Final Questions Before I Get My First Oscilloscope

[billfernandez]

Thank you Wuerstchenhund for going to the trouble to create this clear and informative demonstration. 

[Wuerstchenhund]

Thank you Wuerstchenhund for going to the trouble to create this clear and informative demonstration. 

No worries! If it helps to stop the spread of misinformation then it was worth it 

[Mechatrommer]

No worries! If it helps to stop the spread of misinformation then it was worth it 

misinformation of what? that 24Mpts scope is better than 10Mpts scope? that somebody said 16Kpts is the same as 1Mpts FFT? who said that? what are you trying to create? i was trying to stop the spread of misinformation that the current DS1054Z is using 4Kpts FFT,  that was a 6 months old history. also the misinformation that FFT is not the only factor when judging DSO spec.

if the idea is to buy all packed FFT, LA, DSO in a one piece, i better get the DS1074Z-S in the first place... same price as GDS1104B, i got extra FG. fanboys may mourn its utter useless, but something is better than nothing,  GDS got nothing, for the same price...

[Muxr]

Thank you Wuerstchenhund for going to the trouble to create this clear and informative demonstration. 

Indeed. Very nice demonstration.

[Helix70]

The OP wants a modern scope in the $1200 range, which he will be happy with for the next 5 years and have some soft unlock room to grow. I think HMO1202 fills that requirement perfectly.

Having used both Rigol scopes and R&S scopes, I believe anyone is going to prefer using an R&S scope over a Rigol scope on a day to day basis for the next 5 years. The UI and the firmware is significantly more polished. The controls feel better and the scope is more responsive.

For me personally, 4 channels wins. The OP wants a 5 year scope, I reckon he will have a need for 4 channels before any silly FFT. Hard to debug an SPI bus conversation with only 2 channels. Impossible to monitor the power supply, or the CS line at the same time without 4 channels. It is horses for courses. This argument about the FFT is laughable. No one is seriously using an entry level scope as a substitute for a real spectrum analyzer. Now a 4 channel R&S, or Agilent, or Tek, or Lecroy......... That's another story, and another price bracket.

[Fungus]

For me personally, 4 channels wins. The OP wants a 5 year scope, I reckon he will have a need for 4 channels before any silly FFT.

Me too. 4 channels wins. You can put up with all sorts of limitations for things like bandwidth and user interface but when you need more channels, you need more channels. I really don't think I could point to any 2 channel scope (no matter how nice) and say, "I will never need more than 2 channels, that 'scope will be all I need for the next five or ten years".

YMMV.

The fact that certain people have chosen to center the buying advice for a "first oscilloscope" around FFT is idiotic. The OP didn't even mention FFT. 

[zapta]

... The fact that certain people have chosen to center the buying advice for a "first oscilloscope" around FFT is idiotic. The OP didn't even mention FFT. 

https://wikipedia.org/wiki/Narcissism_of_small_differences

[nctnico]

For me personally, 4 channels wins. The OP wants a 5 year scope, I reckon he will have a need for 4 channels before any silly FFT.

Me too. 4 channels wins. You can put up with all sorts of limitations for things like bandwidth and user interface but when you need more channels, you need more channels. I really don't think I could point to any 2 channel scope (no matter how nice) and say, "I will never need more than 2 channels, that 'scope will be all I need for the next five or ten years".

YMMV.

The fact that certain people have chosen to center the buying advice for a "first oscilloscope" around FFT is idiotic. The OP didn't even mention FFT. 

If that is what you think then you have missed the point. The point is that features on some oscilloscopes may be nothing more than checkbox items with very little practical use.

[markone]

Sorry but this is just BS. Off the bat the HMO1202 has no carrying handle, the run/stop button is in the wrong place and where is the 'single' button? If you compare the HMO1202 Dave took apart with the GDS2204E you will see their construction is very similar. 2 plastic shells and a couple of PCB boards. Actually you could argue the way the board is mounted in the HMO1202 makes it susceptible to flexing when the oscilloscope is shaken. There is absolutely no support in the middle  And then there are the solder mounted BNCs in the HMO so all the force used when connecting a probe or cable gets transferred into the PCB versus the BNCs bolted onto the chassis with washers and nuts in the GW Instek. Must I continue? All in all I think you are just parrotting Dave here. If it has a name brand on it he immeditialy calls it a quality bit of kit  Yeah right...

