Choosing between entry-level 12-bit DSOs

[2N3055]

Make note that RMS values of noise of 20MHz BW limited front end should not change, even when undersampled. Frequencies will just fold down but energy stays the same.

i dont know. if we go back to 1st principle... https://en.wikipedia.org/wiki/Root_mean_square lower RMS value means more samples are very near to best fit line vice versa, so i dont know if the noise is "non-random" resulting varying RMS, or implementation is wrong. i dont know which one.. but cases such as switching noise of smps specified in mVpp, we dont need any of RMS formula, just eyeballing down to noise floor say.. 300uVpp, not easy to achieve smps that clean. but for dut with white noise very close to dso noise floor, we need to make assumption, say dso noise is gaussian or white or blue and use appropriate formula to estimate dut noise, no need to rely on dso built-in measurement if suspected to be buggy, they are just bell and whistle. we have cursors that can help to measure Vpp as well... i dont know much details of those statistical measurements. but imho lower uV/div scale can make visual estimation easier for low noise dut. ymmv.

I'm going to try to explain: if you sample with same ADC, and make no changes in BW before ADC , when undersampling ADC will still sample undersampled frequencies with same amplitude as before, they will just "land" in a "wrong" place.
Undersampling RMS converters have been used for ages.

Your statements about how measurements are "bells and whistle", it doesn't matter if they are buggy and that eyeballing is enough is simply a cope of a person that owns a scope with defect.

Of course measurements are important and useful. What are we going to do, go back to counting lines of graticule?

Maybe problems you have with the scope are result of Frankenstein combination of running it as 900 on 800 hardware? Some people didn't have this problem, their scopes worked well.

[gf]

its possible i was activating dc+ac rms in dho800...

Seems so. The screenshots show VRMS, not AC RMS. Can happen...

[Mechatrommer]

I'm going to try to explain: if you sample with same ADC, and make no changes in BW before ADC , when undersampling ADC will still sample undersampled frequencies with same amplitude as before, they will just "land" in a "wrong" place....
Maybe problems you have with the scope are result of Frankenstein combination of running it as 900 on 800 hardware? Some people didn't have this problem, their scopes worked well.

i'm not sure why undersampling issue arised... my test was 20MHz limited at 312.5MSps... even if BW limit is not activated, undersampling due to large enough time scale can cause aliasing on any brand dso, we went through this already. i just did what ebastler asked me to do at 10ms/div. but since BW limit is on, there should be no issue.

[2N3055]

I'm going to try to explain: if you sample with same ADC, and make no changes in BW before ADC , when undersampling ADC will still sample undersampled frequencies with same amplitude as before, they will just "land" in a "wrong" place....
Maybe problems you have with the scope are result of Frankenstein combination of running it as 900 on 800 hardware? Some people didn't have this problem, their scopes worked well.

i'm not sure why undersampling issue arised... my test was 20MHz limited at 312.5MSps... even if BW limit is not activated, undersampling due to large enough time scale can cause aliasing on any brand dso, we went through this already. i just did what ebastler asked me to do at 10ms/div. but since BW limit is on, there should be no issue.

Because you originally undersampled, and when you sampled with higher sampling rate, RMS should not have changed. But in 3 measurements you had 3 different results.
For RMS undersampling doesn't matter.

Your problem is why there is 3x difference in RMS value when you change things. It shouldn't do that.
Small changes yes, but not 3 x.

As GF said, you better check same three settings but making sure you use ACRMS (stdev).
If then these same three are similar, you're OK.
I personally think it probably is something like that. Varying DC offset would explain it and that would be OK.

[Mechatrommer]

now using AC RMS.. energy not too much changing , but i guess Vpp and acRMS not measured synchronously, update rate is quite slow (1-2fps) at this timescale and memory length...

[shapirus]

What are you measuring here, anyway? I've lost the point.

Same vertical and horizontal scales, same sampling rate, same memory depth, apparently the same signal. Different trigger levels?

