How much noise floor and other things matter in oscilloscope usability - Page 1
Forum section: electronics / testgear

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 23, 2021, 12:00:05 pm
content: Hello,I am in the process to "buy" an oscilloscope and I really need some clarification because, even if I've read almost everything I have been able to find on the web and on this forum, there are some technical things I cannot sort out by my self.For example the noise floor:In what situation really matter to have an oscilloscope with a "low" noise floor?I am going to use It for many different things, I am a "begginer" but I do digital stuff with embedded electronics and I also aim to learn more things as possible about analog electronics starting from working on an old valve radio that i would like to repair and experiment with.Actually I bought few days ago a Rigol mso5000 and I did not be aware about its noisy front end.After a lot of searching on the web and experimenting with such instrument It seem to me that It is at least 3 times more noisy than other comparabile oscilloscopes.So how much this matter in electronics? How this could preclude its usability?I have still about 30 days to give It back for free to Amazon but only one week to decide if I want to buy its direct competitor siglent "sds2000x plus" that now Is on offer with the LA probe discount bundle until 30dicember.The Siglent appear to have a low noise front end but a different way to handle signal recording in its internal memory that i don't understand if it Is bad due to the fact that It cannot "zoom out"...Also the Rigol has a very fast ADC when working in interleaved mode but at the same time I still don't understand if 8 Gsa/s are really needed with frequency up to 500Mhz and maybe the Siglent with Its 2Gsa/s is enough.... I don't find clear infos on the web apart the nyquist theorem.I would be gratefull if someone with experience could help me because all this matter a lot for me, electronics has been in my heart from when I was young and I am keen to improve as best as possible day after day....Thank you

author: Kleinstein
author_rank: Super Contributor
timestamp: December 23, 2021, 12:47:34 pm
content: For most uses the noise of the scope is not really an issue. This is because a 1:10 probe is often the mayjor noise source. Unless the scope is rather high in noise, the noise floor is mainly an issue with the few measurements done with an 1:1 probe or similar signal via coax.For digital signals itself the scopes noise is usually not an issue, but it may be when looking at the supply ripple.For comparing the noise, one should take the bandwidth into account. With a higher BW the RMS noise naturally goes up. This effect can make a new higher BW scope look higher noise. So one usually should compare at the same BW, like the usual 20 MHz BW setting.2 Gs/s are a bit on the low end for 500MHz BW. This may lead to some aliasing and a few more thoughts about what one is actually seeing at the short time scale end.

author: nctnico
author_rank: Super Contributor
timestamp: December 23, 2021, 01:28:17 pm
content: Quote from: Kleinstein on December 23, 2021, 12:47:34 pmI strongly disagree with this. An oscilloscope with a lot of noise gives thick traces which make it hard to see the actual level of a signal. Ofcourse you can use high-res or bandwidth limiting but IMHO these should be targeted at cleaning up a signal and not masking a poorly designed analog front end. An oscilloscope with a low noise floor is easier to work with. I used to own an Agilent DSO7104A and it was just horrible to work with for analog stuff due to the massively thick traces it has due its own noise.Also note that the noise doesn't only apply to the most sensitive V/div setting, it applies similar to all V/div settings. The noise level is usually specified in Volts using the most sensitive V/div setting but it would be more accurate to specify it as a percentage of a division or full range. In the end the V/div setting adjusts an input divider but the actual noise level (what goes into the ADC and what gets added by the ADC) stays the same; it is just scaled differenty.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 23, 2021, 02:05:29 pm
content: I find your replies very interesting.So now I am thinking: for what type of signal and in what situation the noise floor of the oscilloscope is impacting the anologue measurements?

