Common misunderstandings about digital oscilloscopes - Page 1
Forum section: electronics / testgear

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 05, 2015, 07:50:48 am
content: I found a nice tutorial from Rohde & Schwartz regarding common misunderstandings about digital oscilloscopes. Believe it is very useful for beginners on this forum1) Your digital oscilloscope's bandwidthToday's digital scopes use digital processing and employ very sharp, high-order frequency responses that trade minimum sampling rates for maximum bandwidth. The result is high overshoot and ringing when measuring typical digital signals.http://rohde-schwarz-scopes.com/scope_lie_01.php2) Your digital oscilloscope's noise specificationMost high sample rate scopes will interleave two, four, eight (or maybe more) digitizers to obtain a sample rate that high. The digitizers need to be accurately interleaved to prevent interleaving spurs in the frequency domain, which manifests itself as noise in the time domain.http://rohde-schwarz-scopes.com/scope_lie_02.php3) Your digital oscilloscope's waveform update rate:Can your oscilloscope really achieve its specified high waveform update rate (acquisition rate) using real signals?Digital scope manufacturers specify high update rates in excess of 1 million waveforms per second which can be misleading. These update rates are usually stated for certain circumstances or settings, but typically do not include measurements or mask testing which may be turned on when acquiring waveforms.http://rohde-schwarz-scopes.com/scope_lie_03.php4) Your digital oscilloscope's analog triggerAre you really triggering on the waveform you see on the screen?Most scopes (analog and digital) utilize a separate trigger circuit and a different circuit to acquire the waveform. Since the trigger circuit and acquisition circuit have different bandwidths, different sensitivities and different characteristics, this can cause trigger jitter which appears as jitter on the signal, but is actually jitter coming from the trigger circuit.http://rohde-schwarz-scopes.com/scope_lie_04.php

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 05, 2015, 03:11:40 pm
content: Quote from: pascal_sweden on August 05, 2015, 07:50:48 amAside from the fact that there's a beginner's section in this forum where stuff like this should be placed, I hope you're aware that you're citing marketing arguments.QuoteThat might be true for some entry-level scopes but most mid-range and high-end scopes do have a slow roll-off beyond the 3dB point, which obviously is news to R&S, as they seem to believe that their scope is exceptional in this area (which it isn't).I'm not sure what a beginner is supposed to do with that information, or why R&S labels that as "scope lie".QuoteAgain, this might be a problem for cheap/low-end scopes, but interleaving spurs aren't a problem for most mid-range and high-end scopes. Aside from the fact that in the price segment of the R&S RTO other manufacturers use much faster single-block ADC hybrids, which again seems to be news to R&S.Again, I'm not sure where the "lie" is, or what relevance this has for a beginner.QuoteMask testing isn't a problem for any decent somewhat modern DSO except maybe some bottom-of-the-barrel scopes, and these are hardly the class of scopes that compete with an R&S RTO (a $15k+ scope). Math operations are different, but even the RTO slows down when using advanced math.As before, I can't see where the "scope lie" should be, and as with the topics before it's generally not of much relevance for a beginner who's unlikely to use advanced maths anyways.QuoteTrigger jitter isn't a problem for most mid-range and high-end scopes, which also can trigger on any point in the signal. R&S seems to believe that other scopes work like an old Hameg CRO, which they don't.Seriously, I'm not sure why you're posting such marketing drivel which R&S uses to promote their $15k+ high end scope, something that isn't of relevance for a beginner who'll very likely start with a slow and limited bottom-of-the-barrel scope like a Rigol DS1054z, or in some cases even with an old analog scope.I'd also caution you to not blindly buy into any marketing BS, as you seem to do. Most of such stuff where one manufacturer compares his product with their competitors isn't worth the paper/the bytes its written on/with.

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 05, 2015, 03:36:31 pm
content: Thanks for pointing out that marketing buzz should be taken with a pinch of salt .. even if it comes from a big companyI thought that a reputable company like R&S would tell mostly the truth.So, all manufacturers use this approach? Agilent/Tektronix? Even your favorite top-of-the-barrel brand LeCroy? =)Maybe the Chinese are more honest then in the end of the day. They advertise their low end scopes as bottom-of-the-barrel scopes, to use your definition

author: Lukas
author_rank: Frequent Contributor
timestamp: August 05, 2015, 03:41:48 pm
content: Quote from: Wuerstchenhund on August 05, 2015, 03:11:40 pmRohde&Schwarz rolled their own monolithic 10GSa/s folding/interpolation ADC when they got into the oscilloscope market . Others  interleave like crazy. Looks like R&S are very proud of their monolithic ADC, so marketing tries to make use of that.https://www.mikrocontroller.net/topic/182804#1801224andhttp://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6226133http://poulton.net/papers.html

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 05, 2015, 04:22:13 pm
content: Note that even beginners, who can not afford high-end scopes, might want to get a good understanding about the differences between low-end scopes and high-end scopes.So from that perspective, I think information like this can not just be classified as the "non beginners" section in the librarySome beginners are very curious, and question the underlying implementation and design decisions, which other industry veterans might just take for granted, because it has been drilled in their mindset.Maybe beginners want to use the knowledge for having a better view on the limitations in their bottom-of-the-barrel scope, and want to explore ways on how they can work around these limitations. Or maybe they just want to learn more out of theoretical interest. Maybe they want to challenge their technical knowledge which they learned at university.Even beginners with a limited budget and limited practical experience, might have a good theoretical understanding of signal sampling theorems and digital signal processing. I am sure that there are many "practical beginners" here on this forum, who have an engineering degree in electronics. A practical beginner is not per definition a high school student.The practical stuff is simply not taught at universities, and sometimes you just get overwhelmed with so many mathematics during classes, that you forget basic principles and common sense. This is very unfortunate, but it is a reality among engineering students.

author: Lukas
author_rank: Frequent Contributor
timestamp: August 05, 2015, 04:31:20 pm
content: For beginners interested in 'how it's done/has been done in the industry' I can strongly recommend the HP journalshttp://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/hpjindex.html. Sure, many of them are pretty dated now, but they still a good job at explaining the design process that lead to the final product.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 05, 2015, 04:56:15 pm
content: Quote from: pascal_sweden on August 05, 2015, 03:36:31 pmPretty much, except (yes, you guessed it) LeCroy (which btw is one of the reason I do have a lot of respect for them). Agilent/Keysight and Tek are the worst offenders, they pretty much go the full mile including twisting reality if necessary. They also publish tons of "ours-vs-theirs" compare sheets and videos where they compare their scope against a (usually smaller model) competitor's scope in dubious setups, and massage the outcome so that their product looks better.R&S isn't half as bad as Tek and Keysight, however either R&S has no clue what their competitors are up to (well, they aren't in the scope business for that long) or believes their customers are morons, because none of the points they highlighted on their "scope lies" page is actually an issue for any scope that competes with their very expensive RTO Series. Yes, it's marketing, but it doesn't really give me a lot of incentive to consider their products when the manufacturer has to resent to deception.LeCroy doesn't seem to do ours-vs-their-comparison, at least so far. They're also not constantly harking on the competition, but let their products speak for themselves (but then, LeCroy is still very much lead by engineers, even most of their sales team comes from engineering). In fact, the only document they published which I'm aware off where competitors' scopes were used is this one talking about interpolation:http://cdn.teledynelecroy.com/files/whitepapers/wp_interpolation_102203.pdfAnd even there the test parameters are clearly defined so anyone should be able to reproduce the results.QuoteMaybe you're right. Both Rigol and Siglent have pretty much lied in the past about the capabilities of their products, so I'm not holding my breath, though.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 05, 2015, 05:28:27 pm
content: Quote from: Lukas on August 05, 2015, 03:41:48 pmYes, in 2010. That's 9 years after LeCroy rolled out their 10GSa/s monolithic ADC in the WavePro 7k/WaveMaster 8k. Agilent came out with theirs not too long after. If I remember right even Tek had their own 10GSa/s ADC at that time.QuoteNot really, the big competitors only interleave to allow even higher sample rates in 2ch config. Just to give you an idea, when R&S came out with their 10GSa/s ADC, others were already at 20GSa/s in a single ADC, and up to 80GSa/s in interleaved configuration.QuoteThey can be, but not because it's such an advance over the competition (which it wasn't, in the scope market R&S is mostly following, not leading). They can be proud of having produced the first 10GSa/s 8Bit ADC that didn't originate in the US and at that time would have fallen under export limitations due to its dual use in military applications.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 05, 2015, 05:49:09 pm
content: Quote from: pascal_sweden on August 05, 2015, 04:22:13 pmWith that argument we should also discuss cooking of shellfish, as this might be something that a EE beginner could also be interested after allIn all seriousness, if it's something that mostly a beginner would ask then it should be in the beginner section.QuoteYou have a pretty crude imagination about experienced engineers. I'm pretty sure that the majority doesn't just take things for granted because it has been "drilled in their mindset" (although that does happen, even in this forum we have a certain group of backwarders that regularly appear and tell people how much better analog scopes are and what hogwash all this new-fangled digital stuff is; pretty much the EE equivalent of HiFi vodoo), but simply because they know and are aware how stuff works and how to deal with it.QuoteAnd in your opinion you believe the marketing pages of a test instrument manufacturer is the right source for that? Seriously?QuoteWell, please enlighten us then what you have learned from these R&S webpages that give you a better understanding of practical electronics engineering? Or are you already off to order a R&S scope?

