Is there a cheap oscilloscope with responsive controls? - Page 1
Forum section: electronics / testgear

author: mjs7
author_rank: Newbie
timestamp: March 27, 2017, 07:04:51 pm
content: I'm looking for an oscilloscope to display various signals around a physics lab. No fancy features are required (signal decoding, FFT, etc.), but I will be adjusting the waveform a lot so I need a responsive UI. I've heard that the Rigol 1054Z takes a second or two to update after moving the waveform up and down, which would be a big annoyance for me. In comparison, I have a GW Instek GDS-2104E which updates instantly, but it costs more than 3x as much.Usually I buy used analog scopes off Ebay, but they often turn out to be duds. Is there a modern digital scope in the price range of the Rigol with responsive controls? Thanks.

author: ataradov
author_rank: Super Contributor
timestamp: March 27, 2017, 08:00:49 pm
content: I'm not sure what you've heard, but 1054Z feels as responsive as most scopes out there. At least it does not feel slow to me personally, and I worked with a lot of different scopes.I'm also not sure why you are adjusting things that much

author: wraper
author_rank: Unknown
timestamp: March 27, 2017, 08:05:14 pm
content: Quote from: mjs7 on March 27, 2017, 07:04:51 pmThen why don't you look on GW Instek GDS-1000B series?

author: nctnico
author_rank: Super Contributor
timestamp: March 27, 2017, 08:05:51 pm
content: How about the GDS-1000B series? Basically the same as the GDS2000E series but without decoding and a smaller display and thus cheaper.

author: wraper
author_rank: Unknown
timestamp: March 27, 2017, 08:07:07 pm
content: Quote from: ataradov on March 27, 2017, 08:00:49 pmDon't have 1054Z but even DS2000 series have quiet laggy controls.

author: ataradov
author_rank: Super Contributor
timestamp: March 27, 2017, 08:09:29 pm
content: Quote from: wraper on March 27, 2017, 08:07:07 pmWell, by some measure all scopes have laggy controls. I would not say 1054Z much worse than the average scope out there.

author: JPortici
author_rank: Super Contributor
timestamp: March 27, 2017, 08:21:32 pm
content: Quote from: ataradov on March 27, 2017, 08:09:29 pmlet's just say it's on par with tektronix..well that's not true. a tek is actually capable of updating the trace while moving it, so you can tell when to stop

author: RoGeorge
author_rank: Super Contributor
timestamp: March 27, 2017, 08:32:13 pm
content: If you don't need digital features, then try old analog oscilloscopes. Nothing can be more responsive.Also, they can be way cheaper then a new digital scope.

author: DaJMasta
author_rank: Super Contributor
timestamp: March 27, 2017, 08:59:29 pm
content: Maybe this has to do with the timebase setting you're using?Even my old DS1052E was pretty quick in at very small time divisions, but like any other scope, if waits for a full frame worth of data to be captured to display it, so using divisions of hundreds of milliseconds or more or using the highest memory depths can take more time to update.There is definitely some variability in responsiveness to controls, but most models are fairly reasonable as it's an important usability feature and that performance depends on the architecture of the scope, so it's not like all of one brand's scopes will be superior or something. I'd advise that you take a look around and when you find a scope you think is suitable, then look for videos that include people using it to test or experiment. That will give you the best idea of how responsive it is to inputs aside from trying them in person.

author: mjs7
author_rank: Newbie
timestamp: March 27, 2017, 11:31:39 pm
content: Great, I didn't know that the GDS-1000B series was so similar to the GDS-2000E. I just bought a 1054B -- if it's as nice as my other Instek for <$400 that's pretty incredible. Thanks for the help.

author: Someone
author_rank: Super Contributor
timestamp: March 28, 2017, 12:23:02 am
content: Quote from: mjs7 on March 27, 2017, 07:04:51 pmThey can be slow to respond if you've set a long memory depth or enabled maths or display settings vector/dots/interpolation/filtering so its often up to the user to balance performance to their preference. This has been common on most digital scopes for some time.

