Why don't you tell us, Mr. self-appointed Rigol expert? The schematic is out there.I've never claimed to be a Rigol expert. I'm a USER of this model scope-- at least I try to use its features and functions, in spite of its many problems. My post points out that we may not be justified in having supreme confidence in the hardware design, bearing in mind the many software problems that plague this model scope.
Why don't you tell us, Mr. self-appointed Rigol expert? The schematic is out there.I've never claimed to be a Rigol expert. I'm a USER of this model scope-- at least I try to use its features and functions, in spite of its many problems. My post points out that we may not be justified in having supreme confidence in the hardware design, bearing in mind the many software problems that plague this model scope.
The problem being discussed applies to many more oscilloscopes than Rigol but you came in here with your usual Rigol-bashing post.
(and not just oscilloscopes, it's a general problem with op-amps)
Scopes have horizontal zoom functions, why not vertical? Why not capture scope at 1V/div, and display it at say 100mV/div?
If still you think making measurements with periodically clamped signals is an invalid use-case of a oscilloscope, please explain a productive (not just functional) way to make said measurement without fiddling around the knobs half a dozen times every trigger attempt. Because in my experience these are user error prone and frustrating to do.
Reading some of the comments here make me almost cry inside because of it's ignorance.
If still you think making measurements with periodically clamped signals is an invalid use-case of a oscilloscope, please explain a productive (not just functional) way to make said measurement without fiddling around the knobs half a dozen times every trigger attempt. Because in my experience these are user error prone and frustrating to do.
Scopes have horizontal zoom functions, why not vertical? Why not capture scope at 1V/div, and display it at say 100mV/div?
Reading some of the comments here make me almost cry inside because of it's ignorance.
If still you think making measurements with periodically clamped signals is an invalid use-case of a oscilloscope, please explain a productive (not just functional) way to make said measurement without fiddling around the knobs half a dozen times every trigger attempt. Because in my experience these are user error prone and frustrating to do.
Scopes have horizontal zoom functions, why not vertical? Why not capture scope at 1V/div, and display it at say 100mV/div?General DSO comments, all brands.
1 Know the limitations of your instrument.
2 Learn the capabilities of your instrument.
3 For accurate representation of waveforms keep them within the confines of the display at all times.(excepting captures)
4 The triggering suite in your scope is the most powerful tool you have, use it.
5 Before connection attempt to deduce the waveform you expect and set the scope accordingly.
6 If all this is above you use Autoset.
To get real info from any scope you must drive it, yes there are several knob adjustments required, learn them.
Edit
Added "DSO"
I think you misunderstood the meaning of my post.
Having to fiddle 6 knobs to make 1 measurement, and then doing it all over again 2 minute later after a change is not productive. That is my view on it anyway - I'm fine turning all the knobs a hundred times on an oscilloscope to find, lock and explain the details I am looking for (I disgust auto set), but not when I'm measuring 1 quantity repeatably in a very limited changing environment while still needing to make adjustments back and forth for the scope to work. This level of interface is maybe acceptable for some, but not for me.
Like I said, a vertical zoom level would be most helpful. Unfortunately the Rigol does not have this feature (like nctnico explained) - changing vertical settings in "zoom" mode also changes vertical level of acquisition. In the test signal I referred to, the dynamic range of interest is only 1:25 or so (there are other current pulses swamped in the noise of the scope though). 1:25 is still measurable on a 8-bit ADC, but not good for eye fatigue if you want to make horizontal measurements on 1/5 of a division.
Unfortunately, my measurement shows the limitations of the oscilloscope very clearly. I can't have vertical acquisition zoom in, or it will cause overdrive and make any measurements post-overdrive impossible. If I don't zoom any, any horizontal measurements are hard to make (unless the turning-a-dozen-knobs-every-2-minutes story), and vertical are downright inaccurate to any satisfactory level (unless you want >10% error).
Why don't you tell us, Mr. self-appointed Rigol expert? The schematic is out there.I've never claimed to be a Rigol expert. I'm a USER of this model scope-- at least I try to use its features and functions, in spite of its many problems. My post points out that we may not be justified in having supreme confidence in the hardware design, bearing in mind the many software problems that plague this model scope.