author: Grandchuck
author_rank: Super Contributor
timestamp: December 23, 2021, 02:50:11 pm
content: https://keysightoscilloscopes.wordpress.com/tag/noise-floor/

author: Fungus
author_rank: Super Contributor
timestamp: December 23, 2021, 02:51:59 pm
content: Quote from: Fiorenzo on December 23, 2021, 12:00:05 pmWhen you're measuring very small signals.Quote from: Fiorenzo on December 23, 2021, 12:00:05 pmIt won't make any difference at all on your digital stuff.For the radio?Ifit turns out to be a problem you can easily add a preamplifier and make iteven betterthan a lower-noise oscilloscope.Quote from: Fiorenzo on December 23, 2021, 12:00:05 pmIt's not a showstopper. You can still doeverything, just maybe not as easily for a few specific things.The real questions are: How often do you do those things? How much would you have to spend to get a lower-noise 'scope with the same abilities as your Rigol? Is the extra money well-spent?

author: nctnico
author_rank: Super Contributor
timestamp: December 23, 2021, 02:53:04 pm
content: Quote from: Fungus on December 23, 2021, 02:51:59 pmActually not because the relative noise floor remains more or less constant!I just tried on an R&S RTM3004. At 1V/div I get 17mV stdev. At 10V/div I get 170mv stdev (Stdev= RMS with DC removed). The noise floor scales with the V/div setting.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 23, 2021, 03:01:05 pm
content: Grandchuck I read that article and many others but they doesn't give example of practical situation that are impatted from the noise floor of the oscilloscope. Which kind of signal need an oscilloscope with a low noise frontend?I ask these because I do not have a clear comprehension of such subjects.

author: Fungus
author_rank: Super Contributor
timestamp: December 23, 2021, 03:03:25 pm
content: Quote from: nctnico on December 23, 2021, 02:53:04 pmIf the signal is large, you can see it, it's just that the traces on screen are thicker.If the signal is small, it gets lost inside the trace.

author: Fungus
author_rank: Super Contributor
timestamp: December 23, 2021, 03:06:33 pm
content: Quote from: Fiorenzo on December 23, 2021, 03:01:05 pmA 1mV signal.(for example)

author: nctnico
author_rank: Super Contributor
timestamp: December 23, 2021, 03:15:51 pm
content: Quote from: Fungus on December 23, 2021, 03:03:25 pmYes, and thick traces just suck. Try to make a cursor measurement on a trace that is 20% of a division even with V/div set to 1V/div. Needless to say that small variations of a signal are also lost in a noisy oscilloscope.Don't confuse needing a pre-amplifier to look at signals that are outside the V/div range of an oscilloscope. That is a different subject!

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 23, 2021, 03:24:21 pm
content: Ok, you all are giving me many usefull information, but now give a look to the attached photos.The first image shows the apparent noise of CH1, It is set in AC mode, 1X attenuation, without bandwith limit and is also sampling in normal mode with the probe attached and grounded to its own tip.The second image shows the same configuration but with the probe attached to the output of and old transformer just to check its ripple.I see a lot of noise floor in this photos.Do you agree? It seem too much to me, but as I said before I am not an expert in analoge stuff so maybe I am doing something wrong... Or maybe this oscilloscope is particularly noisy...

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 23, 2021, 03:36:01 pm
content: Quote from: Fungus on December 23, 2021, 03:06:33 pmWhat circuits works with such a low signal? This is my question from the beginning.I understand that noise sucks but it is the practical application of a low noise oscilloscope that i cannot figure out.For example, if I work with on an old valve radio am I going to encounter such kind of low signal? It Is only an example....I don't want to buy an oscilloscope and find myself after a year that It is going to particularly limit my study in electronics, this are costly instruments, I can spend some more money than that spent for the Rigol but I must do the right choice and now I don't feel confident with my actual knowledge.

