Year 2013 Oscilloscope Choices...

[Hydrawerk]

Well, maybe in september 2012 I wrote an email to local UNI-T dealer, http://www.tipa.eu/en/oscilloscopes-generators/c-1164/
I asked in the email if they will ever sell the new UTD 2102CM. They haven't answered till now. 

[EEVblog]

and how someone can measure their claimed wfrm/s rate to verify it (without Trig Out)

I saw a method somewhere, but i cannot find the website now. You need a special signal generator or something...

You can use a demo board that provides a known glitch every X cycles.
Then you have to run many tests timing how long it takes before the scope captures the glitch.
But this still only gives you a ballpark estimate.

[marmad]

You can use a demo board that provides a known glitch every X cycles.
Then you have to run many tests timing how long it takes before the scope captures the glitch.
But this still only gives you a ballpark estimate.

A quicker and more precise way to do it is to use a 2-channel function generator - with each channel set to create a pulse burst with the same amplitude (e.g. 1Vpp); a period inverse to the minimum wfrm/s rate (e.g. if the minimum speed expected is 100 wfrm/s, set the pulse period to 10ms); and a pulse width that is a small fraction of the period on channel 1 (e.g. 10us) and double or triple that size on channel 2 (e.g. if using 10us on ch1, then use 20 or 30us on ch2) so that the pulses can be easily visually distinguished from each other.

You then send the two source channels into one input channel on the DSO (which is running in 'Normal' mode with a short persistence) and start doing manual bursts, while adjusting the delay time between the two pulses. When there is a minimal delay between the pulses, the scope will trigger on the edge of pulse #1 - and all or part of pulse #2 will also be captured in the same acquisition, and displayed to the right of the trigger position.  As the delay time between pulses increases, at a certain point pulse #2 will disappear - falling into the dead time of the DSO. As the delay time increases even further, eventually pulse #2 will enter the second acquisition cycle of the DSO, causing a trigger, and you'll see both pulses #1 & #2 appear simultaneously on the DSO screen at the trigger position - being captured in consecutive acquisition cycles. The inverse of the delay time between the pulses at that point is the waveform update rate.

Less time-consuming than running glitch tests - but still a bit of work if you're going to catalog the different timebase settings, sample lengths, etc.

[jebcom]

hgg,

I put a couple of videos on youtube. Sorry, they're not the great quality that we're used to from Dave! The only thing I have right  now that shoots better than standard def is the iPhone 4, so that's what I used. You will notice that the measurement panel on the right washes out with very low contrast at the low angles. That's mostly from the iPhone. The contrast does go down some at the low angles, but it's still perfectly readable. I think tinhead can confirm that.

I just went from high to low on these videos. Side-to-side it is very consistent; I don't notice any change.

http://youtu.be/mslxyUvvXXk
http://youtu.be/sZSzu1XDyI0

I don't see this as looking cheap at all. In fact it's really not bad, considering the bottom scope in this line can be had for US$280 delivered, and it uses the same hardware. The photos that tinhead has posted in the HUGE thread seems to show a well-designed interior.

As you are getting started, I think you would be happy with any of the choices in your list. Of course if you can afford the Rigol 2000 and it meets your needs, go for it. But today, you won't get intensity grading on a new digital scope in the price range you have indicated. Next  year, who knows? But that might be reason to go for the low end now. The lowest cost scope here will still be a very good tool for you as you learn. (But I do agree with you that a higher res display is nice, and I do like the Hantek display.) In a few years you might see something more advanced with more features that you want, and it might be less pain to unload a cheap scope to get something more advanced.

[jebcom]

And by the way, my Hantek does have a fan, and hardly gets warm at all. Not very loud.

[hgg]

I know you have narrowed down your selection already but have you considered buying 2nd hand?

Wuerstchenhund I am open to suggestions.  The problem with the used ones is that first of all you
will not have any warranty and second that you have to trust the seller because you don't know
what you are actually getting...

