing.

    • @uni-byte
      @uni-byte 2 роки тому +1

      Well? Did it?

  • @helmuthschultes9243
    @helmuthschultes9243 2 роки тому +1

    Are you sure the ringing not from the pulse source?

    • @Alamagosa
      @Alamagosa 2 роки тому +1

      The pulse source definitely has some aberrations, however the different DSOs Dave tested showed different results.

  • @thomasw6169
    @thomasw6169 2 роки тому

    So what parts in the frontend do we need to change

    • @thomasw6169
      @thomasw6169 2 роки тому

      Will a sweep find out the dip in the response ?

    • @Alamagosa
      @Alamagosa 2 роки тому +2

      It depends on exactly what the cause is. Many of these aberrations can be caused by non-linear operation which a simple sweep would miss.

  • @xXxbastek
    @xXxbastek 2 роки тому

    Does bandwidth depends to the selected front end attenuation?

    • @Alamagosa
      @Alamagosa 2 роки тому +1

      Bandwidth should not vary with the volt/div setting.

    • @xXxbastek
      @xXxbastek 2 роки тому

      ​@@Alamagosa yep, should not, but what if does?

    • @Alamagosa
      @Alamagosa 2 роки тому

      If the bandwidth varies with volts/div, then the design is flawed. Bandwidth and pulse shape should not change with the position and volt/div setting.
      Modern DSOs which only use one high impedance input attenuator have to operate their high impedance buffer over a much larger signal range, and may be slew rate limited causing variation in their full power bandwidth.

  • @sefarkas0
    @sefarkas0 2 роки тому +2

    check your signal source

  • @mikebarushok5361
    @mikebarushok5361 2 роки тому

    It's invariably true that any engineered product will have design choices made that involve achieving sufficient accuracy without pricing the product out of any reasonable market.

  • @EdEditz
    @EdEditz 2 роки тому +1

    Is that the same on analog scopes?

    • @Alamagosa
      @Alamagosa 2 роки тому +2

      It is. Analog oscilloscope design went to great lengths to remove these types of errors.

    • @aklankrisz
      @aklankrisz 10 місяців тому

      No! Most of analog scopes made in the 80s have been ruled out these errors simply buy using bigger transistors or using jfets in the input stage.

  • @Bluelagoonstudios
    @Bluelagoonstudios 2 роки тому

    Is this typically for digital scopes? Or have analog scopes the same issue? Thanks.

    • @Alamagosa
      @Alamagosa 2 роки тому +2

      Analog oscilloscopes had to deal with all of the same problems and their design was very careful to avoid them. Knowledge of these problems has been lost over time and new engineers may not be aware of them.

    • @Bluelagoonstudios
      @Bluelagoonstudios 2 роки тому

      @@Alamagosa Thank you :)

    • @aklankrisz
      @aklankrisz 10 місяців тому

      This is tipical for shitty smd parts, but not because they are digital. My analog/digital VC-6145 combiscope does'nt have that problem at all, but my GDS-2104E is distorting like hell...

  • @oambrosia
    @oambrosia 2 роки тому

    To jump further down the rabbit hole, now I want to try this on a fast scope! If I remember I'll try it on a Rohde RTP at the office...or maybe a 30GHz Tek 🤣

  • @ikocheratcr
    @ikocheratcr 2 роки тому

    Imagine a review that includes this kind of stuff ... I guess it would be like 8h long.

  • @derkarhu5079
    @derkarhu5079 2 роки тому

    I don't know what you're driving from, but doing 50 ohm into a 1 Mohm input... cable capacitance, awg.
    Without using probe and probe compensation ...

  • @hqiu6828
    @hqiu6828 2 роки тому +1

    Dave, it is just a pulse, representing 1 or 0 in digital world, it does not matter perfect or not. But we do like the perfect square wave oscilloscope, however. 😂

  • @leongyokeloong5083
    @leongyokeloong5083 2 роки тому +1

    Like what you said : " no scope is perfect".

  • @NeverTalkToCops1
    @NeverTalkToCops1 2 роки тому

    Use Leo Bodnar's lovely pulse device.

  • @universeisundernoobligatio3283
    @universeisundernoobligatio3283 2 роки тому

    Interesting, one should always be aware of the uncertainty of a measurement.

  • @donepearce
    @donepearce 2 роки тому +1

    Is there no agreed spec for 20MHz LP filters on scopes? This all looks like a bunch of different impulse responses to me. But I can't explain why it changes with vertical scale.

    • @Alamagosa
      @Alamagosa 2 роки тому

      It changes with the volts/div setting because of switching in and out of the high impedance attenuators, and operating point changes in the high impedance buffer. It is a difficult task to design each to avoid these problems.

    • @donepearce
      @donepearce 2 роки тому

      @@Alamagosa Yes, I was thinking about that. A scope attenuator is composed of capacitors. There are resistors too, but they only serve to allow a response down to DC. Clearly as ranges are switched reactive loads change. Given enough DSP this could be equalised but it really isn't worth it. Nobody expects that degree of accuracy from a scope.

