Information overload. I'm confused. Do I really need four channels?

[Artikbot]

Evening chaps,


First of all, my apologies if this sounds like yet another 'What scope do I buy' thread. I'll try to not make it sound like it.

Here's the deal: I've never had an oscilloscope.

I've borrowed the odd single and dual channel scope from school, from the odd friend, but I've never actually owned one, so this is from where most of my confusion comes from.

Bit of background. I've been doing electronics work for the past 5 or 6 years. I started with basic discrete digital electronics, moved into developing and building e-bike speed controllers, DC burshed motor management... More recently I've been doing most of my work in LED power management, data acquisition and handling on 8-bit PICs and 16-bit dsPICs. I'm also developing my studies and career into the analog side of life (specifically high power PSUs for large stuff and low noise PSUs for minute instrumentation, but mostly the first half), for whatever that's worth.

And I've made the decision that I can no longer do with borrowing equipment here and there, especially as my projects grow larger, more expensive and start to turn a profit (and there's only as long as I'm allowed to stay at the college labs... )


My budget, as you have probably guessed, isn't massive. About 500€ all inc (taxes, shipping...).


I've narrowed it down to two scopes:

-Rigol DS1054Z (who would've thought!)
-Siglent SDS1102X


Here's the reasons for the Rigol:

-Community loves it
-Dave loves it
-Some leftover monies are always good
-Four channels. And I'm bolding this out because part of the work I've taken a liking to doing is AC/BLDC motor management, and as I move from purely modifying and analysing speed controllers onto developing them from the ground up, I'm told four channels become a bit of a requirement - so there's that. Even if there's no external trigger


Reasons for the Siglent:

-On paper, substantially more powerful and capable than the Rigol, as far as the acquisition bit is concerned (60k wf vs 30k, 500uV/div vs 1mV, twice the BW, deeper memory, all the digital analysis bits come for free... or at least all of this is pre-hacking it, which I would definitely do).
-Better handling and feeling? Seems to have more screen estate dedicated to the waveforms, the variable intensity display seems much better executed than the Rigol, also dedicated controls per-channel. Critics seem to mention a generally more 'adequate' feel compared to the Rigol and being more comfortable to work with.
-No need to hack anything to get the whole parade of features - vendor ships the upgrade key free of charge. Including CAN, which considering one of my current ventures is in the automotive field, could be quite handy - although I'm aware there's external USB analysers that do that no problems for a few bucks.

So the real question is - Does on need four channels for the kind of work above, as I have been suggested? Is it more advisable to get the technically superior Siglent over the twice-as-many-channels Rigol?

For the sake of simplicity, let's condense it down to 90% power management and motor control, 10% general basic digital work (discrete CMOS/TTL logic, 8/16bit basic MCUs and such - nothing fancy).


Again, my apologies if this sounds like I have no idea about what I'm looking to buy, but I really don't because I've never had a scope of my own and always had to make-do with whatever I had at the time, ideal or not.


Many thanks!


Edit: For the sake of completeness - I have read through both respective threads quite meticulously - but if anything I am even more confused!

[RoGeorge]

The 4 channels from DS1054Z are very useful, especially when decoding serial protocols.

[tautech]

Welcome to the forum Artikbot.

Had to Google where Andorra was so that I might give some local advice.
https://www.lonelyplanet.com/andorra

Your local Siglent distributors can be found here:
http://www.siglenteu.com/howtobuy.aspx

And now as a EEVblog forum member you can ask for the Siglent supplier Saelig discount code here:
https://www.eevblog.com/forum/testgear/equipment-discounts-from-saelig/



As you've identified Siglent DSO's have an Ext Trigger input that can be used for CS when Decoding and as a result having only 2 main channels is not so much the disadvantage you might think.

[mk_]

I'm also developing my studies and career into the analog side of life (specifically high power PSUs for large stuff and low noise PSUs for minute instrumentation, but mostly the first half), for whatever that's worth.

You will find yourself searching more channels on the backside of your oscilloskop because specialy high power PSU requires constant viewing current, voltage and a lot of  more details.