author: David Hess
author_rank: Super Contributor
timestamp: March 28, 2017, 01:57:20 am
content: Quote from: DaJMasta on March 27, 2017, 08:59:29 pmThat is a reason for the displayed waveform not to be updated but not a reason for the controls to be delayed as well.Some of the oldest DSOs did not have this problem. The ancient Tektronix 2230/2232 (1) at 50ms/div with a 10 division record takes 0.5 second between updates like it should but the position controls update in real time and Tektronix deliberately programmed this behavior in because they recognized that user interface responsiveness is important in an instrument which has both digital and analog operating modes. (2) Rigol is just cheap but so are a lot of other modern DSO designs.I think people have just gotten used to latency in user interfaces making it the new normal. My HP50g calculator is roughly 200 times faster than the HP48g which it replaced but has much higher interface latency. There have been efforts in the past to bring awareness to this as a problem but it has gotten much worse since about the time of managed computer languages like JAVA when they cannot provide real time operation and remote computing when it suffers from horrible communication and interface latency.(1) I am not suggesting that the Tektronix 2230/2232 is suitable for mjs7's application. I am just using it as an example where the manufacturer knew responsiveness would be an issue and designed with that in mind. Another good example is the WordStar word processing application where screen refreshes are interrupted by user keystrokes.(2) I'm talking about the vertical position controls and the cursor controls which operate through the CPU in storage mode. The horizontal position control literally operates at the speed of light since it works in the analog domain and does not go through the CPU. Tektronix actually added a separate circuit path to the vertical position controls so they both operate as analog offset controls *and* get read by the CPU so it can update the existing display to match the future offset although they did not get it quite right. Modern DSOs already knows the state of their vertical position controls yet they do not bother updating the screen. WTF?

author: Muxr
author_rank: Super Contributor
timestamp: March 28, 2017, 02:16:27 am
content: My DS2000 Rigol is definitely a bit on the annoying side when it comes to responsiveness, in some scenarios more than others. You get used to it and it's not an issue, but you definitely notice it once you use a nicer scope. I think the bigger issues is that the encoders all have linear speed. No acceleration when spinning really fast. So you can sometimes find yourself just spinning the encoders like a mad man, to me this is a far bigger issue when it comes to fast scope use OP is interested in.Rohde & Schwarz HMO scopes look responsive and quick to get around, perhaps the latest GW-Instek scopes, or Agilent/Keysight scopes all look very responsive. I'd give those a look.

author: genghisnico13
author_rank: Regular Contributor
timestamp: March 28, 2017, 03:32:07 am
content: Maybe you should check out the new keysight 1000x series. I haven't used them personally, but they are comparable in price to the rigols and they seem to be as responsive as keysight's higher end models. This new series uses the same MegaZoom ASIC.Edit: I just realized that you already made a purchase

author: Fungus
author_rank: Super Contributor
timestamp: March 28, 2017, 05:37:27 am
content: Quote from: mjs7 on March 27, 2017, 07:04:51 pmThat's simply not true.Watching any of the hundreds of videos on youtube will show this.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: March 28, 2017, 07:31:29 am
content: Quote from: David Hess on March 28, 2017, 01:57:20 amThat's one of the best scopes ever.

author: JPortici
author_rank: Super Contributor
timestamp: March 28, 2017, 10:47:35 am
content: Quote from: Fungus on March 28, 2017, 05:37:27 amcorrect, it's more half a second / 1 second

author: Fungus
author_rank: Super Contributor
timestamp: March 28, 2017, 12:00:30 pm
content: Quote from: JPortici on March 28, 2017, 10:47:35 amNope.It actually depends on how you turn the knob. Better technique = faster response.See my video here:https://www.eevblog.com/forum/testgear/the-ds1054z-vertical-response-discussion-thread/