I could share some of your observations, i could admit that UI approach is quite sobjective, but regarding "you will see their construction is very similar" i would say that IT's NOT TRUE at all.

For what is worth now, i would elaborate my claims

first :i'm not parroting anyone, i'm only able to understand by myself that the design effort put to develop a scope like the HMO1212 on a single custom board, aside a very well built custom shielded PSU is several times higher than take and put togheter :

- one off the shelf not shielded cardboard PCB, whining noise source, PSU
- one very likely off the shelf Zynq processing board fixed with plastic clips and plastic floating turret
- one connectors only PCB to adapt the very likely off the shelf Zynq to LCD flat cable
- one generic base board with analog front-end and ADC chip

Respect the GDS-2000A, the GDS-2000E series is a clear cost & build quality step down, i'm not saying it's crap, but i would say that also Rigol DS1000Z and DS2000A have a significantly higher construction quality.

And yes, i too also like the R&S care for design &  assembly details (as Dave do, actually), it's simply on a superior level, even with this bottom line scope.

Dunno if you are not able to detect it or if you do not want to admit it, not my fault anyway.

[EEVblog]

All in all I think you are just parrotting Dave here. If it has a name brand on it he immeditialy calls it a quality bit of kit  Yeah right...

You are right about the GW Instek build quality being good. Too bad it looks and works like a toy, it doesn't instill a lot of confidence in you. IMHO of course
But of course it offers a lot of bang-per-buck.
I'd rather have the R&S any day of the week. Smaller, silent, near instant boot, great clean screen and UI, excellent auto-measure mode, and just feels like a professional scope. It's "the vibe".

[nctnico]

@markone:
Sorry but the way the HMO is constructed WITHOUT any support for the circuit board and no fixations for the BNC connectors to the chassis is a big fail. Regarding the GW Instek Dave took apart: it must be an early model because my GDS2204E has a single board with all the analog and digital electronics integrated. The PSU GwInstek uses isn't a flyback one but resonant and therefore it doesn't need so much shielding (it is mounted on the chassis which offers shielding BTW). Note the screendumps I posted elsewhere with the inputs open and the vertical sensitivity set to 1mV/div.

There really is nothing superior about the way the HM1200 is constructed. That is all in your mind because there is an R&S sticker on it! Your notes about 'off-the-shelve' components are outright hilarious! BTW I noticed R&S uses off-the-shelve chips on their boards  But maybe R&S etched their own boards, you never know. The bottom line is: it makes sense to buy off-the-shelve components because you can concentrate on what you are good at (concentrate on your core business) and use knowledge from others (for example regarding PSUs) to your advantage. R&S wasted a whole lot of money slapping a PSU together, putting it in a shielded box and get it certified where GWInstek just orders the PSUs without the headache of certifying it or (due to the PWM method) needing a lot of shielding. It is all about seeing the big picture while doing clever engineering.

BTW I don't think I have ever seen a PSU designed by Tektronix themselves in any of their DSOs or logic analysers. It is not their core business so they leave it to someone else who is good at it!

@Dave: your remark 'Too bad it looks and works like a toy' makes me raise my eyebrows and wonder what your reviews are worth if they are based on a vibe. There are differences in how people look at test equipment, use of colors, etc based on where they are located. Put a Yokogawa scope next to one from Keysight and you'll notice a day and night difference in the user interface. However at the end of the day both will get the job done.

[Gandalf_Sr]

Dave hits on a good point, hardware build quality is important but the bad software can make good hardware useless.  I own an Instek scope and it's under my bench gathering dust, it was my first digital scope, it's 2 channel and has no features.  The next scope I bought was the Rigol MSO2072A which quickly became a MSO2302A - it's a good scope but I find the screen a bit cramped (I have bad (old) eyes) and the serial decode is difficult to work with. Notice that, as others have just said, 2 channels are not enough to decode an SPI bus but 4 analog channels isn't strictly necessary to do this, by going for say the MSO2072A, the OP would get 16 digital + 2 analog channels and the decode can be set up to work from any combination of these.

