Article on DSOs. Praise to analog scopes - Page 1
Forum section: electronics / testgear

author: PartialDischarge
author_rank: Super Contributor
timestamp: July 21, 2017, 05:28:32 pm
content: Take a look at page 54 of this months issue of BodosPower , "Don’t let your Digital StorageOscilloscope betray you"http://www.bodospower.com/restricted/downloads/bp_2017_07.pdfQuotes:"Lucky who still owns an analog scope, preferably aTektronix 7000 series model.""Refrain from buying or using any DSO with less than 1 MB""DSO’s only show a more or less distorted rough and jittery reconstruction of the signal or artifacts which bear no resemblance to it.There are no “Real Time DSO’s”, this term is misleading as it infers that a DSO were able to show a signal in real time. All DSO’s are sampling scopes""DSO’s were massively forced into the market, not because of any better performance, but because the profits exceed those on analog scopes by orders of magnitude!"

author: nctnico
author_rank: Super Contributor
timestamp: July 21, 2017, 05:36:41 pm
content: Who dares to write such nonsense in 2017? And who is going to bring up a DSO with only 10kpts of memory? I think someone found an old article from 1985 and reprinted it.

author: PartialDischarge
author_rank: Super Contributor
timestamp: July 21, 2017, 05:46:01 pm
content: These are still being offered and in my understanding is what the author refers to. This article was written recently and Jim Williams would agree for sure with it

author: PartialDischarge
author_rank: Super Contributor
timestamp: July 21, 2017, 05:52:05 pm
content: I'm lucky

author: capt bullshot
author_rank: Super Contributor
timestamp: July 21, 2017, 05:57:21 pm
content: Oh, Bodo's postilleRead the "green tip of the month" on a regular base - Always good for a laugh, but true.Sometimes there are really interesting articles inside, great on fundamentals and of huge knowledge.Sometimes "interesting" English translationsOften Marketing stuffBut this one's a rant of an austrian engineer (look up his homepage) on Tek DSO's. His writing is correct, but nothing new to an experienced engineer who knows how to use his tools. And yes, for a long time one of these 2.5kSamples scopes mentioned there is one of my favourite scopes for various other reasons - but you've got to know what you do with it. The peak detect function is quite useful ...

author: exe
author_rank: Unknown
timestamp: July 21, 2017, 06:01:07 pm
content: QuoteLooks like the article is 10-15 years outdated. Anyway, I think it's a fail of both the author and editor.But the message is correct. Me, ex-user of DSO-138 (google it if you never seen it), totally agree with the article, 1kpts of memory sucks. Also don't buy scopes with only one channel. And less than 1MHz bandwidth

author: rf-loop
author_rank: Super Contributor
timestamp: July 21, 2017, 06:01:24 pm
content: Quote from: nctnico on July 21, 2017, 05:36:41 pmExample some Tektronix and Keyshit fan´s. Couple of Tek models with 2.5 and 10k still in production.Also Keyshit sell 100k models to happy end end and so on.You think no one buy these. I do not believe they manufacture these if no one buy.Glad I have still some real oscilloscopes.It was best and nice reading after long time. Still laughing.

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 21, 2017, 06:06:16 pm
content: In the 1990s I worked for a company which made TV signal processors (Analog NTSC and PAL).In our workbenches we had two scopes, an analog and a digital one, both Tek.The digital was a God-send to capture the digital control signals, but the analog scope was used to actually view the video signal. Other than the annoying flicker at frame rates, the analog scope would definitively better show the nuances of the analog TV signals. (*)As a matter of fact, if the engineering manager walked into the lab and saw someone troubleshooting video on a digital scope, he would give to the engineer an earful.I've not worked in the video field since then, and I wouldn't know how digital scopes would compare nowadays. Although it is a moot point, since most video is digital nowadays.(*) Capturing a waveform on a Polaroid film camera was also a big pain in the rear-end.

author: rstofer
author_rank: Super Contributor
timestamp: July 21, 2017, 06:12:06 pm
content: I think the memory issue has been settled. Even the lowest priced models have multiple megabytes of memory. What is the DS1054Z, 12 MB? 80% of the article is nonsense.What is important is to realize that what you see on the display is a programmer's drug induced hallucination. There is not a part of the trace that hasn't been subjected to some kind of mathematical manipulation.But the DSO has single-shot and it really is important despite the author trying to downplay its significance.I think there is room in the world for both technologies. There certainly is around here. I like my DS1054Z but I'm not going to get rid of my Tek 485 any time soon.

author: nctnico
author_rank: Super Contributor
timestamp: July 21, 2017, 06:19:42 pm
content: Quote from: rstofer on July 21, 2017, 06:12:06 pmOn a good DSO (which doesn't include the DS1000Z because it seems the sin x/x reconstruction isn't working correctly on this one) you'll always have the actual samplepoints where the parts in between have been reconstructed. You can mathematically prove this is a good representation of the signal within the scope's bandwidth and accuracy limits. Where people go wrong is thinking an analog oscilloscope is the same thing as a digital oscilloscope. If it looks like a hammer, it is a hammer. As someone else already noted: peak-detect is an essential feature to prevent aliasing problems. Digital oscilloscopes without peak detect are intended to be used on signals which don't exceed the Nyquist frequency at any samplerate and are therefore less usefull as general purpose oscilloscopes.

author: exe
author_rank: Unknown
timestamp: July 21, 2017, 06:23:45 pm
content: Quote from: rstofer on July 21, 2017, 06:12:06 pmThat's very precise description of software developmentQuote from: rstofer on July 21, 2017, 06:12:06 pmWell, how many analog scopes produced noways? I think DSOs already conquered the market. Just let's not compare hobby-level DSOs with top analog devices.