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 28, 2017, 12:45:42 pm
content: Quote from: ataradov on March 27, 2017, 08:00:49 pmmy earlier scope was DS1052E. DS1054Z is way several magnitude slower in responsiveness. in another word, what you've heard about DS1000Z series UI laginess is 100% valid.Quote from: ataradov on March 27, 2017, 08:00:49 pmsignal is too long or too big, we want to see what is off the screen, we want to maximize graticules usage in positive or negative vertical region etc. i thought i would get acquainted with DS1054Z laginess through "predictive knob fast incrementation without waiting for UI to update", i've not been that successfull, time or volt origin usually went away more than i wanted them to be, so i need to back few steps up most of the time.Quote from: Fungus on March 28, 2017, 12:00:30 pmDS1052E doesnt need better technique, its just responsive with any technique you use. and its several magnitude better than your video demo. i remember this as crystal clear like yesterday. because i was studying just this by comparing them before i handed over my DS1052E to my brother.having said that, my DS1052E is with my brother now, i still pick DS1054Z because its 4 channels and longer memory. something that in no way my older DS1053E can do with any imaginable technique. as the UI laginess i'll work around it with the "better technique", yet it still cant beat my earlier scope.

author: tecman
author_rank: Frequent Contributor
timestamp: March 28, 2017, 12:49:23 pm
content: Buy a used analog scopepaul

author: ci11
author_rank: Regular Contributor
timestamp: March 28, 2017, 01:00:12 pm
content: Quote from: tecman on March 28, 2017, 12:49:23 pm+1"hybrid" scopes with measurement readouts and CRT are usually responsive and relatively inexpensive. Some measurements will not be as accurate as bench instruments but that's how it goes. Tek 2247A is what I use for exactly this purpose, it even has "hands-off" cursors so no fiddling of knobs needed to get a t, 1/t, f or 1/f reading.

author: nctnico
author_rank: Super Contributor
timestamp: March 28, 2017, 01:08:15 pm
content: Quote from: Mechatrommer on March 28, 2017, 12:45:42 pmThere is little point in argueing over the DS1054Z. The scope the OP ordered/bought is cheaper and the OP can be sure it will work just like the scope he already owns.

author: David Hess
author_rank: Super Contributor
timestamp: March 29, 2017, 12:25:41 pm
content: Quote from: ci11 on March 28, 2017, 01:00:12 pmThe 2247A series is an interesting example of this. All of the controls operate through the processor which is what allows its automatic setup feature to work but the added latency is very small. Most of the rotary controls use resistive potentiometers as encoders but they also implemented a form of acceleration on them so they manage both coarse and fine adjustments. Tektronix put a lot of thought and design into the user interface.The 2247A series would probably be my first choice if I was looking for a fast response but inexpensive oscilloscope and could not afford a suitable new DSO. They are pretty old but unusually reliable and fully documented.

author: Specmaster
author_rank: Super Contributor
timestamp: April 04, 2017, 09:57:27 pm
content: Quote from: mjs7 on March 27, 2017, 07:04:51 pmYou really should be sticking to used analogue scopes for ease of use. Unless you need the maths capabilities of digital scopes, which in my experience will be costing many times more then the cost of a good used analogue scope.I have now sourced 5 perfectly good working scopes on Ebay ranging from 20Mhz through to 100Mhz ones, some are dual trace and 2 of them have 4 and 3 traces respectively, 60Mhz and 100Mhz ones. The most I have paid is £130 and the least is £20 and the only repairs I have had to effect is to clean some of them up both internally and externally, replace a power on LED and just some minor calibrations to make them all perfectly useable scopes.I have 2 x 20hz Rapid Electronics and 1 x 25Mhz Rapid Electronics, all of which are very simple and robust machines and the other two are Iwatsu 60Mhz and Goldstar 100Mhz with advanced features such as multiple traces, delay timebases etc.

author: ebastler
author_rank: Super Contributor
timestamp: April 04, 2017, 10:03:09 pm
content: Quote from: mjs7 on March 27, 2017, 11:31:39 pmGlad you found a solution that seems to meet your needs!Once you have had the scope for a few days and have taken it out for a spin, maybe you could add your assessment to this thread -- does the 1000B series indeed feel "as nice as the 2000E"?Thanks!

