Rigol DS 1054Z behavior: normal or defective? - Page 1
Forum section: electronics / testgear

author: ballen
author_rank: Regular Contributor
timestamp: November 26, 2020, 07:57:36 pm
content: Hi All,I've been doing electronics as a hobby since I was a teenager 40+ years ago, and decided it was finally time to retire my 1970s Tektronix 2-channel CRT scope. After a few minutes of on-line research I ordered a Rigol DS 1054Z (with 24 Msamples memory and all possible options enabled the price was still low) which arrived earlier today. I've been playing around with it for a couple of hours, and am impressed by what it can do.One odd thing I have noticed: if I look at the built-in calibration signal (1kHz square wave, 3v amplitude) the horizontal traces at 0 and 3v look broader than in the manual. If I zoom in on them, I can see that they are each made of a pair of lines of equal brightness, separated in amplitude by tens of mV. I'm not sure how many bits are used internally, but I guess this might be quantization noise from the input ADC. I can also see this if I (electronically) ground the input. I would have hoped that the electronics noise at the input is not enough to dither the ADC. I've also noticed that as I shift the position of the trace vertically, the relationship between the two lines shifts and distorts.My question: is this behavior "normal" or did I get a scope with a bad input amplifier or noisy ADC? Easy to send it back now, if that's the case.Cheers,BruceEdit: when I shift the vertical gain from 500mV per division to 200mV, I can hear a relay click shut internally. That's when the shape of trace near zero distorts and becomes dependent on the Y-axis offset. I don't think this should happen, is it "normal"? Also, I can see the doubling of the horizontal trace lines when the gain is set so that 3V is full scale, so it's got to be at least 30 mV, meaning that it's in the 8th or 9th bit of an ADC.Here's a photo of the calibrator signal, I have turned off the display grid to make the structure more visible:

author: Fungus
author_rank: Super Contributor
timestamp: November 26, 2020, 08:35:41 pm
content: Quote from: ballen on November 26, 2020, 07:57:36 pmYes, it's normal. It's an aliasing effect from decimating a small sine wave.https://www.eevblog.com/forum/testgear/help-my-new-rigol-ds1054z-shows-a-weird-double-trace/msg1363145/#msg1363145

author: ballen
author_rank: Regular Contributor
timestamp: November 26, 2020, 11:33:54 pm
content: Thank you for the link -- it is exactly the issue that I see.I read through the thread, and it appears that you and the original poster see this behavior, but that another person with a DS1054Z (emocabras) did not.I don't see how aliasing (in the traditional sense of sampling a signal with power beyond the Nyquist frequency of half the sample rate) would produce this. And if I insert a 20MHz filter (here Nyquist is 500 Mhz) the problem persists.A simpler explanation would be if the scope use two interleaved ADCs and they have slightly different zero points. Do you know if that's the case? That would also explain why the size of the effect is different in the two cases reported in the thread.

author: Fungus
author_rank: Super Contributor
timestamp: November 27, 2020, 08:06:29 am
content: Quote from: ballen on November 26, 2020, 11:33:54 pmIt's not aliasing on the ADC/signal, it's aliasing together with quantization errors in the screen display algorithm.Whatever it's doing in the display subsystem is get a disproportionate number of dots at top/bottom. At some zoom levels it looks like two lines on screen.Quote from: ballen on November 26, 2020, 11:33:54 pmThe 'scope only has one ADC so that's not it.

author: 2N3055
author_rank: Super Contributor
timestamp: November 27, 2020, 08:46:11 am
content: Quote from: ballen on November 26, 2020, 11:33:54 pmTry performing Self calibration.Any time temperature changes more than few degrees C from last call, you need to perform Self Cal.It should align any misalignments.Also, you should try doing same measurement using external, independent signal source. Relaxation (RC) oscillator with 74HCT14 will do and can be made in 10 minutes, dead bug style.Quote from: Fungus on November 27, 2020, 08:06:29 amNot quite accurate.. It does have 1 A/D chip, but... HMCAD1511 consists of 4 interleaved A/D converters internally, 250 MSPS each. They have fine gain adjustments for each individual converter.Calibration is not automatic inside chip, scope performs it during self cal, and then sets gain coefficients for HMCAD chip. .

