When do you need a 4 channel scope??? - Page 1
Forum section: electronics / testgear

author: RissViss
author_rank: Regular Contributor
timestamp: March 02, 2017, 11:36:45 pm
content: Hello everyone.Have been reading posts and watching Dave on youtube. This statement in one way or another comes up " Get a scope with 4 channels " , but I have not seen or heard why?Looking on the forum and lists of scopes to purchase under $600 and most are 2 channel with Rigol and GW having scopes with 4 channels.So if 4 channels is the thing to get and the Rigol is the scope to beat, why is there no other company besides GW that I have seen making scopes with 4 channels.Keysight's new scope has two channels and is the price range of the Rigol, why would they even bother to make it, if 4 channels is the thing to get.This is what is going through my mind when do you need 4 channels as a hobbies how much of your scope using time will you need 4 channels?Just trying to make sense of this, if some hobbies who have scopes and use 4 channels could give some examples would be great, and people who have 2 channeled scopes wishing they had 4 channels and give those examples.I hope this make sense.Have a day

author: ataradov
author_rank: Super Contributor
timestamp: March 02, 2017, 11:58:22 pm
content: For example, when debugging SPI interface, or even typical I2C + IRQ line.Or, just recently I was debugging screen interface, and I needed to see relation between HSync, VSync, and source clock at the same time.A lot of that can be solved by a logic analyzer, of course, but sometimes you also need to ensure signal integrity.

author: RissViss
author_rank: Regular Contributor
timestamp: March 03, 2017, 12:06:40 am
content: Thanks for the info.How much of your scope usage is 3 or more channels. And how much of that would a signal analyzer and a 2 channel do?Just trying to gather as much info as I can.Have a day

author: ataradov
author_rank: Super Contributor
timestamp: March 03, 2017, 12:12:08 am
content: It is hard to tell. Most of my personal usage is 1 channel. This "mode" used with hand-held probe to check on individual test points. This ensures basic signal integrity.Then things may diverge. Depending on a situation, you can either use logic analyzer, or go with the scope. Logic analyzer is mostly used for protocols, since they are mostly slow. Scope is used when you are dealing with high speed signals (> 10 MHz), and logic analyzers are just not fast enough to capture accurate timing picture.I would not go for 2 channels on a primary scope.

author: georges80
author_rank: Frequent Contributor
timestamp: March 03, 2017, 12:14:31 am
content: They make 2 channel scopes since they are cheaper and plenty good enough for schools/colleges/unis etc.Often I use 1 channel just to check a signal, but beyond 1 it is typically 3 channels -> 1 on the trigger input (e.g. PWM input), 1 on the voltage output and 1 to a current probe. And I DO want to see the signal rise/fall time of each of those 3 signals and their time relationship.Obviously for SPI etc, 3 or 4 channels is also often used.All depends on your needs and typical use case. Easier to have 4 channels and mostly ever use 1 or 2 channels than vice versaAnd this question has come up often enough before that search should likely find similar threads...cheers,george.

author: hammy
author_rank: Unknown
timestamp: March 03, 2017, 12:17:35 am
content: RS232 uses four signal wires. rx, tx, dtr, cts and gnd. Hook them all up and watch the screen to determine each of them.

author: Smokey
author_rank: Super Contributor
timestamp: March 03, 2017, 01:10:47 am
content: You can use any 4channel scope for only looking at 2 signals. Try that in reverse.I'm actually surprised they don't make more 6 or 8 channel scopes these days considering that it doesn't take an old school Tektronix mainframe level black-magic circuit to collect the data anymore.

author: guenthert
author_rank: Frequent Contributor
timestamp: March 03, 2017, 02:00:08 am
content: I never used all four at the same time, but three I did use.Unless you spend good money on (or build yourself) a differential probe amplifier, you'll have to do the subtract-one-channel-from-another trick for signals which aren't ground based. RS485 comes to mind, but also current measurements (using a shunt resistor, if you don't have a current probe). If you want to measure the voltage at a node at the same time (for power measurements), you need then three (generally speaking, sometime you get away with two).My first scope had four inputs, so I'm spoiled. If I am going to replace it (as opposed to expand my pool of test gear), I'll be looking for another one with at least three inputs.

author: RissViss
author_rank: Regular Contributor
timestamp: March 03, 2017, 02:33:58 am
content: Thanks everyone for the info.Very happy with the responses.Have a day

author: David Hess
author_rank: Super Contributor
timestamp: March 03, 2017, 02:48:49 am
content: The only times I have absolutely needed 4 channels was when I needed to combine channels to make 2 differential channels and for synchronous protocols like SPI with data in, data out, clock, and chip select and even then, I could have done what was needed with 2 channels and a trigger. Some people need 3 or more channels which in practice means 4 channels to make 3 phase power measurements.For a majority of uses, 2 channels plus a trigger is fine. 2 channel oscilloscopes also have a trigger channel and having 4 channels was an outgrowth of being able to display the trigger signal as a third trace; before 4 channels was common, 2 channels + 2 auxiliary channels was common.

author: DaJMasta
author_rank: Super Contributor
timestamp: March 03, 2017, 02:56:51 am
content: I've your monitoring a signal path, maybe at a couple points, and then also monitoring a secondary voltage derived from it (a peak detector output, for example), or power rails for noise.If you've got a controlled environment and a repetitive signal, you can just use a two channel and move things around, but you don't always have that luxury, and having them all hooked up definitely saves time over having to swap them around to get the full picture.If you're working with very simple circuits or when you're absolutely sure of your power supply, two is probably plenty... but if you're doing more elaborate stuff, debugging with power noise as a consideration, or chasing down an intermittent fault, having more channels is very valuable. Not even talking about for digital purposes, it can be really nice to probe a signal path between several elements and see how each is modifying the signal in real time and time-correlated.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: March 03, 2017, 04:33:44 am
content: Maybe sometimes you just need to impress the person who pays the bills!