author: bdunham7
author_rank: Super Contributor
timestamp: December 23, 2021, 04:03:34 pm
content: I haven't compared those two models directly, but comparisons with two lower models of Rigol and Siglent were enough to convince me that low noise was an important factor in some cases. The Rigol was a lot noisier than typical analog scopes, whereas the Siglent is comparable with a good basic CRO. The Siglent also has a for-real 500uV/div capability and the Rigol actually only went down to something like 2mV/div (or perhaps 5mV/div) and then expanded the signal and decreased the resolution for the lower ranges, a sort of digital zoom. They had a 500uV/div range if you hacked them, but it was pretty useless.As for some previous responses, I disagree that the 10X probe will be noisier than the scope, that might apply to a very quiet scope but with either of these the scope front-end noise will be the issue when you are looking at small signals with a 10X probe. And you'll almost always be using a 10X probe because 1X is very limited bandwidth, so a 'low' signal will be anything below 50mV. So when I've used a 10X probe with scopes like this on small signals (the lower versions of Siglent and Rigol) the Siglent is clearly superior (3-4X better at least) but sometimes I wish it were even better. Always remember the bandwidth limiter will help if your signals are below 20MHz.There was a mention that the noise appears on all scales, not just the lowest volts/div settings. There's some of each, I suppose you could call them the analog-front-end noise and the ADC noise. The Siglent clearly has more noise on the lowest volt/div settings and above 2mV/div, the 'ADC' noise is pretty minimal. The Rigol will be worse in this regard because of the digital expansion for the lowest ranges.You asked about sample rate and bandwidth. 2GSa/s is just enough for 500MHz, but the Siglent only has that with two channels active and so the BW is limited with 4 channels. The Rigol has more than adequate samples for its 350MHz bandwidth under any conditions. I'm not sure how much this matters for your uses.The memory configuration and lack of zoom-out on the Siglent is a baked in trait that I don't think is going to ever change. I find it to not be problem, but it has annoyed some people who are used to a different configuration. I'm also annoyed because I think its usability could be improved with trivial effort by reducing the whole-record display to a bar on the top. This whole thing is less of a problem on the SDS2000X series because in zoom mode you are wasting 1/4 of a fairly large screen. Earlier models were wasting 1/2 of a much smaller screen.

author: bdunham7
author_rank: Super Contributor
timestamp: December 23, 2021, 04:11:46 pm
content: Quote from: Fiorenzo on December 23, 2021, 03:36:01 pmOn an old valve radio you might want to use a 100X probe, in which case a 'small signal' that would merit using the lowest range of the scope might be hundreds of millivolts. With a 10X probe, which is what you will almost always use, you might start caring about front-end noise at 50mV. Low front end noise gives you better FFT performance as well. There are all sorts of cases where noise is an issue and if you are just starting out, I can't predict which ones you will run into.

author: Fungus
author_rank: Super Contributor
timestamp: December 23, 2021, 06:31:40 pm
content: Quote from: Fiorenzo on December 23, 2021, 03:24:21 pmNever use 1x mode without the bandwidth limit.nb. 10x mode is what you should be using almost all the time. 1x mode is only for very special cases.

author: Fungus
author_rank: Super Contributor
timestamp: December 23, 2021, 06:34:32 pm
content: Quote from: Fiorenzo on December 23, 2021, 03:36:01 pmThe example that's usually given is "power supply ripple", but unless you'redesigninga switched mode power supply then you probably don't need that.Quote from: nctnico on December 23, 2021, 03:15:51 pmPut it in the middle of the trace.Oscilloscopes aren't that accurate anyway - only about 5% even on a low-noise oscilloscope.Edit: You can also turn on color gradient mode and the true signal will be highlighted for you.(I just learned that trick from the video below and you can be sure it will be repeated in all future "Rigol noise" threads...)

author: Fungus
author_rank: Super Contributor
timestamp: December 23, 2021, 06:50:07 pm
content: If the signal you're looking at is periodic (repeatiing) then you can turn on hires mode and look at the average of multiple waveforms:

author: egonotto
author_rank: Super Contributor
timestamp: December 23, 2021, 07:39:53 pm
content: Quote from: nctnico on December 23, 2021, 02:53:04 pmHello,this is much better than on RTA4004. R&S says: (50 Ohm 1GHz)1 V/div 31.4 mVBest regardsegonotto

author: nctnico
author_rank: Super Contributor
timestamp: December 23, 2021, 07:42:20 pm
content: Quote from: egonotto on December 23, 2021, 07:39:53 pmI switched the 20MHz bandwidth limit on in order to allow making comparisons with other scopes. The example is just to show that the noise floor scales with the V/div setting.