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 05, 2015, 06:00:20 pm
content: Quote from: Lukas on August 05, 2015, 04:31:20 pmI can second the recommendation, the HP Journal was from a time before they engaged in 'optimistic marketing'.For those that are looking for stuff about more modern kit, some interesting documents covering the basics can also be found in LeCroy's (pretty badly organized) app note and whitepaper portfolio:http://teledynelecroy.com/resources/details.aspx?doctypeid=1&mseries=352http://teledynelecroy.com/resources/details.aspx?doctypeid=5&mseries=352Beginners might be interested in particular stuff like that:Understanding scope probes:http://teledynelecroy.com/doc/probes-probingHow to calculate ENOB and SNR:http://cdn.teledynelecroy.com/files/appnotes/computation_of_effective_no_bits.pdfEquivalent Time Sampling:http://cdn.teledynelecroy.com/files/whitepapers/wp_ris_102203.pdfX/Y plots:http://teledynelecroy.com/doc/calculating-area-in-xy-displays-waveform-math-finds-area-enclosed-by-xy-displayTroubleshooting high speed serial signals with a DSO:http://teledynelecroy.com/doc/troubleshooting-high-speed-digital-signals-with-dsosFFT:http://teledynelecroy.com/doc/more-about-the-fftAveraging:http://teledynelecroy.com/doc/eres-vs-boxcar-averaging

author: Lukas
author_rank: Frequent Contributor
timestamp: August 05, 2015, 06:24:31 pm
content: Quote from: Wuerstchenhund on August 05, 2015, 05:28:27 pmAs in my  reference, most of the Agilent ADCs are based on interleaving a massive amount of ADC slices on a single die. You still have to accurately align their individual sampling phases.Quote from: Wuerstchenhund on August 05, 2015, 05:28:27 pmSee above. I guess R&S marketing is targeted against on-chip interleaving. That's how I at least understood it.Quote from: Wuerstchenhund on August 05, 2015, 05:28:27 pmSample and 'number of bits' rate isn't everything. R&S specify an ENOB of ?7bit for their 8bit ADC, Keysight specify the ENOB for their 10bit scopes. Lecroy doesn't even specify an ENOB for their 12bit scopes. If the ENOB would be noteworthy, they'd specify it. In a 'competitive comparison'  Agilent states an ENOB of 6.4bits@1GHz for LeCroy's 12bit scope, whereas their 10bit scope has an ENOB of 8 bits. Go figure.http://cp.literature.agilent.com/litweb/pdf/5991-4437EN.pdf

author: commie
author_rank: Frequent Contributor
timestamp: August 05, 2015, 06:42:44 pm
content: I believe Teledyne(pls correct me if I am wrong) in 1975 introduced the 4558 dual opamp, fantastic symmetric opamp. They now cost as little as £8.00/100, why? because everyone is using them.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 05, 2015, 07:10:39 pm
content: Oft-repeated lie:"You need a sample rate significantly faster than the signal bandwidth, to see anything at all"

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 05, 2015, 07:37:42 pm
content: Quote from: Lukas on August 05, 2015, 06:24:31 pmI'm sorry but your "reference" just goes to a website containing a list of other documents (of which many aren't even oriented correctly). You'd have to be more specific as just off-loading a list of documents and expecting me to find the one that supports your statements.QuoteThat's a good example of someone falling into the trap of marketing BS (and using an Agilent "infomercial" isn't really helping your case). LeCroy doesn't specify ENOB because as a figure it is worthless without a description of the environment (i.e. frequency) it was calculated at, which of course you'll rarely find in Agilents or even R&S's marketing blah.You might want to read this paper from Analog Devices which should explain what ENOB really does:http://www.analog.com/media/en/technical-documentation/technical-articles/MS-2124.pdfLet me quote:"Though often quoted, the ENOB is insufficient to describe a high speed converter’s performance. High speed converters are famously multiparametric, and no single number can hope to capture what takes an entire specification table to describe. ENOB does make a reasonable starting point for comparing candidate converters,so long as you do not depend excessively on the number’s significance."and"More valuable are the SINAD vs. frequency characteristic curves, which many high speed converters present in their data sheets (Figure 2). These allow you to identify at least typical performance at the frequencies of interest to your application instead of at the spot frequencies the converter manufacturer chose for the data sheet’s specification table."If you really think when R&S says their ADC has an ENOB of 7bit and Agilent that their ADC has an ENOB of 8bit that you know which ADC is better then you've been taken for a ride.LeCroy doesn't publish ENOB numbers because as a single figure they are useless. However, in an example in one of their app notes they measure and calculate the ENOB for the WaveMaster 820zi 20GHz scope, which for their test parameters (1.4GHz sine) comes out at 5.33bit, which isn't bad for a 20GHz 40GSa/s scope. But thankfully aside from that well documented example they leave the ENOB BSing to their competitors and focus on the relevant parameters.

author: tautech
author_rank: Super Contributor
timestamp: August 06, 2015, 03:01:14 am
content: Quote from: Wuerstchenhund on August 05, 2015, 03:11:40 pm+1Like any bias comparative analysis, they are alwaysto make themselves look/spec better.This marketing "oneupmanship" has been going on for decades.

author: vk6zgo
author_rank: Super Contributor
timestamp: August 06, 2015, 03:25:25 am
content: I'm a bit dubious about the triggering one:-http://rohde-schwarz-scopes.com/scope_lie_04.phpIf their argument here is justified,then my old BWD which obtains triggering from a 220k Ohm resistor hanging off the output of the vertical deflection amplifier should have great triggering.I can't remember any radical problems with triggering in the many good quality analog 'scopes ,or in the few DSOs I have used."Straw man"?

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 06, 2015, 04:42:55 am
content: DSO, digitizing systems are going to slide, dice and chop up what once was a constantly varying natural event into bits and pieces.These bits and pieces will be reconstituted into a form of visual information.Each step of this process contains and results in distortions of what once was the original constantly varying event. Limitations and advantages of this process must be kept in mind by digitizing systems to avoid being fooled by the information presented.Core difference between digitizing systems (DSO) and Analog time domain instruments, Analog O'scopes process the signal as is with great fidelity if they are any good. This difference is why high fidelity, high quality analog O'scopes do not lie while DSO can lie and deceive it's users that are un-aware of limitations baked into their design.If would be ignorant and claim one technology is always better than the other as both technologies have their advantages and disadvantages. Best and most accurate results can occur when the measurement need determines instrument and measurement choice.All else is marketing and taking advantage of user-market ignorance.Bernice

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 06, 2015, 05:15:18 am
content: Oh boy, that didn't take long, did it?Quote from: Rupunzell on August 06, 2015, 04:42:55 amI'm sure it's complete news to you, but FYI, analog scopes *do* lie, they lie a lot (Dave did even a video about that some time ago). In fact, *every* test instrument lies to an extend, and any engineer worth it's merits should be very well aware of that.But thank you for proving my point:Quote from: Wuerstchenhund on August 05, 2015, 05:49:09 pm

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 06, 2015, 05:20:17 am
content: Yep, this point will never end until YOU get some real world experience with serious Analog design and why high quality, high fidelity analog O'scopes DO NOT LIE if the user knows instrument limitations and how to apply said instrumentation properly.Can you prove DSO's don't lie? If yes, post your results. I don't care about what Dave or others have posted. Present the facts, test conditions and results completely for all to examine, duplicate and prove as fact.Then prove high quality, high fidelity analog O'scopes lie.Nuff said.BerniceQuote from: Wuerstchenhund on August 06, 2015, 05:15:18 am

author: dadler
author_rank: Unknown
timestamp: August 06, 2015, 05:23:03 am
content: Ahh ad hominem, condescension....not long until we have a nazi reference.Oh Internet, I love thee.

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 06, 2015, 05:41:46 am
content: Indeed, trolling with baiting often brings up NAZI at some point. That is pretty much when any meaningful discussion of any topic has flat-lined.BerniceQuote from: dadler on August 06, 2015, 05:23:03 am

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 06, 2015, 05:44:15 am
content: Issues with DSO signal fidelity and information presentation has been discussed once before.https://www.eevblog.com/forum/testgear/my-first-oscilloscope/75/Bernice

author: ale500
author_rank: Frequent Contributor
timestamp: August 06, 2015, 05:48:41 am
content: The video from the signal path about the 100 GHz Teledyne-Lecroy Oscilloscope have a nice but not very in deep explanation of a modern interleaving system. In the end, they use digital signal processing to reconstruct the original signal. If I understood correctly one could use the same method at lower frequency, just as a proof-of-concept right ?Agilent/HP also published a paper on how their 8 bit ADCs (several GS/s) worked a couple of years back, and they talked about ENOB quite lengthly... but where is that document again...