There are interesting things coming out from this discussion like how to actually measure
a scope's wfrm/s even if it does not have any trigger out.

My first thought was the same as Dave's but Marmad's method looks like a more accurate
approach. 

Dave that is a nice idea for new video tutorial !

What do you say?  Maybe you can measure Rigol's ds1052e wfrm/s and see if its the same
as the specs.

jebcom thank you very much for the videos !!  The angle its not bad actually.  It can go a few
degrees beyond the horizontal with no problem.  I don't need wider angles than that.
Maybe only at the extreme the image will get dark.

Wytnucls I can't wait to hear the reply from UNI-T !

[EEVblog]

What do you say?  Maybe you can measure Rigol's ds1052e wfrm/s and see if its the same
as the specs.

he 1052E doesn't have such a spec.

[hgg]

  Strange.     I think that this spec is quite important in debugging a signal.
Maybe more important that the oscilloscope bandwidth!  You will use your
scope to find problems, not just look at nice waveforms.

What about the 100Mhz Rigol or the 2072?  Do they have the wfrm/s listed?

[Gunb]

Strange.     I think that this spec is quite important in debugging a signal.
Maybe more important that the oscilloscope bandwidth!  You will use your
scope to find problems, not just look at nice waveforms.

What about the 100Mhz Rigol or the 2072?  Do they have the wfrm/s listed?

Cheap scopes usually have less wfm/s, the reason why it often is not mentioned.

wfm/s is only important if you search for glitches / jitter, for other debugging purposes
cheap scopes are just as useful.

As attached in one of my previous comments there are very good Agilent documents where
you can calculate the probability to catch a glitch depending on the wfm/s.

By the way: even if a scope offers 1Mio. wfm/s, as long as persistence mode of the screen is
not used, it can become difficult to see it. So the real question is how often users really need
high wfm/s.

European RIGOL website has listed wfm/s for most scopes:
http://eu.rigol.com/prodserv/DS4000/property/


Kind Rgds,
Gunb

[marmad]

@hgg:

I'm sorry to have had a hand in diverting such a large portion of the thread into a discussion of waveform update rates - as a beginner, there are more important issues for you to think about than that; I just didn't want you to make a decision based on this unqualified and unverified specification of UNI-T.

One of the big reasons that people keep buying the Rigol, Owon, and Hantek models listed is because of the large support group of other owners offered by forums like this - which have developed a huge knowledge-base about the DSOs - including, in the case of the Rigol and Hantek, hacks for increasing the bandwidth for free.

As you mentioned in your opening post, the Siglent and UNI-T DSOs have not been adequately reviewed, torn apart, or examined in detail by users like the other three DSOs have, so the true positive and negative attributes of these DSOs is not known. Of course, if you want to be a trail-blazer in this regard, I'm sure there will be other prospective buyers after you who would be happy to hear your findings. For you, I think this is much more crucial to consider than wfrm/s.

[Wuerstchenhund]

Wuerstchenhund I am open to suggestions.

It very much depends on what you actually want to do with it (i.e. features you actually need and not just want to have for the sake of it) and how many channels and what bandwidth, but general suggestions would be HP's 54500/54600 Series, or Tek's TDS300/500/700 Series. With some patience and luck you might even be able to get a LeCroy 9300/9400 Series scope, or one of the Hameg hybrid analog/digital ones.

The problem with the used ones is that first of all you will not have any warranty and second that you have to trust the seller because you don't know what you are actually getting...

On the other side, that warranty may not be worth much if it means having to ship the scope back to China, and unlike modern low cost scopes (which essentially are throw-away items) much older kit can actually be fixed if required.

In addition, on the 2nd hand market you can get a mature, durable and reliable instrument made for many years of professional use instead of a product that was designed with the lowest possible price in mind.

[Wuerstchenhund]

Strange.     I think that this spec is quite important in debugging a signal.
Maybe more important that the oscilloscope bandwidth!

