Choosing between entry-level 12-bit DSOs

[Mechatrommer]

To not have a decent feature set is a significant handicap, if not immediately certainly in the future when skill and knowledge develops.

"Not owning a car is a significant handicap, if not immediatelly certainly in the future when you are old enough to reach the pedals and get a license to drive"
Got it!

countering argument with wrong analogy, strawman fallacy? got it!

[tautech]

To not have a decent feature set is a significant handicap, if not immediately certainly in the future when skill and knowledge develops.

"Not owning a car is a significant handicap, if not immediately certainly in the future when you are old enough to reach the pedals and get a license to drive"

Got it!

Likewise owning a bicycle like the many CRO's I've had and never going back there thanks. Not for anyone and the last scruffy old non working HP I have is to be given away for Defpom to try and fix and make vids doing so.
 
Rightly these old CRO's belong in the last millennia or with collectors.

[gf]

Which square wave do you prefer? Figure7, or figure8?

<ignorance alert>Help me to understand what I am seeing in these two diagrams? I don't know enough to predict which is from which scope, or why one is better than the other.</ignorance alert>

You are seeing two imperfect reproductions of a square wave as you might see them on a scope. I'm not asking to speculate about the exact differences between them, I'm just asking for a subjective vote on which one you prefer. I'm not even asking why you prefer the one or the other. The question was primarily addressed to @shapiros, in response to his statement I quoted, but of course everyone is welcome to vote.

[shapirus]

You are seeing two imperfect reproductions of a square wave as you might see them on a scope. I'm not asking to speculate about the exact differences between them, I'm just asking for a subjective vote on which one you prefer. I'm not even asking why you prefer the one or the other. The question was primarily addressed to @shapiros, in response to his statement I quoted, but of course everyone is welcome to vote.

That's a bit strange way of putting it. I would not exactly "prefer" either of them. They are both non-ideal reconstructions, and I would have to interpret either of them given all other circumstances such as the scope's bandwidth and sample rate, probing technique and setup in use, etc., and understand that there is some extent of uncertainty between the actual wave (after it passes the bandwidth limiting filter) and what's displayed on the screen. I would think that the amount of this uncertainty is lower in the second waveform.

[gf]

That's a bit strange way of putting it. I would not exactly "prefer" either of them. They are both non-ideal reconstructions, and I would have to interpret either of them given all other circumstances such as the scope's bandwidth and sample rate, probing technique and setup in use, etc., and understand that there is some extent of uncertainty between the actual wave (after it passes the bandwidth limiting filter) and what's displayed on the screen. I would think that the amount of this uncertainty is lower in the second waveform.

Then it seems that you intuitively prefer the softer, Rigol-like interpolation filter. At least in this particular context. And I think my vote would be the same. I do not see what additional useful information I could obtain from figure7.

To clarify the context: It is a 10MHz square wave with steep edges (like you would get it from a Bodnar pulser), passed through a 4th order maximally flat filter with a -3dB bandwidth of 250 MHz (simulating a frontend), sampled at 312.5 MSa/s, and then interpolated with two different reconstruction filters in order to obtain the two plots. Figure7 uses a sharper filter (more like Siglent) and figure8 uses a softer filter (more like Rigol). The traces calculated for different sampling phases are aligned at the trigger point and overlaid.

[tggzzz]

A beginner is unlikely to require 12 bits for time domain measurements.

The key word here is "require". Yes, true, 12 bits are hardly required, in the strict sense.

However, having 12 bits of vertical resolution (assuming other parameters equal) simply makes the experience of using the scope more enjoyable: less pixelation and all, you know what I mean. That's important. Tools that are more pleasant to use encourage the user to spend more time with them and thus learn more and become more proficient.

Pixelation is inevitable with digitizing scopes and digital displays

Someone interested in scopes will use any scope regardless of pleasantness.
Someone not interested in scopes will use it for the minimum possible time.
Only a few people are TE addicts

A beginner can be overwhelmed by complexity; without a deep interest in the subject, the overwhelmed tend to quickly move elsewhere. Simplicity and a gentle learning curve can pay dividends.