    • @Alamagosa
      @Alamagosa 2 роки тому

      The high impedance attenuator sections are designed to be constant input and output impedance so switching them in and out should not affect anything except the attenuation. Some DSOs implement corrections using DSP, but I do not know that any modern low end DSOs do.
      The displayed results are likely within the specifications, but do reveal some real flaws. I would not tolerate that slope shown on the on the Rohde & Schwarz RTB2000 on any of my oscilloscopes. Some of the other results are questionable also.

    • @aklankrisz
      @aklankrisz 10 місяців тому

      @@donepearce I would expect that precision! Its easier to redesign the analog frontend than equalise that with a DSP.

  • @TingILi
    @TingILi Рік тому

    No teardown

  • @johnlegros1586
    @johnlegros1586 2 роки тому +1

    you know what ? am ready to have this scope and pay for all costs to have it here in france next to my tek465 , by the way in my past engineers in rf experience R&S was already the best for ease of use reliability and support , way better in RF than HP....but COSTLY ! in this tests be sure of adaptation , the gen should have at least a 10 dB attenuator on output , coax and connectors should be rated to at least 4 gHz then we may talk about perf...this is why it is strange behavior IMO issue is SWR ...even at 1kHz at good gen as a rise time of gHz and so ...

    • @aklankrisz
      @aklankrisz 10 місяців тому

      The setup was good. You not need GHz generator for precison 1kHZ flat pulses. The key is here flatness, not rise/fall time. I have 3 scope, only the newest (DSO) have this problem. My combiscope and my fully analog scope made in 70s does not show any flatness error.

  • @uni-byte
    @uni-byte 2 роки тому

    It's strange how the more expensive scopes have that annoying glossy look to them. It Siglent and UNI-T can put a proper low reflection screen on even their low-end scopes, why can't R&A or Tek? Annoying.
    My Siglent SDS2504XP scope does not have this problem from a 10mV input up to a 10V input. Not even slightly. My Siglent SDS1204X-E has it, but to less extent than the ones shown here. No hint of it on my old Tek 465 either - made when Tektronix care more about the quality of their products than their executive bonuses.
    What's up? Just because a lot of scopes do this, does not excuse it. Especially when those scopes have names like R&S, Tektronix and Agilent on them. Should we not expect more for the higher price we pay?

  • @_-martin-_
    @_-martin-_ 2 роки тому

    I would like to see you repeat this after calibrating the probe.

    • @Alamagosa
      @Alamagosa 2 роки тому +3

      No probe is being used.

    • @derkarhu5079
      @derkarhu5079 2 роки тому

      Which is likely a problem, since the front end 1 meg input has part of the probe compensation in it, as I recall, so a 50 Ohm cable has little chance of matching the probe cable and compensation?

    • @Alamagosa
      @Alamagosa 2 роки тому +1

      @@derkarhu5079 It does not work like that. Like a x1 probe which is 1 megohm, a 50 ohm direct connection requires no compensation. What is required is a 50 ohm termination at higher frequencies.

    • @uni-byte
      @uni-byte 2 роки тому

      @@derkarhu5079 No. A straight, properly terminated good quality coax will perform well into the 10's of GHz and requires no compensation.

  • @aklankrisz
    @aklankrisz 10 місяців тому

    Dave, please don't call your oscilloscope videos a full review if they don't include a DC coupled 10Hz/100Hz square wave flatness measurement using a coax cable! In December 2021 I wrote here "EEVblog Electronics Community Forum »Products »Test Equipment »GW Instek GDS-2000E teardown /short review, comparison with Rigol DS2000(A)" under the name "Krisztián" that the GDS-2104E has serious problems with e.g. the 10Hz square wave flatness. The same signal is perfectly straight on the excellent JFET input Hitachi VC-6145 combiscope.

  • @alexkaidon8700
    @alexkaidon8700 2 роки тому

    Why is it so damn hard to get a decent and cheap oscilloscope in a modern world! Everything else electronic gets cheaper way faster than these tools.

  • @eimparas
    @eimparas 2 роки тому

    first

    • @EEVblog2
      @EEVblog2  2 роки тому +12

      Say Hi to your mum for me.

  • @IU3EVR
    @IU3EVR 2 роки тому

    pointless

    • @aklankrisz
      @aklankrisz 10 місяців тому

      This scope has a low quality front-end just like my GDS-2104E.

  • @pixiepaws99
    @pixiepaws99 Рік тому

    My SDS2504X+ doesn't have this problem. My SDS1204X-E is also fairly consistent except on the 200mV/div range which actually shows a sharper edge. Either way, it's a non-issue and neither are anywhere close to as bad as the Rhode & Schwarz.

    • @aklankrisz
      @aklankrisz 10 місяців тому

      "it's a non-issue" Wrong.

    • @pixiepaws99
      @pixiepaws99 10 місяців тому

      @@aklankrisz Explain...