(Ripplecurrents - primary and secondary, Voltagedrops when jumping from 10 to 90% power... you got the idea)

So don`t ask if 2ch are enough, ask yourself if 4ch are enough...

and - reserve some money for good probes...

Michael

[nctnico]

Go for 4 channels and never ask again if 2 channels is enough because it isn't!

[sambran]

I still regret getting a 2 channel scope.

[Artikbot]

The 4 channels from DS1054Z are very useful, especially when decoding serial protocols.

That's most helpful to know, I've not done any digital analysis on an already working setup yet, but no doubt I will.

Welcome to the forum Artikbot.

Had to Google where Andorra was so that I might give some local advice.
https://www.lonelyplanet.com/andorra

Your local Siglent distributors can be found here:
http://www.siglenteu.com/howtobuy.aspx

And now as a EEVblog forum member you can ask for the Siglent supplier Saelig discount code here:
https://www.eevblog.com/forum/testgear/equipment-discounts-from-saelig/



As you've identified Siglent DSO's have an Ext Trigger input that can be used for CS when Decoding and as a result having only 2 main channels is not so much the disadvantage you might think.

Thanks

For all intents and purposes I'm in Spain, although I'll be buying everything from Germany (what a surprise, heh).

I wasn't so sure about the disadvantage, rather, since I've never had to spec a scope for myself to own I've never really known what would it really need to have, hence throwing the question out there on whether 2Ch+trigger is enough, or 4 channels are much more desirable.

I'm also developing my studies and career into the analog side of life (specifically high power PSUs for large stuff and low noise PSUs for minute instrumentation, but mostly the first half), for whatever that's worth.

You will find yourself searching more channels on the backside of your oscilloskop because specialy high power PSU requires constant viewing current, voltage and a lot of  more details.

(Ripplecurrents - primary and secondary, Voltagedrops when jumping from 10 to 90% power... you got the idea)

So don`t ask if 2ch are enough, ask yourself if 4ch are enough...

and - reserve some money for good probes...

Michael

Michael,

Now that hits close to home. PSUs are pretty much my bread and butter, so it would make sense to go for what is best for that. Just as you mentioned ripple currents I had this train of thought of everything I just realised I can't do with just two channels, even adding an external trigger.

That answers my question, thank you!

Go for 4 channels and never ask again if 2 channels is enough because it isn't!

...I think I just might haha

I still regret getting a 2 channel scope.

Confirmed, DS1054Z it is!


Thanks for the replies everyone, it all makes a lot more sense now!

[JPortici]

I still regret getting a 2 channel scope.

i still regret buying the 1054z.

i'd rather have a 2 channel scope that works as it should (2+ext trig, 2 chan on its own is very limiting)
i can't comment on the channel requirements as i don't do power electronics. My 2 cents on the 1054 itself

[Artikbot]

Interesting...

How is that? What kind of work do you usually do that it falls short on?

[rstofer]

Good choice on the DS1054Z, I certainly like mine!  I wanted 4 channels for serial decoding and I almost never get involved with PSUs.

If you want to use the X-Y math function (differential measurement of current through a resistor?), you just used up two of the four channels and you probably want to view a voltage or two to go along with the current (phase relationships?) so that's why 4 channels is a good idea.

[alsetalokin4017]

In XY mode the 1054z can only use two channels. The other two are turned off automatically.

The maximum sample rate of XY mode is 500 MSa/s. Generally, longer sample
waveform can ensure better display effect of Lissajous figure. But due to the
limitation of the memory depth, you have to reduce the waveform sample rate
to acquire longer waveform (refer to the introduction in “Memory Depth”).
Therefore, during the measurement, reducing the sample rate properly can
acquire better display effect of Lissajous figure.
? When XY mode is enabled, “Delayed Sweep” will be disabled automatically.
? Press X-Y to select “CH1-CH2, CH1-CH3, CH1-CH4, CH2-CH3, CH2-CH4,
CH3-CH4”. After you choose any of the options, the instrument automatically
turns on the two corresponding channels and turns off the other two channels.
The X-axis tracks the voltage of the first channel in each option; the Y-axis
tracks the voltage of the second channel in each option.
? The following functions are not available in XY mode:
“Delayed Sweep”, “Vectors”, “Protocol Decoding”, “Acquisition Mode”,
“Pass/Fail Test”, “Waveform Record” “Digital Channel” and “To Set the
Persistence Time”.