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 06, 2015, 06:14:22 am
content: LeCroy short on what they are doing..http://cdn.teledynelecroy.com/files/whitepapers/interleaving_process_in_dbi_scopes.pdfNote the use of a mixer and how the bits and pieces of information is to be sorted out and presented to the user.Alternatively, Hypress did a superconducting Josephson junction based 50 Ghz sampling scope in 1987.http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=1487395&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F9953%2F31997%2F01487395And a bit of history:http://www.kahrs.us/~mark/pdf/papers/MTT2003.pdfBerniceQuote from: ale500 on August 06, 2015, 05:48:41 am

author: Lukas
author_rank: Frequent Contributor
timestamp: August 06, 2015, 06:29:49 am
content: Quote from: Wuerstchenhund on August 05, 2015, 07:37:42 pmhttp://poulton.net/papers.public/2010_cicc_GHz_ADCs.pdfSlide 27. Their 20GSa/s ADC is made up of no less than 80 ADC slices.Regarding ENOB, etc: Still wonders me why I get more specs for a $50 ADC than for a $50k 'scope.Quote from: ale500 on August 06, 2015, 05:48:41 amVery likely to be there, since this guy seems to be one of the ADC gurus at HP/Agilent/Keysight:http://poulton.net/papers.html

author: ebastler
author_rank: Super Contributor
timestamp: August 06, 2015, 07:50:41 am
content: Quote from: Rupunzell on August 06, 2015, 05:20:17 amI'm afraid that would get you into a bit of a logical dilemma...

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 06, 2015, 07:53:21 am
content: Question for the interleaving experts in this threadWhat is special about the ADX Interleaving Technology from this Swedish company (SP Devices)?http://spdevices.com/index.php/technologyInterleaving is a technology that has been out there for several decades. So what makes their IP special? They claim to have several patents in this area.Note that SP Devices is based in Linköping. My office was less than 300 meters from their officeThey have 14 bit digitizers with a sample rate of 2GS/s, 12 bit digitizers with a sample rate of 4GS/s, and 8 bit digitizers with a sample rate of 7 GS/s.http://spdevices.com/index.php/products/digitizer-product-overviewThey provide a development kit for developing custom firmware in the FPGA of their ADQ-series digitizer:http://spdevices.com/index.php/adqdevelopmentkitCould this technology be used for a modern digital scope? Interleaving two ADCs is much cheaper than using a higher end ADC, but it comes with compromises. But maybe with the SP Devices technology these compromises can be kept to a limit.Can the interleaving experts here give their two cents on this technology? =)

author: dom0
author_rank: Super Contributor
timestamp: August 06, 2015, 08:18:19 am
content: Quote from: Rupunzell on August 06, 2015, 05:20:17 amYep, this point will never end until YOU get some real world experience with serious analog design and why high quality, high fidelity digital O'scopes DO NOT LIEif the user knows instrument limitations and how to apply said instrumentation properly.

author: Hugoneus
author_rank: Frequent Contributor
timestamp: August 06, 2015, 03:26:22 pm
content: As far as ADCs are concerned, whether they are time-interleaved, frequency-interleaved or both (which by the way anything over ~80GS/s at the moment uses both at the same time as of today) or whether they are SAR, flash, pipeline, folding, delta-sigma, etc. (all of which have their own unique characteristics), all I care about is the performance at the end of the day. High-end scopes have one major advantage that other systems using ADCs do not have, they are calibrated for hours and hours for every single range, frequency, phase, etc. A lot of imperfections can be corrected this way.In my line of work, I wouldn't even consider analog scopes because they would be the wrong tool to use for me. And I would argue that no analog scope can hold a candle to the very good digital scopes like the S-series scope from Keysight for combined great noise/bandwidth/linearity and the MDO4000B from Tektronix for correlated measurements.Having said that, making good measurements is an art. If you don't understand the limitation of your instrument, then it doesn't matter what you use.

author: GlowingGhoul
author_rank: Regular Contributor
timestamp: August 06, 2015, 03:31:39 pm
content: Lets talk about the merits of $10,000 1M audio interconnects vs standard cables.

author: nfmax
author_rank: Super Contributor
timestamp: August 06, 2015, 03:59:40 pm
content: Quote from: Hugoneus on August 06, 2015, 03:26:22 pmThis! With knobs on!

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 06, 2015, 05:56:04 pm
content: Quote from: Rupunzell on August 06, 2015, 05:20:17 amIt's getting better by the minuteOf course, whoever disagrees with your "wisdom" must be young and inexperienced, something you resort to like a broken record. I guess your next post will contain some "Jim Williams only ever used analog scopes so they must be better" or similar drivel to get your point across, as usual.You know, until now I thought you're just an old guy who couldn't make the mental leap to the modern day, and therefore clings to what he learnt 30+ years ago. But now I seriously start to wonder if you even have any engineering background, or if you just want to troll, because I severely doubt that any engineer worth its salt would refer to any analog scope as "high fidelity" instrument. You sound more like the kind of guy that would pay $500 for a HiFi HDMI cable.QuoteInteresting, so now it's not "a high fidelity scopes DO NOT LIE" (whatever "high fidelty" is supposed to mean here, considering how shit the specs of even the best analog scopes are in most areas!), now you're actually retreating ("they don't lie if you know their limitations").QuoteNo. Which is a strange and frankly pretty moronic question when I only in my last post said this (I highlighted the important bit, just in case you lose the plot again):Quote from: Wuerstchenhund on August 06, 2015, 05:15:18 amBut as I said, it's getting better by the minuteQuoteIt's clear you don't care what Dave has posted (same as you don't care about how shit your full quotes look), and I guess most of this stuff is lost on you anyways. However, just for the sake of it, Dave made a nice episode showing how your "high fidelity" analog scope can trick you:There are many more situations where your "high fidelity" analog scope will lie or hide stuff from you. Which should be obvious once you understand the principle, and that the on-screen luminance for a specific component of the input signal very much depends on two things, a) that it's position remains stable on the time axis, and b) the period of occurrence. If the component moves on the time axis (i.e. it's period of occurrence varies, or if the period of occurrence is pretty long then there's a good chance it won't cause sufficient luminance for the user to notice it. Plus, the analog scope suffers from blooming (more or less any CRT does to some extend, but analog scope CRTs are pretty bad), which can easily cover signal components that due to the mentioned factors only cause low luminance. You could turn up the brightness and therefore make these components brighter, but unfortunately with increasing brightness blooming gets a lot worse.Then there are the specs, which for today's standards are pretty poor on most analog scopes. Just as an example, the pretty expensive Tek 7B92 dual time base for the 7904 500MHz analog scope (all pretty much high end in the 80s) has a time base accuracy of (depending on the setting) 2-10% which is a huge. Compare that to a cheap-ass Rigol DS1054z (hardly the epithome of DSOs) which is spec'd with<+25ppm. That's like day and night. Most analog scopes are even worse. "High fidelity", yeah, right.However, all that's pretty basic stuff.Quote from: Wuerstchenhund on August 05, 2015, 05:49:09 pmSo once again, thanks for proving my point. I couldn't have done it without you

author: mtdoc
author_rank: Super Contributor
timestamp: August 06, 2015, 06:21:23 pm
content: I just watched Dave's video (again). There is nothing in there about analog scopes "lying". It is only showing an advantage of digital scopes that make it easier on them to view switching noise (especially if one does not know how to properly use an analog scope!).I love my Rigol scope as well as my analog scopes. Both have their purpose. Arguing that one is always better for every task is just silly IMHO.It may be true that high end (very expensive) digital scopes allow one to overcome many of the shortfalls of lower end DSOs but how many can afford a Keysight S series scope, etc. High end, used analog scopes on the other hand are very affordable.Quote from: Rupunzell on August 06, 2015, 04:42:55 amSeems like a very reasonable statement. Not sure why your post generated so much hate...

author: Hugoneus
author_rank: Frequent Contributor
timestamp: August 06, 2015, 06:43:08 pm
content: I would like to see a video of an analog scope measuring/capturing something that a digital scope cannot.