The FFT thing is a gimmick IMHO, if you really need to do FFT buy something designed for that like an FFT SA.

Going for pre-owned quality is also an option that the OP should seriously consider - e.g. the Aglient 2000 series I linked to a few posts back.

[ebastler]

Wuerstchenhund, thanks for the nice demonstration of various FFT point lengths. However, I'm not quite sure what settings you used for the short window sizes. On my DS1054Z, I get much more satisfying results. The attached is for the 1kHz test signal -- I was too lazy to get the function generator out, but with regard to FFT resolution, the result should be comparable to yours, right?

This is taken with the older SP2 firmware, i.e. the smaller FFT dataset (presumable 4k points). Normal acquisition mode; high res mode reduces the noise a little bit further, but not significantly.

I would argue that there are two major use cases for FFT, and that the Rigol scopes are not suited for the one, but very useful for the other:

• Modulated carrier, where the modulation bandwidth is typically small vs. the carrier frequency, and you want to see a narrow spectral window around the carrier. This is where large FFT windows are needed, and the Rigols (and other scopes with just a few kPoints FFT) will simply not resolve enough spectral detail around teh carrier.
• Unmodulated signal, where you want to observe harmonic content -- e.g. in acoustics, vibration analysis, to check spectral purity of an unmodulated carrier etc.. A few kPoints are perfectly fine for me to assess harmonic content in these applications, so my DS1054Z is certainly useful to me.

Hope this makes sense?

[nctnico]

The FFT thing is a gimmick IMHO, if you really need to do FFT buy something designed for that like an FFT SA.

It depends on what you want to do. I use FFT for hunting EMC problems and it helps to see the time domain signal and the frequency spectrum in order to determine what is causing the problem. In the past I have also used FFT on a scope to measure the bandwidth of audio paths in telecom systems.

[markone]

For me personally, 4 channels wins. The OP wants a 5 year scope, I reckon he will have a need for 4 channels before any silly FFT. Hard to debug an SPI bus conversation with only 2 channels. Impossible to monitor the power supply, or the CS line at the same time without 4 channels. It is horses for courses. This argument about the FFT is laughable. No one is seriously using an entry level scope as a substitute for a real spectrum analyzer. Now a 4 channel R&S, or Agilent, or Tek, or Lecroy......... That's another story, and another price bracket.

I'm spot on this view of things.

The reason why i bought my four channels Rigol is that i play a lot with stepper motor drivers (CNC and telescope mounting), where six channels would be even better.

I could effort much expensinve equipment, but for hobby activity woul be an overkill.

The 1MEG FFT function on a 8bit system (with ugly UI) does not impress me at all, the DSA815 is the "cheap" way to go if you have to do any serious (or near to) EMC pre-compliance testing activity or RF DIY.

Personally i use the Elad FDM-S2 16bit -122MSa/s sampler (actually conceived as HF receiver) as high resolution / high sensitivity real time spectrum analyzer for some rough EMC assessment, clock source phase noise analysis or HF filter stuff; it's actually limited to 60Mhz max freq & 6Mhz SPAN, but within this limits blows out the windows any 8-12bit and some 16bit DSO's FFT, and can store live spectrum portion to HDD in I/Q format for post analysis.

For serial protocol analysis one can always buy a dedicated stand alone 8 channel device like the new SALEA LOGIC 8 fpga based logic/protocol analyzer with analog capabilities.

Said that, right now if you prioritize the bandwidth over the channels number, the DS1072A expanded to 300Mhz for free, gimmick functions talking apart, @840USD seems a wise choice, but i would consider also the MSO version to cover possible mixed signal systems in a Five-Year plan 

[Fungus]

If that is what you think then you have missed the point. The point is that features on some oscilloscopes may be nothing more than checkbox items with very little practical use.

I haven't missed the point at all.

The point is that you need to assign a value to each of those features for your own personal use.

According to this thread: "FFT" has a value of 10/10 to everybody. That's idiotic.

[Fungus]

All in all I think you are just parrotting Dave here. If it has a name brand on it he immeditialy calls it a quality bit of kit  Yeah right...