author: james_s
author_rank: Super Contributor
timestamp: March 03, 2017, 05:41:56 am
content: I think I used 3 channels once at a previous job to capture the power up sequence of several power rails, but I've never had more than a 2 channel scope at home. I have a logic analyzer with 136 channels so that has me covered if I need to capture anything digital. I also have one of those little "Bus Pirate" doohickies that is handy for sniffing SPI and I2C and such among other things.

author: tautech
author_rank: Super Contributor
timestamp: March 03, 2017, 06:45:59 am
content: In answer to the OP, rarely is thereneedfor a 4 ch scope if you had a scope with the additional inputs a MSO unit can provide. Some call these Logic Analyser channels and in some way they are but not as good as a dedicated LA only unit. These in many ways are things of yesteryear but some find a need for them even today. Before MCU's, Logic circuitry was common and the best way to see what was going on was with many channels and see/check the inter-relationship between the gates and timings etc.Dedicated scopes on the other hand have a much wider range of applications particularly as their inputs can withstand much higher voltages than a LA. The best of both worlds is a MSO, it might be a 2 or 4 ch scope with 8 or more low voltage (LA) digital inputs.Power electronics and particularly 3 phase control circuitry need higher voltage capable inputs and in many cases 4 channels won't be enough to monitor all that's going on.Some 2 and 4 ch scopes have an Ext Trig input which can double as a extra channel albeit at lower voltages than the main input channels.Quote from: RissViss on March 02, 2017, 11:36:45 pmBecause as yet you haven't looked hard enough.http://siglentamerica.com/pdxx.aspx?id=1488&T=2&tid=1

author: Howardlong
author_rank: Super Contributor
timestamp: March 03, 2017, 06:56:42 am
content: I guess I'm an outlier, but it's pretty common for me to use three or four channels. Four a while, before I had a decent 4ch DSO, I used two pretty good 2+16 MSOs with the trigger out from the first plumbed into the trigger in of the second. Before that I used a 2465B and a TDS2024B, both 4ch.It's standard troubleshooting analysis, which is an iterative process. You're lucky if you find the answer with your first probing. Typically it'll take several attempts before you find the problem. Multiple channels means you can still examine several other probe points as you apply stimulus or otherwise recreate the problem.With two channels you can usually achieve pretty much everything a four ch can, but it will sometimes be a tedious and manual process.

author: Richard Head
author_rank: Frequent Contributor
timestamp: March 03, 2017, 07:21:40 am
content: I've used all four channels for monitoring the gate drives of a full bridge converter with a pair of differential probes for the high side devices. It's very convenient but if I had to choose between a high bandwidth two channel scope a low bandwidth 4 channel I'd take the two channel high bandwidth every time.

author: RissViss
author_rank: Regular Contributor
timestamp: March 03, 2017, 07:35:14 am
content: Yes the Siglent is a 4 channel, but it is not in the same price range as the Rigol or GW sub $550 range scope.As far as I can tell there is only two scopes 4 channel below $550 USD.I was just wonder, why no other company tries to compete with Rigol for the spot of best bang for the buck. This was just an observation and not a criticism of scope manufactures. It is good that Rigol has provided a good scope for the people that can not spend the money on higher priced scopes.Have a day

author: nctnico
author_rank: Super Contributor
timestamp: March 03, 2017, 07:48:55 am
content: Quote from: tautech on March 03, 2017, 06:45:59 amBut the SDS2000X series is 1) more expensive compared to GW Instek and 2) has way less features than GW Instek. Also according to the most recent posts on this forum the SDS2000X firmware still has a lot of bugs and other shortcomings.

author: BravoV
author_rank: Super Contributor
timestamp: March 03, 2017, 07:53:21 am
content: Quote from: RissViss on March 03, 2017, 07:35:14 amIts a big business decision , risky too, and Rigol took that big bet earlier compared to other competitors, and I guess they won looking at they're selling like hot cakes.Other companies have to think seriously before following this step, as Rigol already has the advantages as early adopter. Rigol could easily slash the price to kill or hurt the competitors.

author: sibeen
author_rank: Frequent Contributor
timestamp: March 03, 2017, 07:56:15 am
content: I'm definitely an outlier. Four channels is not enough which is why I use a Yokogawa DL708 scopecorder which contains 8 channels of goodness. It is very slow, with even the high speed channels only operating at 100 kS/s with the modules I use with it, but that matters not as most of the signals I'm looking at operate at 50 Hz.I work in the power industry and looking at 3 voltage waveforms, 3 current waveforms and a circuit breaker or two switching signals is something I do on a regular basis. Quite often I pine for even more channels and will eventually upgrade the now very old 708 for a newer 16 channel model. I just have to convince SWMBO that approximately $25k is still a good spend.

author: james_s
author_rank: Super Contributor
timestamp: March 03, 2017, 08:26:02 am
content: Wouldn't it be easier, cheaper and provide more choices to use a stack of 4 channel scopes rather than something as esoteric as a 16 channel scope?