author: mtdoc
author_rank: Super Contributor
timestamp: August 06, 2015, 06:57:56 pm
content: Quote from: Hugoneus on August 06, 2015, 06:43:08 pmYes. But of course the question is "which digital scope?"No doubt that there are many things that even a budget digital scope can do that no analog scope can do.In my mind the real question is - Are there cases where an analog scope can display a more accurate representation of a waveform than a digital scope?.If your digital scope budget is unlimited then the answer is probably no. But for hobbyists or even professionals doing work at home whose scope budget is more modest then I think the answer is probably yes.Seethis threadfor an example of the latter.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 06, 2015, 07:14:21 pm
content: Quote from: Hugoneus on August 06, 2015, 06:43:08 pmTo be fair, someone could use one of the antique sampling scopes with ridiculously low sample rates from the 80's and easily find cases where an analog scope might be superior. After all, that's roughly the DSO generation many analog scope proponents seem to believe reflects a modern day DSO (plus, that's also roughly the period from which articles are often cited to demonstrate the flaws of digital scopes)But seriously, I'm waiting for at least 15 years on some kind of demonstration where an analog scope captures/measures something a decent digital scope can't (and where any problems a digital scope might have to capture/measure it isn't caused by an operator who doesn't know how to operate a DSO). So I hope you're a patient person as you might have to wait a while for that video

author: nctnico
author_rank: Super Contributor
timestamp: August 06, 2015, 07:26:07 pm
content: I agree. The first DSO I got was one which could be switched to analog mode (Tektronix 2230). It quickly got 'stuck' in DSO mode because even despite the low sampling rate (10MS/s) analysing and capturing signals just worked much better in DSO mode than the analog mode.

author: retrolefty
author_rank: Super Contributor
timestamp: August 06, 2015, 07:28:36 pm
content: This is all getting too religious for me, as in which scope type would Jesus choose? Bad tools in good hands can still get results, bad hands with good tools can still fail.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 06, 2015, 07:53:06 pm
content: Quote from: mtdoc on August 06, 2015, 06:57:56 pmHardly. As I said before, just look at the specs of your typical analog scope, and compare that with the specs of even a very cheap digital scope like the DS1054z. And it doesn't get much cheaper or low end than scopes like this Rigol.And specs only get better for mid-range and high-end DSOs.QuoteUnlikely. The thing is that analog scopes were never precision instruments. As the name implies, they were made for people to *look* at a waveform and draw their conclusions from what they see, and any "measurements" were made by reading from a pretty coarse scale (some analog scopes had cursors, but that's not much more precise than without, just quicker). The specs of analog scopes are mostly pretty wide like a barn door, with large tolerances, and they have pretty much *no* analysis capabilities whatsoever (but again, an analog scope is made for *looking* at the waveform, the "analysis" is up to the user, which is pretty limited).On the other side, even the (compared to what's available in the DSO market) most basic entry level DSO has much better specs than most analog scopes, plus a set of decent basic math capabilities, and the storage capabilities are world's apart from any analog storage scope (which tend to use storage tubes which were already a crutch back in the days and come with their own set of problems). For little money they provide sufficient real-time sample rates, and even cheap scopes offer true scrolling/zooming capability to examine glitches and other deviations in more detail (some analog scopes could use delayed trigger for that, which also was merely a crutch).The only area where I can see an analog scope having an advantage is if you need a Z input (i.e. luminance modulation), which most digital scopes lack, probably because these days there isn't much demand for it.QuoteThat thread is actually a good example of what I meant with the resident backwarders, because it completely ruined the thread for the OP who only wanted a recommendation for a decent entry level scope for a beginner doing his first steps in electronics into a drivel about analog scope models and repair. It could be worse, though, instead of just leaving (probably frustrated) the OP could have found himself wasting a lot of money on an old boat anchor just to find out that it's absolutely useless for anything than the most basic measurements.Maybe this forum could use some "Nostalgia" corner where analog scope proponents can dive into the "good ol' times". Actually, they could just create a separate thread instead of raiding threads like the one above.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 06, 2015, 07:54:30 pm
content: Quote from: retrolefty on August 06, 2015, 07:28:36 pmNot really. Ever heard the saying "a chain is only as good as its weakest link"?

author: Hugoneus
author_rank: Frequent Contributor
timestamp: August 06, 2015, 08:08:26 pm
content: Quote from: mtdoc on August 06, 2015, 06:57:56 pmOk, lets narrow the digital scope to the DS1054Z which costs $399. I think that qualifies as entry level. So, what can an analog scope do that this digital scope cannot? By the way, I am not asking this in a sarcastic way at all. I really want to see an example.

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 06, 2015, 08:09:59 pm
content: What about the Tektronix 2225 analog scope?It has a 500 uV/div vertical resolution. Try to beat that with a digital scope!Or what about the Integrated Superconductor Sampling Oscilloscope?http://www.google.com/patents/US4926067

author: dadler
author_rank: Unknown
timestamp: August 06, 2015, 08:11:52 pm
content: Quote from: pascal_sweden on August 06, 2015, 08:09:59 pmUm, Rigol DS2000 has 500uV vertical resolution.

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 06, 2015, 08:24:53 pm
content: Does anybody here in this thread, know the current status of this project?https://www.eevblog.com/forum/beginners/500uvdiv-oscilloscopes/msg462736/#msg462736There is no update in the beginners section, so I thought it might be worth asking the rookies

author: Hugoneus
author_rank: Frequent Contributor
timestamp: August 06, 2015, 08:26:04 pm
content: Quote from: pascal_sweden on August 06, 2015, 08:09:59 pmAt 500uV division the bandwidth of the 2225 drops to 5MHz. If you limit your bandwidth to 5MHz on a digital scope you will get (if not better) at least as good of a result. Furthermore, the DS2000 series has 500uV vertical resolution anyway.

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: August 06, 2015, 08:40:16 pm
content: Quote from: Hugoneus on August 06, 2015, 08:08:26 pmMy Tek 2247A from the stone age has a 5 MHz BW limit ... on its Z modulation input. Displaying analog video signals must probably be considered a niche application these days, yet still.

author: G0HZU
author_rank: Super Contributor
timestamp: August 06, 2015, 08:41:32 pm
content: I don't understand why there has to be an outright winner here. I have both analogue and digital scopes here and I also have access to some really nice DSO/MSOs at work.But for some things here at home I still use my old Tek 465 as favourite. For many other things it's fairly hopeless in comparison to a modern(ish) DSO. But I still have it here when it is the right thing for me to use.Part of the fascination of this forum (for me) is how superficial it is. It's often like a bunch of kids playing top trumps over DMMs and scopes and time/voltage references.

author: dadler
author_rank: Unknown
timestamp: August 06, 2015, 08:41:51 pm
content: Oh, I got it!http://youtu.be/aMli33ornEUfails spectacularly on most digital scopes, hence analog is better.

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: August 06, 2015, 08:53:04 pm
content: Quote from: dadler on August 06, 2015, 08:41:51 pmI'm not suggesting analog scopes are 'better', but Hugoneus asked for an example and I gave him one. The 2247A also has dual timebase, not to mention an 8 digit interval/hardware counter, combined with an external 10 MHz reference clock input. This makes it useful for many timing and frequency measurements over a wide range of input amplitudes. Though those last features are not unique to analog scopes, of course, but the DS1054Z would fall short here if you need any of this.

author: tautech
author_rank: Super Contributor
timestamp: August 06, 2015, 08:55:06 pm
content: Quote from: pascal_sweden on August 06, 2015, 08:09:59 pmIf you'd taken the time to inspect the new Siglent SDS1000X series specs:Quote

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: August 06, 2015, 08:57:10 pm
content: Quote from: G0HZU on August 06, 2015, 08:41:32 pmShh! You are not supposed to utter reasonable arguments. Polarization provides entertainment!

author: dadler
author_rank: Unknown
timestamp: August 06, 2015, 08:58:15 pm
content: Quote from: ElectroIrradiator on August 06, 2015, 08:53:04 pmSorry I didn't even see your post. Was not referring to you at all. Entirely tongue-in-cheek, no offense intended :grouphug:

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: August 06, 2015, 09:02:31 pm
content: Quote from: dadler on August 06, 2015, 08:58:15 pmOK, no worries.

author: nixxon
author_rank: Frequent Contributor
timestamp: August 06, 2015, 09:07:52 pm
content: Quote from: pascal_sweden on August 06, 2015, 08:54:35 pmYou really got this thread goingAre you from Sweden and/or from Norway? (Nick vs Flag)

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 06, 2015, 09:10:50 pm
content: Have been living 9 years in Linköping, Sweden (explains the nick).Currently living in OsloJag pratar väldigt bra svenska, nästan flytande, og jeg forstår norsk også ganske bra.Men mitt modersmål är flamskWhere do you buy your test gear?Instrumentcenter Sweden AB or Venotek AS?I buy outside Scandinavia as well, such as Batronix GmbH and AR Benelux BV =)

author: tautech
author_rank: Super Contributor
timestamp: August 06, 2015, 09:12:51 pm
content: Quote from: ElectroIrradiator on August 06, 2015, 08:57:10 pm

author: Lukas
author_rank: Frequent Contributor
timestamp: August 06, 2015, 09:22:49 pm
content: Analog scopes still shine when you need high bandwidth on a budget. I got my 400MHz tek 7834 storage scope with a 500MHz (7A19) and a 10µV/div (7A22) and two more general purpose plugins for less than €50. With a bit of fiddling it, can barely do a singleshot capture at full sweep speed. It'll take a long time for 500MHz DSOs to come down to this price level.