author: ballen
author_rank: Regular Contributor
timestamp: November 27, 2020, 10:34:25 am
content: Quote from: Fungus on November 27, 2020, 08:06:29 amI'm afraid that I don't understand that either. The display has a resolution of 600 pixels in the vertical direction. The ADC (I just googled, Analog Devices HMCAD1511 with 8 bits) has 2^8=256 different output values and with built-in digital gain it should be able to resolve this 0 to 3V signal into (say) 200 distinct values, which would be at most 3 pixels wide. The two lines I am seeing are separated by much more than 3 pixels.Another way of stating my ignorance: when the calibration signal is at 0V with (say) a mV of noise, the 8-bit ADC should be producing the same value for each sample. The scope should display those values at the same height. If there is dither, one ought to see two values displaced by a few pixels. So I don't understand what "aliasing together with quantization errors in the screen display algorithm" means.Edit: I just saw the reply that the ADC is actually four interleaved ones. An offset there would explain it. I will try running the calibration signal into all four channels.

author: ballen
author_rank: Regular Contributor
timestamp: November 27, 2020, 11:05:05 am
content: Quote from: 2N3055 on November 27, 2020, 08:46:11 amDid that, made no difference.QuoteOK, I'll hook it to the calibration signal of my Tex scopeQuoteI ran the full auto-calibration yesterday (took quite a long time) but that made no difference.I tried running all four channels together, and that indeed changes the "double-valued" behavior. So I think the issue is that the four A/D have different offsets and these are not correctly compensated. When each A/D is assigned to its own channel, then the double-trace goes away for certain values of the vertical position offset, and is present (dithering?) for other values of the position offset. Fungus, could you try this on your scope, to see if using all four channels make a difference?One last question: it appears that the ADC is 8 bit but the Rigol specs say "up to 12 bit resolution". They could get the additional four bits by summing sets of 16 samples, which could be done at speeds of up to 64 Msamples/second. Is this done in software? I could see two ways of doing this. One is "postprocessing": acquire at 1Gs/second, then afterwards sum groups of 16 samples. The other is "realtime", so sum groups of 16 samples as the ADC is running, and only record those samples into memory at 64MHz. Does the scope do either/both of these?

author: Fungus
author_rank: Super Contributor
timestamp: November 27, 2020, 11:10:42 am
content: Quote from: ballen on November 27, 2020, 10:34:25 amYes, there's noise on the input. It's not just the lowest bit of the ADC.

author: Fungus
author_rank: Super Contributor
timestamp: November 27, 2020, 11:14:35 am
content: Quote from: ballen on November 27, 2020, 10:34:25 amLook at this image:The un-zoomed version (top half of the screen looks horribly wrong. The zoomed version (bottom of the screen) shows the samples.Where did the two separate lines come from? From whatever algorithm is being used to generate the un-zoomed image.You want to fix it? Push the Acquire button and turn on "Average" in the Acquisition Mode.Will it affect you in reality? No, because you'll hardly ever look at a signal that way, see next part.Quote from: ballen on November 27, 2020, 10:34:25 ama) Note that you're really zoomed in and most of the signal is off screen. This means you're pushing the outer limits of the vertical amplifiers, etc., which is never a good idea because you get into a whole class of problems with amplifier overloading and recovery times onanyoscilloscope (although I'm sure those $10,000 'scopes will have better opamps!)b) By pushing the limits of the opamps youmightalso be revealing tiny differences in calibration between ADCs. This would explain why everybody sees something different when they try this.In practice it won't affect you. Most owners never even noticed their 'scope does this. I never noticed it until it was pointed out in that other thread.

author: Miti
author_rank: Super Contributor
timestamp: November 27, 2020, 12:29:51 pm
content: Nope, I don't see this. Not even when the top side is way out of screen.

author: tom66
author_rank: Super Contributor
timestamp: November 27, 2020, 01:09:45 pm
content: I'm unable to replicate this on my old DS1074Z running 00.02.03.SP5 (not upgraded since I bought it)

author: 2N3055
author_rank: Super Contributor
timestamp: November 27, 2020, 02:41:09 pm
content: Quote from: Fungus on November 27, 2020, 11:14:35 amWhen I had 1000Z I never had that problem at any range.. it was 2016 vintage...

author: Fungus
author_rank: Super Contributor
timestamp: November 27, 2020, 03:41:54 pm
content: Quote from: 2N3055 on November 27, 2020, 02:41:09 pmLike I said, it takes a particular combination of signal/noise/zoom. You might have had it but never noticed.(or lived in a place where it doesn't happen).

author: tooki
author_rank: Super Contributor
timestamp: November 27, 2020, 04:43:53 pm
content: Quote from: Fungus on November 27, 2020, 03:41:54 pmBut even assuming a particular combination of conditions enabled this bug, the conditions shown in the image aren’t it: that’s a simple view (auto, then scaled back one detent of the horizontal scale) of the built in calibration signal, which most definitely shouldnotproduce double traces.