The problem being discussed applies to many more oscilloscopes than Rigol but you came in here with your usual Rigol-bashing post.
(and not just oscilloscopes, it's a general problem with op-amps)
My point, which you seem deliberately to miss, is that this usage might even put the RIGOL DS1054z scope's inputs at risk of permanent damage, which is not likely to be covered under warranty, as it is a misuse or user error. Do YOU have the confidence to test YOUR DS1054z with a maximum voltage input, then zooming in to extremely sensitive vertical resolution? If you do, fine, demonstrate it. I base my _lack_ of confidence and my caution on my experience with the scope. Go ahead and prove that my lack of confidence is not justified, by performing your own tests and demonstrations and reporting them, on your RIGOL DS1054z.
Look again. Start with the discrete components in the input stage signal path. Then move onto looking inside the ICs such as the LMH6552 (or similar), and others.
Hint: all oscilloscopes have multiple amplifiers, some in series and some in parallel.
QuoteApart from that, I'm pretty sure even the Rigol DS1000Z will have some clamping diodes at the input - just clamping to the supply rails instead to a specific voltage level that prevents the amplifier from leaving its specified common mode range.
They do have diodes, just like other low-end scopes. But they are nothing whatsoever to do with common mode ranges.
Have a look at ... or similar; if you spot what you are thinking of, please point to it.
Maybe.
You mean this post?
https://www.eevblog.com/forum/testgear/new-rigol-ds1054z-oscilloscope/msg868911/#msg868911
Me too.
But there are other ways to make these measurements.
100:1 probes
Current probes.
[..]
Filters can be useful.
I disagree.
Not all instruments will easily deliver the measurements you need, when they don't/won't it's time for other solutions and they might include investment in other scope accessories.
Most measurement is easy, how you solve the trickier ones is partly experience, available tools and full use of the functionality within your scope.
But there are other ways to make these measurements.
100:1 probes
But there are other ways to make these measurements.
100:1 probes
Current probes.Yes there are alternatives and supplements to measurements units. Unfortunately, as a hobbyist on a budget, I do not have access to those. Hence the purchase of a "budget" 4-ch scope like the Rigol DS1000Z.
Most measurement is easy, how you solve the trickier ones is partly experience, available tools and full use of the functionality within your scope.
Yes I can see what you're trying to say. The scope is a powerful instrument because of the 'many knobs' and supplements available.
Arguably this scope is not the best weapon of choice for my measurement......
But there are other ways to make these measurements.
100:1 probes
Well, it is just worst with 1:100 probes. Here are the limits, when this phenomenon starts to occur (again, HMO1002), 0-10 V, square wave:
BNC: 242 mV -> 8.1x zoom
1:10: 121 mV (adjusted value to the probe) -> 16.2x zoom
1:100: 1.21 V (also adjusted)-> 1.6x zoom
In this regard and range, the 1:100 probe is the worst by far, actually, you can't zoom 1 step without distortions. With the 1:10 probe, however, I have pretty awesome range without any distortions, and after that the distortions are much smaller than with straight connection.
Which essentially means, this vertical zooming method is perfectly works in a useful range with 1:10 probes. I don't have 300 V square wave to test, sorry, there are no problems with mains, though
Here are the limits, when this phenomenon starts to occur (again, HMO1002), 0-10 V, square wave:
BNC: 242 mV -> 8.1x zoom
1:10: 121 mV (adjusted value to the probe) -> 16.2x zoom
1:100: 1.21 V (also adjusted)-> 1.6x zoom
Look again. Start with the discrete components in the input stage signal path. Then move onto looking inside the ICs such as the LMH6552 (or similar), and others.Why should I do this? If there are active discrete components not just dedicated to some auxiliary task, well, then there is a discrete amplifier, but it’s still just an amplifier.
Well, some scope vendors don't need to, as with proper design all these nasty things will not happen in the first place. It's just a matter of having a proper limiter at the input of the amplifier, preventing it to get overloaded.
Plus, of course, there are many amplifiers in a scope, any of which could be overloaded. "Protection" would require many non-linear elements in the signal path, which is even more problematic!No, there aren't. Neither many amplifiers, nor particular non-linear elements.