author: tautech
author_rank: Super Contributor
timestamp: August 06, 2015, 09:29:05 pm
content: Quote from: Lukas on August 06, 2015, 09:22:49 pmGood price.Try carrying it with one finger.

author: G0HZU
author_rank: Super Contributor
timestamp: August 06, 2015, 09:31:09 pm
content: Old school analogue scopes often have some hardware features that can be exploited.One neat trick with the old Tek 465 is that you can couple up a decent counter or a spectrum analyser to the CH1 OUT BNC at the back.When used with an external frequency counter (up to the BW of the scope front end) you can 'see' on the scope CH1 via the scope probe what you are also measuring with the counter via the rear panel CH1 o/p and also it improves the sensitivity of the counter because there is gain at the rear CH1 o/p. The counter can be something much better than the limited counter you get in a typical cheapo DSO.When used with a decent spectrum analyser you can see lots of spectral detail that you can't see with the DSO in FFT mode. So you can get time domain and frequency domain with one common scope probe. OK the scope is only doing part of the work but it can be a useful marriage of two bits of test gear especially when trying to measure a low level signal inside a radio that the counter (on its own) can't reliably detect/measure.The other trick you can do here is deliberately tweak the compensation on the x10 scope probe to squeeze a tiny bit more counter sensitivity out of the system and you can see this 'working' on the CRT display whilst you tweak. This can make the difference between a shaky reading on the counter and a stable one and you can optimise the tweaking/peaking on the CRT as you measure with the counter.Most people use their bench frequency counter 'blind' but you can overcome this with the Tek 465.

author: mtdoc
author_rank: Super Contributor
timestamp: August 06, 2015, 10:14:04 pm
content: Quote from: Hugoneus on August 06, 2015, 08:08:26 pmIt's a good question.There's the specific example in thepreviously mentioned threadbut perhaps that doesn't qualify.How about this- correct me if I'm wrong, but with a 1GS/s sample rate aren't you going to get significant aliasing at higher frequencies?-3dB bandwidth limitations aside, with a similar bandwidth analog scope, the waveform will be preserved. Significantly attenuated, but preserved, correct? And if this is true, isn't it also going to be true that complex signals with very high frequency components may also be subject to similar issues?Of course as others have pointed out, a high bandwidth analog scope can be had for the price of a DS1054Z but that's probably not a fair comparison. What I'm referring to is an apples to apples comparison - same bandwidth scopes - analog is going to give a truer representation of the waveform at higher (above bandwidth) frequencies, no?.I claim no expertise so if this is wrong, I'm sure someone will correct me. Also, I'm no analog scope evangelist - I just think unqualified statements that they have no advantages are probably not justified.

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 07, 2015, 12:41:20 am
content: Quote from: Lukas on August 06, 2015, 09:22:49 pmThat's actually one of the best explanations up to nowLet's say your budget is limited. Then the best option is to go for a combination of a low-end digital scope (Rigol DS1054Z) with a limited BW (50-100 MHz), and an analog scope with a much higher BW (e.g. 400 MHz) or an analog scope with a similar BW but a higher vertical resolution (e.g. Tektronix 2225).Having two scopes also fills your bench, and the combination of a digital scope and an analog scope, gives your bench a professional lookEOD - End Of Discussion

author: tautech
author_rank: Super Contributor
timestamp: August 07, 2015, 01:46:06 am
content: Quote from: pascal_sweden on August 07, 2015, 12:41:20 amQuoteSays who?

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 07, 2015, 05:30:31 am
content: Quote from: Lukas on August 06, 2015, 09:22:49 pmThe argument was that the analog was the better instrument on a technical/capability level, not that it's cheaper.For €50 that's a great buy, though, and you're unlikely to get any digital scope for that price (even antique sampling DSOs go for much more).

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 07, 2015, 05:39:25 am
content: Quote from: pascal_sweden on August 07, 2015, 12:41:20 amAnalog scopes don't have "higher resolution", thei're analogThe vary in sensitivity and noise but the "resolution" is more or less limited by the waveform on the screen (i.e. its blooming).I'm also not sure if what you suggested is really the best option, as it still means you can't do a lot of things at the higher bandwidth since you're stuck with an analog scope there. Really, if your budget is limited then an older 2nd hand DSO with the required bandwidth (i.e. 500MHz) is very likely the better option. There are several very good older DSOs (i.e. LeCroy 9354) in a similar price range as your two-scope solution.

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 07, 2015, 06:17:30 am
content: As the number of samples diminish with increasing input test frequency -vs- sampling frequency, how can a sampled data conversion system maintain identical information content equal to lower input test frequencies?Sampled systems relies on samples of data to reconstruct the information..The conversion process is not noise free, why is this? What are the potential sources of noise and where to they come from, how does this affect data integrity and conversion accuracy?Analog systems do not function in this way.Your claim of blooming, noise and lack of resolution of analog O'scopes illustrates your ignorance and lack of real world experience with high quality, high fidelity analog O'scopes..Again those who are astute and fully understand the limitations of each technology will own both Analog and DSO applying them as required.The modern DSO has become essentially a signal digitizer for gathering data which allows this data to be analyzed, altered, modified, stored and more. This has resulted in the wave form data box common in so many DSO today. While all this can be a good thing for those who are focused in this data set alone, the skill of rapid interpretation of waveform content on the display has become a distant secondary item of test information. This is one of the difference between a past generation of time domain users of today -vs- those analog folks who can decipher a great deal about circuit behavior by waveform observation alone and very careful instrumentation set-up. Know this skill set is not easy to learn or gain from reading a book, learning this skill required un-counted hours in front to a high quality, high fidelity analog CRT O'scope and a highly experience mentor.What has changed, "electronics" has become data and software centric along with those who purvey and work in that cyber world (This is where the funding lives today). Yet, nature remain analog.. no matter how one tries to slice, dice and chop it up into points of information.BerniceQuote from: Wuerstchenhund on August 07, 2015, 05:39:25 am

author: ebastler
author_rank: Super Contributor
timestamp: August 07, 2015, 07:30:03 am
content: Quote from: Rupunzell on August 07, 2015, 06:17:30 amBernice - I'm not sure I can follow that argument. Present-day DSOs (even entry-level models like the DS1000Z series) are great for visual interpretation of signals, and specifically of rare events, in my opinion.I would certainly agree that this has not been the case in the "dark ages" of DSOs, before intensity graded displays were available. But with a decent intensity graded display, you can easily assess recurring vs. exceptional signals, vary the intensity scale as needed to make rare events more visible, look at a larger representative set of your rare events captured in memory etc.. And I am sure there is a reason why most users prefer DSOs with knobs, rather than PC-based -- the tight interaction between display, user interpretation and tweaking the scope settings must mean something to them...Sorry, but claiming that "visually interpreting signals is a lost art, people are just working with data sets today" does not reflect (my) reality.

author: dom0
author_rank: Super Contributor
timestamp: August 07, 2015, 08:28:27 am
content: Come on Bernice, you can do better than that.QuoteEven the best analog scopes achieve only a spatial resolution of 10 lp/div. But even a Hantek manages >20 lp/div.Analog scopes have their place, for various reasons. One is nostalgia. Another is how it feels to use them (essentially nostalgia), or how they look (nostalgia). They also cansometimesprovide featuresfor moneythat you simply won't get with a Rigol or Hantek, 7A22, 7A13 are often noted here. Also, the X-Y displays of the cheap DSOs are still crap. With the Hanteks, for example, you can't do any filtering or BW limiting in X-Y mode, so you always get a 3 mm wide trace in X-Y mode.Yes, of course, you can build your own pre-amp, and yes, you can today build something like a 7A22 even with opamps and get better specs, but until you reach the same level it will take a good while. I'd expect at least a month or so of fiddling to built an equal-or-better pre-amp. Parts cost during that period will be much higher than an entire 7000 system.Something like a 7A13 would be much harder ; flat, gaussian response from DC to >100 MHz isn't easy to achieve, although you could probably get away with an integrated JFET FDA in the frontend and a single-ended CFA gain stage (one could skimp here, too, and call for 5 mV/div or lower input sensitivity of the following scope input). Still, would take significant time and parts.