As with any new technology to them, analog or digital.

A scope is a scope is a scope and a DSO is no different to drive yet offers a massive amount of additional features which is entirely up to the user whether they use them or not.

To not have a decent feature set is a significant handicap, if not immediately certainly in the future when skill and knowledge develops.

Yes, it applies to any new technology.

That doesn't change certain important considerations as to whether an instrument is more or less complicated and the scope of the learning curve:

• more controls => more difficult
• all controls immediately visible => easier
• some "internal" controls to be discovered and used after multiple user interactions => more difficult
• evident difficulty many people have understanding the core sampling and reconstruction theory => more difficult
• more tools in one box => more difficult

Of course there are compensating advantages; if there weren't tautech would have a much smaller market for his products.

An engineer chooses tools based on their suitability for a specific purpose. Different purposes can lead to a different choice.

For a completely off-topic analogy, consider learning to fly. Modern gliders have high performance laminar flow wings, with flaps, many instruments, radios, navaids, and in a few instances engines. Nonetheless nobody learns to fly in those. Beginners always learn to fly in gliders without flaps, without radios, navaids, engines, and with only an altimeter, ASI and vario[1]. (The 1930s Luftwaffe learned to fly on gliders without fuselages; some are still flying )

The reasons for learning on simple machines should be obvious - and certainly will be if you learn to fly.
Ditto the reasons for using complex machines for long-distance flights.
Too often salesmen manage to get newly qualified pilots to buy machines that are too complex; the mortality rate amongst middle-aged doctors/lawyers is higher than expected.

[1] It is also good practice to demonstrate flying with all those instruments covered up

[Fungus]

Since eyesight is a thing you mentioned, I will say the ONLY benefit to you for the Rigol is the HDMI out.

The way the text is rendered makes a huge difference.

[tggzzz]

Or perhaps you think the Nyquist limit only applies to sine waves? Hint: it doesn't.

I think a better way to describe it is that Nyquist is about sinewaves and that all other waveforms can be constructed by a Fourier series of sinewaves. Then you think about what those other waveforms look like when the higher frequency components of the Fourier series are attenuated or removed. Having someone understand this goes a long way to them realising why their traces look like they do.

My comment should be read in the context in which it was written (this isn't stackexchange nor edaboard: multilevel quoting is possible).

Apart from that, while your statements are correct, clearly too many people don't understand them. Hence the preponderance of "cargo cult engineering statements" about 5*frequency, and similar.

[Antonio90]

If cost is a dominant concern, then there are much cheaper alternatives than 8bit scopes.

You can get a 2 channel 12 bit scope for $390, or 4 channel for $440. True, for some that price is too high, and they'll stick with less expensive 8 bit scopes. But that's a pretty small percentage on the grand scheme of things.

I was thinking of more extreme constraints and radically different solutions.

I get your point, but I'm not sure it's good advice without someone knowledgeable to help you. My experience wasn't good with analog CRT scopes, even though it's purely anecdotical, might be useful.

When I was just starting out I bought a Tek 466 "untested" (LOL). Unsurprisingly, it did not work. After a long time studying the service manual, I traced a couple failures, on the PSU. The big caps were letting through all the ripple after the rectifier, a couple transistors were blown, and one or two blue "teardrop" caps (tantalum?) were shorted. I did a lousy repair job with my lousy soldering iron and skills.
A few hours later, no trace at all on the screen. I can't remember the details, but I think i traced the failure to the high voltage part on the bottom board, next to the PSU. And that's where the repair ended.
No skills and no HV tools, with my not-too-strong conservation instinct barely holding up.

Next was (I think) a Tek 2465B. Sold as working, and it did work as long as the readout was deactivated. If you activated it, some kind of digital signal appeared to ride on top of the trace, and the readout numbers were "pushed" upwards. After opening it, I saw liquid damage, corrosion and grime, and a resistor was open just before a pair of transistors driving the readout position on the screen. I, again, did a terrible job of removing the opened resistor with my cheap-ass soldering iron. The fact that the liquid damage had left some lime-like residue that could not be cleaned up with isopropanol did not help. Thankfully, I didn't break the pads. Then I found I did not have the right value resistor with the right power rating, but tested it anyway, and everything worked well.