author: David Hess
author_rank: Super Contributor
timestamp: December 24, 2021, 04:04:59 am
content: Noise level almost never matters because oscilloscopes are time domain instruments with two more significant limitations:1. Noise is typically lower than the aberrations in the pulse response, and this is also a limit for instruments with resolution higher than 8 bits, so removing the noise just gives a clearer view of an inaccurate result where it counts.2. Input stage offset and drift is usually greater than the noise.And unlike the above errors, a digital storage oscilloscope can reduce noise with averaging.Where noise does matter is spectrum analysis, but again, other limits like distortion have a greater effect. Optimizing oscilloscope input stages for pulse response requires compromise in noise and distortion.Good low noise performance for a 100 MHz instrument should be about 40 microvolts RMS based on a input JFET source follower with 3.2 nV/Sqrt(Hz) noise, and many old analog oscilloscopes and DSOs achieve this. This is also why sensitivity below a couple millivolts/division is questionable except if bandwidth is limited.For instance my 2232 DSO has 25 points per division so at 2 millivolts/division each point is 80 microvolts, and peak-to-peak noise is 3 points or 240 microvolts which comes out to 40 microvolts RMS. I measured slight lower than this on some of my analog oscilloscopes under similar conditions, although my favorite analog oscilloscope has a noise level about 3 times higher than this.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 06:15:24 am
content: So, with these settings:1x probe, no BW limit, normal acquisition modeI did other photos:1) probe grounded to its tip2) probe connected to a Power supply to check the ripple3) no probe attached to the oscilloscopeWhat do you think about the noise floor?It seem high to me....

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 06:18:01 am
content: Here same settings but hi-res mode.

author: bdunham7
author_rank: Super Contributor
timestamp: December 24, 2021, 06:38:26 am
content: Can you try again only set the vertical scale to 1mV/div and measure with no probe and with the shorted probe? Then do the same at 100mV/div.

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 06:55:13 am
content: Quote from: Fiorenzo on December 24, 2021, 06:15:24 amAgain: You're not supposed to use 1x with no BW limit. Ever.1x with no BW limit = noise.Quote from: Fiorenzo on December 24, 2021, 06:15:24 amYou can see the ripple, right? That's what counts.Try the same thing with the bandwidth limiter on.

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: December 24, 2021, 06:57:43 am
content: For very small signals, use the FFT mode on the scope to find the amplitude. FFT does help to bring out signals from the noise (for periodic signals). For e.g. you could observe a 2mVrms sine wave with even 10mVrms of noise, by using FFT.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 07:52:00 am
content: Ok I have taken other photos but now with BW limit set to 20Mhz and the probe connected but grounded to its tip.Photos:1) 1x probe2) 10x probe

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 07:57:37 am
content: Quote from: Fiorenzo on December 24, 2021, 07:52:00 amWhat does it look like at 1v/div? That's what you'll normally be seeing when you're working.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 08:01:55 am
content: Fungus you asked me to what I am comparing the noise:I saw some photos on the web of the siglent sds2000x+ and the measured RMS and peak to peak value, what I see on the Rigol seem to me many times higher....Because I am no expert I cannot say the Rigol have too much noise and this is a problem for me. I am trying to understand/learn from you if It could be acceptable or a problem in some circumstance because I hope to do not change the oscilloscope for at least 5/10 years.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 08:03:17 am
content: Quote from: Fungus on December 24, 2021, 07:57:37 amI didn't change the volt scale only the probe attenuation.In the afternoon I am going to take the photos you asked, I cannot now.

author: Andreas
author_rank: Super Contributor
timestamp: December 24, 2021, 08:45:41 am
content: Quote from: Fiorenzo on December 23, 2021, 12:00:05 pmThe most annoying situation is when you use a FFT to detect small signals within a larger complex signal.E.g. 50 Hz mains hum within a pre-amplified signal. (AC transformer too near to the setup creating a large error nearly not visible in the time domain).E.g. actual Chopper frequencies and overlay of different stages (dependant on temperature) at the output of a Chopper stabilized OP-Amp. (had the problem that the measured noise increased suddenly at special temperatures due to interferences)with best regardsAndreas

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 09:38:12 am
content: Quote from: Kleinstein on December 23, 2021, 12:47:34 pmThank you Kleinstein for your reply.What typology of circuits/signals need measurements with a 1x probe?Does a higher sample rate give a better visual resolution of square wave signals at high frequency or its benefit is reduced by the amount of noise of the front end?