author: vk6zgo
author_rank: Super Contributor
timestamp: August 07, 2015, 08:55:03 am
content: The basic fact of life is that analog Oscilloscopes with specs like the 7000 series mainframes plus pluginsare no longer made.The few analog 'scopes available new are very much lower in performance,& lack such facilities as Delayed timebases.Secondhand modern DSOs are few & far between on eBay,etc.Those few that do appear are overpriced compared to new instruments.Older DSOs (1980s-90s) are generally very limited for general use,are often as large as,or larger than analog instruments,& in many cases have faults.The decision is then,between older Teks,HPs,etc & new DSOs.Apart from the ever-present "hopefuls" & commercial entities who want ridiculous prices for old instruments,many analog instruments in the same class as a 7613,465.etc are around $A100-$A200 range.Despite comments to the contrary,these are very capable instruments.After all,they were used extensively in Industry for many years until DSOs became the useful devices they are today.New DSOs are good instruments if you can afford them,but many people cannot.In my case,a DS1054z is totally out of my financial reach.The days where the $A was at better than parity with the $US are gone now!The question is,do you buy an older CRO from a reputable maker,which will do most of the things you want to do,or "save a bit longer" to buy a DSO,which will again do most of those things,plus others which may be those you never thought of?My decision had to be,buy the CRO-------at $135 at the Hamfest there was no question!The early introduction of DSOs was something of a "public relations nightmare":-Many of us "greybeards" initially approached the early DSOs with enthusiasm, looking forward to great display linearity,improved triggering,& of course,storage.We were not disappointed in some of those things,but we were with triggering & general usability.People who fix Electronic stuff with analog CROs commonly set the 'scope to "free run" at around the signal frequency they are looking for,with the 'scope set to DC at a convenient v/div setting.The process may be :-"OK,let's look at the input---yep signal is there ""Now let's look at the dc supplies--yeah roughly right""Now,signal trace through the equipment".The old DSOs didn't seem to have an equivalent to "free run"---"roll" isn't the same!Signal tracing didn't seem to work very well,& of course ,looking at dc levels was pretty much impossible.Another problem presented itself when we tried to look at a PAL field group.At 5mS/div,the sample rate dropped so low that aliasing made the display unusable.OK,PAL TV is obsolete---but any application where you need to look at high frequency signals at a long time/div setting will exhibit the same problems with these old instruments.We all gratefully went back to our analog CROs.It is the "received wisdom" that analog people didn't like DSOs because fast transitions were the same thickness as slower ones---in other worlds they didn't look like the phosphor on a CRO.I can't speak for others,but that wasn't my reason.I simply didn't think they were usable for my work,time was money,& I didn't have the time to learn "workarounds".By the way,we were called "Dinosaurs" back in the 1990s,too!The years have gone by,& I am no longer in the position where the Boss will buy me a new "scope,so I have no direct experience with modern DSOs----with"pretend phosphor" or not,but from the postings on this forums,they are light years better than the earlier versions!

author: MadTux
author_rank: Frequent Contributor
timestamp: August 07, 2015, 12:30:32 pm
content: Don't get this stupid discussion. Except for single shot events I never missed a DSO. And since I do analog stuff/repairs mostly, that's rarely the case. That's why the Tek 744A with broken screen is stacked somewhere and a Tek 7904A, some HP and Keithley DVMs, a logic analyzer and some spectrum analyzers and counters are stacked on my bench.High end analog Tek scopes are currently ~1/2 price of low end crap Rigols. They last forever, parts are cheap, I can follow the signal from input to CRT and fix them, they trigger beyond 1GHz, although signal amplitude isn't correct any more. Controls are intuitive and quick, compared to Tek 744A and I can see a trace as soon as the cathode is warm (a few seconds after power button is pressed).Now if I'd use a cheap Rigol, there isn't even a chance to see signals/pulses above 500MHz (Nyquist), bad thing if repairing PLLs (mostly use spectrum analyzers anyway) or pulse generators. If something is broken, also big trouble because everything is on a single multilayer PCB and no boards can be swapped to isolate the fault. Digital repair is nightmare and my impression is that ASIC failure rate among the higher priced DSO is rather high (TDS 7xxx trigger chips for example). 1000+$ repair each time that happens. Sure, digital scopes are nice when working with digital (microcontrollers and FPGAs), but I can almost always use a logic analyzer instead, which is also superior because it's not limited to 2/4 channels. A bad clock or incorrect signal levels can be seen as well on a old analog scope. Fast LA with deep memory are cheap on ebay, while equally fast working DSO with deep memory costs a fortune.Signal fidelity arguments are stupid, because I can use dedicated instruments for that. No scope timebase is as accurate as a good counter with Rb reference connected to the back. No scope FFT will have equal dynamic range and sensitivity as old skool swept SA. FFT math also hasn't nowhere near the same RBW of a classic SA. No scope will measure voltages as accurately as a dedicated multimeter.

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 07, 2015, 04:32:09 pm
content: Good illustration of what digital-cyber centric folks has become.Analog signal fidelity, accuracy and reproduction has little to do with optical resolution as expressed in line pairs per div.For those who believe they can easily replicate the specifications and performance of the Tek 7A22 using monolithic Op-Amps, better read, study and fully understand the specifications for the 7A22. Much the same applies to the idea and belief that a monolithic silicon solution can be easily applied to replicate the specification and performance of the 7A13.Tek 7104 can be phase coherent within 2-3 degrees to 350 Mhz on the X channel with the proper option. Since digital centric folks do value X-Y displays with this level of performance, it is not really a design consideration.All of this illustrates the current level of understanding of digital-cyber centric folks have of high performance analog deign and electronics.This was posted some time ago, how would a DSO behave if treaded in the same way as this Tek 7104, 7A26, 7A19, 7B10, 7B15? The inout is over driven by no less than 5 divisions off screen. Effective dynamic range of a DSO cannot be increased by using the DC offset control as the input is symmetrical above and below zero volts. Beyond this, there is how the noise is presented on the display, on the 7104 CRT, one can discern the type of noise and approximate the noise spectra if they know what to look for.https://www.eevblog.com/forum/projects/lm317-lm337-current-noise-tektronix-7104-and-more/msg643737/#msg643737Beyond this, I'm not convinced modern digital instrumentation with their switching power supplies, on board computers and more are NOT going to pollute the test environment with conducted and radiated emissions. In an environment full of RF pollution, there is a belief that a bit more of this is not going to matter. Except for some it actually does.Yes, this discussion has become rather stupid with those who claim to know, but really do not.BerniceQuote from: dom0 on August 07, 2015, 08:28:27 am

author: dom0
author_rank: Super Contributor
timestamp: August 07, 2015, 04:56:01 pm
content: QuoteIt's funny that you reply in that way, because no one ever said that.

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 07, 2015, 04:58:59 pm
content: "Yes, of course, you can build your own pre-amp, and yes, you can today build something like a 7A22 even with opamps and get better specs, but until you reach the same level it will take a good while. I'd expect at least a month or so of fiddling to built an equal-or-better pre-amp. Parts cost during that period will be much higher than an entire 7000 system.Something like a 7A13 would be much harder ; flat, gaussian response from DC to >100 MHz isn't easy to achieve, although you could probably get away with an integrated JFET FDA in the frontend and a single-ended CFA gain stage (one could skimp here, too, and call for 5 mV/div or lower input sensitivity of the following scope input). Still, would take significant time and parts."-Who posted this?Quote from: dom0 on August 07, 2015, 04:56:01 pm

author: dom0
author_rank: Super Contributor
timestamp: August 07, 2015, 05:04:18 pm
content: I did - but you obviously fail to understand it, since you write things like "easily replicated" or "easily applied".

author: nctnico
author_rank: Super Contributor
timestamp: August 07, 2015, 05:13:13 pm
content: Quote from: Rupunzell on August 07, 2015, 04:32:09 pmI think we have another item for the list in the first post. FYI: a decent DSO allows a lot of offset. Usually far more than an analog scope. My Agilent DSO allows an offset of up +/-2000 divisions depending on the input range.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 07, 2015, 07:43:48 pm
content: Quote from: MadTux on August 07, 2015, 12:30:32 pmThat was pretty obvious, as you missed the point completely.QuoteYeah, well, the thing is it's not about if you ever missed a DSO, really. I never missed an analog scope since around 1993, so what. It also wasn't about the price of used analog scopes vs new DSOs, it wasn't about nostalgia, or anything like that.What this is about is that within this discussion (and what you obviously missed, which apparently makes it a "stupid thread" to you) is that claims were made that an analog scope performs better and is more precise than a DSO, in addition some other closely related but equally ridiculous statements.QuoteYeah, except it's one of the many proprietary ICs in these Teks and many other scopes which are out of production for decades.QuoteIn short, you see something which may or may not represent the actual input signal.QuoteWell, the TDS744A is 20 years old, and hardly representative of a somewhat modern DSO. But it roughly represents the period where the DSO knowledge of many analog scope proponents has ended.QuoteThat's great, although I wonder that if time is of such essence why you just don't switch on the scope when before beginning your work. Especially since almost every test instrument requires a warm-up period to be within spec, which for the 7904 btw is around 20mins.QuoteWell, just don't use a cheap Rigol then. There are many good DSOs out there. I mean, you're using Tek scopes at the moment, right? Not something like this I guess:If something is broken, also big trouble because everything is on a single multilayer PCB and no boards can be swapped to isolate the fault. On the other side, many DSOs have pretty good self diagnostic capabilities which can make fault finding pretty simple (but of course that depends on the specific scope).And as I said, many analog scopes have components that these days are unobtainium. Good luck fixing one of those.QuoteNot really, many people do it quite successfully. Even hobbyists.QuoteWell, that may be your impression, but that's equally outdated as your 2 decades old TDS700 example. In fact, at least for the big brands (can't say for the Chinese brands, sorry) the failure rates of somewhat newer DSOs are pretty low, even lower than for many (most) analog scopes which often suffered from mechanical problems as well, which don't exist in most DSOs. I still think back with horror on all the problems we had with our Tek 7000 plugins. I've yet to see any DSO that's even only half as fragile.QuoteYeah, good luck measuring excessive clock jitter of a somewhat modern highspeed serial bus with an analog scope. I'm eagerly awaiting the link to the video showing a demonstrationQuoteWell, depends on what you consider "a fortune" of course, but yes, a MSO is more expensive than a cheap USB LA, simply because it can do much more.QuoteI agree that talking about signal fidelity in connection with an analog scope is stupid, but that's because of the poor specs of most analog scopes and not because what *you* use.QuoteIt really shows that your awareness of DSOs has clearly stopped with the TDS744A 20 years ago. While most digital scopes don't have the same dynamic range, FFT on scopes has come a long way since the TDS700, and in many areas is even better than a cheap low end swept SA.QuoteYes, and it won't make coffee as good as a coffer maker. To come back to what I said above, all this is irrelevant, as it has nothing to do with what this "stupid thread" is about, which clearly has passed you by.