author: MrW0lf
author_rank: Frequent Contributor
timestamp: March 03, 2017, 08:27:03 am
content: Quote from: Smokey on March 03, 2017, 01:10:47 amHm... 8channel, 12bit, 20MHz, 256MBhttps://www.picotech.com/oscilloscope/4824/8-channel-oscilloscopeAlso they seem to launch 4chdifferentialsoon (4x2=8 signal wires, floating), other specs similar, but already 14bit.But of course these are not for general hobbyist use at around 2000€, you need to be into something specific and cool to need this sort of thing.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: March 03, 2017, 08:33:19 am
content: Quote from: james_s on March 03, 2017, 08:26:02 amWell you can "stack" any scope if using 1ch for some kind of sync signal, some have special inputs for that. I had need for 4ch signal gen. Bought 2x2ch and synced with 10MHz in/out BNC & event trigger BNC. A bit cumbersome to use sometimes to get the job done but it gets done. It does not make sense for 99%+ of users so most manufacturers do not bother because to really sync it all in single screen / interface with all triggering stuff working as single scope would be pretty nasty engineering task.

author: capt bullshot
author_rank: Super Contributor
timestamp: March 03, 2017, 09:59:45 am
content: My first scope ever has been a 5MHz single channel analog CRO.This was way much better than having no scope.Next bigger thing to work with was an 100MHz analog two channel dual timebase boat anchor with plugins per channel and timebaseQuite impressive compared to what I had beforeNext one was a real neat, lightweight and easy to use dual channel 100MHz / 1Gs DSO with b/w LCD screenQuite impressive compared to what I had before, never used that boat anchor anymore, gave away my 5MHz analog scope somewhenNext one was the same real neat, lightweight and easy to use100MHz / 1Gs DSO with b/w LCD screen, but 4 channelNot so impressive to have 4 channels on a b/w LCD, otherwise handy since I was used to the UISeen and used some others DSOs in the meantime, color, up to 1GHz / 10Gs, typically 4 channels, up to 8 channels.I use quite often one channel only, but there's a lot of opportunities when 4 channels come in real handy.Now I have in my home lab:the good 'ol "easy to use dual channel 100MHz / 1Gs DSO with b/w LCD screen"the 200MHz 4 ch, colour LCD variant of the abovea boat anchor 1GHz, 4ch DSOan old 100MHz portable boat anchor 2 ch analogMost used: the good 'ol "easy to use dual channel 100MHz / 1Gs DSO with b/w LCD screen"And I want back the "100MHz analog two channel dual timebase boat anchor with plugins per channel and timebase"Most wanted: the new giveaway scope from Keysight - wouldn't buy it, but for free it would be an great toy, would show it to my boss and colleagues here at work to persuade them to buy some new scopes here (of the higher series)

author: rf-loop
author_rank: Super Contributor
timestamp: March 03, 2017, 10:42:18 am
content: Quote from: nctnico on March 03, 2017, 07:48:55 amWhere is 2 x 140Mpts memory in 4 channel GWGoodWill can not at all do 500000 segment/sGoodWill do not at all have all time background real time running waveform history buffer up to 80000 last wfm (same speed as current wfm/s speed).Also unlike GW, SDS2x04X can do 2GSa/s for two channels simultaneously?Afaik GW do not have real time output for full speed mask test.Also 2000X have 16 channel MSO hardware 16ch, 140Mpts/ch (activation need license)Made like tank compared to GW.Siglent do not want follow this "as cheap as possible" trend like Rigol and Keyshit.Road to A brand is still very long but distange is infinite if not even slowly walk and try. This can not do if go "price on front".There is lot of what need do better and better in hardware side (and in this area they have developed big steps and if they can continue this developing, only sky is limit. ). But when look software side, at this time it is bottle neck and need urgently develop better inside factory culture - but, after next 5 - 10 year we know more.For topic:It depends what and how I define it for MY use:93% 1 ch5% 2 channel2% 3 or more channelsEvery user have digfferent needs.But also, I have two hand. Of course if I have more hands I can perhaps then use more hands.Do we urgently need channels or just for fun to play.Some times also need human brain to do things with simple methods, like example using razor blade and candle you can inspect even 1/10000 mm class anomalies in telescope head mirror diy manufacturing.First is problem, after then thinking and then designing how to test and how to do probing etc and in very final after all thinking start move the muscles and play with test equipments and solve problem. Some do opposite order. They want and "need" all features and bells and whistles , because do not know what need and why.

author: tggzzz
author_rank: Super Contributor
timestamp: March 03, 2017, 10:44:10 am
content: Youneeda 4 channel scope when you have 3 or 4analoguesignals that you need to probe simultaneously.If your signals are known to be valid digital signals then you can use a protocol analyser or printf statements. They have the advantages of having >4 channels, being faster/cheaper, having smaller probes, and being able to have more protocol analysis and triggering functions.There is, of course, a lot of overlap - some low-end scopes can do limited protocol analysis in software, and medium-range "mixed signal" scopes combine digital and analogue operation.And never neglect the possibility that a scope is the wrong tool; the canonical example is that a spectrum analyser is usually better for RF work.

author: cgroen
author_rank: Unknown
timestamp: March 03, 2017, 11:16:42 am
content: Quote from: hammy on March 03, 2017, 12:17:35 amAhmm, no ?You could just as easily say that "RS232 uses 2 signals"What if you want look at DSR, RTS, RING, DCD etc ?

author: nctnico
author_rank: Super Contributor
timestamp: March 03, 2017, 11:55:38 am
content: Quote from: rf-loop on March 03, 2017, 10:42:18 amThat is what I have been writing all along. Meanwhile all Siglent does is compete on price and use their customers as beta testers. Maybe Siglent gets there eventually but why bother if less money buys you a scope from GW Instek which works as advertised, can actually use all the memory, has many useful features and where firmware updates to fix a bug take a couple of weeks instead of months or years? BTW there really is no difference between the build quality of GW Instek and Siglent. All boards firmly attached to the chassis and input BNCs bolted to the chassis as well.To get back on topic. IMHO for R&D work you need as many channels as you can get and then some so getting at least 4 channels is a no brainer. For most repair jobs two channels will do fine because you'll likely be following one signal without needing to do much cross referencing between other channels or protocol decoding.