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 09:40:17 am
content: Quote from: nctnico on December 23, 2021, 01:28:17 pmThank you, interesting.

author: Sighound36
author_rank: Frequent Contributor
timestamp: December 24, 2021, 10:03:06 am
content: This was one fo ther main reasons for purchasing Lecroy scopes, (we also have Rigol 8000's) which are great general scopes and have some cracking features, but for low noise rail voltage measurments (and 2 channel FFT's) that are consistant, accurate (gain accuracy of 0.5%) and reliable coupled with the superb selection of probes then Wavepro HD is the R&D go to. We alosmuse powerananlysers (both DC and AC which are again very accurate) along with a 6705C.nctnico is on the money, scope accuracy is very important imho

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 10:10:59 am
content: Quote from: Fungus on December 23, 2021, 02:51:59 pmYes I understand what you mean, but I don't have the knowledge to understand ​all the "abilities" of my scope.My budget is <2000€ but if it is possible to spend less of 500€ It would be (offcourse) better because I could buy other equipments.It Is a difficult decision because there are so many models of oscilloscopes and no one is perfect.I would like to have the right instrument that will let me expand my knowledge and build circuits without particular constrains, maybe I am exagerating because I don't have a complete understanding of all the fields of electronics, but at the same time I do not expect to work with Ghz exotic electronics.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 24, 2021, 10:15:06 am
content: For the DSO there are 2 types of noise: noise relative to the input (e.g. input amplifier noise) and noise relative to the output (ADC noise). For the noise relative to the input the amplifier a 10:1 probe can be a major noise source. The 1 M resistor in the divider has a natural noise of some 130 nV/sqrt(Hz), which is higher than a reasonable JFET based input stage (more like 10 nV/sqrt(hz) range). A low noise for the input is nice, but not relevant when using a 10:1 probe. It can be when using a 1:1 probe.An 1:1 probe is mainly used when one rellay needs low noise for very small signals (e.g. noise at some point on a circuit, supply ripple). It comes with the price of reduced bandwidth (except with a special, expensive active probe), but with significant lower input noise (e.g. factor 10 from the divider ratio and an additional factor of some 3-10 from not having the resistor noise).The lower gain settings usually use an internal input divider and if not designed good this may add some noise to 1 or 2 of the higher ranges, which can be a bit annoying as it is avoidable. So ideally a full noise testing would test all ranges, at least with 1 BW setting.The output related noise, e.g. from the limited resolution ADC noise, of just ADC noise because of a limited effective ADC resolution that may be lower.For the ADC noise the sampling rate can make a difference. So the same DSO may look noisy at the higherst sampling rate but looks much better at a lower sampling rate when more samples are averaged. The noise relevant bandwidth is different from the 3 dB bandwith and can be quite a bit higher if the sampling rate is high, or closer to the -3dB BW when the sampling rate is barely sufficient. So it needs some case for the comparison to get comparable condictions (e.g. same sampling rate, relatively close to the maximum, like some 1 Gs/s for the scopes in question).With the high speed scopes the ADC noise can be a factor.This is mainly relevant with non repetitve (single trigger) relatively fast signals (so one needs a high sampling rate).Spectrumanalysis (FFT) is also an example where the noise can matter. Here also the way the math is done (e.g. does it support averaging, if so the unused time for the math) can make a difference.Besides the noise of the raw data the methods available for noise reduction can also make a difference. So how good is the averaging over multiple triggers or bandwidth limiting working.A higher sampling rate can reduce the artifacts from signal parts beyound the Nyquist limit (f_s / 2). With a relatively low sampling rate for a given BW it would need either some extra anti aliasing filtering that can add phase shifts or one has to accept some artifacts if the signal actually contains very fast components. At the same BW, the higher sampling rate scope would usually give a slightly more accurate response.Noise whise the highest sampling rate often comes with more noise, but after averaging of consecutive samples (the usual way to reduce the data rate - though it can be done worse) the noise improves and thus no panelty from a faster ADC.edit: I just remembered: the 10:1 probe is resistive only for low frequencies (e.g. < 10 kHz) but capacitive at higher frequenices. So there is not that much extra noise from the divider and input amplifier noise can still be a factor with the 10:1 probe (at least in the lower ranges).