No, it isn't. In fact, in many applications it's probably rather irrelevant as long as as it's somewhat reasonable. The lack of high wfm rates hasn't prevented engineers from debugging fast signals in the past. It may help in certain situations (especially on scopes with limited signal analysis capabilities) but you should not get distracted by the marketing blah.

At the end of the day, the most important thing is that you understand your scope and know its limitations.

[jpb]

You can use a demo board that provides a known glitch every X cycles.
Then you have to run many tests timing how long it takes before the scope captures the glitch.
But this still only gives you a ballpark estimate.

A quicker and more precise way to do it is to use a 2-channel function generator - with each channel set to create a pulse burst with the same amplitude (e.g. 1Vpp); a period inverse to the minimum wfrm/s rate (e.g. if the minimum speed expected is 100 wfrm/s, set the pulse period to 10ms); and a pulse width that is a small fraction of the period on channel 1 (e.g. 10us) and double or triple that size on channel 2 (e.g. if using 10us on ch1, then use 20 or 30us on ch2) so that the pulses can be easily visually distinguished from each other.

You then send the two source channels into one input channel on the DSO (which is running in 'Normal' mode with a short persistence) and start doing manual bursts, while adjusting the delay time between the two pulses. When there is a minimal delay between the pulses, the scope will trigger on the edge of pulse #1 - and all or part of pulse #2 will also be captured in the same acquisition, and displayed to the right of the trigger position.  As the delay time between pulses increases, at a certain point pulse #2 will disappear - falling into the dead time of the DSO. As the delay time increases even further, eventually pulse #2 will enter the second acquisition cycle of the DSO, causing a trigger, and you'll see both pulses #1 & #2 appear simultaneously on the DSO screen at the trigger position - being captured in consecutive acquisition cycles. The inverse of the delay time between the pulses at that point is the waveform update rate.

Less time-consuming than running glitch tests - but still a bit of work if you're going to catalog the different timebase settings, sample lengths, etc.

I was planning to do this on my WaveJet that doesn't have trig out, but I've not yet acquired a function generator.

What I'd thought of doing was similar but using a ramp amplitude modulated sin wave in a burst form with the ramp up being such that a few waveforms at least would be captured and the amplitude step between captured waves would give the time step between waveforms (i.e. the waveforms per second).

You might be able to do a similar thing with a rapid frequency sweep and observing the step in carrier wave frequency between waveforms.

When I eventually get a waveform/function generator I hope to have fun experimenting.

Though on the WaveJet it captures a history of waveforms so a simple burst of say a 1000 waveforms could be used and the number actually captured just read off.

[marmad]

I was planning to do this on my WaveJet that doesn't have trig out, but I've not yet acquired a function generator.

What I'd thought of doing was similar but using a ramp amplitude modulated sin wave in a burst form with the ramp up being such that a few waveforms at least would be captured and the amplitude step between captured waves would give the time step between waveforms (i.e. the waveforms per second).

You might be able to do a similar thing with a rapid frequency sweep and observing the step in carrier wave frequency between waveforms.

When I eventually get a waveform/function generator I hope to have fun experimenting.

I was able to accomplish the same thing with a single channel AWG using a waveform consisting of a pulse at the beginning and a pulse (with greater amplitude) towards the end - and then changing the frequency of the AWG. But it was a much bigger pain in the ass to control because, of course, the pulse widths are also affected, the AWG can skip samples, etc, etc.

[Gunb]

No, it isn't. In fact, in many applications it's probably rather irrelevant as long as as it's somewhat reasonable. The lack of high wfm rates hasn't prevented engineers from debugging fast signals in the past. It may help in certain situations (especially on scopes with limited signal analysis capabilities) but you should not get distracted by the marketing blah.

At the end of the day, the most important thing is that you understand your scope and know its limitations.

Exactly, also my opinion. wfm/s means nothing when more important functions/features are missing.