author: Hugoneus
author_rank: Frequent Contributor
timestamp: August 07, 2015, 08:33:16 pm
content: Quote from: Rupunzell on August 07, 2015, 04:32:09 pmIf I ever need to lower the NF of my digital scope beyond its already amazing NF, I will use an external low-noise amplifier. If Silicon can't do it, so what? We have GaAs, GaN and InP with more dynamic range. Monolithic can't do it? We will go discrete, solid-state can't do it? Vacuum it is. I don't have to be stuck with analog scopes for that, not to mention the bandwidth limitations.QuoteOh common now. I showed in my review of the S-Scope that I could demodulate a 16-QAM constellation signal at a 2.5GHz carrier with a total power of less then -73dBm. In the presence of an interferer which has 26000 times more power, I could demodulate a -48dBm signal in a similar fashion. The scope captures the signal, processes it, does digital down-conversion, CDR and displays the result live.

author: G0HZU
author_rank: Super Contributor
timestamp: August 07, 2015, 09:39:21 pm
content: QuoteI think you may have missed the point Bernice was making here...I think what she says is valid but only for a few specific cases. Most of us don't need to worry about RF pollution from equipment. But sometimes I do. For example, I recently did some research work designing specialist types of (active) antenna some of which were tiny yet worked down to a few kHz.Obviously, I should really do this work in a screened room but I also did some research here at home in my main workroom. I found that I had to turn off pretty much every modern bit of test gear I had in my workroom (and adjoining rooms) including bench DMM, my Tek TDS scope, some other meters and obviously all laptops and PCs and anything with USB and all ES lightbulbs. Wall wart battery chargers and laptop PSUs were probably the worst offenders.Otherwise I just saw loads of interference. By turning off everything bar an old school spectrum analyser, a linear PSU and my Tek 465 |I could get reasonable noise floor performance. But I could still detect the high voltage circuits inside the 465 if I went very near its CRT with the antenna. But I needed the scope and the analyser to do my testing!But in terms of (near field) RF pollution my old Tek TDS2012 is much dirtier than my Tek 465. The levels are easily 40dB higher. The bench DMM was quite dirty too.Obviously, this is a very uncommon scenario (i.e. an extremely rare form of testing) but the Tek 465 was almost benign. The analyser was very good here too as long as I kept away from the CRT area. By comparison, some bench meters with scanning displays could be detected with huge signals and I could detect my PC keyboard and some other PC activity at quite a distance.

author: miguelvp
author_rank: Super Contributor
timestamp: August 07, 2015, 10:16:19 pm
content: TL;DRRigol DS2000 max wfrms/s is 48,000 with only 700 points mem depth automatic selection.minimum manual selection is 14K points for mem depth and that brings the update down to 5,000 wfrms/sA 1973 Tek 7613 with a 7A26 dual trace plug-in and a 7B53A time base module I can get 600,000 wfrms/shttps://www.eevblog.com/forum/testgear/first-personal-'scope-purchase/msg681691/#msg681691But yeah, you can set more complex triggers to capture what you need, so 100-200 times slower update might not be a big deal. (the DS1000z is even slower with a max of 30,000 wfrms/s so probably at 14Kpoints is just 3,000 wfrms/s)

author: nctnico
author_rank: Super Contributor
timestamp: August 07, 2015, 11:44:43 pm
content: Quote from: miguelvp on August 07, 2015, 10:16:19 pmNow you are comparing a $25k (in today's money) scope with a $500 scopeAnd that it assuming waveforms per second is actually an important feature (no, it really isn't).

author: miguelvp
author_rank: Super Contributor
timestamp: August 08, 2015, 12:09:07 am
content: I paid $50 (in today's money) for that scope and a 2nd one (5000 series) combined.But like I said, triggering options are better on new and even entry level DSOs so you can find those runts (if you knew they are there to begin with and there is where the CRO comes in handy).Also, the question is not about price but what do Analog scopes have that newer entry level DSOs don't have and the DS1054z was mentioned as the base DSO earlier on, so I'm just pointing out that the entry level DSO will miss rare events since it's only showing half a percent of what the CRO shows you on the screen, so you have 99.5% chances that it won't show those glitches even with persistance turned all the way up.FWIW I tend to use my DSO more often than the two 7000 series scopes I have, and the 5000 rarely gets turned on.Edit: BTW the CRO is only showing one out of three waveforms on that test so it only shows 33% of what is really in the signal because the retrace is double the time than the acquire time, so the DSO is only seeing 0.13% of the actual signal, so 99.8666% chances that it won't show you a runt.

author: tautech
author_rank: Super Contributor
timestamp: August 08, 2015, 01:01:17 am
content: Quote from: miguelvp on August 08, 2015, 12:09:07 amHow so?Isn't this what Single shot mode is for?QuoteTheres plenty of perfectly capable DSO's cheaper than the 1054 with sufficiently complex trigger suites to do most tasks.In fact more complex than all the CRO's that I have owned.

author: miguelvp
author_rank: Super Contributor
timestamp: August 08, 2015, 01:32:42 am
content: Quote from: tautech on August 08, 2015, 01:01:17 amIf you know what you are looking for. It could be a duty cycle problem for example once every many tens of thousand cycles the duty cycle is way off so the trigger level might not help so you have to hunt the problem down by setting the right window, or it could be a rise time and you have to set the right slope trigger, or it could be a pulse that is too narrow or too wide.Modern DSOs even entry level ones do have outstanding trigger capabilities but you have to find what the problem is first so you can set the trigger to confirm the suspected fault. I'm not saying that this is a hard problem because you know what to expect so you can set a series of tests to find the problem once you suspect what signal might be problematic.Also if waveforms per seconds is not important, then why get a DSO that can do a million of them per second and pay to the nose if a $500 entry level can find it with a single shot capture?

author: vk6zgo
author_rank: Super Contributor
timestamp: August 08, 2015, 01:33:52 am
content: Sorry,Wuerstchenhund,but this thread was really a discussion about Rohde & Schwarz's credibility,until you turned it into an "analog bashing" thread by posting the following non sequitur (bold italics):-Quote from: Wuerstchenhund on August 05, 2015, 05:49:09 pmUp to that point,I was following it with interest,& I was looking forward to your take on the "triggering"comments in the R&S Notes.I personally think that R&S are talking nonsense.