author: gf
author_rank: Super Contributor
timestamp: December 24, 2021, 10:35:16 am
content: Quote from: nctnico on December 23, 2021, 01:28:17 pmEventually it depends on the individual attenuator and front end design. For instance, I'm aware of a low-cost scope model where the relative noise levels are best at 100mV/div, 1V/div and 10V/div; already a bit worse at 50mV/div, 500mV/div and 5V/div; even worse at 20mV/div, 200mV/div and 2V/div; and finally getting more and more worse at 10mV/div, 5mV/div and 2mV/div

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 12:12:21 pm
content: Quote from: Fungus on December 23, 2021, 03:06:33 pmA 1mV signal.(for example)What kind of electronics works with such low intensity signals?

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 12:29:55 pm
content: Quote from: bdunham7 on December 23, 2021, 04:11:46 pmThank you for all your explanations. Very usefull. I am trying to understand: what kind of electronics work with such kind of low signals?

author: tautech
author_rank: Super Contributor
timestamp: December 24, 2021, 01:42:30 pm
content: Quote from: Fiorenzo on December 24, 2021, 12:29:55 pmFew but if ever needing to measure low values indeed noise can get in the way.When probing high impedance circuits and connection can effect the circuit operation and as 10x probes are most commonly used a 1mV/div scope setting need be used for a 10mV signal however it will only be displayed ~1div high.To take this to extremes a popular tablet DSO has just 50mv/div max sensitivity which when coupled with a 10x probe permits only 500mV/div sensitivity which is useless for anything but the simplest of tasks.When we need higher sensitivity 1x is used but at the expense of higher probe capacitance loading on the circuit so such use is often restricted to low impedance measurements like the ripple on a DC rail or that of a PSU.When most move to a DSO forgetting to set the input attenuation to match the probe is a common newbie error instead of letting the scope display the correct measured value. This is where probe autosense like in the other DSO you are looking at is of substantial value.