author: David Hess
author_rank: Super Contributor
timestamp: March 03, 2017, 03:03:03 pm
content: Quote from: MrW0lf on March 03, 2017, 08:33:19 amA few years ago when I needed a 4 channel DSO, I opted for a pair of stacked 2230s which eventually became a pair of stacked 2232s. This was more cost effective than a modern budget DSO but only for someone prepared to maintain old instruments.With 2 channel oscilloscopes, there is no need to sacrifice a channel for triggering; practically all of them have a flexible external trigger input.

author: David Hess
author_rank: Super Contributor
timestamp: March 03, 2017, 03:18:08 pm
content: Quote from: capt bullshot on March 03, 2017, 09:59:45 amI use my 4 channel dual dual timebase boat anchor when I need differential inputs, high sensitivity, or any of the various auxiliary signals like gate, ramp, and vertical outputs which are not provided by a modern DSO.

author: capt bullshot
author_rank: Super Contributor
timestamp: March 03, 2017, 05:30:45 pm
content: Quote from: David Hess on March 03, 2017, 03:18:08 pmExactly thats the reason why I'm thinking about getting such a boat anchor again

author: Fenichel
author_rank: Contributor
timestamp: March 03, 2017, 06:30:44 pm
content: One value of more than two channels, not yet mentioned here, is facilitation of teaching. One may indeed be able to look at two signalsA&B,figure out from that how one wants to look atA&C,and finally get what was really wanted by looking atCagainstD,but the process may be hard to describe to anyone who hasn't walked through its development. That sounds abstract: look athttp://www.fenichel.net/pages/Indoor_Activities/metalworking/lathe/timing%20light/timing%20light.htmandhttp://www.fenichel.net/pages/Indoor_Activities/metalworking/lathe/autostop/lathe_autostop.htmfor two concrete examples.

author: Smokey
author_rank: Super Contributor
timestamp: March 04, 2017, 12:16:58 am
content: The problem with stacking scopes is the visualization of the data. For a lot of problems you better be able to suck all that data out to something that can display all the traces together.

author: tggzzz
author_rank: Super Contributor
timestamp: March 04, 2017, 08:57:00 am
content: Quote from: Smokey on March 04, 2017, 12:16:58 amAnd that hints at a problem with 4 channel scopes, particularly those with small screens and/or VGA resolution: being able to see all the relevant information on the screen.When, not if, you need more than 4 channels while debugging digital systems that becomes even more apparent - and is only partially ameliorated by combining multiple "signals" into a single "bus".

author: nctnico
author_rank: Super Contributor
timestamp: March 04, 2017, 11:30:06 am
content: When you need to look at many digital signals a logic analyser is the right tool (especially if you can use a PC with a high resolution monitor to run the application). Then again an MSO is very usefull but going over 8 channels is pushing the limits when it comes to space on the screen.

author: Avacee
author_rank: Unknown
timestamp: March 04, 2017, 11:45:18 am
content: Do any (non-USB/PC) oscilloscopes come with HDMI and direct output to a 1080p (or greater) monitor?Having such large screen real-estate and being able to see so many channels sure would be a nice selling point!

author: nctnico
author_rank: Super Contributor
timestamp: March 04, 2017, 12:45:08 pm
content: The Micsig TO1000 series has a HDMI output. But many oscilloscopes have a VGA output. Either way you'll have to realise this output will have the scope's native resolution so all you'll get on an external monitor is an enlarged version of what is on screen (assuming the monitor has a bigger screen than the scope).

author: tggzzz
author_rank: Super Contributor
timestamp: March 04, 2017, 12:58:51 pm
content: Quote from: Avacee on March 04, 2017, 11:45:18 amHave a look at the Keysight Infinium 9000 series. I saw something similar a couple of weeks ago and it was gorgeous. But costs as much as a Tek 465 did when I was starting out, about twice an annual salary

author: Someone
author_rank: Super Contributor
timestamp: March 04, 2017, 10:22:08 pm
content: Quote from: nctnico on March 04, 2017, 12:45:08 pmThats true of scopes using hardware to plot the waveforms, but not true for the windows based Lecroy scopes:https://www.eevblog.com/forum/testgear/upgrading-mainboard-in-lecroy-dda-3000-(aka-wavepro-7300a)/?allAnd similarly for the modern Agilent/Keysight infiniium scopes that do software plotting, as discovered after people on here discarded the hardware plotter in one of their older scopes:https://www.eevblog.com/forum/testgear/agilent-54831d-modernising/?all

author: David Hess
author_rank: Super Contributor
timestamp: March 05, 2017, 03:05:00 am
content: Quote from: Smokey on March 04, 2017, 12:16:58 amThere are advantages also. With two separate two channel oscilloscopes, you get separate timebases and separate flexible triggering which is something I miss on modern DSOs.

author: kcbrown
author_rank: Frequent Contributor
timestamp: March 05, 2017, 04:06:16 am
content: Quote from: David Hess on March 05, 2017, 03:05:00 amWhich CROs were able to do separate timebases per channel? Seems like that would be a specialty feature.

author: TNorthover
author_rank: Contributor
timestamp: March 05, 2017, 04:29:24 am
content: Quote from: kcbrown on March 05, 2017, 04:06:16 amI think he means that each scope gives you a separate timebase. So two 2-channel scopes next to each other gives you more timebase options than a single 4-channel one.

author: David Hess
author_rank: Super Contributor
timestamp: March 05, 2017, 06:06:15 am
content: Quote from: kcbrown on March 05, 2017, 04:06:16 amMost dual timebase oscilloscopes can apply either or both timebases to all channels. Some can apply one timebase to one channel and the second timebase to the second channel; oddly enough, this is a *very* old feature going back to the era of tube oscilloscopes. And then there are oscilloscopes like the Tektronix 7000 series which can do practically any combination of channels, triggers, and timebases; a 4 bay 7000 mainframe can even operate as two separate dual channel oscilloscopes each with dual delayed timebases so it is like having two stacked 2 channel dual delayed timebase oscilloscopes in one instrument.

author: Andreas
author_rank: Super Contributor
timestamp: March 05, 2017, 08:24:19 am
content: Hmm,perhaps you are looking only for the wrong term with dual timebase.On my scope I can make up a 2nd Window simultaneously to the first.In the 2nd window I can do a zoomed view for the x-axis.And also for the y axis (here for each channel individually up to a factor 50).Of course you need enough resolution for x and y axis so that it makes sense.In this case I used 12 bits in y-axis and 5 MS in x-axis.What do you want more?with best regardsAndreas

author: tautech
author_rank: Super Contributor
timestamp: March 05, 2017, 09:32:17 am
content: A simple to use DSO Zoom is all you need, much more user friendly that the old dual delayed timebase on a CRO.While you may have to toggle in and out of Zoom to adjust the main timebase it is no chore with a single push of the timebase knob. In the main timebase you can use the horizontal position to get a waveform point of interest on screen and then navigate to any part of it and any further timebase magnification needed with the horizontal position control in Zoom mode.

author: bson
author_rank: Unknown
timestamp: March 05, 2017, 10:03:44 am
content: Four channels comes in handy once in a blue moon. Here's from the other day when I wanted to verify that the outputs of a quad 8-bit DAC (TI DAC5574) were updating synchronously. So two digital channels on the I2C bus and four probes on the outputs, and sure enough it looked perfectly good. (I was then curious about the clock stretching, hence the zoom trace below.)

author: Howardlong
author_rank: Super Contributor
timestamp: March 05, 2017, 10:37:51 am
content: A separate trigger & timebase function would sometimes be useful if you are measuring two largely uncorrelated signals, for example a PWM fan controller measuring the tacho feedback of the fan. I do have an OWON handheld scope that does that, so it's not unheard of.Your only other options are to either manually alternate trigger, or to use two scopes.

author: nctnico
author_rank: Super Contributor
timestamp: March 05, 2017, 11:56:23 am
content: Quote from: David Hess on March 05, 2017, 03:05:00 amOn some DSOs (like the one I have) you can select alternate triggering where you can trigger on each channel seperately. However you have to realise the signals on screen are not related anymore.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: March 05, 2017, 05:20:57 pm
content: Quote from: Howardlong on March 05, 2017, 10:37:51 am...or look fore some correlation and trigger using logic triggers. With (somewhat) repeating signals usually there is some logic condition you can match.

author: David Hess
author_rank: Super Contributor
timestamp: March 06, 2017, 06:28:26 pm
content: Quote from: Andreas on March 05, 2017, 08:24:19 amRigol and other cheap DSO manufacturers have not helped by confusing delayed sweep or acquisition and dual timebases with pan and zoom. For example the DS1000Z series specifications and manual explicitly mention delay, delayed sweep, delayed timebase, and delayed trigger giving the false impression that they support these features but what they have is pan, zoom, and a trigger qualifier which has nothing to do with a trigger after delay or a delayed timebase.I became very weary of Rigol and the other cheap DSO manufacturers several years ago when I was looking for a DSO after I found that the Rigol DS1000B/CA/D/E series "peak detection" mode was envelope detection and not peak detection. (1) After I talked with Rigol who assured me that they had peak detection, a hands on evaluation saved me from a frustrating mistake. At least the DS1000Z series has real peak detection.Quote from: tautech on March 05, 2017, 09:32:17 amI actually find a dual delayed timebase to be easier to use because the horizontal controls scale with the timebase setting sort of like how when automatic peak-to-peak triggering is used, (2) the trigger level control scales with the waveform levels. It is easier to design a poor user interface for pan and zoom.Pan and zoom is very useful but not always a replacement for delayed acquisition with a second timebase. The sample rate is limited by the main time/div and record length (3) no matter what the zoom is set to. This came up here a couple months ago here with a Rigol DS1000Z where a new user wanted to delay 1 second to capture the following pulse from the 1 PPS output of a GPS receiver and found that the sample rate was then too low to capture the edge accurately even with the Rigol's long record length.Older and higher end modern DSOs have delayed acquisition and triggering as well as pan and zoom which can get confusing when both are used at the same time. More than once I have used automatic setup or restored the default state on the DSO I was using because that was faster than figuring out how to undo the combined pan, zoom, unlocked horizontal traces, and delayed sweep features. Or in the case of recent DSOs, combining delayed acquisition with pan and zoom caused them to crash.(1) Oddly enough Tektronix made the opposite error in the distant past. Their 2440 series of DSOs only have envelope detection listed as a feature but support peak detection as well.(2) Automatic peak-to-peak triggering is another feature almost all DSOs lack but the last generation of analog oscilloscopes also lacked it. (4) Auto level is a poor substitute and is a major reason I often use an old analog oscilloscope or DSO which support automatic peak-to-peak triggering for rapid diagnostics.(3) This is a good justification for large record lengths if dual timebase capability is not present and explains why dual timebase capability was common even in low end DSOs up until recently. Single timebases with pan and zoom replaced dual timebases in low end DSOs when large acquisition memories became inexpensive enough.(4) Automatic level triggering is cheaper to implement than automatic peak-to-peak triggering if the trigger level is set digitally which explains why the last generation of analog oscilloscopes and almost all DSOs with an analog trigger lack automatic peak-to-peak triggering. Automatic peak-to-peak triggering should be free on DSOs which have digital triggering but inexplicably they lack it.

author: nctnico
author_rank: Super Contributor
timestamp: March 06, 2017, 06:46:45 pm
content: Quote from: David Hess on March 06, 2017, 06:28:26 pmOn Japanese DSOs peak detect is typically called envelope mode so when it comes to envelope mode and peak detect you really need to read the manual to check what the oscilloscope manufacturer has implemented.QuoteI never heard of this mode until now. I had to look it up and it may be handy for repair work. It automatically triggers on the largest peak of the input signal.

author: David Hess
author_rank: Super Contributor
timestamp: March 06, 2017, 07:13:39 pm
content: Quote from: nctnico on March 06, 2017, 06:46:45 pmIt makes sense but I wish they would be consistent and some manufacturers definitely take advantage of the confusion between the two. Marketting is hardly going to advertise that their product lacks a significant feature if obfuscation produces sales.So what do they call envelope mode?QuoteAutomatic peak-to-peak triggering sets the trigger level range to the negative and positive peaks of the signal in real time so the trigger level becomes a percentage of the peak-to-peak signal level, is continuously updated, and the trigger sensitivity tracks the signal level making triggering on low level signals easier. (1) This often replaced AC trigger coupling as a default so some oscilloscopes which had it dropped AC trigger coupling. Switching between AC and DC coupling has no effect if automatic peak-to-peak triggering is used.The problem with auto level is that it fixes the trigger level, sometimes at the wrong level, and then there is annoyingly significant delay if it has to reset the trigger level again which if you are rapidly probing signals is all the time. Auto level effectively just presses the 50% Set Level control for you.I was so used to automatic peak-to-peak triggering that I took it for granted until it vanished as a feature. When I refurbished my Tektronix 7603, I missed automatic peak-to-peak triggering which is not supported with the standard 7B53A dual timebase so I bought a 7B92A dual timebase to replace it ... not realizing that the 7B92A and none of the 7000 series dual timebases support automatic peak-to-peak triggering. The more recent 7000 series single timebases do support it however so often I use one of them in my 7603.(1) I suspect Jim Williams liked this feature although I think his favorite but older oscilloscopes did not support it. He called it out once as the basis of a triggering circuit that he designed which duplicated it.

author: tautech
author_rank: Super Contributor
timestamp: March 07, 2017, 07:59:52 am
content: Quote from: David Hess on March 06, 2017, 06:28:26 pmI've read, re-read and thought about this all day.Sure it's been a little while since I've had to use a CRO and I used the Dual timebase heaps BUT with the Siglent's I have I can't see a use case or any CROfeatureyou've listed unsurmountable with the UI in a SDS1kX.The Zoom gives me 2 independent timebases that with one push of the timebase control lets me toggle between each, the holdoff and Horizontal position (pan) give me any delay I might need and I can pan in either timebase if needs be.The Trigger level is common to the main and Zoom windows and in the case with Siglent's can be set to 50% of the waveform amplitude with a push of the Trigger level control.All trigger, pan and level controls can be returned to their default positions with a single push of each.A screenshot, switching PSU charging a SLA battery.Some Holdoff, Delay, Pan, Normal Trigger, Peak detect and AC input coupling.

author: Howardlong
author_rank: Super Contributor
timestamp: March 07, 2017, 02:56:17 pm
content: Dual timebase isn't the same as a dual independent trigger.The example I gave, that of a PWM fan controller with tacho feedback, is probably the most obvious example of where this might be convenient.The Tek 2465, for example, has a VERT trigger mode where, when in ALT mode (as opposed to CHOP) and _not_ in AUTO LVL mode, "each displayed channel in turn provides the triggering signal".

author: guenthert
author_rank: Frequent Contributor
timestamp: March 07, 2017, 06:06:31 pm
content: Naiively perhaps I would have thought I would get away with a large memory and properly selected sampling rate. In the PWM fan example, assuming PWM frequency is 400kHz, we might want to have at least 10 samples per period, hence I'd chose a sampling rate of 4MHz (or thereabout). If I have a memory depth of 12MS, a full buffer gives me 3s (well, 1.5s for two channels). This clearly doesn't work for all conceivable use cases, but should be more than enough to clearly see the fan's tacho output (a few dozen to a few hundred Hz), no?

author: nctnico
author_rank: Super Contributor
timestamp: March 07, 2017, 07:31:46 pm
content: No. Only with alternate triggering you can get the two signals stable on the screen.

author: bson
author_rank: Unknown
timestamp: March 07, 2017, 08:08:30 pm
content: Quote from: guenthert on March 07, 2017, 06:06:31 pmUse the scope to inspect the waveforms to make sure they're clean and at the proper levels, then feed them into a dual channel counter. It will tell you all about the two signals in terms of frequency, duty cycle, etc.

author: guenthert
author_rank: Frequent Contributor
timestamp: March 08, 2017, 12:24:56 am
content: Quote from: nctnico on March 07, 2017, 07:31:46 pmWell, single shot of course. Not sure what 'stable on screen' would mean for two unrelated signals or why I would want it.