Later on, I found on this forum the usual problems with the Dallas NVRAM, and the custom IC that gets way too hot. Replacing the NVRAM would have meant a desoldering gun (nothing under €100, even second hand), another dallas (€20? plus shipping), and a programmer (~€120 minimum). Plus the €120 of the 'scope. I ended selling it for what it did cost me.

Last try was one of the latest HAMEGs CRO, full SMD. It did cost me 10 bucks, but no schematics and it had been canibalized.

I reckon I made a lot of mistakes, but bear in mind I did know next to nothing about electronics. I learned a lot, too, one of the main ones being that if you need a tool, buy a properly working and supported one. All of this would, most likely, have ended differently if I had someone experienced guiding me a bit, but I didn't and still don't.

Take all of this with a grain of salt, of course, but if you don't have experienced hobbyists/engineers near you willing to help, my recommendation is do not buy an analog CRO. They are proper tools and the service manuals are a thing of beauty, but most of the people recommending them are experienced engineers that know their way around HV and these complex devices.

[shapirus]

• more controls => more difficult
• more tools in one box => more difficult

I'll disagree with these two.

1) as long as sane defaults are used, that is not true: the user doesn't need to touch the unknown controls until they become required for a specific task;
2) again, the user can use only the familiar tools, keeping the rest aside until it's time to use them.

Then again, we're talking about an electronics test and measurement instrument, the mere fact of using which assumes that the user has at least basic understanding of school-level physics and electricity and can read, and that means that the user can make use of the instruction manual that comes with equipment, which will resolve most of the confusion that may arise from seeing all the controls and menu options.

[DimitriP]

I didn't use to have anything against siglent, but I am slowly developing an aversion.

[Antonio90]

I didn't use to have anything against siglent, but I am slowly developing an aversion.

¿Why? They make rather good TE at a rather good price. Just don't you dare critizise anything about any current Siglent offering on this forum and you are set 

[tautech]

A beginner is unlikely to require 12 bits for time domain measurements.

The key word here is "require". Yes, true, 12 bits are hardly required, in the strict sense.

However, having 12 bits of vertical resolution (assuming other parameters equal) simply makes the experience of using the scope more enjoyable: less pixelation and all, you know what I mean. That's important. Tools that are more pleasant to use encourage the user to spend more time with them and thus learn more and become more proficient.

Pixelation is inevitable with digitizing scopes and digital displays

Someone interested in scopes will use any scope regardless of pleasantness.
Someone not interested in scopes will use it for the minimum possible time.
Only a few people are TE addicts

A beginner can be overwhelmed by complexity; without a deep interest in the subject, the overwhelmed tend to quickly move elsewhere. Simplicity and a gentle learning curve can pay dividends.

As with any new technology to them, analog or digital.

A scope is a scope is a scope and a DSO is no different to drive yet offers a massive amount of additional features which is entirely up to the user whether they use them or not.

To not have a decent feature set is a significant handicap, if not immediately certainly in the future when skill and knowledge develops.

Yes, it applies to any new technology.

That doesn't change certain important considerations as to whether an instrument is more or less complicated and the scope of the learning curve:

• more controls => more difficult
• all controls immediately visible => easier
• some "internal" controls to be discovered and used after multiple user interactions => more difficult
• evident difficulty many people have understanding the core sampling and reconstruction theory => more difficult
• more tools in one box => more difficult

Of course there are compensating advantages; if there weren't tautech would have a much smaller market for his products.

An engineer chooses tools based on their suitability for a specific purpose. Different purposes can lead to a different choice.