[DimitriP]

What are you measuring here, anyway? I've lost the point.

Same vertical and horizontal scales, same sampling rate, same memory depth, apparently the same signal. Different trigger levels?

Lost the point  "already".    It's still early!  We are only  on page 9 and we haven't even discussed :  using the probes that come with the scope vs aftermarket, high vs low impedanc,e the correct colors coding for each channel and I'm sure a plethora of other off-topic ( the topic being A or B - based on unknown uses I still don't know about yet)   derailments.


      

[Mechatrommer]

What are you measuring here, anyway? I've lost the point.

to fullfill the doubtful eyes... originally to show noise floor, but of course in real measurement we will tune and change setting when result is doubtfull, google theories etc. frankly i never reach this limit since my circuits are too much more noisy but good enough for me cheers...

[Harrow]

I think this is the common way of implementing it; certainly all entry-level scopes I have used or seen demonstrated in videos behave the same.

As long as the frozen trace follows the encoder movement smoothly and with little lag, I don't find that too bad: You can still position the frozen trace nicely relative to the grid and to the other traces. It would be much worse if they tried to continue "live" updates of the trace, but with a jerky movement.

Interesting, the FNIRSI moves the traces continuously as you turn either the vertical or horizontal encoders with the trace remaining live the whole time with virtually no lag. You just need to keep in mind that the magnitude only has 5% accuracy.

[Martin72]

Interesting, the FNIRSI moves the traces continuously as you turn either the vertical or horizontal encoders with the trace remaining live the whole time with virtually no lag.

Well, the Finirsi has something of an oscilloscope, so there's hardly anything in it that needs to be controlled.

[vk6zgo]

Make note that RMS values of noise of 20MHz BW limited front end should not change, even when undersampled. Frequencies will just fold down but energy stays the same.

i dont know. if we go back to 1st principle... https://en.wikipedia.org/wiki/Root_mean_square lower RMS value means more samples are very near to best fit line vice versa, so i dont know if the noise is "non-random" resulting varying RMS, or implementation is wrong. i dont know which one.. but cases such as switching noise of smps specified in mVpp, we dont need any of RMS formula, just eyeballing down to noise floor say.. 300uVpp, not easy to achieve smps that clean. but for dut with white noise very close to dso noise floor, we need to make assumption, say dso noise is gaussian or white or blue and use appropriate formula to estimate dut noise, no need to rely on dso built-in measurement if suspected to be buggy, they are just bell and whistle. we have cursors that can help to measure Vpp as well... i dont know much details of those statistical measurements. but imho lower uV/div scale can make visual estimation easier for low noise dut. ymmv.

I'm going to try to explain: if you sample with same ADC, and make no changes in BW before ADC , when undersampling ADC will still sample undersampled frequencies with same amplitude as before, they will just "land" in a "wrong" place.
Undersampling RMS converters have been used for ages.

Your statements about how measurements are "bells and whistle", it doesn't matter if they are buggy and that eyeballing is enough is simply a cope of a person that owns a scope with defect.

Of course measurements are important and useful. What are we going to do, go back to counting lines of graticule?

Maybe problems you have with the scope are result of Frankenstein combination of running it as 900 on 800 hardware? Some people didn't have this problem, their scopes worked well.

When we see screenshots of DSOs we don't have, often with fussy, cluttered screens, we often have to revert to counting graticule lines to obtain some sort of sane basis to compare them.

[tggzzz]

When we see screenshots of DSOs we don't have, often with fussy, cluttered screens, we often have to revert to counting graticule lines to obtain some sort of sane basis to compare them.

+1 ! It can be surprisingly difficult to locate the sweep speed and vertical sensitivity hiding in the hieroglyphs.

I like the way Horowitz and Hill present oscillograms in all editions of TAoE: the traces, with the time/div and V/div in the figure's text. Very clear to spot and understand the important features they are illustrating/explaining.