author: Fungus
author_rank: Super Contributor
timestamp: November 27, 2020, 07:00:52 pm
content: Quote from: tooki on November 27, 2020, 04:43:53 pmNope. It's set to 20mV vertical. The full signal is way off screen (150 grid squares tall!)Quote from: tooki on November 27, 2020, 04:43:53 pmIt's not a double trace when you zoom in, it just looks like one when you zoom out due to a quirk in the decimation for that particular signal.

author: 2N3055
author_rank: Super Contributor
timestamp: November 27, 2020, 07:40:44 pm
content: Quote from: Fungus on November 27, 2020, 07:00:52 pmWe are talking about OP. His photo shows simple 500 mV/DIV with scope probe calibration source connected. Nothing off the screen, no zoom, nothing.. And double lines clearly visible. That is wrong.

author: Fungus
author_rank: Super Contributor
timestamp: November 27, 2020, 08:14:12 pm
content: Quote from: 2N3055 on November 27, 2020, 07:40:44 pmOh, duh! I hadn't spotted that.Yeah, that's not good. I retract all posts.Send it back!

author: ballen
author_rank: Regular Contributor
timestamp: November 28, 2020, 07:51:06 am
content: In the photo attached to my original starting post in this thread, there are three "non-standard" settings, intended to make the effect clearer and to prevent my camera from saturating. Miti, Tom66, could you please try this one more time but with exactly the settings I have used? To ensure this, first set the scope to default settings by puttingUtility->System->Power Set=default and power cycle.Then input the calibration signal on channel 1, use "Auto" to pick trigger/timing/gains, and setDisplay->Type=dotsDisplay->Grid=offDisplay->Intensity=25%Last step, shift the vertical position up and down. I am starting to think that what I am seeing here is just the discrete quantization of levels from the 8-bit ADC. Meaning: I have the vertical position set so that the max and min square wave values split between two adjacent ADC output steps, and the display algorithm has each ADC output step illuminate only half the pixel height to the next output step. Hence a black band appears between adjacent ADC levels.

author: tautech
author_rank: Super Contributor
timestamp: November 28, 2020, 08:19:30 am
content: Quote from: ballen on November 28, 2020, 07:51:06 amI doubt this.SDS1104X-E with those settings ^ and imperfectly compensated probe.The Rigol pusher in this forum Fungus has told you to quit it...take his advice.

author: ballen
author_rank: Regular Contributor
timestamp: November 28, 2020, 09:24:18 am
content: OK, another theory, the ADC has a broken bit or bit combination. For example here is a screen shot showing some power supply noise (a few mV) AC coupled on the output of a power supply. Notice the horizontal black striped bands -- it's as if some ADC output combinations are missing. Hard to imagine that this could get past QC at either the chip fab or at Rigol.

author: ballen
author_rank: Regular Contributor
timestamp: November 28, 2020, 09:28:29 am
content: Quote from: PeDre on November 28, 2020, 09:22:57 amPeter, thank you, this would indicate that my scope is "normal" rather than "defective". The stripes seem to be discrete ADC output levels, normally hidden in vector mode.

author: Fungus
author_rank: Super Contributor
timestamp: November 28, 2020, 10:54:52 am
content: Quote from: ballen on November 28, 2020, 09:24:18 amThat's normal in dots mode. The ADC only has 200 values and the screen has 400 pixels. There's also all sorts of amplification in between.Bottom line: Don't use dots mode. The display is only valid when the dots have been mathematically reconstructed.(A lot of more expensive 'scopes don't even have dots mode...it's an anachronism)

author: rf-loop
author_rank: Super Contributor
timestamp: November 28, 2020, 12:17:36 pm
content: Quote from: PeDre on November 28, 2020, 09:44:06 amThis your image Ch2 is because afaik it do not have at all true 500uV. Its is just "pixel" zoom. There is roughly only 100 steps in screen vertical area. Other v/div have 200 steps.

author: TurboTom
author_rank: Super Contributor
timestamp: November 28, 2020, 12:58:09 pm
content: It's true, the highest sensitivity that the DS2000 series of scopes features is 1mV/div, the 500µV/div is just a magnification witout additional sampling data.The funny thing is: these "double trace effects" on the Rigol scopes appear to be an artefact of the way the intensity grading on these machines is processed. It seems that almost right from the beginning after release of their "UltraVision" intensity grading engine, there's been a bug (feature??) in it that as yet didn't get addressed: When the sampling memory gets decimated (horizontally) to fit the screen resolution, the samples that represent a position on screen get summed up / averaged, which makes sense of course. It's just that if this summing up overflows the size of the summing memory that rigol chose, the corresponding pixel gets set dark instead of maximum brightness. So what's visible on screen when displaying a (gaussian) noisy signal, is two bright bands where the sum just doesn't overflow, and a dark region in between, where it does overflow. This effect can be easily demonstrated when taking a single shot of a noisy signal at slow time base where the effect is visible, and then zooming in with the timebase. The effect disappears and the trace looks completely normal, with a proper density distribution as one would expect from a noisy signal. See the attached screenshot to get an idea of what I mean. I guess Rigol should look into their display engine's basic algorithms... But to just correct the "intensity overflow clipping" shouldn't be too difficult.Edit: Added another screenshot with a noise signal from an AWG fed to the input of the scope. In order to demonstrate this effect, a high sampling memory depth is required.