You are right about the GW Instek build quality being good. Too bad it looks and works like a toy, it doesn't instill a lot of confidence in you. IMHO of course
But of course it offers a lot of bang-per-buck.
I'd rather have the R&S any day of the week. Smaller, silent, near instant boot, great clean screen and UI, excellent auto-measure mode, and just feels like a professional scope. It's "the vibe".

Yeah, but... only 2 channels.

I can understand wanting the "best vibe" scope for daily use when you've got shelves full of other scopes behind you and can easily pull out a 4-channel device for the days when you need one.

But as my only 'scope...? I'd have a problem picking something with only 2-channels, no matter what the vibe.

[markone]

@markone:
Sorry but the way the HMO is constructed WITHOUT any support for the circuit board and no fixations for the BNC connectors to the chassis is a big fail.

This is one of your criticisms with which I can agree, on the other hand if this R&S scope is actually used in educational enviroment it should not be so weak mechanical wise, anyway i'd be curious to know from david its feeling about that.

Regarding the GW Instek Dave took apart: it must be an early model because my GDS2204E has a single board with all the analog and digital electronics integrated.

Ok, this is a good news, i apologize, i was not aware about that, i assumed that your was identical to the model showed in the Dave's tear down, so my comments should be valid only for B series.

The PSU GwInstek uses isn't a flyback one but resonant and therefore it doesn't need so much shielding (it is mounted on the chassis which offers shielding BTW). Note the screendumps I posted elsewhere with the inputs open and the vertical sensitivity set to 1mV/div.

Here you have to be a little more fair, you (as other owners) complain whining noise problem coming from your scope PSU and you have to admit that its construction quality it's a bit so-so and the absence of shielding case can never be considered a positive point, also for safety reason, especially over 1K euro/usd.

There really is nothing superior about the way the HM1200 is constructed.
That is all in your mind because there is an R&S sticker on it!

Ok, on this i cannot see a compromise, we are on opposite side, i accept it.

Your notes about 'off-the-shelve' components are outright hilarious! BTW I noticed R&S uses off-the-shelve chips on their boards  But maybe R&S etched their own boards, you never know. The bottom line is: it makes sense to buy off-the-shelve components because you can concentrate on what you are good at (concentrate on your core business) and use knowledge from others (for example regarding PSUs) to your advantage.

I see the matter in another way, putting togheter off-the-shelf boards is much easier that using properly off-the-shelf chips on a custom board, the latter require much higher expertise.

The scope that Dave showed in it's tear down looks more like a young start-up product, sure not a well engineered equipment,
nothing hilarious there, if not the way the Zynq board is fixed to the rest.

R&S wasted a whole lot of money slapping a PSU together, putting it in a shielded box and get it certified where GWInstek just orders the PSUs without the headache of certifying it or (due to the PWM method) needing a lot of shielding. It is all about seeing the big picture while doing clever engineering. BTW I don't think I have ever seen a PSU designed by Tektronix themselves in any of their DSOs or logic analysers. It is not their core business so they leave it to someone else who is good at it!

Considering the complexity of what R&S produces from decades, say that they wasted a whole lot of money to design a single 12v PSU in metal shield box sounds hilarious at very best.

I'm starting to think that you never even come close to any of their products, i did, i wrote some control application for RF test benches with R&S equipment (mainly RF network analyzer &  signal generator) and i have a lot respect for them, sure not DIY toys.

[markone]

Smaller, silent, near instant boot, great clean screen and UI, excellent auto-measure mode, and just feels like a professional scope. It's "the vibe".

I agree Dave, great screen readability and very responsive UI, would be good for my tired eyes.

Taking some pics from your video i roughly measured the screen portion dedicated to waveform graph, is actually bigger than what fixed menus leave on DS1000Z screen and text fonts seems much easyer to read.

About the matter of BNC connector not directly fixed to chassis, have you spotted some mechanical weakness ?

[Muxr]

If that is what you think then you have missed the point. The point is that features on some oscilloscopes may be nothing more than checkbox items with very little practical use.

I haven't missed the point at all.

The point is that you need to assign a value to each of those features for your own personal use.

According to this thread: "FFT" has a value of 10/10 to everybody. That's idiotic.