Oh... perhaps you mean the A minus B math function. OK, then you can have five traces showing: the two channels that are in the subtraction, the other two channels, and the math result of the subtraction.

[CatalinaWOW]

As someone who has worked with oscilloscopes since two channels was a great leap forward, there is no number of channels which is either too few or too many.  You can do a great deal of work with one channel.  There are many more things you can do with two.  In today's world I would absolutely not go less than two, which allows you to compare phase of two signals.  If you have four you will find uses for all of them, and sometimes wish you had more.  I do find that for my general hobby electronic work that I seldom have all four channels of my scope active, but often have three.

[tggzzz]

The trick is to ask the right question, because then the answer is easy.

Perhaps a better question is "what instruments do I need?".

Consider buying an Analog Dialogue. That will give you a simple 100MS/s pattern generator & logic analyser, a waveform generator and a 10MHz digital scope.

Where you need more bandwidth, e.g. for signal integrity, get an old analogue scope - but make sure it is working! 100MHz is insufficient for modern logic w.r.t. signal integrity.

Look at my .sig, and relate it to electronic instruments  And distrust those that say X is the only choice, especially if they don't limit the applicability of their pronouncements!

[tggzzz]

I have never find a 4-channel scope useful. I almost always find I need up to 2 channels. If I need more, it is definitely for digital purpose, so I would instead just fire up my logic analyzer.

Very true, in my experience. But I would add "printf" to that toolset.

When in the digital domain, use digital tools. Ditto analogue domain. But use a scope to ensure that the analogue signal will be interpreted correctly by the digital input - I.e. ensure the signal integrity.

[DaJMasta]

You can do almost everything you can do with a 4 channel scope with a 2 channel scope and the SDS1102X is a great two channel scope.


That said, it is MUCH easier to find correlations with more channels and MUCH faster to debug issues with virtually any kind of circuit.  Take a simple amplifier with a couple of stages.  With a two channels scope you could measure the input and the output and see how it works, maybe switch to get the intermediate signal step or swap to measure the rails or whatnot.  With a 4 channel scope, you can measure the input, the output of the first stage, the output, and a supply rail all at once, which means you'd be able to troubleshoot glitches at any one of the points and if they're intermittent or if (for example) the glitch is caused by the power supply but only when the input is doing something specific, you'll be able to trace down the issue much faster.

I'd think in power supply design, it would be especially useful because you could get a couple of current probes and then measure current and voltage activity at an input and an output (or any two points, really) all at once, making it really easy to track power on/off/brownout behaviors, track down noise sources, etc.


So especially if you know your application, two channels can be enough and two channels is WAY WAY WAY better than having nothing.  4 channels makes most things more convenient, gives you a few more options, and helps you correlate signals in different parts of what you're testing more quickly and reliably.

[tggzzz]

Consider buying an Analog Dialogue. That will give you a simple 100MS/s pattern generator & logic analyser, a waveform generator and a 10MHz digital scope.

It's Analog Discovery .

Picky, picky, picky

[imidis]

When I purchase something I like to know that I won't need to go to another anytime soon. I believe if I were purchasing one I would go with the Rigol 1054Z. I believe it's decent value for a four channel scope and though I may not need the four channels, if I need them they would be really handy to have.

[nctnico]

The trick is to ask the right question, because then the answer is easy.

Perhaps a better question is "what instruments do I need?".

The answer to that is simple: the best and most you can buy. Better tools will always allow to do a job better and quicker. If you are really serious about electronics then it may be worthwhile not to go for the cheapest but aim a couple of steps higher.

[tggzzz]

The trick is to ask the right question, because then the answer is easy.

Perhaps a better question is "what instruments do I need?".

The answer to that is simple: the best and most you can buy. Better tools will always allow to do a job better and quicker. If you are really serious about electronics then it may be worthwhile not to go for the cheapest but aim a couple of steps higher.

No it isn't simple, because it ignores the interesting real-world dilemma: to go for a slightly better (in some respect) X, or to go for a better (in another respect) X plus a Y plus a Z.