author: Miti
author_rank: Super Contributor
timestamp: November 28, 2020, 01:33:30 pm
content: Quote from: ballen on November 28, 2020, 07:51:06 amYes, I see the two lines now.

author: tom66
author_rank: Super Contributor
timestamp: November 28, 2020, 05:05:19 pm
content: The probable reason Rigol don't do what you suggest is because it would require using saturating arithmetic, which adds additional logic to the FPGA. I have considered how to solve this problem for some time and it seems that you realistically need 12-14 bit depth accumulators which is quite memory and logic expensive. Rigol use an external SRAM chip of ~4Mbit attached to the FPGA to do the render task. Many FPGAs have only half that much BRAM on the chip itself. Using SRAM means they can do random read and writes with little penalty but the part they use is at least $20 (from memory) on Digi-Key so no doubt a significant BOM expense.

author: ballen
author_rank: Regular Contributor
timestamp: November 28, 2020, 06:22:23 pm
content: I'm not sure that I can live easily with this - I have spent most of my life with analog scopes and want to be able to trust what I see and not wonder if it's an artefact of the scope. So if there is a single voltage I'd like to see a single thin horizontal line. A thicker line means that there is hash or noise on it. If a waveform is spending most of its time in a particular region, that region should be brighter not darker.Do other entry-level digital scopes behave this way? The second most popular model comparable to the Rigol is the Sigilent SDS1104X-E, which costs about an extra 30 Euros. Does it not have these peculiarities or other such issues?

author: tom66
author_rank: Super Contributor
timestamp: November 28, 2020, 06:37:17 pm
content: Every digital scope is lying to you.The Rigol also aliases and it appears some firmware versions have a timebase bug causing times to be off between 4-8%.Other scopes have bugs too. If you want the scope to behave identically to an analog scope you will, unfortunately, be disappointed. However, the chance of these bugs causing anything other than curious EEVBlog posts is close to nil.Despite its limitations the Rigol DS1074Z I have has been a trusty workhorse for the last 5 years. I used it during my masters' degree, in the office and on personal projects. Most recently, I used it to analyse the performance of a >1Gbit/s serial bus with some little tricks. Despite it being a sub-$600 scope, I've never found it lacking in performance - it punches well above its weight for its class.I know there's a trend towards Siglent on this forum and that's fair, they make good kit too (I really liked the SDS5000X we had in for evaluation) but haven't personally tried using any of their lower end scopes. The Rigol definitely has a few more limitations that Siglent have fixed on their instrument.

author: Fungus
author_rank: Super Contributor
timestamp: November 28, 2020, 07:24:17 pm
content: Quote from: ballen on November 28, 2020, 06:22:23 pmFirst of all: Don't use dots mode. Ever. There's people here who imagine they can squint their eyes and see something but it's not true. It doesn't tell you anything useful. The true signal comes from applying a reconstruction filter to those dots.Secondly: Learn to use the settings under acquisition. If it's a simple repetitive signal then you can set "average" mode to get a pixel perfect trace on screen. The other modes can reduce noise, etc.Thirdly: I don't recall ever seeing a double line on my DS1054Z without weird settings.

author: Fungus
author_rank: Super Contributor
timestamp: November 28, 2020, 07:26:37 pm
content: Quote from: tom66 on November 28, 2020, 06:37:17 pmUsually the lies are small.Quote from: tom66 on November 28, 2020, 06:37:17 pmYep. The Siglent bug thread is busy, the Keysight bug thread is busy, the Rigol bug thread is busy.Quote from: tom66 on November 28, 2020, 06:37:17 pmYep. But I get accused of things if I say that.

author: Miti
author_rank: Super Contributor
timestamp: November 28, 2020, 08:03:16 pm
content: Quote from: ballen on November 28, 2020, 06:22:23 pmYou're in the first stages of change, see the attached graph. Change the angle of view, don't let few quirks blind you. All DSOs have their issues, even the expensive ones but they are the present and the future. Analog scopes are the past. This thing can do so many things for relatively little money that it's worth forgiving few sins. My 2 cents...