You are making things up again. No one said FFT should be the top priority in anyone's buying decision. It's just a feature that anyone buying a scope might or might not care about. FFT has just been one example of a well implemented feature you get with R&S (and Gw-Instek) oscilloscopes.

People shopping for modern offerings in oscilloscopes can read the feature lists themselves. And can see that for instance Rigol offers everything every other scope offers for the most part. But it is important to let them know that just because Rigol has that feature, doesn't mean it's implemented as well as it is on the other scopes. Those who have used these scopes can provide this insight. This is kind of the point of coming on here and asking advice on a scope from people who have used them.

I have 1st hand experience with both Rigol and R&S scopes and I am in a pretty good position to offer advice on what you get with both products. Should I talk about similarities like the ability to terminate signals to 50 ohms, or should I talk about the differences like FFT (serial decode, UI, responsiveness..)?

Which topic do you think is more useful for someone evaluating which one of these scopes to get?

[Fungus]

You are making things up again. No one said FFT should be the top priority in anyone's buying decision.

Half (or more) of the replies in this thread have been about FFTs. 

[Muxr]

You are making things up again. No one said FFT should be the top priority in anyone's buying decision.

Half (or more) of the replies in this thread have been about FFTs. 

That happens as people delve into it. This is a technical forum people like to know the details. But it has no bearing on the importance of the feature in the overall oscilloscope package.

[Wuerstchenhund]

If that is what you think then you have missed the point. The point is that features on some oscilloscopes may be nothing more than checkbox items with very little practical use.

I haven't missed the point at all.

The point is that you need to assign a value to each of those features for your own personal use.

According to this thread: "FFT" has a value of 10/10 to everybody. That's idiotic.

I'm sorry to have to say this but the only thing that is idiotic is your statement . *No-one* in this thread has argued that the DS1000z is a bad scope or not worth buying because its FFT sucks and serial decode is poor, nor has anyone suggested that good FFT is the most important thing in a beginner's scope. Only god knows why the hell you constantly attempt to turn the discussion in a direction as if that was the case. I wonder why this is, I doubt it's a language isse so it looks like there's some kind of agenda here.

The simple point was that FFT on the DS1000z is pretty poor, and while the recent upgrade from 4k to 16k (which in Rigol's term is "High Resolution FFT Deep Memory FFT" ) is nice, it doesn't change the fact that it's still not very useful, something any prospective buyer should be aware of. Does it make the DS1054z a bad scope? Not al all. But it's one (of several) limitations which come from being a very low cost bottom-of-the-barrel scope from a Chinese B-brand. Is that really so hard to understand for you?

For me personally, 4 channels wins.

Right, and because it does so for you it seems you think this must be the same for everyone else, and you already made it clear that you seem to consider any discussion about any of the shortfalls that don't affect you personally as "silly". Talk about a person with blinkers on 

You seem have some kind of agenda here (like Mechatrommer), and that doesn't do you any favors to get across any reasonable argument or contribution you might have.

The OP wants a 5 year scope, I reckon he will have a need for 4 channels before any silly FFT. Hard to debug an SPI bus conversation with only 2 channels. Impossible to monitor the power supply, or the CS line at the same time without 4 channels. It is horses for courses. This argument about the FFT is laughable. No one is seriously using an entry level scope as a substitute for a real spectrum analyzer.

The idea that a beginner (probably the biggest audience of these scopes) will not ever want to use the scope's FFT and use a real spectrum analyzer instead is honestly utterly moronic (someone who can't afford more than a $400 scope has the funds for a real SA? Seriously?  ). The simple reality is that actually FFT is a very good aid for a beginner as it helps to understand basics i.e. that all non-sine waveforms are actually made up from a set of sine waves. It also helps to identify interference and other issues in your circuits. But for that FFT needs to implemented in a way that's actually useful. Plus having a tool to watch the frequency domain in your scope is often pretty handy, and not all frequency domain measurements are best done with a SA.

As to the four channels, yes its great but it's still a bottom-of-the-barrel scope with a sample rate that drops to 250MSa/s with all four channels enabled, which isn't enough for lots of tasks where four channels would be beneficial.