author: dimkasta
author_rank: Regular Contributor
timestamp: April 05, 2017, 12:22:02 am
content: Just for reference, if the encoders on the 1054 are anything like those on 1052, then in a few months they will start bouncing around, and they will have to be cleaned or replaced.It is a pretty easy fix, but it is annoying on a relatively new scope. Especially for people that want fast response.I just changed mine (couldn't find the heart to open it up earlier) and now it feels awesome to use.

author: andrija
author_rank: Regular Contributor
timestamp: April 05, 2017, 09:22:48 pm
content: Rigol 20**A is absolutely terrible in this regard. Even if 2 seconds is an exaggeration, half a second is not and still is way beyond what I find acceptable. To make it worse it does not have acceleration (trace moves faster if you turn encoder faster). It changes how one feels using a scope - it becomes a chore when it should be fun. I mean I am personally on a lookout for a new scope for that reason alone, even though hacked Rigol is beyond what I need. Control responsiveness will be high on my list when shopping for next scope.

author: Keysight DanielBogdanoff
author_rank: Unknown
timestamp: April 05, 2017, 09:25:36 pm
content: It was mentioned already, but our new InfiniiVision 1000 X-Series oscilloscope is super snappy:http://bit.ly/1000X-Series

author: boggis the cat
author_rank: Regular Contributor
timestamp: April 06, 2017, 12:55:37 am
content: Quote from: andrija on April 05, 2017, 09:22:48 pmHaving recently calibrated two Rigol MSO1074Z models I would say that control (non)responsiveness is a serious usability issue. Perhaps not a problem if you have all day to turn the controls and wait for something to happen, but not great when your customer has to pay for your wasted time.I also noticed that a Tektronix TDS 3034C 'scope calibrated shortly before these two was also fairly horrible. The Rigols are around $2k in local money compared to $16k+ for the Tektronix, so it was disappointing to find usability issues in such an expensive piece of equipment.(Taking a PNG screen-shot to USB caused similarly long delays on each, suggesting that they're under-powered in terms of available processing power to drive the UI. This is surprising when there are so many extremely fast embedded systems designed for driving smart phones and the like.)

author: phliar
author_rank: Contributor
timestamp: April 06, 2017, 01:05:25 am
content: I just bought a 1054Z last week, and I too find the lag unacceptable -- especially the vertical move. It's almost unusable. (But of course you can't beat $400 for a new 4x100MHz scope....)I remember that even the crappy sub-MHz analog scopes I got to use ages ago as an undergrad were wonderful to use, absolutely no lag. If I can't find the money for a fancy HP (I refuse to use the crap new names) or R&S in the next few months I'm getting a CRO.

author: rstofer
author_rank: Super Contributor
timestamp: April 06, 2017, 01:44:24 am
content: Quote from: phliar on April 06, 2017, 01:05:25 amOf course the analog scopes are responsive, all the knob does is change the DC offset on the deflection grids or the gain of some amplifier or timer.With the analog scope you will give up single-shot mode, decoding and measurements. That's kind of a big deal. You can probably get a 4 channel analog scope. I have a Tek 485 for the high frequency stuff but I find the DS1054Z just fine for my hobby projects.For those who want faster response, the GW Instek is probably the way to go (I don't have one). Assuming the cost and features are similar... If they aren't then trade-offs have to be made. Given enough money you can buy all the UI response you want (I guess).Given that I already had a fast/responsive scope, the only reason for buying the DS1054Z was 4 channels, decoding, measurements and one-shot mode. I wanted all those features enough to own two scopes. The 485 tends to sit under my table.

author: Someone
author_rank: Super Contributor
timestamp: April 06, 2017, 03:33:39 am
content: Quote from: rstofer on April 06, 2017, 01:44:24 amPlenty of CRO storage scopes (http://w140.com/tekwiki/wiki/CRT_storage_scope) still around, so you don't have to be stuck without single shot capture and with a horizontal vernier/uncal/var you can do serial decoding by eye when needed.