author: TurboTom
author_rank: Super Contributor
timestamp: November 28, 2020, 09:58:49 pm
content: Quote from: Fungus on November 28, 2020, 07:24:17 pmSorry Fungus, I tend to disagree with that statement of yours. At times, especially when trying to visualize statistical effects (cumulative phase jitter and the like), dot mode in combination with infinite persitance can be very useful to observe a temproal distribution over prolonged periods of time, while vector mode will just swamp your screen with an undefined mess.But at those time base settings that are required for this kind of measurement, the "screen buffer overflow effect" (double-line) never occurs.I agree though, that for just displaying "wiggly lines", dot mode is pretty much redundant.

author: bdunham7
author_rank: Super Contributor
timestamp: November 28, 2020, 10:23:38 pm
content: Quote from: ballen on November 28, 2020, 09:28:29 amWhat do you see if you increase the sweep to 5nS/div? Don't use zoom, use the horizontal position to move the trigger far enough off screen so that you are looking at a flat section of the signal where it is split.EDIT: And when you have that set up, then try it in SINGLE mode--just one capture.

author: james_s
author_rank: Super Contributor
timestamp: November 28, 2020, 10:29:56 pm
content: Quote from: ballen on November 28, 2020, 06:22:23 pmALL digital scopes have quirks, it's a mistake to view a DSO as a digital version of an analog instrument. It's a different beast altogether and requires different techniques to use. They offer so many additional capabilities that once you get used to it you won't want to go back. It took me a while to adapt but these days the only time I get out my Tek 465 is when I want XY mode.

author: tom66
author_rank: Super Contributor
timestamp: November 28, 2020, 10:36:48 pm
content: Worth noting my DS1074Z achieves 50kwfm/s on dot mode, double what it achieves on vector mode.Drawing vectors is not free, neither is interpolation, so this is not surprising. So there is benefit in other ways too, when you don't care about perfect reconstruction but want to see infrequent jitter or more detail from waveform data.

author: ballen
author_rank: Regular Contributor
timestamp: November 29, 2020, 05:12:55 am
content: Quote from: bdunham7 on November 28, 2020, 10:23:38 pmThank you Peter, this was very instructive!Ground the input, single mode, push the force button to capture a trace of DC + input noise.If I do this on the highest-gain setting, the input amplifier noise gets spread among ~8 adjacent ADC levels. If you horizontal-zoom in on these, you can clearly resolve the 8 levels, and can see that the levels near the middle are the most commonly occurring ones - a Gaussian distribution centered on the mean. But then as you zoom out in time (as you say, "horizontal decimation") the most common levels in the middledisappearand only the least frequent "top and bottom" edge levels are visible!To me this seems like a horrible show-stopping software or hardware bug. I presume the latter since otherwise it would have been fixed long ago. Can you really learn to live with this?EDIT: here is a detailed report about this problem:https://www.eevblog.com/forum/testgear/rigol-ds1000z-series-buglist-continued-(from-fw-00-04-04-03-02)/msg1442914/#msg1442914Cheers,Bruce

author: james_s
author_rank: Super Contributor
timestamp: November 29, 2020, 05:17:39 am
content: It seems you may be expecting too much from a budget instrument aimed at hobbyists. The Rigol is not a $10k Keysight or Tektronix, but thousands of people seem to be using them effectively. Using the highest gain input setting seems like an edge case, my Tek scopes are not super useful at the highest gain setting.

author: ballen
author_rank: Regular Contributor
timestamp: November 29, 2020, 06:01:00 am
content: I am using the high-gain setting only because that makes it easy to generate a "signal" by grounding the input. The display problem occurs with real signals anytime there is enough noise present to jitter the ADC.

author: Fungus
author_rank: Super Contributor
timestamp: November 29, 2020, 08:28:13 am
content: Quote from: TurboTom on November 28, 2020, 09:58:49 pmOK, dot modecombined with infinite persistencemight reveal something when you're at the very edge all channels turned on and Gibbs phenomenon is starting to appear but you'll still get better results in vector mode and a single channel.Dots mode by itself though? Not useful.

author: Fungus
author_rank: Super Contributor
timestamp: November 29, 2020, 08:32:03 am
content: Quote from: ballen on November 29, 2020, 05:12:55 amI say it again: Ineversaw a double line on mine at ordinary zoom levels. Other people here are also saying they don't see this under these conditions. If you have a chance to exchange yours then do so.

author: Miti
author_rank: Super Contributor
timestamp: November 29, 2020, 02:26:53 pm
content: Quote from: tom66 on November 28, 2020, 10:36:48 pmAnd how do you measure that, by looking at the trigger out?