For a completely off-topic analogy, consider learning to fly. Modern gliders have high performance laminar flow wings, with flaps, many instruments, radios, navaids, and in a few instances engines. Nonetheless nobody learns to fly in those. Beginners always learn to fly in gliders without flaps, without radios, navaids, engines, and with only an altimeter, ASI and vario[1]. (The 1930s Luftwaffe learned to fly on gliders without fuselages; some are still flying )

The reasons for learning on simple machines should be obvious - and certainly will be if you learn to fly.
Ditto the reasons for using complex machines for long-distance flights.
Too often salesmen manage to get newly qualified pilots to buy machines that are too complex; the mortality rate amongst middle-aged doctors/lawyers is higher than expected.

[1] It is also good practice to demonstrate flying with all those instruments covered up

Right, daughter is a commercial pilot and would struggle with any scope.
You and your analogies. 

I had an interest in scopes at 13 to check the ripple of my valve based HV PSU.
Never used one however as an avid follower of 70's Popular Electronics had some basic idea of how to use one and conned the HS Science teacher to let me use the lab scope....50+ years ago.

Maybe you overlooked where I stated the obvious, a scope is a scope is a scope.
They all operate the same, exactly the same !
V/div and s/div, really how hard is that ?
Certainly not rocket science.

The modern DSO is no different and I still use one eyeballing the graticules for signal levels just as you would with a CRO yet wouldn't dream of ever using one again....clunky knobs, dodgy switches, outta spec timebases and all that obsolete BS.
Repaired enough old clunkers to flick them to well know their weaknesses, some you have probably never heard of, BWD and Bradley as examples.

How one advises the beginner to get some obsolete scope that will need repair is beyond me. 

[2N3055]

I didn't use to have anything against siglent, but I am slowly developing an aversion.

Why?

[Mechatrommer]

• more controls => more difficult
• more tools in one box => more difficult

I'll disagree with these two...

if Grampy cant fix it, you are screwed..

[nctnico]

It's not (only) a bandwidth issue. It's the failure to interpolate the sample data points correctly.

EDIT: Rephrased the question.

@shapirus, assume that you probe an almost ideal square wave and a scope would show you either figure7 or figure8.
Which one would you prefer subjectively? [ I'll explain the difference later in order to get an unbiased vote. ]

Neither pictures are correct. They both show Gibbs ears which do not exist in the real world. If you want to prevent seeing Gibbs ears, you need to use extra bandwidth limiting so the sin x/x   reconstruction does not add the Gibbs ears. IOW, for the best view of a square wave you need to bandwidth limit it in respect to the oscilloscope's bandwidth.

[awakephd]

• more controls => more difficult
• all controls immediately visible => easier
• some "internal" controls to be discovered and used after multiple user interactions => more difficult
• evident difficulty many people have understanding the core sampling and reconstruction theory => more difficult
• more tools in one box => more difficult

As illustrated in the responses above, there are always exceptions to any rule-of-thumb list such as this, but in general - as a sample newbie - I agree. A couple of comments, FWIW:

1 - A significant factor that can make a difference in the difficulty of "more controls" is the way the controls are laid out. Visually - which is all I have to go on at the moment - the Rigol wins in this regard. Rather than multiple buttons that all look more-or-less the same, the Rigol has used arrangement, size, and shape to distinguish at least some of the buttons from each other. Again, I stress this is based only on seeing the pictures; it may be that the layout does not match the logic, or some other issue that renders the Rigol's advantage moot. (Note that this comment applies to the on-screen layout as well as the physical controls - again a reason that the Rigol screen seems, to my inexperienced eye, to be far more usable despite the noted limitations.)

3 & 5 - One of the responses rightly points out that appropriate defaults can offset these issues. On the other hand, I have experienced the overwhelming frustration (with other sorts of instruments) of somehow changing one of those settings, and since I don't know enough to even know the setting is there - up to now the default has conveniently hidden it - I spend hours trying to figure what I'm doing wrong.

[bdunham7]

3 & 5 - One of the responses rightly points out that appropriate defaults can offset these issues. On the other hand, I have experienced the overwhelming frustration (with other sorts of instruments) of somehow changing one of those settings, and since I don't know enough to even know the setting is there - up to now the default has conveniently hidden it - I spend hours trying to figure what I'm doing wrong.