For example, compare this with an earlier screendump.
One is clear.
The other has pictures of rulers, calendars, logos, and and half-a dozen hieroglyphs that wouldn't be out of place on an ancient Egyption tomb - and you need a calculator to figure out the scales (i.e. 1.76- -0.24 ns/div and -653.184- -701.784 V/div)

[Mechatrommer]

When we see screenshots of DSOs we don't have, often with fussy, cluttered screens, we often have to revert to counting graticule lines to obtain some sort of sane basis to compare them.

+1 ! It can be surprisingly difficult to locate the sweep speed and vertical sensitivity hiding in the hieroglyphs.

I like the way Horowitz and Hill present oscillograms in all editions of TAoE: the traces, with the time/div and V/div in the figure's text. Very clear to spot and understand the important features they are illustrating/explaining.

For example, compare this with an earlier screendump.
One is clear.
The other has pictures of rulers, calendars, logos, and and half-a dozen hieroglyphs that wouldn't be out of place on an ancient Egyption tomb...

you are comparing book with years of editing, and quick screendump in forum discussion... if you are comfortable with CRT by all means stick with it, not everybody needs infinite persistence.. if its too difficult to understand, causing a headache etc... then maybe a pause time to rest... cheers

[shapirus]

if you are comfortable with CRT by all means stick with it, not everybody needs infinite persistence..

there's no infinite persistence on CRT lol. Digital scopes, however, can do it :).

But, seriously, that one was a strange comparison. Yes, the figures from the book are obviously easier to read, because there's no unnecessary information, but if you crop the scope screenshot to leave just the central section, then it'll be as easy, if not easier, to see the values indicated right on the graticule. In that particular screenshot that the post includes now (after editing) the values are hard to read, because they aren't round numbers, but the author of the screenshot had no intention to adjust them, as the purpose of the screenshot was only to demonstrate the bug where the scope shows the bottom part of the wave way below zero whereas in reality it was a unipolar signal never going below zero. Once you set them to be round, it's a piece of cake, and ready to be put in a book as is.

[2N3055]

When we see screenshots of DSOs we don't have, often with fussy, cluttered screens, we often have to revert to counting graticule lines to obtain some sort of sane basis to compare them.

+1 ! It can be surprisingly difficult to locate the sweep speed and vertical sensitivity hiding in the hieroglyphs.

I like the way Horowitz and Hill present oscillograms in all editions of TAoE: the traces, with the time/div and V/div in the figure's text. Very clear to spot and understand the important features they are illustrating/explaining.

For example, compare this with an earlier screendump.
One is clear.
The other has pictures of rulers, calendars, logos, and and half-a dozen hieroglyphs that wouldn't be out of place on an ancient Egyption tomb - and you need a calculator to figure out the scales (i.e. 1.76- -0.24 ns/div and -653.184- -701.784 V/div)

Excellent comparison of apples with crocodiles!!

[tggzzz]

When we see screenshots of DSOs we don't have, often with fussy, cluttered screens, we often have to revert to counting graticule lines to obtain some sort of sane basis to compare them.

+1 ! It can be surprisingly difficult to locate the sweep speed and vertical sensitivity hiding in the hieroglyphs.

I like the way Horowitz and Hill present oscillograms in all editions of TAoE: the traces, with the time/div and V/div in the figure's text. Very clear to spot and understand the important features they are illustrating/explaining.

For example, compare this with an earlier screendump.
One is clear.
The other has pictures of rulers, calendars, logos, and and half-a dozen hieroglyphs that wouldn't be out of place on an ancient Egyption tomb - and you need a calculator to figure out the scales (i.e. 1.76- -0.24 ns/div and -653.184- -701.784 V/div)

Excellent comparison of apples with crocodiles!!

It is, isn't it

Nonetheless, there is far too much distracting rubbish on that scope display.

Nonetheless, it does "turn up the contrast" on the sheer amount of content-free eye candy on that display. A scope ought to be a tool for giving engineering information, not a visual artwork.