author: rstofer
author_rank: Super Contributor
timestamp: July 21, 2017, 06:27:42 pm
content: The article was aimed straight at the entry level scopes. There is no question that the higher level scopes are going to be superior in every way (or it won't be on the market very long). It is still possible to buy DSOs for well over $100k. I have to believe these are going to be very good scopes. I doubt that memory will be an issue.

author: exe
author_rank: Unknown
timestamp: July 21, 2017, 06:36:31 pm
content: Quote from: rstofer on July 21, 2017, 06:27:42 pmI thought so too. But I opened the list of his publications and found the author has something against digital. For example, look at this article:http://members.aon.at/aseibt/publications/The%20Superiority%20of%20Analog%20Audio%20tape%20Recording%20.pdf"The Superiority of Analog Audio Tape Recording vs. Digital Recording" (rf-loop, it's totally worth your time reading it).

author: vk6zgo
author_rank: Super Contributor
timestamp: July 25, 2017, 04:54:44 am
content: Quote from: schmitt trigger on July 21, 2017, 06:06:16 pmAt my old job,we would display two fields of PAL video on an oscilloscope.This enabled us to see if there was any 50 or 100Hz hum on the signal,or field "tilt" (using a 50Hz) square wave .Another very important use, was to determine if there was any line clamping degradation during the field group ( vert sync area).This was more of a problem with older high level modulated transmitters,but was still possible with the more modern types.HP & Tek would demonstrate their latest DSOs, & inevitably, they would fall at this first hurdle, with the signal looking more like my unmown backyard than any video signal.Insufficient memory meant the sampling rate would reduce, not only below the highest video frequencies, but to less than the line rate as well, resulting in a display which was a jumble of aliasing.The earliest instruments couldn't even display a line rate signal!Eventually, Tek came up with one with a useable display at field rate, although the sample rate was still marginal, beating with the 4.43MHz colour subcarrier, but we could live with that.People whose day to day work could not be done by early DSOs hung onto the analog instruments thatcoulddo the job.

author: nctnico
author_rank: Super Contributor
timestamp: July 25, 2017, 08:37:31 am
content: This story must be about the late 80's because DSOs with 1MPts where available in the 90's (that is nearly 30 years ago already).

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 25, 2017, 10:32:36 am
content: Quote from: MasterTech on July 21, 2017, 05:28:32 pmHas the author been frozen for the last 30+ years or so? That reads like the rants of some backwarder who never made the mental leap to digital technology.My "favorites" from a quick glance over this garbage:While analog scopes are easy to understand and use, DSO’s are extremely complicated, this explains why even electronics engineers miss the stern warning which is implied in the advertisements “max. sampling rate 5 GS/s, bandwidth 500 MHz”...Really, if in 2017 a trained EE misses the fact that stated sample rates in DSO specs are max figures then he's an idiot.The author took the trouble to download the 200 page manual of a 500 MHz, 5 GS/s model with 10 K memory..Yeah, right, a 500Mhz 5GSa/s scope with 10k memory in 2017Time to pull out the manual of some old shitty Tek TDS scope from the early '90s to make (another silly) point....?DSO’s only show a more or less distorted rough and jittery reconstruction of the signal or artifacts which bear no resemblance to it.OK, so someone obviously doesn't understand sampling theory and has no clue how to operate a digital scope properly...There are no “Real Time DSO’s”, this term is misleading as it infers that a DSO were able to show a signal in real time. All DSO’s are sampling scopes, one operating mode is called “Real Time Sampling”. When the reconstruction becomes visible on the screen, the signal has long disappeared.Correct, but the same is true for an analog scope. What this guy misses is that even an analog scopes "samples", which it does by moving the electron beam across the CRT phosphor. Any event that is drawn on the CRT will be drawn with a delay which, while it might be shorter than on a DSO, still means that the analog scope is also not really "real-time".Oscilloscopes must be designed for a Gaussian frequency response...Nonsense, as pretty much any DSO with bandwidths of 1+Ghz are brickwalled. Which obviously the author doesn't know, as he goes on with a BW/Risetime factor of 0.35 which is valid for Gaussian scopes only.Reading this it's clear the author doesn't really have a good understanding of digital scopes, which wouldn't be a problem per se (lots of good engineers still work with analog scopes) but becomes one when trying to lecture others with this nonsense. Not saying he might not be a great EE in some field but his appreciation and understanding of digital scopes is clearly beyond hom.What's worse however is that this article made it through review and ended up being published by Bodo's Power Systems Magazine. They should be embarrassed to publish such drivel in 2017.

author: PartialDischarge
author_rank: Super Contributor
timestamp: July 25, 2017, 12:26:50 pm
content: Again, he's just saying that DSOs with little memory are still used and sold, and they shouldn't.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 25, 2017, 01:15:11 pm
content: Quote from: MasterTech on July 25, 2017, 12:26:50 pmTo be fair to Tek, they probably keep this thing in their portfolio because of existing contracts and not because it's such a great selling scope. And while I agree that these days there shouldn't be any scopes with just 10k sample memory any more and that today there are better options for that money, the low memory hasn't stopped these scopes from being very useful in an uncountable number of situations, if you know how to use them properly and if you're aware of its limitations.Which is what I expect from any trained EE (and even for older EE's, like I assume the author of this drivel, there shouldn't be any reason not to learn how to use digital scopes properly, considering that analog scopes are dead and today's scopes are digital).Just because this guy thinks these scopes are worthless or just showing gibberish doesn't mean it's true.

author: JPortici
author_rank: Super Contributor
timestamp: July 25, 2017, 01:37:37 pm
content: Quote from: nctnico on July 21, 2017, 05:36:41 pmi think mid 90'si remember reading such quotes on a simillar article from that era