[jpb]

I was able to accomplish the same thing with a single channel AWG using a waveform consisting of a pulse at the beginning and a pulse (with greater amplitude) towards the end - and then changing the frequency of the AWG. But it was a much bigger pain in the ass to control because, of course, the pulse widths are also affected, the AWG can skip samples, etc, etc.

As I've not yet had the chance to try it I've no idea if my approach would work. But the difference between your (very sensible) suggestions and my yet untried plans is that I wouldn't adjust frequency to make things disappear, I'd thought of using say a 50MHz carrier and a ramp between 1V and 5V in say 20mS then the WaveJet if it was capturing at around 1000 wf/s would capture about 20 waveforms in persistence mode (the trigger level set below 1V). The peaks increase in amplitude at the rate of 1V every 5mS so if the amplitude difference over 21 waveforms was say 3V (for arguments sake) I'd estimate the gap between waveforms as 0.75ms and the capture rate as 1,333 waveforms per sec.

Of course this is only for a time base where the 50MHz carrier would be shown well say 5nS/div.

With an arb you could perhaps use steps rather than a ramp so essentially you are translating time markers into steps in amplitude say every 10 microsecs. On the WaveJet you can go back through the history of the last 1000 captures so at slower time bases you could measure the steps even though you'd only see a blur in persistence mode.

[tinhead]

The lack of high wfm rates hasn't prevented engineers from debugging fast signals in the past.

... and some of them still wating for the first glitch appearance on the screen ... the best job protection method 

[Wuerstchenhund]

Exactly, also my opinion. wfm/s means nothing when more important functions/features are missing.

Indeed.

I also think that interpolation (or better: the lack of a facility to disable it on some scopes) is a much bigger issue than the wfm rate.

[hgg]

Exactly, also my opinion. wfm/s means nothing when more important functions/features are missing.

Indeed.

I also think that interpolation (or better: the lack of a facility to disable it on some scopes) is a much bigger issue than the wfm rate.

So do you know in which scope of the 5 you can disable it?

[hgg]

Whoever thinks that wfrm/s is not so important should state the wfrm/s of his scope...   

I am not choosing an oscilloscope based on my current knowledge on electronics.
What I want is the best oscilloscope that I can buy in that price range.
I will not be able to use all its functions in the beginning, but I am a fast learner.

So I am looking for the best one based on the criteria listed on my first post.

[marmad]

So do you know in which scope of the 5 you can disable it?

You can disable it on all 5 models. But what kind of interpolation each DSO uses - and how well they do it - is a whole different matter.

[jpb]

someone needs to produce an oscilloscope top trumps pack (see the link for those who don't remember the game)

http://en.wikipedia.org/wiki/Top_trumps

you could have

bandwidth
channels
memory
sampling rate
waveforms per second
triggering options

[hgg]

Wytnucls do you have any news from Uni-T ??

[Wuerstchenhund]

Whoever thinks that wfrm/s is not so important should state the wfrm/s of his scope...   

Which one? I don't know the wfm rate of my LeCroy Waverunner LT. The Agilent DSO9000A I often use at work apparently does 400k wfms/sec according to their spec sheet. We also have some older Agilent and Tek scopes but I can't say what their waveform update rate is. So what?

What I want is the best oscilloscope that I can buy in that price range.

The best scope is the one that does what you need it to do, reliably and without hickups.

If you actually want to use it, that is. If it's just for posing then I guess the best scope is the one with the most features.

I will not be able to use all its functions in the beginning, but I am a fast learner.

Any entry level scope should do fine for almost anything a beginner (and even many more advanced users) throw at it. When you are at a stage where you need more advanced features you will most certainly find you want a new scope anyways.

So I am looking for the best one based on the criteria listed on my first post.

which included

2) Stable firmware.

With the exception of the Rigol maybe, I don't think you find a scope without firmware issues in this price range.

At the end of the day, you get what you pay for.

[Wytnucls]

Not yet, but like others have said, you should not base your buying decision on that feature alone anyway, which is most probably optimistic at best.