author: MadTux
author_rank: Frequent Contributor
timestamp: August 08, 2015, 02:24:39 am
content: QuoteYes, but these lasted for 30 years, so chances are high they last another 30 years. So far, shorted tantalum caps and oxidized connector/relay/switch contacts are far more common than broken custom chips. If they fail, parts or units for parts are cheap and since everything is socketed, parts can be swaped on component level. Now where can I find cheap replacement parts for any new DSO, if it fails? Since new scope ASICs are mostly BGA, soldering these is always great fun.QuoteOn digital scope for 2x the price, I see nothing at all.Most times, some aspects of a measurement aren't important at all, e.g. I'm only interested in the presence and frequency (7D15 or a counter to signal out) of a signal and not its exact amplitude. If I need to know these, I can still use a spectrum analyzer.QuoteIf I would turn on every instrument in my lab before starting work, the fuse in the basement would probably blow. Sure it has a warmup time before it's up to specs, but I don't need that if I quickly want to check the ripple on a power supply rail, test if crystal oscillator signal is present on a failed microprocessor circuit or follow a signal trough an amplifier. If the voltage on a PSU rail is really important I can still use a dedicated voltmeter instead of a 7A13.QuoteAnd what is the cost of a good DSO with the same bandwidth of a high end analog Tek? And what features do I get that I really need? Sure, those TDS 7404 scopes on ebay look nice, but they are like $3000. But then I need new probes and it's always a gamble whether any custom chips crap out.http://www1.tek.com/forum/viewtopic.php?f=5&t=4839Buy a new quality DSO, pay like $10000, have trouble free life for like 3 years of warranty and never see those $10k again. Second hand instruments usually keep their price or can sometimes even be sold at higher price if you fix and clean them and take some nice pictures for sale.QuoteYes, I can also find leaked EPROMs or busted TTL chips. But digital repair in BGA/multilayer PCB age without schematics isn't fun any more, especially if the board is mostly populated with custom chips.QuoteHP 8566 and 8568 are cheap nowadays. Dynamic range is close to 100dB if RBW is equal/below 10kHz. Now, where's your 16bit/1.5 GHz scope?

author: vk6zgo
author_rank: Super Contributor
timestamp: August 08, 2015, 06:52:13 am
content: Quote from: Wuerstchenhund on August 07, 2015, 07:43:48 pmFunny you should say that!After I left my job at the TV Studio,I had "withdrawal symptons" from not having an Oscilloscope ready to hand,so decided to fix my old BWD on which the triggering had completely failed.I found I needed a "scope to fix the 'scope"so I picked up a "Jaycar" 'scope which was the twin of the one pictured.As it happened,I never fixed the BWD,the Jaycar (I nicknamed it the "Crudscope") being all I needed for "messing around at home",as I was back at work with access to reasonable equipment.The next job after that one was different in that it had a halfway decent Spec An,but no operational 'scopes at all .(they did have a dead Tek 545B mainframe with a Spectrum Analyser plugin,only.)It would have been nice if the Employer would have sprung for a nice Rigol,but that wasn't to be.The RF equipment at this place suffered from numerous faults.Those in the RF area were covered by the SA,but the many others,which were mainly in the control circuitry were the very devil to troubleshoot with just a DMM,so the "Crudscope" was pressed into service.With a 'scope,things which were not apparent with a DMM became obvious,& it contributed in large part to the successful repair of these units.I have made the remark in this forum that "any Oscilloscope is better than no Oscilloscope",& the above story bears that point out.Oscilloscopes aren't always used for "bleeding edge" technology---sometimes it is sufficient to be able to verify if a signal,or a voltage is present or not.A 'scope display is often easier to see than a DMM reading.

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 08, 2015, 10:15:24 am
content: Why all these discussions about which scope is better or worse, when Agilent already knew the answer back in 2000https://www.tessco.com/yts/resourcecenter/pdfs/tenstepstoselectingtherightoscilloscope.pdfIf I only knew about this document, before I initiated this threadAnd yes, this document is not up to date, but it should lead the discussion in a more narrow direction at least!Please also consider reading this document! And especially take a look at the Questions and Answers section!http://materias.fi.uba.ar/6644/info/osciloscopios/basico/HP%20-%20Digitizing%20Oscilloscopes%20Basics.pdf

author: nctnico
author_rank: Super Contributor
timestamp: August 08, 2015, 10:48:30 am
content: The whole analog versus digital scope argument reminds me of vacuum tubes versus mosfet and CD versus vinyl records discussions.

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: August 08, 2015, 11:29:48 am
content: Quote from: nctnico on August 08, 2015, 10:48:30 amThe curious thing being, that tubes are still the right answer for afewvery specific applications.

author: G0HZU
author_rank: Super Contributor
timestamp: August 08, 2015, 12:02:17 pm
content: Quote from: ElectroIrradiator on August 08, 2015, 11:29:48 amSame applies for for vinyl

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 08, 2015, 01:02:13 pm
content: Quote from: vk6zgo on August 08, 2015, 01:33:52 amI'm not bashing analog scopes (I worked long enough with analog scopes, which were the only type of general purpose scopes available when I started my career, as back then DSOs were still in its infancies), but I don't have to lie myself to make them into something they simply aren't, as certain people seem to have the urge to do (probably because their understanding of DSOs ended in 1991).The simple fact is that analog were instruments of a different era which are pretty crude and primitive compared to what modern DSOs can do, and reality is that analog scopes are dead now for a very long time, even in the entry level, and that is for a reason. They surely did the job back in the days but that was when there weren't much alternatives (very early DSOs were mostly crap for real-time measurements) and even back then we often had to work around the shortcomings of these scopes. But seriously, it's no longer 1981, technology has moved on a lot, not just in test instruments but also in what type of circuits people build these days, and an analog scope is simply inadequate. It's like hammer and anvil compared to a modern CNC milling machine.These days an analog scope makes a pretty poor beginner's scope, not just because of its limitations (which usually aren't much of a problem for a beginner in the early stages of his hobby) but also because it trains and reinforces obsolete techniques. I can't tell you how often I come across engineers (even younger ones than myself) who have spend most of their career with analog scopes, and who have no appreciation for how a DSO works and how to get useful data out of a modern DSO because they treat it like their analog clunkers (i.e. ask them to measure some parameters and they start fiddling with cursors). Thankfully, this is now less of an issue with graduates as most EEs these days start on DSOs, which is a good thing.Analog scopes are fine if you're into retro test instruments, or say you get one for very cheap/free to get an impression how things worked back then, but if the intention is to get a serious start into EE then an analog scope is definitely the wrong investment.I also find it pretty sad that certain people here pretty regularly try to talk newcomers into buying old analog scopes because of "high fidelity" and other nonsense, which in the worst case means a beginner following this recommendation spending a lot of money on an old clunker just to find out it's useless, which very likely will drive him off electronics for good. If you really have to display in public that your mind is incapable of dealing with the here and now and that you're mentally stuck in the 60's then at least do it without ruining someone else's day.Quote from: pascal_sweden on August 08, 2015, 10:15:24 amIt's a good find, as it covers the basics without the typical Agilent spin on their own product range, and while some parts are outdated (i.e. 2+2 channel scopes are pretty much a thing of the past) it's still a very good description of what the important properties are for a (digital) scope.QuoteNow that's more like what we've come to expect from Agilent. In essence, they took the information from the first one and drenched it in marketing spin around their own technology.Not even worth the download, as everything that isn't marketing can already be found in the first document.

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 08, 2015, 04:28:05 pm
content: Welcome to my world.In today's switching centric world where digital systems are the norm with switching power supplies, high speed digital and all similar. Realities such as what happens when conducted or radiated RF spewing from test gear and other related electronics is often un-noticed and of absolutely zero concern. until one tries to work with circuits and systems that function at very low signal levels in the analog world. It is also often assumed that any low frequency (less than 1 Mhz) is easy, simple and could not be difficult. Reality is, that is just not true. Until one tries to do detailed work in these areas the lessons of how difficult all that low frequency stuff could be will never be appreciated. On the other end, try making receiver performance measurements in a noisy RF environment with test gear that produces significant RF pollution.Core to what has happened here is the often held belief and ideology that newer is always better and anything from the past must be relegated to the scrap heap pile as the march of technology pushes forward. My reply to this has always been that this simply is NOT true. Much if not all depends on what one is working on, what performance levels are expected-required, where the funding for such work comes from and what market revenue might result from said work done. Technological items from the past are often not appreciated by purveyors of technology of new as each new generation is caught up in the idea and belief that they, "already know all that stuff and have a much better way." This is not always true as there are hard realities of Physics and laws of nature at work here along with basic human factors. What is a market reality is, newer techno items can be marketed and sold to generate revenue and profits which stock holders, investors and all related are deeply interested in.Why all this text, too many here are myopically focused all this modern stuff with less than a broader perspective of what has been done and how it can related to the world of science and technology beyond digital-cyber items. Being blinded to the lessons offered by history often has unpleasant results.*No replies, comments on the post regarding current noise from a three terminal voltage regulator (LM317 & LM337).. why is this?BerniceQuote from: G0HZU on August 07, 2015, 09:39:21 pm

author: NoItAint
author_rank: Contributor
timestamp: August 08, 2015, 05:03:37 pm
content: Which one doesOscillofunthe best?https://www.eevblog.com/forum/chat/surely-i'm-not-the-only-one-who's-seen-oscillofun/

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 21, 2015, 10:17:06 am
content: Quote from: Wuerstchenhund on August 05, 2015, 04:56:15 pmNow I know why you like LeCroy so much! Because of Ralphie!

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 21, 2015, 12:41:38 pm
content: Quote from: pascal_sweden on August 21, 2015, 10:17:06 amYou bet it's Ralphie!Unfortunately I bought my LeCroy scope second hand and the Ralphie that came with it wasn't in as great of a shape: