Analog Oscilloscope vs. Digital Oscilloscope - Page 1
Forum section: electronics / general

author: djcrunkmix
author_rank: Contributor
timestamp: February 20, 2013, 03:56:45 am
content: Hi guys,I am a novice electronics enthusiast. After watching Dave's review of the good ol' Tektronix 2225 50Mhz scope here:I thought, I'd get myself an analog scope. I bought one from eBay for $250 USD. The model I found was slightly more advanced - Tektronix 2440 w/300Mhz bandwidth.I was a little bit disappointed with the fact that I cannot really "properly" learn how to use an oscilloscope without getting a really old school one like Tek 2225. To my surprise, the Tek 2440 is a digital scope with storage capabilities and tons of math functions.My question now is how do I view the tracing (from left to right) of the cursor? Is it not available in digital scopes? When I switch my horizontal axis to larger time scales, I get something like this:Triggering is in "Roll" mode.Is this how digital oscopes work? They seem to have a memory buffer where the waveform gets saved and displayed. Do analog scopes also have a buffer?I think I am going to sell this one and get the exact model as Dave has recommended...i.e. Tektronix 2225. I really like the tracing of the cursor...Thanks for the adviceNeil

author: c4757p
author_rank: Super Contributor
timestamp: February 20, 2013, 04:10:24 am
content: Switch the trigger mode out of "roll", to "auto". Roll just displays the signal rolling out of the right side of the screen with no triggering. Auto will lock the signal to a trigger point so it stands still.Yes, that is how digital scopes work. The signal is read into a buffer, then displayed digitally. Analog scopes do not have a buffer (except for analog storage oscilloscopes, which are rare). They display the signal in literal real time - the signal pretty much just goes through an amplifier right to the vertical deflection plates of the CRT. (If you're curious, look up a schematic for one of the very old, simple vacuum tube-based scopes like the Heathkit ones. The circuits are very basic and you can see the pattern: Signal -> Amplifier -> Vertical deflection. Ramp generator -> Amplifier -> Horizontal deflection.)FWIW, you were only off by 0.2% on your model number!I have a 2445Aand it's a quite sophisticatedanalogscope.

author: c4757p
author_rank: Super Contributor
timestamp: February 20, 2013, 04:16:07 am
content: Quote from: djcrunkmix on February 20, 2013, 03:56:45 amIf you're in the $250 range, I recommend the 2400 series ofanalogscopes - shame they had to make the model numbers so similarYou get higher bandwidth plus some useful "analog+digital" features - mine has movable cursors for taking measurements, automatic trigger level, a full automatic configure like the "auto" button on many newer digital scopes (which you shouldnotbe using), a digital frequency counter (this is optional, though), and a few other things that make it just as easy to use as a digital scope.

author: djcrunkmix
author_rank: Contributor
timestamp: February 20, 2013, 04:23:33 am
content: Quote from: c4757p on February 20, 2013, 04:10:24 amLOL..yes. I was like, that looks older than the internet. Must be analog. Close enough model number...Quote from: c4757p on February 20, 2013, 04:16:07 amThanksI shall look into it. Also, I love the facepalm icon:

author: c4757p
author_rank: Super Contributor
timestamp: February 20, 2013, 04:30:04 am
content: The facepalm icon is very useful here - you're in electronics now. Give it a couple weeks and you'll have a permanent palm print in your forehead. Not to mention a few soldering iron marks

author: c4757p
author_rank: Super Contributor
timestamp: February 20, 2013, 04:32:01 am
content: Quote from: djcrunkmix on February 20, 2013, 04:23:33 amLook at some mid-late 90s test equipment - you'll be surprised how "old" a lot of the equipment looks to a new eye. A lot of the newer stylings are quite recent.

author: Spawn
author_rank: Frequent Contributor
timestamp: February 20, 2013, 04:57:59 am
content: I got a Tek 2221A 100MHz digital storage oscilloscope, with cursor to measure various things, you can turn off its storage mode and use it as normal analog oscilloscope. Unit itself is same size as a 2225.Here a picture of its console to give you a idea (the picture is not mine)

author: c4757p
author_rank: Super Contributor
timestamp: February 20, 2013, 05:18:34 am
content: Looks nice. I'd miss my dual timebase and four channels though.

author: codeboy2k
author_rank: Super Contributor
timestamp: February 20, 2013, 08:37:04 am
content: found a 2445A for $160 , including shipping.http://www.ebay.ca/itm/Tektronix-2445A-Oscilloscope-/251179698826?pt=LH_DefaultDomain_0&hash=item3a7b7a0a8aNeeds a little work though...

author: BravoV
author_rank: Super Contributor
timestamp: February 20, 2013, 08:45:50 am
content: Quote from: codeboy2k on February 20, 2013, 08:37:04 amHaha.. almost got heart attack seeing the pictures of that poor thing.Yeah.. little work in this case here is not to fix it but to desolder the precious unobtainium U800 chip that is still sticking at the main A1 board, presumably not toasted of course.

author: EEVblog
author_rank: Unknown
timestamp: February 20, 2013, 09:23:35 am
content: As someone else mentioned, roll mode is not the correct mode to use for general digital storage scope operation.As you found out, you have a purely digital scope with the 2440, not an analog scope.There are "combi" scopes that have switchable true analog and digital storage modes, but they aren't that common (the 2221 shown is a good example), and sometimes not obvious! Check out the Hameg 1507 below and try and figure out what type it is...Nothing special about the 2225, apart from the 500uV/div mode. Any basic analog scope will let you learn the basic.Dave.

author: Hydrawerk
author_rank: Super Contributor
timestamp: February 20, 2013, 10:41:16 am
content: Quote from: Spawn on February 20, 2013, 04:57:59 amI would miss theautosetbutton.

author: c4757p
author_rank: Super Contributor
timestamp: February 20, 2013, 11:47:58 am
content: The what? Why?

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: February 20, 2013, 06:59:58 pm
content: Quote from: djcrunkmix on February 20, 2013, 03:56:45 amDon't know why you think this is the case but that's not true. While it's certainly not a bad way to get introduced to scopes through an analogue scope, it's not the only way. I have learnt on both analogue scopes (because this was the predominant type of scope at that time) and DSOs, and I say You can learn the basics with any decent DSO as well (just keep the hands off from the automatic functions!), and once you're done with the basics you may want to learn the more advanced analytical stuff and then an old analoge scope won't cut it anyways.QuoteNice scope! 500MSa/s are a bit low but as a first scope this should do well.QuoteI will certainly get burned for saying this but...You apparently got a very nice 300MHz DSO there, and now that you have it I think it would be silly to sell it just to get an old analog banger 'for learning'. It's like passing your driving test and then getting a hearse to 'learn the basics' before driving a car. At the end of the day, a scope is a tool, and to make use of this tool you need to understand what it does and learn how to use it. Analog scopes were great in their days (and it certainly doesn't hurt to have one as a secondary scope if that's what you want), but their time is gone. And while knowledge in handling an analoge scope is not a bad thing, the main aim for you as a starter should be to learn the basics. And you can do that as well on your scope.

author: djcrunkmix
author_rank: Contributor
timestamp: February 20, 2013, 08:41:53 pm
content: Quote from: Wuerstchenhund on February 20, 2013, 06:59:58 pmThanks for the advice. I think I am going to buy another oneOne can never have too many scopes.

author: Hydrawerk
author_rank: Super Contributor
timestamp: February 20, 2013, 09:52:54 pm
content: Quote from: c4757p on February 20, 2013, 11:47:58 am"Autoset" button can be found on Dave's HM1507 scope above.

author: c4757p
author_rank: Super Contributor
timestamp: February 20, 2013, 09:59:09 pm
content: Quote from: djcrunkmix on February 20, 2013, 08:41:53 pmI've decided to stop at two before I go completely oscilloscope-crazy.Quote from: Hydrawerk on February 20, 2013, 09:52:54 pmAnd on pretty much every other scope with any digital anything in it. I'm not convinced it has a purpose, though...

author: Lukas
author_rank: Frequent Contributor
timestamp: February 21, 2013, 12:53:47 am
content: Autoset might be of limited usefulness, indeed. Although, I once had a german Grundig MO53 (analog scope with digitally controlled timebase) which had an automatic timebase setting which set the timebase to display a few cycles in less than one second (!). I haven't encountered any DSO which this feature, despite it would only be a bit of software.

author: c4757p
author_rank: Super Contributor
timestamp: February 21, 2013, 01:12:11 am
content: I have one use for the autoset on my Tek 2445A - quickly getting out of weird modes. I'll admit to not being fully aware of every setting of the dual timebase and digital counter/timer module, and a quick press of "auto" cancels all of them.

author: codeboy2k
author_rank: Super Contributor
timestamp: February 21, 2013, 11:03:56 pm
content: I'm not sure why so many people are against the autoset buttons found on most every digital scope these days.I started in the late 60's /early 70's using simple scopes made with vacuum tubes, so I am certainly no beginner and know my way around the scopes settings, in other words, I know how to find a trace.But the autoset in my opinion is just a time saver for me, when I switch from one signal to another that may be two very different signals.It can make all the same decisions I can make regarding timebase, volts/div, offset, and trigger level, and much faster than me to get a stable image.So I use it as a starting point, almost always. It's useful.Perhaps a beginner should hook the autoset button to a high-voltage spark coil under their seat cushion, until they have learned the other settings.But I'm an old timer, I don't have much life left in me, I can use all the seconds I have been given

author: c4757p
author_rank: Super Contributor
timestamp: February 21, 2013, 11:09:40 pm
content: I find it un-intuitive, in that if I press it, I don't know what I'm looking at. I have to take time to read off the scale indicators to know the difference between a 100uV signal and a 500mV signal, and between 1 MHz and 1 kHz. If I scale the signal manually, I quickly get a feel for the magnitude of the scales based on how much I had to turn the knobs.If I have multiple different signals that I will be switching between quickly, I connect them to separate channels and just enable/disable the channels.

author: EEVblog
author_rank: Unknown
timestamp: February 21, 2013, 11:24:10 pm
content: Quote from: codeboy2k on February 21, 2013, 11:03:56 pmBut don't forget to enjoy it!The auto-set button has no joy...Dave.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: February 22, 2013, 06:28:34 am
content: Quote from: codeboy2k on February 21, 2013, 11:03:56 pmProbably because when autoset first came up on some more advanced analogue scopes it was limited and often turned out to be no help. While the trace would generally end up somewhere on the screen the settings choosen by autoset often didn't lead to a useful display. And because it was slow it didn't really save time, and you had to press other buttons to find out what settings have been choosen so that you knew what you're looking at. It's not quite the same on somewhat modern DSO, where autoset acts relatively fast and almost always chooses at least very good settings, and on most DSOs the chosen parameters are already indicated on the screen so with a quick look you know what you're looking at.I guess it's a similar thing as analogue vs digital scopes, where some are against DSOs because the first scope generations came with very low sample rates and memory, and were only good for repetitive signals and useless for finding glitches. That's probably also the reason why common belief is you can only learn using a scope properly with an analogue one.QuoteSame here (except that I'm slightly younger). I know how to set my scopes up correctly but autoset is a time saver, especially with unknown signals.

author: PA4TIM
author_rank: Super Contributor
timestamp: February 22, 2013, 08:49:13 am
content: I use auto to reset the scope after setups that involved lots of settings, but never when measuring.I had a 2445A, i gave it away when I got a DS1102E and two Tek 7000 scopes.After the DS1102 I rather hated DSOs and it retired to a corner of the shack using only anlog scopes. But without the 2445A I missed cursormode so I ended up with a 350 MHz Hameg DSO and this is now the scope I use 99% of the time. It has taken me one year of therapy, but now I am able to tell ; "if I had to choose between analog of digital I would choose digital"

author: Martin.M
author_rank: Frequent Contributor
timestamp: February 23, 2013, 06:49:35 pm
content: hello friends,this is a oftenly used analog scope of my collection. For faster moments there is a 7104 also...and most used are still the glowing beauties, like 556, 549 and a little 323 for outdoor. 422 is also oftenly running.No, I don`t need DSO.greetingsMartin

author: PA4TIM
author_rank: Super Contributor
timestamp: February 23, 2013, 07:21:22 pm
content: Is this a blue trace or does it only look blue. I like it very much. My second most used scope is my beautifull 547 and one of the 15 plugins ( or use them in one of my 132's to a 7603/7704)

author: SeanB
author_rank: Super Contributor
timestamp: February 23, 2013, 07:29:32 pm
content: I want that current shunt there on the side.............. blue green phosphor tubes, the best ever, depending on the type either a short or a medium persistence. All you are missing is the Polaroid camera back ( not that you can get the film any more, but you can modify it to accept a digital back instead)

author: Martin.M
author_rank: Frequent Contributor
timestamp: February 23, 2013, 08:20:55 pm
content: Oh that 547 have a original sun protection? very rareYes, the 7844 is a blue dual beam, "option 78", Phosphor P11.this is a old 551, also with P11 (fast blue)a 555 Triple Nickel, with Phosphor P7 (witheblue = fast, covered with yellow-green = slowly),P7 is the most exciting color of old scopes.this is a Tek 565, Phosphor P31 grass greenand a Tek533A, Phosphor P2, bluegreen...keep it glowinggreetingsMartin

author: PA4TIM
author_rank: Super Contributor
timestamp: February 23, 2013, 10:55:32 pm
content: Great scope pornvery nice collection. You have the same scope mobile as my 547. If i had the space the 556 would be on top of my list. I have a fairchild 777, that is about the same size, all transistors, same time area, 100 MHz, 4 plugins but 2 defect, no manual, psu problems and the dual beam CRT turned out to be at its end.That is indeed the original sun protection. It came with a 535A.I have a HP VNA ( 8407 or 8704 alway mix them up) with a long persistence white trace and a Tek XY monitor with orange screen and orange long persistance Phosfor and a vector monitor with dark green phosfor.I never seen the blue traces, real cool. I once seen pictures if the LCD shutter thing in front of a Tek scope. That gave several collored traces, looked awsum.Do you know if there was a red gratitude option for the 547 like your 533 has and my 535A. That was the thing i liked the most on my 535A. Would love to have it on my 547@seanBmore amps, this as part of the diff probe kit. Also have the 900 MHz FET probe with amplifier.

author: npgatech
author_rank: Newbie
timestamp: February 23, 2013, 11:36:03 pm
content: Holyshit guys...this thread has blown up. This community is pretty boss. O0Some good quality o-scope pr0n here...btw, I am same as OP but I registered with a more sane username.I think I've decided to keep my Tek 2440Here are some pictures of me playing around with 555 IC.Just wanted to thankDave & this communityfor inciting me into electronics & sparking my interest. I am a mechanical engineer by profession.pr0n:

author: Martin.M
author_rank: Frequent Contributor
timestamp: February 24, 2013, 08:53:19 am
content: hello Tim,the graticules,there are 2 different styles: internally graticule as part of the CRT,and graticule as part of the plexi plate in the bezel of the scope.Red graticule is only to see at scopes with the plexi plate,in the plexi is 2 holes for the illumination bulbs, on both sides.the one side is withe and the other side red. To get a red graticule there is simply: turn the plexi (rotate it)When the graticule is a part of the CRT you can onle change the bulbs to painted bulbs to get that.Tek 323, it eat only 1,6W from the internal accu. Build 1967, in the same time then the big brothersThe cute little classic Tek, smallest of the old family, still made from metal, all transistors in sockets.greetingsMartin

author: PA4TIM
author_rank: Super Contributor
timestamp: February 24, 2013, 09:34:53 am
content: I knew about flipping the gratitude but i had tried to use that 535 one on my 545, bit that does not fit. I never tried the 547 because a fiend told me that does not fit eihter, if I remember well the gratitude is on the CRT here.That scope is is real cute, never seen one before. There also is a "portable" tube version. There was one for sale some years ago for 10 euro or so, stillfor not buying it.My smallest Tek

author: Martin.M
author_rank: Frequent Contributor
timestamp: February 24, 2013, 10:02:53 am
content: 212 I love thattake care of that cutie.I have a little DSO, 222A, with defect CRT. Very hard to find that CRT ... I you see one anywhere please tell me.So you need a 556 ? I got an offer, 556 , the HiFi Fans have part out a lot of tubes the rest is complete. Interesting ? I am planing to save the life of that wonderful Tek. may be the Compactrons and 8608 are still inside, I can ask.greetingsMartin

author: BravoV
author_rank: Super Contributor
timestamp: February 24, 2013, 10:15:40 am
content: Talking about an extreme out of topic, you guys analog scopes hoarders are riot.But I like it.

author: Martin.M
author_rank: Frequent Contributor
timestamp: February 24, 2013, 11:03:52 am
content: excuse please, we are collecting thatThere is no place for vintage discussions here on the board.Btw. is the fastet analog Tek, the 7104 a true 1GHz Scope. For a DSO in this area you need some money more.greetingsMartin