author: kcbrown
author_rank: Frequent Contributor
timestamp: April 06, 2017, 05:30:34 am
content: I'm still on DS1054Z firmware 04.03.01.05, and have been reluctant to upgrade it past that because of the reports of the slow responsiveness of the scope with the recent versions of the firmware.Is the responsiveness of the scope any worse with the latest firmware than with the firmware that I'm on, particular with respect to movement of traces?I wouldn't hesitate to upgrade if it were possible to revert, but it's not.EDIT: Nevermind. I looked at Fungus' video and used that as a baseline for comparison. My scope was no more or less responsive than his, so I went ahead with the firmware upgrade (which appears to have worked), and am doing the self-cal now after performing the factory reset.

author: Fungus
author_rank: Super Contributor
timestamp: April 06, 2017, 08:40:01 am
content: Quote from: phliar on April 06, 2017, 01:05:25 amThey were literally a potentiometer connected directly to the vertical offset op-amp so of course there was no lag.Quote from: rstofer on April 06, 2017, 01:44:24 amSure, but the featuresaren'tsimilar.Until the last month or so, extra responsiveness would have cost you $600+. That's an awful lot of money to fix a minor problem.Even now it's still going to cost you hundreds of $$$ to get better response unless you give up a couple of channels or half your bandwidth and a lot of features.I don't see it as a deal breaker really. If I sit down and obsess over the response knob then it it looks/feels like a problem, yes. In real use I don't really spend much of the time moving the trace up/down, so...PS: A lot of the perceived lagisdown to your finger technique. It works much better if you 'twiddle' the knob. Here's a slightly out of focus video I recorded a while back:https://www.eevblog.com/forum/testgear/the-ds1054z-vertical-response-discussion-thread/

author: nctnico
author_rank: Super Contributor
timestamp: April 07, 2017, 07:32:31 am
content: Quote from: Keysight_DanielBogdanoff on April 05, 2017, 09:25:36 pmMaybe but the single row of on-screen menus makes the scope much harder to drive. You need to go through a lot more sub-menus to setup things like decoding, triggering, probe attenuation scale, etc.

author: AndyP
author_rank: Contributor
timestamp: April 08, 2017, 07:17:16 am
content: The MicSig TO1104 interface speed is quite quick and the serial decoders are now available (if you have a chat with sales). It has all the features I've needed, and running of battery is useful for quick grab the scope and measure jobs.

author: saturation
author_rank: Super Contributor
timestamp: April 09, 2017, 09:18:45 pm
content: The lowly GW Instek 1054B will show no lag in screen response using 4 channels on _and_ FFT [ that's 5 traces simultaneous] at 100K memory depth.The higher the mem depth the greater the lag. It will show a similar lag at 1 Mpts 4 CH + FFT similar to 10 Mpts at 4 CH with no FFT; in place of the FFT if you use the advance math functions it will start to lag depending on mem depth and complexity of your equation.Sold as 50 MHz, with v1.17 firmware it is - 3dB at 80 MHz at 3 or 4 CH, 110 MHz at 2 CH and 120 1 CH, unmodified. In empirical use the usable response [ down to-30dB] is sampling rate/3 to as high as /2. Typically response sampling rate /2.5.It does not have any serial decode.

author: boggis the cat
author_rank: Regular Contributor
timestamp: April 10, 2017, 05:37:38 am
content: Quote from: Fungus on April 06, 2017, 08:40:01 amSetting the trigger point also causes the display to blank while you move the point.It seems that these 'scopes just can't manage to present traces on screen while controls are adjusted.QuoteThat isn't a technique, it is just creating delays long enough for the 'scope to try to draw the traces. Laggy control use doesn't actually 'fix' laggy response.It is still going to be faster to move the controls quickly if you know where you want to get to. If you need to watch the trace, however, then you have to creep the controls forward.Poor response, making usage difficult. It may not apply to a particular type of usage, of course, but you shouldn't pretend it isn't an issue.