At the end of the day, it should be remembered that this is not about what we use at home, it's about helping someone else to choose a right scope within his budget that satisfies his requirements, and part of helping is that we talk honest and open about the benefits *and shortcomings*. So how about we focus on the OP's question instead?

BTW, the OP has $1200 for a scope which means he isn't forced to go for the $400 bottom-of-the-barrel Rigol, so why should he have to live with its shortcomings when he can get something better for his money?

[Mechatrommer]

I would argue that there are two major use cases for FFT, and that the Rigol scopes are not suited for the one, but very useful for the other:

• Modulated carrier, where the modulation bandwidth is typically small vs. the carrier frequency, and you want to see a narrow spectral window around the carrier. This is where large FFT windows are needed, and the Rigols (and other scopes with just a few kPoints FFT) will simply not resolve enough spectral detail around teh carrier.
• Unmodulated signal, where you want to observe harmonic content -- e.g. in acoustics, vibration analysis, to check spectral purity of an unmodulated carrier etc.. A few kPoints are perfectly fine for me to assess harmonic content in these applications, so my DS1054Z is certainly useful to me.

Hope this makes sense?

i slightly disagree. build a 3rd party software for it, it got 24Mpts nothing else in the market at the cheap. the good thing about rigol is they provide a way to download the data to PC, or maybe saved in usb drive as wfm file for later off-processing if noise leakage from pc and smps is really an issue. other brands' SDK may look interesting from the covering, but when read in detail, its not that stellar for quick off-processing job... like the one brand i recently read, it got nothing to download realtime or deep memory data into pc, all i see is remote control command that is similar to pressing buttons on the dso... btw this type of special job (RF) as you mentioned is not that frequent, so a dso tucked into a pc is acceptable on several not so frequent occasions, imho.

[Wuerstchenhund]

Wuerstchenhund, thanks for the nice demonstration of various FFT point lengths. However, I'm not quite sure what settings you used for the short window sizes. On my DS1054Z, I get much more satisfying results. The attached is for the 1kHz test signal -- I was too lazy to get the function generator out, but with regard to FFT resolution, the result should be comparable to yours, right?

No, not necessarily. You have to see the screenshots in context. They have been made on a 3Ghz 20GSa/s high end scope, and are merely an illustration of the relevance of FFT sampling points (all other parameters are static). If you look at the lower right-hand corner you'll see the frequency resolution (the same as RBW on a SA) which for that sample rate is 19.53MHz at 1kpts and 1.19kHz at 16Mpts. Obviously, because the DS1054z samples much slower it's 16k sample points will capture a longer interval, which affects the frequency resolution.

In addition, the signal I used is a 30MHz square wave on a 200MHz span. Had I used a 1kHz signal (which is 1/30000th of the 30Mhz fundamental) then the 1kpts screenshot would show a clearer FFT spectrum (essentially a roughly 19.53MHz wide spike) than it does for the 30MHz signal.

This is taken with the older SP2 firmware, i.e. the smaller FFT dataset (presumable 4k points). Normal acquisition mode; high res mode reduces the noise a little bit further, but not significantly.

The low number of sample points works OK with a low frequency signal, and because of that you'll see little change when going to a higher number of sample points. That will change however if you look at signals of higher frequency.

I would argue that there are two major use cases for FFT, and that the Rigol scopes are not suited for the one, but very useful for the other:

• Modulated carrier, where the modulation bandwidth is typically small vs. the carrier frequency, and you want to see a narrow spectral window around the carrier. This is where large FFT windows are needed, and the Rigols (and other scopes with just a few kPoints FFT) will simply not resolve enough spectral detail around teh carrier.
• Unmodulated signal, where you want to observe harmonic content -- e.g. in acoustics, vibration analysis, to check spectral purity of an unmodulated carrier etc.. A few kPoints are perfectly fine for me to assess harmonic content in these applications, so my DS1054Z is certainly useful to me.

Hope this makes sense?

Yes, it does, although the issue is not the presence of modulation but the absolute frequency of the various signal components that make out the original waveform. Acoustics and vibration analysis are pretty low frequency and for that the 16k are adequate (and you'd see little improvement from a larger FFT sample size), but you'll have difficulty appropriately resolving a MHz signal or probably even a 100kHz signal.