The LMH6552 is just a differential amplifier – albeit a very good one. Neither does the datasheet include any circuit details for its proprietary differential current mode input stage architecture, nor do I get the point why to analyze the internals of an IC, all the more so as it’s not even used in the Rigol DS1000Z.
In a scope like the DS1000Z, we have a total of two amplifiers: the input buffer and the PGA.
Anything else not in the signal path, like all the amplifiers dedicated to the DC offset generation, is purely auxiliary and irrelevant when we’re looking for distortion.
QuoteHint: all oscilloscopes have multiple amplifiers, some in series and some in parallel.Hint: While you can connect any two-terminal-pair networks in series or parallel in principle, I have never seen any practical application of this with amplifiers in a scope.
So we’re rather talking about cascading amplifiers, when we connect the output of the first one to the input of the next one.
And we use split-path amplifiers if we have to process several frequency bands differently, such as in a scope frontend where we want to have wide bandwidth and high DC accuracy at the same time – a principle introduced by Tektronix in the early 70s of the last century.
So we still have a total of two amplifiers: A split path input buffer and a PGA.QuoteQuoteApart from that, I'm pretty sure even the Rigol DS1000Z will have some clamping diodes at the input - just clamping to the supply rails instead to a specific voltage level that prevents the amplifier from leaving its specified common mode range.
They do have diodes, just like other low-end scopes. But they are nothing whatsoever to do with common mode ranges.
Diodes have nothing to do with low end. Rigol resembles pretty closely what has been published by Tektronix around 1971, who of course have used protection diodes as well - and these scopes were certainly high end back then.
Other than that, not sure why you felt like repeating what is already quoted, i.e. that there are most likely diodes, but only for the sake of input protection. And of course, for a single ended JFET buffer, there is no common mode range. But for any differential amplifier there is.
Anyway as I had a closer look in the meantime, it might be that the DS1000Z only protects the discrete HF path, but leaves the LF path (with the OpAmp) alone. But on the HF path they might have even done the right thing, as the diodes are actually used as limiters here. Only question is, if it always works as intended, given the high manufacturing tolerances of the JFET behind.
This could explain why the distortion effect is worse at lower frequencies, as the OP seems to indicate.
Maybe someone could test this at frequencies >10MHz?QuoteHave a look at ... or similar; if you spot what you are thinking of, please point to it.I had a look at the schematics – and I might post some analysis later.
Here are the limits, when this phenomenon starts to occur (again, HMO1002), 0-10 V, square wave:
BNC: 242 mV -> 8.1x zoom
1:10: 121 mV (adjusted value to the probe) -> 16.2x zoom
1:100: 1.21 V (also adjusted)-> 1.6x zoom
@tautech, I wonder, how the SDS2000X behaves with the above premises. I am still looking for a 4ch scope
You sound defeated, you shouldn't be, think of it as a challenge and the opportunity to learn new tricks.
I can't see any reason why you can't get the measurements you require with any reasonably modern DSO like the 1054, really I can't.
From the images I've seen there are several levels and durations of current pulses, each of which can be targeted with trigger levels and/or pulse duration trigger settings to obtain Single shot captures than then can be analysed.
This is how I've broken down my measurement requirements in the past with DSO's far less capable than a 1054.
The problem being discussed applies to many more oscilloscopes than Rigol but you came in here with your usual Rigol-bashing post.
(and not just oscilloscopes, it's a general problem with op-amps)As alsetalokin4017 owns one, has found bugs in it, struggles with trust of it, has documented such, he has more right than most to offer comment. That you take it as personal is a surprise are you Rigol's knight in shining armour?
Having to fiddle 6 knobs to make 1 measurement, and then doing it all over again 2 minute later after a change is not productive. That is my view on it anyway - I'm fine turning all the knobs a hundred times on an oscilloscope to find, lock and explain the details I am looking for (I disgust auto set), but not when I'm measuring 1 quantity repeatably in a very limited changing environment while still needing to make adjustments back and forth for the scope to work. This level of interface is maybe acceptable for some, but not for me.