author: Fungus
author_rank: Super Contributor
timestamp: April 10, 2017, 07:56:13 am
content: Quote from: boggis the cat on April 10, 2017, 05:37:38 amNo it doesn't.Quote from: boggis the cat on April 10, 2017, 05:37:38 amWrong.At no point does a DS1054Z display 'blank' when you twiddle the controls.(unless you manage to set the trigger to a value which doesn't trigger, and even then it doesn't 'blank')Quote from: boggis the cat on April 10, 2017, 05:37:38 amMe? You're the one pretending it's more than a minor niggle.The only control that's really laggy is the vertical position control. Me? I don't actually spend much time adjusting that in real life, normally only after switching channels on/off or switching AC/DC mode. YMMV but to me it doesn't seem worth spending several hundred $$$ to 'fix' it.

author: nctnico
author_rank: Super Contributor
timestamp: April 10, 2017, 08:49:15 am
content: The scope the OP ended up buying is cheaper than the Rigol DS1054Z so why do you need to spend hundreds of dollars to fix it? Besides that laggy controls are a nuisance so it is worth spending the extra money especially if the scope is used professionally.

author: Fungus
author_rank: Super Contributor
timestamp: April 10, 2017, 08:52:30 am
content: Quote from: nctnico on April 10, 2017, 08:49:15 am...is what? I must have missed that post.Quote from: nctnico on April 10, 2017, 08:49:15 amI'm quite sure the OP didn't get a 100MHz four channel 'scope for less money than a DS1054Z.

author: The Soulman
author_rank: Super Contributor
timestamp: April 10, 2017, 09:01:23 am
content: Quote from: Fungus on April 10, 2017, 08:52:30 amQuote from: mjs7 on March 27, 2017, 11:31:39 pm

author: Fungus
author_rank: Super Contributor
timestamp: April 10, 2017, 10:17:54 am
content: OK, so he took half the bandwidth and gave up a whole lot of features instead.

author: nctnico
author_rank: Super Contributor
timestamp: April 10, 2017, 10:25:45 am
content: Quote from: Fungus on April 10, 2017, 10:17:54 amIf you read the first post carefully you should understand that the OP was looking for an oscilloscope for a specific purpose. Protocol decoding and high bandwidth clearly aren't necessary (the OP has that covered with the scope he/she already owns) but responsive controls are. All in all it seems the OP bought the right tool for the job for as little money as possible and in the end that is what counts.

author: Fungus
author_rank: Super Contributor
timestamp: April 10, 2017, 11:26:58 am
content: OK, you win the "drag the argument as far away from context as possible" debate.I was only replying to somebody who claims the DS1054Z screen somehow "blanks" whenever you touch a control.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: April 10, 2017, 04:03:29 pm
content: Quote from: GeorgeOfTheJungle on March 28, 2017, 07:31:29 amI was just using mine yesterday. It had been a while since the fan was failing. I opened it up and lubed the fan, and all is well.Man, what a great scope the 2232 is. All the DSO features, peak detect, vector display, the ability to switch to non-storage regular CRO behavior that is of course lightning fast. Not to mention the Tek magician guy Easter egg!I can't stand the cheap, modern, slow DSOs. Keysight FTW there.

author: David Hess
author_rank: Super Contributor
timestamp: April 10, 2017, 06:31:22 pm
content: Quote from: FlyingHacker on April 10, 2017, 04:03:29 pmThe 2232 and its close cousins are the oldest DSOs that I will usually recommend because they support peak detection. I always wished though that Tektronix had made a combination analog and digital storage oscilloscope faster than 100 MHz like Philips did.

author: timb
author_rank: Super Contributor
timestamp: April 10, 2017, 08:52:35 pm
content: Quote from: rstofer on April 06, 2017, 01:44:24 amThat's not *always* true. For example, the Tek 2465 Series (which is an analog scope, no digital storage) used a series of pots for the front panel controls. A reference voltage was applied to each pot and the wiper voltage scanned in sequence by a mux and ADC to determine the position. (Some of the controls even used two pots ganged together, without end stops [so they were continuous rotation]; by using two pots the direction and speed could be determined.Anyway, on this scope the horizontal and vertical position controls were scanned, the data stored and then the deflection voltage set by a DAC. The only front panel controls not digitally set were focus, graticule illumination (though it could still be turned on an off digitally by the scope) and trace intensity.This wasn't uncommon amongst high end analog scopes of the era.