This is why most DSOs have a "Default" button that completely (almost, anyway) restores the scope to an original configuration.  I use it routinely when I can't remember what I was using the scope for last and just want to start over.  This prevents me missing something like having turned up the holdoff time that won't immediately be obvious but might cause some issues.

[awakephd]

3 & 5 - One of the responses rightly points out that appropriate defaults can offset these issues. On the other hand, I have experienced the overwhelming frustration (with other sorts of instruments) of somehow changing one of those settings, and since I don't know enough to even know the setting is there - up to now the default has conveniently hidden it - I spend hours trying to figure what I'm doing wrong.

This is why most DSOs have a "Default" button that completely (almost, anyway) restores the scope to an original configuration.  I use it routinely when I can't remember what I was using the scope for last and just want to start over.  This prevents me missing something like having turned up the holdoff time that won't immediately be obvious but might cause some issues.

Good point!

[gf]

It's not (only) a bandwidth issue. It's the failure to interpolate the sample data points correctly.

EDIT: Rephrased the question.

@shapirus, assume that you probe an almost ideal square wave and a scope would show you either figure7 or figure8.
Which one would you prefer subjectively? [ I'll explain the difference later in order to get an unbiased vote. ]

Neither pictures are correct. They both show Gibbs ears which do not exist in the real world. If you want to prevent seeing Gibbs ears, you need to use extra bandwidth limiting so the sin x/x   reconstruction does not add the Gibbs ears. IOW, for the best view of a square wave you need to bandwidth limit it in respect to the oscilloscope's bandwidth.

Nobody said they are "correct". Yes, both are imperfect (similarly imperfect as the 3rd screenshot here).
My question was just "which one [of the two imperfect ones] would you prefer subjectively".

[KungFuJosh]

Since eyesight is a thing you mentioned, I will say the ONLY benefit to you for the Rigol is the HDMI out.

The way the text is rendered makes a huge difference.

Yes, but whether or not that's a pro or con depends on your eyesight. AA can cause text to look blurry. Non-AA may look sharper. Depends on your eyeglasses prescription which you might prefer. 😉

[KungFuJosh]

VESA solution for the SDS800XHD: https://www.eevblog.com/forum/testgear/siglent-sds800x-hd-12-bit-dsos-coming/msg5478262/#msg5478262

[awakephd]

HDMI solution for the SDS800XHD: https://www.eevblog.com/forum/testgear/siglent-sds800x-hd-12-bit-dsos-coming/msg5478262/#msg5478262

That link takes me to a solution for the VESA mount. I'm still wading through that thread as (limited) time permits; is there a post in there about HDMI?

[KungFuJosh]

HDMI solution for the SDS800XHD: https://www.eevblog.com/forum/testgear/siglent-sds800x-hd-12-bit-dsos-coming/msg5478262/#msg5478262

That link takes me to a solution for the VESA mount. I'm still wading through that thread as (limited) time permits; is there a post in there about HDMI?

Wrong 4 letter acronym, I was still waking up. My bad. 😉

[nctnico]

It's not (only) a bandwidth issue. It's the failure to interpolate the sample data points correctly.

EDIT: Rephrased the question.

@shapirus, assume that you probe an almost ideal square wave and a scope would show you either figure7 or figure8.
Which one would you prefer subjectively? [ I'll explain the difference later in order to get an unbiased vote. ]

Neither pictures are correct. They both show Gibbs ears which do not exist in the real world. If you want to prevent seeing Gibbs ears, you need to use extra bandwidth limiting so the sin x/x   reconstruction does not add the Gibbs ears. IOW, for the best view of a square wave you need to bandwidth limit it in respect to the oscilloscope's bandwidth.

Nobody said they are "correct". Yes, both are imperfect (similarly imperfect as the 3rd screenshot here).
My question was just "which one [of the two imperfect ones] would you prefer subjectively".

You need to keep in mind that sin x /x interpolation on the Rigol is broken resulting seriously distorted results. So there is little use in selecting either imperfect one.