The red airbrush illustrates bits of eye candy that could/should either be omitted or which could be significantly reduced. That would leave more space for the useful information.



But then magazine editors wouldn't have so much to witter about, and yoootoob unboxing "reviews" would be much shorter.

[2N3055]

When we see screenshots of DSOs we don't have, often with fussy, cluttered screens, we often have to revert to counting graticule lines to obtain some sort of sane basis to compare them.

+1 ! It can be surprisingly difficult to locate the sweep speed and vertical sensitivity hiding in the hieroglyphs.

I like the way Horowitz and Hill present oscillograms in all editions of TAoE: the traces, with the time/div and V/div in the figure's text. Very clear to spot and understand the important features they are illustrating/explaining.

For example, compare this with an earlier screendump.
One is clear.
The other has pictures of rulers, calendars, logos, and and half-a dozen hieroglyphs that wouldn't be out of place on an ancient Egyption tomb - and you need a calculator to figure out the scales (i.e. 1.76- -0.24 ns/div and -653.184- -701.784 V/div)

Excellent comparison of apples with crocodiles!!

It is, isn't it

Nonetheless, there is far too much distracting rubbish on that scope display.

Nonetheless, it does "turn up the contrast" on the sheer amount of content-free eye candy on that display. A scope ought to be a tool for giving engineering information, not a visual artwork.

The red airbrush illustrates bits of eye candy that could/should either be omitted or which could be significantly reduced. That would leave more space for the useful information.



But then magazine editors wouldn't have so much to witter about, and yoootoob unboxing "reviews" would be much shorter.

I'm glad you took my joke in good spirit.
Well I agree with you on this one. I think this Rigol interface is not very good, I don't like it either.

[shapirus]

Nonetheless, there is far too much distracting rubbish on that scope display.
[...]
The red airbrush illustrates bits of eye candy that could/should either be omitted or which could be significantly reduced. That would leave more space for the useful information.

Yes, that's what others and I have mentioned many times: this UI either was designed by a clueless kid or it was done deliberately to attract "outside" audience. It is outrageous how they waste the precious (even more so given the tiny screen size!!) space for useless crap. Especially vertical space! This damn screen is already very narrow, yet when they decide to waste screen space, they waste the vertical space. This is beyond understanding.

Borders, where they are necessary, must be 1 pixel wide. Padding around the borders must be 2-3 px wide.
Windows do not require titlebars: titles and controls can be drawn semi-transparent in the main window area.
Icons serve no purpose here, especially this small icons on a tiny screen, so they can and must be removed without any negative impact to usability.
The bottom bar has extremely thick borders and other crap, yet it lacks essential info: the currently selected probe attenuation ratio (but that's hackable btw). The "start" button could be made 1/4 the size without losing its functionality. Same for the rightmost area with status icons. With proper design, the bottom bar could fit the status panels for all the 4 channels *and* 4 math traces.

I simply don't understand. Does Rigol *really* have no money to hire a couple of decent UI/UX specialists with engineering background? Or was it a deliberate political decision to shove this kind of toy UI into an engineering instrument and they really think it's the way it should be?

[ebastler]

It is outrageous how they waste the precious (even more so given the tiny screen size!!) space for useless crap. Especially vertical space! This damn screen is already very narrow, yet when they decide to waste screen space, they waste the vertical space. This is beyond understanding.

If you want to waste some horizontal space for better balance, switch on the hardware counter. 

[tggzzz]

Modern GUI design tends to be crap. Gray characters. Flat, so you can't tell whether a widget is a control or an indicator or neither. Does a white "On" On a black background mean it is on or should be clicked.to turn on?

I haven't bothered to critically examine Siglent screens, but that screen puts me off buying Rigol. That's a shame, because I prefer to select/reject items based on core functions, not on superficial glow such as the colour of the case.