author: bdunham7
author_rank: Super Contributor
timestamp: November 29, 2020, 05:31:53 pm
content: Quote from: ballen on November 29, 2020, 05:12:55 amNo, if the acquisition mode is not set to 'PEAK', then that looks broken. I wouldn't live with it.

author: bdunham7
author_rank: Super Contributor
timestamp: November 29, 2020, 05:44:18 pm
content: Quote from: Fungus on November 29, 2020, 08:28:13 amAs implemented by Rigol, at least on the one I had, I agree that dots mode is misleading and useless. I have no issues with it on my Tek models, and so far, my Siglent. For the vast majority of cases, I'd be perfectly happy with either display method.

author: tom66
author_rank: Super Contributor
timestamp: November 29, 2020, 05:48:56 pm
content: Quote from: Miti on November 29, 2020, 02:26:53 pmYes, exactly. The trigger out frequency roughly doubles in dot mode.

author: mawyatt
author_rank: Super Contributor
timestamp: November 29, 2020, 07:19:26 pm
content: Quote from: ballen on November 28, 2020, 06:22:23 pmI've been using scopes probably longer that most here have been alive, over 50 yearsLike you I've grown up with analog scopes, just about every Tektronix model you can think of, and like you had come to "trust" what the Tek scope was trying to tell me, they were and are still marvelous instrumentsThe most important "feature" I needed from a DSO over the older analog scopes was the ability to capture and store a waveform, and the ability to perform simple mathematics on the waveform. Since a DSO is nothing more that a data capturing device with a built-in display, these two features are natural to the DSO.Anyone that tells you that not having a accurate and good resolution ADC, a good low noise front end with low end range and an accurate, reliable and believable displayed DSO waveform probably has a technical IQ equal to their age!! The old Tek analog scopes gave you these features (of course no ADC), so why settle for a modern DSO that can't even perform the most important feature of a scope, to show waveforms that are accurate, low noise and believable.As you probably know there are numerous fanboys and girls here, pushing there own agenda and bashing everyone's else's option if it doesn't align with theirs. Claiming this feature matters (if their DSO has it) and that feature doesn't (if their DSO is lacking). I just wanted a DSO to work like my old Tek analog scopes, give me nice believable displays without too much added noise, allow some simple math functions and be able to reliably capture and store waveforms. I ended up with a DSO more akin to a sophisticated data capturing device than a scope, and delivering so much more that I expected, but still can perform the basic functions of an analog scope with a believable display.Like you I was exposed to all the DSO BS flying around, and had to sift thru everything to find the truth. I'm sure you'll find your way thru the DSO BS maze and select a DSO that meets your requirements and budget, whichever brand it is!!My only recommendation is to look towards the upper end in features and cost, even push your budget because a scope is the 2nd most important instrument you will own, a quality DVM is 1stBest and good luck,

author: _Wim_
author_rank: Super Contributor
timestamp: November 29, 2020, 07:39:12 pm
content: Quote from: mawyatt on November 29, 2020, 07:19:26 pmCan you share which DSO you are using? I am currently using a picoScope 5000 series for its high resolution, but the small signal performance could still use some improvement...

author: mawyatt
author_rank: Super Contributor
timestamp: November 29, 2020, 07:57:49 pm
content: Quote from: _Wim_ on November 29, 2020, 07:39:12 pmEnded up selecting the SDS2102X Plus which has exceeded my expectations in just about every way. It's been "enabled" with the kind help of folks here to 350MHz and just yesterday with help from tv84 to 500MHz which just quickly measured to 615MHzI can't speak about other brands or Siglent scopes, but this SD2102X Plus is a stunningly good little DSO IMO. Wanted the 2104X+, but that was BO so settled for the 2102X+. The ADC they are using is quite good, much better than one would expect from an 8 bit device, I posted some statistics measurements and well you judge for yourself!Here's some measurements from another thread.First off DC measurements of the SDS2102X Plus input using statistics of C1Input KS34465A of 5.00021VDC, DSO reads Mean C1 5.000398VDC (mean of mean)Input of 10.00001VDC, DSO reads 10.0031VDCInput of 7.04184VDC, DSO reads 7.04192VDCInput of 0.99985VDC, DSO reads 999.39mvDCInput of 100.0073mvDC, DSO reads 99.825mvDCNow AC measurement with 50% duty cycle square wave of 5.00021V peak value, so Mean & StdDev (RMS) should be 5.00021/2 or 2.500011VInput at 250Hz KS34465A 2.49993VAC, DSO reads 2.4916VDC (mean) and 2.5085VAC (stddev)500Hz 2.49993VAC, DSO reads 2.4912VDC & 2.5094VAC1KHz 2.49886VAC, DSO reads 2.4910VDC & 2.5095VAC4KHz 2.49452VAC, DSO reads 2.4913VDC & 2.5092VAC8KHz 2.48868VAC, DSO reads 2.4921VDC & 2.5085VACNote: The peak to peak readings of ~6Vpp include waveform ringing.This is better performance than I would expect from this DSODon't know if I got lucky or this is typical performance from the SDS2102X Plus, maybe others could make some measurementsHere's snip on the ENOB & ERB behavior from another thread, which you can compare with other DSO scopes ENOB & ERB measurements by others.Just did a quick test of the SDS2102X Plus in 8 bit, 10 bit, and ERES (3) modes using this as a means to evaluate Effective Resolution in bits. I'm not saying this is right or wrong way, just the way I chose to measure and calculate. Used 20MHz BW with 50 ohm in-scope termination, 1us/div sweep. Noise was averaged Standard Deviation to remove DC offset effects as mentioned.Effective Resolution Bits (ERB) = {10*log[(8*(SF/N)^2 +1)] -1.76}/6.02, where N is Standard Deviation noise, SF is Scale Factor in V/divScale 500uv 1mv 2mv 100mv 200mv 500mv 1v8 bit N 23.4uv 24uv 38.6uv 1.47mv 2.95mv 7.55mv 14.56mvERB 5.63 6.59 6.90 7.30 7.29 7.26 7.3110 bit N 16.9uv 17uv 20uv 316uv 432uv 1.83mv 2.32mvERB 6.10 7.09 7.85 9.50 10.06 9.72 9.96ERES N 12uv 12uv 14uv 132uv 190uv 725uv 860uvERB 6.59 7.59 8.37 11.60 11.89 11.80 11.39FFT NF -122 -120 -120 -118 -108 -100 -97in dBmAdded FFT noise floor in 8 bit mode using 2.5MSPS, 2097512 pts, delta f 1.19Hz and 16 average.I computed these on my HP32 calculator, so hopefully no mistakesHere's the thread for some other DSO ENOB measurements by Howard Long.https://www.eevblog.com/forum/testgear/benefits-of-going-with-all-siglent-setup/msg3281580/#msg3281580Best,

author: Miti
author_rank: Super Contributor
timestamp: November 30, 2020, 03:04:41 am
content: Quote from: mawyatt on November 29, 2020, 07:57:49 pmFor me, to spend that amount of money, it must make money afterwards. Just for hobby, naaah...And then I need 4 channels more than 600 MHz.

author: james_s
author_rank: Super Contributor
timestamp: November 30, 2020, 06:47:50 am
content: Quote from: Miti on November 30, 2020, 03:04:41 am~800 bucks? That's not impulse purchase territory for me but it's certainly well within the hobby budget. I've spent more than that on toys on multiple occasions. I do agree that 4 channels is nice to have, although when I think about it I only use more than 2 channels maybe 10% of the time.

author: mawyatt
author_rank: Super Contributor
timestamp: November 30, 2020, 02:12:31 pm
content: Quote from: james_s on November 30, 2020, 06:47:50 amI do appreciate making $ with these as an investment, since I still do consulting hopefully this will be true.As far "toys" go, yes I've spent a few more $, look at my avatarThe red 911 is worth more today than when I purchased it new in 1996 (last of the air cooled), my daily drive until I acquired the black 911 in 2007I find 2 channels sufficient most of the time also, but have had an occasion or two where a couple extra channels were required.Best,

author: _Wim_
author_rank: Super Contributor
timestamp: November 30, 2020, 09:32:10 pm
content: Quote from: mawyatt on November 29, 2020, 07:57:49 pmThose results do look quite impressive. I will give this a try this weekend on my Picoscope 5442B. How was the "standard deviation noise"-value measured? Is this the standard deviation on the measured AC pp value?The smallest range on the Pico is 2mV/div (which is one of the disadvantages), so the lowest ranges I cannot do.I theory it has a 16bit mode without ERES, and 20bit with ERES. In reality there is not so much difference between the 12 to 16 bit mode, but quite a bit of difference compared to the 8 bit mode. Due to the relative low bandwidth in 16bit mode (62.5MS/s), ERES will not by possible on a 1µs/div time scale.

author: tautech
author_rank: Super Contributor
timestamp: November 30, 2020, 09:38:18 pm
content: Quote from: _Wim_ on November 30, 2020, 09:32:10 pmSDS2000X Plus have both a 10 bit mode (limited to 100 MHz) and a 3 bit ERES mode and both can be used together.Early in the SDS2000X Plus thread Performa01 posted some screenshots about this.