author: David Hess
author_rank: Super Contributor
timestamp: April 10, 2017, 09:33:01 pm
content: Quote from: timb on April 10, 2017, 08:52:35 pmThe Tektronix 4 channel 22xx series oscilloscopes do this as well and it is one of the things that allows automatic setup to work.What is interesting is that Tektronix took advantage of the extra functionality that this can provide; the potentiometer controls are used as absolute encoders but when you change directions, there is a region of fine control so each individual potentiometer used as an encoder is both coarse and fine.Considering that all of the analog inputs and outputs for the controls are multiplexed and the processor is low performance, the latency is pretty low although noticeable.Tektronix also implemented continuous turning encoders this way by placing two normal potentiometers on the same shaft but out of phase to remove the ambiguity where the resistive elements are interrupted. These compare well to the various digital encoders and I wish they were available as standard parts. I did a search for them a couple months ago and found nothing.

author: timb
author_rank: Super Contributor
timestamp: April 10, 2017, 09:56:09 pm
content: Quote from: David Hess on April 10, 2017, 09:33:01 pmYeah, it was a very clever system and the way they transitioned from coarse to fine actually works really well.The 2465 Series has no noticeable lag to me; everything is basically instantly responsive. This is pretty impressive as you'd think the processor (an M68K) is handling quite a lot. However, they used numerous tricks to offload tasks from the CPU. The way character generation was handled was pretty clever. The CPU simply drops the readout data onto a specific memory location and a separate circuit takes care of decoding it, reading the character data from a ROM and loading it into a DAC, byte by byte. The time multiplexing of the beam between trace and readout is also handled by a dedicated circuit.Basically there was a data/address bus that ran across the main board and onto the expansion backplane and each module ran pretty much independently, taking a few instructions from the main processor and putting data back onto the bus. This was accomplished with nothing more than logic gates and a master clock, for the most part.There was also a single ADC and a few DACs on the main board, which were used in place of calibration pots. The DACs were multiplexed, with sample and hold circuits to maintain the voltage when the DAC was scanning. They would also use the ADC to read back the output of the DACs, which increased effective resolution and reduced INL/DNL errors. The CPU spends most of its time reading the front panel and scanning the cal ADC/DACs.I've looked at the M68K assembly from a system ROM of a 2465B and it seems to be very well written. They clearly had some high end programmers that knew what they were doing. The whole thing is very optimized.

author: David Hess
author_rank: Super Contributor
timestamp: April 10, 2017, 10:14:40 pm
content: Quote from: timb on April 10, 2017, 09:56:09 pmI have not used my 2445B much because my 2247A has the gated universal timer/counter and continuous automatic measurements.QuoteThat is not how the 2465 series works; it is worse than that.All of the analog inputs, and there are a lot of them (16?), are multiplexed to drive an LM311 comparator. The single 12 bit AM6012 current output DAC drives the same LM311 and the processor implements successive approximation or whatever itself. The DAC also drives another set of multiplexers to drive the sample and hold capacitors which are buffered by TL071 type operational amplifiers.ADCs and DACs were expensive back then so they got by with a single DAC yet the control response was still good.The 2247A series works the same way but has a separate 12 bit AM6012 DACs for the inputs and outputs. I suspect this has something to do with controlling the automatic measurements which work through the trigger system and operate continuously.

author: timb
author_rank: Super Contributor
timestamp: April 11, 2017, 06:10:29 am
content: Quote from: David Hess on April 10, 2017, 10:14:40 pmAhh yes, right you are. I was remembering some of the details of another scope. After awhile, all the service manuals just sort of mesh together in your head.