[shabaz]

The Rigol screenshots looks good from far, but far from good, it is breaking some conventions, like there's no need for the orange text*, it should (if needed) be exactly the same as everything else, because orange sticks out for no reason, it's not a selected item. The text sizes seem unnatural, like the digits 1-4 for the channels, only needed to be slightly larger than the remainder text, and not massively larger, and large+bold combined just feels wrong!

Now that things like custom zoom windows are becoming popular with 12-bit 'scopes, I've noticed some of the same problems regarding quickly identifying the division values. My older 'scope didn't need that since it had no similar zoom windows. And it's especially harder on those without the same 'scope, because you don't want others to waste time scanning all the periphery only to find that information isn't there.

Even though the larger-screen MXO 4 is ordinarily clear to read with very little clutter, when zoom windows are added based on user-defined window sizes (i.e. a dragged custom rectangle) then it can for sure take some mental time to figure out what the scales are. I've taken to manually post-annotating, since then I can make it as clear as I can, or bring things to attention with an arrow etc.

The instrument internally supports annotations, but I prefer some consistent shapes/styles, so I prefer to do it myself in PowerPoint etc. Helps others because they can see the annotations have whatever context you wish to include. I did the same with older 'scopes, i.e. glue a 'scope trace in a lab book, and draw arrows etc manually.
But many people just dump 'scope traces with no markup : (

Maybe instrument built-in preset annotations for time/div and volts/div could be useful though, i.e. allow the user to drag-and-drop the annotations in a clear part of the display, or in a single inset box just listing both of these, e.g. "75 mV/div, 1.16 ns/div". I might raise it as a feature request for MXO anyway, in case it gets taken up.

* Also, H,A,D,T feel meaningless. Takes longer to interpret them as Horizontal, Acquisition, etc., than if they were totally omitted and people could see the meaning from the units alone (e.g. ns/div etc) or smaller full text like the MXO 4, but appreciate that might not be possible on the smaller screen Rigol.

[Harrow]

Interesting, the FNIRSI moves the traces continuously as you turn either the vertical or horizontal encoders with the trace remaining live the whole time with virtually no lag.

Well, the Finirsi has something of an oscilloscope, so there's hardly anything in it that needs to be controlled.

Haha, yes, I was going to say it's not doing much else so it should be able to manage at least that. 

[tggzzz]

* Also, H,A,D,T feel meaningless. Takes longer to interpret them as Horizontal, Acquisition, etc., than if they were totally omitted and people could see the meaning from the units alone (e.g. ns/div etc) or smaller full text like the MXO 4, but appreciate that might not be possible on the smaller screen Rigol.

Squeezing the important information onto a limited display isn't a new issue. It was addressed successfully in the '80s by many pieces of equipment from many manufacturers. Start with scopes, spectrum analysers, logic analysers, ... from LeCroy, TK, HP....The

Why can't today's weenies do better?

[Harrow]

It is outrageous how they waste the precious (even more so given the tiny screen size!!) space for useless crap. Especially vertical space! This damn screen is already very narrow, yet when they decide to waste screen space, they waste the vertical space. This is beyond understanding.

My guess is that the designer is probably working on their 32-inch monitor and is probably 24 years old, so when they check it on the 7-inch screen and are already familiar with what they are looking at, it looks fine to them. Would also be a product of maintaining 'look and feel' across their product lines that have larger screens?

Unfortunately, marketing has overtaken engineering principles in just about every industry. I bought a kitchen appliance recently that has about 30 presets that are totally useless and just make the device harder to use. Give me two adjustments, temperature and time, to set. But then you couldn't print "30 Presets" on the box to outdo the other brand that only has 25 presets.

Anyway, I'll have the Rigol later this week, so I'll be able to give my unbiased viewpoint very soon. I wonder how it will match up against the FRINSI? 

[shabaz]

Agree. For instance, HP spectrum analyzers packed all manner of useful information within a low-res monochrome printout.
The Rigol display should be able to do far better, I'm speculating, but it's possible they are using GUI frameworks intended for much higher-res larger displays, and that's causing the very awkward look/feel.