author: mawyatt
author_rank: Super Contributor
timestamp: December 01, 2020, 03:25:26 am
content: Quote from: _Wim_ on November 30, 2020, 09:32:10 pmI doubt this will compete with the true core 16 bit ADC in your Picoscope.Yes the SD is measured on the peak to peak value and then the statistics is the mean value of the SD. The AC waveform is almost a perfect square wave at these low frequencies up to ~500Hz with a max value set by a precision 5.000V voltage reference source used for VDD. The precision by design waveform was created from a 4.096MHz crystal osc. divided by cascaded CMOS Flip-Flops which drive a discrete CMOS inverter with low Rdson N and PMOS devices. The SD, RMS are the same and so is the MEAN or DC term and ideally should be 1/2 the VDD voltage reference.Best,

author: _Wim_
author_rank: Super Contributor
timestamp: December 01, 2020, 06:33:35 am
content: Quote from: mawyatt on December 01, 2020, 03:25:26 amI agree that this unlikely for the higher voltage ranges (where the true advantage of the 16 bit can be used), but I suspect this will be the case for the 2 and 10mV ranges and probably even beat it. For these small signals I wish the pico was a little better...

author: 2N3055
author_rank: Super Contributor
timestamp: December 01, 2020, 07:11:58 am
content: I don't have 54xx series Pico. But on my 4262, most sensitive range is also 2 mV/div.But noise is less than 10uV RMS, you can software zoom in 16 times and still have 4000 points vertically, and have 125uV/div on screen...I guess 54xx series noise would be higher (4262 is only 5MHz bandwidth), but you could still software zoom in 4x with very usable results... And that would be 500uV/div, very respectable number..

author: _Wim_
author_rank: Super Contributor
timestamp: December 01, 2020, 08:10:36 pm
content: Quote from: 2N3055 on December 01, 2020, 07:11:58 amThe 4262 is a far far lower noise device than the 54xx series scope. That is a true 16-bit device, while the 54xx are 12-bit devices that use some interleaving tick of the 4 channels to supposedly achieve 16-bit. But in practice the difference between 12-bit and 16-bit mode is not very high, so I do typically use it in the 12-bit mode (when no bandwidth limit filter is used, you do see more “improvement” of the 16-bt mode, but that is just due to the reduced bandwidth)Don’t get me wrong however, the pico 5442 is still a fantastic high resolution device, just the lower range is a bit noisier than I would like (with a pre-amp this is ok), and it is for sure not a 4262. I would love the have a 4262 in my collection also, but so far not have come across a good deal on one of those, and buying a new one on top of my 54xx seems not worth is, as with a pre-amp I can do most things I need any-way.

author: 2N3055
author_rank: Super Contributor
timestamp: December 01, 2020, 09:50:56 pm
content: Quote from: _Wim_ on December 01, 2020, 08:10:36 pmI totally understand you. I had old 212/100 pico, a 12 bit device, and that was already a huge improvement over 8 bitters...If I had 54xx series Pico I probably wouldn't have gotten 4262. But I have 3406D and Keysight 3000T, and 4262 was the thing to complement those two on high precision, low noise, low frequency end. I had a project that benefited from it, so I got it.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: December 01, 2020, 10:22:28 pm
content: Quote from: ballen on November 26, 2020, 07:57:36 pmSorry it took me so long to view this thread.I am unable to replicate the double trace. I've tried everything I can think of. Any suggestions, while I still have the scope set up?(00.04.04.04.02)[ Specified attachment is not available ]

author: alsetalokin4017
author_rank: Super Contributor
timestamp: December 01, 2020, 10:26:49 pm
content: Quote from: ballen on November 28, 2020, 07:51:06 amDone all that, unable to replicate double trace, see screenshot above.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: December 01, 2020, 10:35:56 pm
content: Quote from: Fungus on November 29, 2020, 08:32:03 amI agree, I think. At least, as long as I can't reproduce the OP's original double trace, I have to conclude that there is something wrong with his, or something right with mine.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: December 01, 2020, 10:43:17 pm
content: Interlude: Artifact art?

author: alsetalokin4017
author_rank: Super Contributor
timestamp: December 01, 2020, 11:01:24 pm
content: Trace is singular and well behaved at all zoom levels.

author: Fungus
author_rank: Super Contributor
timestamp: December 02, 2020, 12:37:23 pm
content: Quote from: alsetalokin4017 on December 01, 2020, 11:01:24 pmYep. I'm sticking with "defective scope, send it back for a replacement".