author: David Hess
author_rank: Super Contributor
timestamp: March 08, 2017, 06:16:01 am
content: Quote from: tautech on March 07, 2017, 07:59:52 amZoom only yields 2 independent timebases if the zoomed area is within the acquisition record of the first timebase. If the delay is outside of the acquisition record like in the example I gave (1), then the sampling rate has to be lowered. So the timebases are *not* independent and there is in fact only one timebase and one acquisition record with two different views. Large record lengths make dual timebases unnecessary so long as the delay stays within the acquisition record.So why can't the delay be longer than the acquisition record when digital triggering is used? The problem is that with only one acquisition record, if the delay extends beyond the end, then the sampled data at the trigger point is lost and the trigger cannot be reconstructed. The digitizer logic qualifies the trigger but the processor determines the actual trigger point later after reconstruction is done.QuoteAnd with automatic peak-to-peak triggering, I only have to set the trigger level once (2) and never remove my hands from what I am doing to adjust the trigger level. So for instance when set to 50%, it *always* triggers at 50% of the waveform peak-to-peak amplitude. It is great for rapid probing or if the signal is constantly changing.Automatic level triggering works almost as well but is slow with a significant delay when the probe is moved or the signal changes. (3) It just pushes the 50% trigger level control for you when triggering is lost. Under some conditions automatic level triggering will select the wrong level.I looked through the Siglent SDS1000x manual and found no equivalent to either; the trigger level either has to be adjusted manually or the 50% trigger button has to be used. Does it matter? Not really. It is just a usability issue but I certainly prefer oscilloscopes that have these features over ones that do not because they are faster and easier to use.(1) The Rigol would have needed a 1 gigasample record length to sustain its maximum sample rate over the 1 second delay using just pan and zoom. If the DSO can trigger and then delay before acquisition which is standard with dual timebases and analog triggering but rare with digital triggering for the reason described above, then the record length can be tiny.(2) And usually never because it is difficult to adjust the trigger level such that it will not work. In practice it just gets left somewhere around 50%.(3) With an analog trigger, the delay is because of how the signal levels are measured. The trigger level is iteratively adjusted until the signal peaks are found. This has the advantage of operating over the entire trigger bandwidth without requiring wide bandwidth peak detectors. A DSO with digital triggering should not have this problem but it may still pick the wrong level and stick with it.

author: Howardlong
author_rank: Super Contributor
timestamp: March 08, 2017, 09:19:47 am
content: Quote from: guenthert on March 08, 2017, 12:24:56 amAs I've stated more than once in this thread before, an easy example is a fan PWM controller with tacho feedback. While such situations aren't typical, they're not uncommon either.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: March 08, 2017, 09:27:38 am
content: Quote from: bson on March 07, 2017, 08:08:30 pmWhat is typical real-world accuracy need you have come across? How many digits, at what frequencies? Application? I'm doing some experimentation on this currently.

author: guenthert
author_rank: Frequent Contributor
timestamp: March 08, 2017, 05:17:33 pm
content: Quote from: guenthert on March 08, 2017, 12:24:56 amPoor choice of words on my side. I rather meant that 'stable on screen' for two unrelated signals would be actively misleading. There is after all only one timeline (ignoring relativistic effects here). Take your data, analyze it afterwards, see the relationship between the signals (or the lack thereof). I rather want my instruments to lie to me as little as possible.I think the two different time bases were a (clever) crutch invented for analog oscilloscopes, which just couldn't store sufficient amount of data (not more than one screen). I don't think it has a place in the realm of digital scopes.

author: nctnico
author_rank: Super Contributor
timestamp: March 08, 2017, 08:44:18 pm
content: Quote from: guenthert on March 08, 2017, 05:17:33 pmIt does. As Howard Long already wrote there are good uses to show two unrelated signals stable on screen with the scope in run mode. For example one signal which shows the sample points and the signal to be sampled in order to determine there are enough sample points per period.

author: rf-loop
author_rank: Super Contributor
timestamp: March 09, 2017, 02:24:22 pm
content: This is one example about ALT trigger. XDS3102ATwo separate asyncronous signals also with very different frequency.Both channels have individual trigger. Left bottom see trigger counting freq and right side trigger level markers.Nice feature when example compare two separate unlocked signal generators risetime or signal shape.Also example in cases where signals have same freequency but need watch sender shape and reflected signal shape and there is high jitter due to random travel time. etcBut one "negative point", both channels have same time base.This is why I still like Tek 7844 real dual beam scope.

author: RissViss
author_rank: Regular Contributor
timestamp: March 09, 2017, 04:24:43 pm
content: Thanks for all the reply's.Just wondering about the posts talking about triggers, is this still on topic?Do not get me wrong it is a very interesting discussion, and I do not mind it continuing, just want to know if its on topic?Have a day

author: irakandjii
author_rank: Regular Contributor
timestamp: March 09, 2017, 05:07:16 pm
content: For me, the best reason for a 4 channel scope is: Decoding high speed SPI busses.

author: David Hess
author_rank: Super Contributor
timestamp: March 10, 2017, 03:03:18 am
content: Quote from: rf-loop on March 09, 2017, 02:24:22 pmI do not have the 7844 with its dual beam capability but I do have several other 4-bay 7000 mainframes which can do the same thing in a more limited way by either alternating or chopping the horizontal timebases. I never realized how useful this capability was until I got the first one.Jim Williams gave some examples where independent triggering was used in Linear Technology application note 65. The switching power supply driven Royer converters he worked with operate asynchronously.He makes a comment about figure 42, "Most oscilloscopes, whether analog or digital, will have trouble reproducing this display" which I have never understood since it seems like a 2 channel DSO could replicate it easily. A single beam analog oscilloscope would almost certainly have a problem with it for the reasons he identifies.