[nctnico]

Even though the words 'best' and 'most' where carefully choosen you overlooked them  .

[tggzzz]

Even though the words 'best' and 'most' where carefully choosen you overlooked them  .

No, I didn't overlook them; I took them at their face value.

It is better to have a balance between good enough X and good enough Y, rather than the best X and no Y.

[Artikbot]

I have never find a 4-channel scope useful. I almost always find I need up to 2 channels. If I need more, it is definitely for digital purpose, so I would instead just fire up my logic analyzer.

Very true, in my experience. But I would add "printf" to that toolset.

When in the digital domain, use digital tools. Ditto analogue domain. But use a scope to ensure that the analogue signal will be interpreted correctly by the digital input - I.e. ensure the signal integrity.

Partially why I don't give much credit to the digital analysis capabilities of either scope - there are better tools out there for less than the difference between the devices. But again - digital work is a relative minority of what I do.

The trick is to ask the right question, because then the answer is easy.

Perhaps a better question is "what instruments do I need?".

The answer to that is simple: the best and most you can buy. Better tools will always allow to do a job better and quicker. If you are really serious about electronics then it may be worthwhile not to go for the cheapest but aim a couple of steps higher.

No it isn't simple, because it ignores the interesting real-world dilemma: to go for a slightly better (in some respect) X, or to go for a better (in another respect) X plus a Y plus a Z.

Very good point. In this case it's the obvious benefit of two extra channels versus a technically superior device that outright lacks an important feature of the inferior model. If I had a few grand to drop it'd be much easier, alas it is what it is.

You can do almost everything you can do with a 4 channel scope with a 2 channel scope and the SDS1102X is a great two channel scope.


That said, it is MUCH easier to find correlations with more channels and MUCH faster to debug issues with virtually any kind of circuit.  Take a simple amplifier with a couple of stages.  With a two channels scope you could measure the input and the output and see how it works, maybe switch to get the intermediate signal step or swap to measure the rails or whatnot.  With a 4 channel scope, you can measure the input, the output of the first stage, the output, and a supply rail all at once, which means you'd be able to troubleshoot glitches at any one of the points and if they're intermittent or if (for example) the glitch is caused by the power supply but only when the input is doing something specific, you'll be able to trace down the issue much faster.

I'd think in power supply design, it would be especially useful because you could get a couple of current probes and then measure current and voltage activity at an input and an output (or any two points, really) all at once, making it really easy to track power on/off/brownout behaviors, track down noise sources, etc.


So especially if you know your application, two channels can be enough and two channels is WAY WAY WAY better than having nothing.  4 channels makes most things more convenient, gives you a few more options, and helps you correlate signals in different parts of what you're testing more quickly and reliably.

This bit here is what has made me tip over to the Rigol in this case. I'm by no means an expert, or even remotely experienced - I can use as much help as I can get. It would appear like the help of the extra channels is substantially more desirable than the extra grunt and refinement of the Siglent in this particular scenario...


Really appreciate the thoughts on this matter

[saturation]

2 channels allowed the user to see input and output simultaneously, correlate them and thus speed your evaluation. 

The Z implementation exacts a speed and sampling rate penalty on every other channel you turn on.  The slow down can reduce usefulness markedly.  Also the small screen starts to get crowded as more traces appear but it depends on what type of waveform you are viewing before it becomes unwieldy.

However, you can keep performance up by switch off channels that are hooked up but not important to see at the moment and its easier to turn on a hooked up channel than to move probes about.

[Muxr]

2ch is fine, 4ch is better. That's how I look at it. I used a 2ch scope (and still sometimes do) for a while and never really felt handicapped by only having 2ch. Most measurements I do even on my 4ch scope are with 1 or 2 probes.

[Fungus]

Most measurements I do even on my 4ch scope are with 1 or 2 probes.

But not 100% of them, right? 

If 1% of measurements use 3 probes and only 0.01% of them use 4 probes then you still need a 4 channel scope.

The time you should consider a 2 channel 'scope is when you can do 99% of your work with just 1 channel.

(yes, I know most of EE history used 1 or two channel scopes but most of human history also pooped outdoors and used horses for transport)