author: 123rolle
author_rank: Contributor
timestamp: March 20, 2022, 01:30:41 pm
content: I'm looking for a first scope. First I thought getting Siglent sds1104x-e because of its possibilities for waveform and MSO with extra equipment. But would 2 channel scope + logic analyzer separate be better choice? In which case do I need 3-4 channels if I also get logic analyzer?

author: nctnico
author_rank: Super Contributor
timestamp: March 20, 2022, 02:01:27 pm
content: If you develop circuits, then a 2 channel oscilloscope runs out of channels quickly. You'll often want to see more than 2 signals (looking at various points in a circuit) so a 4 (or more) channel scope is the best choice. Having digital channels is handy but you'll need to verify whether the signal levels / edges are correct first using an analog channel. I'd go for an MSO rather than an external logic analyser because you see the analog and digital signals in the same time domain using an MSO.

author: Howardlong
author_rank: Super Contributor
timestamp: March 20, 2022, 07:59:07 pm
content: Quote from: 123rolle on March 20, 2022, 01:30:41 pmI have experience of the SDS1104X-E, and as a 4-ch scope it's fine, but the MSO SLA1016 option is TERRIBLE!!!! It makes the scope very slow and there are many limitations. For example, the is not even a zoom function with the digital channels enabled. Other limitations are described here:https://www.eevblog.com/forum/testgear/siglent-sds1204x-e-released-for-domestic-markets-in-china/msg2007983/#msg2007983I much prefer using the venerable Rigol DS1000Z Plus series and its RPL1116 LA probes. The limitations with this are the decode being limited to what's on the screen, and that it's only 4+0ch, 3+8ch or 2+16ch analogue/digital split. Bear in mind that the screen's small so it's a tight fit getting all that on anyway. I can't remember finding the analogue/digital split being a limitation for practical use cases, more important is the flexibility. It's not unusual to forego unnecessary analogue channels for digital channels on a scope's screen real estate anyway,Overall despite what some might say, I'm much more a fan of an MSO compared to using a separate scope & LA, but then most of what I do is mixed signal work. The only time I've used a 2ch scope w/o MSO in recent times is out in the field with a handheld unit: even then I'd probably consider myself better off with an Analog Discovery.

author: pdenisowski
author_rank: Super Contributor
timestamp: March 20, 2022, 08:42:55 pm
content: Quote from: Avacee on March 04, 2017, 11:45:18 amThe R&S RTO6 has a really big (15.6") capacitive touch screen and supports both HDMI 2.0 and Display Port+++

author: Martin72
author_rank: Super Contributor
timestamp: March 20, 2022, 10:51:32 pm
content: Quote from: 123rolle on March 20, 2022, 01:30:41 pmSimply when you want to see more than 2 channels...Actual private example:Next weekend I want to monitoring a protection circuit from an audio amplifier.So I want to monitor both inputs, the output and the muting pin at the same time...

author: 2N3055
author_rank: Super Contributor
timestamp: March 20, 2022, 11:27:39 pm
content: Quote from: pdenisowski on March 20, 2022, 08:42:55 pmWow, R&S RTO6 can be had for less than 600 USD ?? I will buy one immediately !!! No, wait, make that 2 !!Seriously, person is discussing sub 600 USD scopes.Statement that R&S RTO6 is a good scope, in this context seems, I don't know, just a bit too enthusiastic, maybe?Even saying that RTB2000 is good scope is not relevant in the price range discussed.

author: tggzzz
author_rank: Super Contributor
timestamp: March 20, 2022, 11:50:26 pm
content: Quote from: Martin72 on March 20, 2022, 10:51:32 pm... and you can't satisfy your objectives without it. (See the aphorism in my .sig!)You need a scope to look at analogue waveforms, in digital systems to ensure signal integrity. That onlyneedstwo channels, to see the time relationships.You need a digitising scope to capture one-off events that cannot be made repetitive.To look at signals that are known to be valid digital signals, you can use a logic analyser or protocol analyser or printf() statements. Those can be particularly effective if you use them to filter out the irrelevant crap so you can concentrate on the fault events; that can be difficult with scopes.Depending on circumstances, a scope with more than two channels may or may not be a cost-effective solution.

author: pdenisowski
author_rank: Super Contributor
timestamp: March 21, 2022, 12:03:03 am
content: Quote from: 2N3055 on March 20, 2022, 11:27:39 pmSorry, I thought it was a general question ("Doany(non-USB/PC) oscilloscopes... "), not specific to sub 600 USD scopes.There are, of course, other ways of putting a scope display on a large monitor, e.g. remote access, which is supported even by many modern lower-end scopes, but if you want an actual HDMI output, you're obviously talking about a completely different class of oscilloscopes.

author: 2N3055
author_rank: Super Contributor
timestamp: March 21, 2022, 12:17:44 am
content: Quote from: pdenisowski on March 21, 2022, 12:03:03 amNo need to be sorry, just a reminder that these topics are sometimes long and have lots of digressions.. Sometimes it's kind of hard to keep track, so some diligence is needed..I wanted to keep light tone.. By all means, please do contribute, it is appreciated...As for HDMI, well, Rigol MSO5000 series has HDMI. Also tiny Micsig Tablet scopes (that are 400-600 USD class) also have HDMI. Not full HD resolution, mind you, but they have HDMI.So these features are trickling down the price range too..Best,Sinisa