author: David Hess
author_rank: Super Contributor
timestamp: December 24, 2021, 02:05:21 pm
content: Quote from: Fiorenzo on December 24, 2021, 09:38:12 am20 MHz AC coupled power supply noise and ripple measurements work well with a 1x probe. This is actually specified in the ATX power supply standard. A 50 ohm cable can be used in place of a 1x probe but it will deliver worse performance.Audio measurements are another area where 1x probes are useful.QuoteIt does give better fidelity but how it affects noise depends on the implementation. High end instruments now use an ADC which can trade sample rate with noise and resolution, but for most, sample rate has no effect. The reason for this is that if the ADC is not doing noise shaping, then it operates at a constant (maximum) sample rate and different sample rates are produced by discarding samples during decimation, which has no effect on noise within the input bandwidth of the ADC.Quote from: nctnico on December 23, 2021, 01:28:17 pmMost DSOs these days only have a single input divider. Older DSOs have at least two which allows the input buffer to operate over 1/10th of input range so the input full power bandwidth does not limit performance.Separately there is a low impedance output divider, usually now in the form of a PGA (programmable gain amplifier), with its own noise characteristics. At high sensitivity noise is dominated by the input buffer, and at low sensitivity noise is dominated by the preamplifier and ADC.Quote from: Kleinstein on December 24, 2021, 10:15:06 amFor a typical tip capacitance of a 10x probe, the 1 megohm shunt resistance is in parallel with about 100 picofarads of compensation capacitance producing a noise bandwidth of only 2.5 kHz, so its noise contribution is only about 6.5 microvolts RMS over a wide bandwidth which is close to insignificant.For the same reason, the noise contribution from the roughly 500 kilohm resistance in series with the gate of the input transistor for protection adds basically no noise. It is bypassed with about 1000 picofarads reducing its noise bandwidth to an insignificant level.QuoteThe internal high impedance input dividers are also capacitively compensated limiting their high frequency noise. The output dividers are low impedance so require no compensation, but have low noise anyway. In a modern DSO, these are part of the PGA.QuoteI have only seen high end DSOs take advantage of noise shaping in the ADC. There is probably some effect on noise for DSOs which use an interleaved ADC for multiple channels.Some old DSOs with relatively low real time sample rates, like 100s of MSamples/second, have less ADC noise (and preamplifier noise) than the quantization noise of their ADC. When I first saw this on my 2232, I thought something was broken or misconfigured. This might actually be considered a disadvantage when averaging where added noise would produce a better result and I have actually seen this happen with the averaged signal producing a stair-step from the ADC's quantization noise.

author: tautech
author_rank: Super Contributor
timestamp: December 24, 2021, 02:07:07 pm
content: Here's a simple example where the noise increases at the higher input sensitivities required to properly scale the higher attenuation probes.Done some years back and grabbed from an old post.SDS1104X-E with 1x, 10x, 100x and 1000x probes all connected to the probe Cal output.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 07:17:44 pm
content: Quote from: tautech on December 24, 2021, 01:42:30 pmThank you tautech and everyone again for the time spent replying. I find everything you wrote very usefull and interesting

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 07:30:31 pm
content: Quote from: David Hess on December 24, 2021, 02:05:21 pmMr. David you gave a lot of explanations, this is very kind and usefull.Trying to do a recap: at this point It seem to me that a "low noise" oscilloscope is important when working with FFT analysis, power supply ripple, audio signal, and high impedance circuits?In regard of the mso5000 with its high sample rate of 8GSa/s I am not sure if in the balance It is an advantage due to its apparently noisy front end.As an ignorant, at the beginning I thought: the Rigol is better because It has better specs, so I bought it. Could you suggest me a different model if you think It could be better?

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 07:40:03 pm
content: Quote from: Fiorenzo on December 24, 2021, 07:30:31 pmIt definitely is. It will help reduce theGibbs Phenomenonon your digital circuits.(Ever wonder how "ringing" can occurbeforea signal starts to rise? Undersampling combined with sin(x)/x reconstruction...)

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 07:41:06 pm
content: Quote from: Fiorenzo on December 24, 2021, 07:30:31 pmAt the same price? Not a chance.You'll have to go up quite a lot in price to get something better. Think: The difference would buy a good multimeter, a soldering ironanda bench power supply.(And the oscilloscope still wouldn't be perfect, you'd just have other things to worry about)OTOH you could even godownto a 500 Euro oscilloscope like the Siglent SDS1204X-E. It's probably all you need and you'd have enough money left over to create an awesome lab.

author: bdunham7
author_rank: Super Contributor
timestamp: December 24, 2021, 07:50:14 pm
content: Quote from: Fungus on December 24, 2021, 07:40:03 pmMeh, ringing on step responses isn't usually Gibbs unless something has been designed or set wrong. You can have ringing (and even pre-ringing) on an analog scope.

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 08:03:33 pm
content: Quote from: bdunham7 on December 24, 2021, 07:50:14 pmIt can be a mixture of both.Quote from: bdunham7 on December 24, 2021, 07:50:14 pmBut you can't have Gibbs.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 08:07:55 pm
content: Quote from: Fungus on December 24, 2021, 07:41:06 pmYes I know, this is one of my doubts. I will check some review of that scope but in the mean time what do you think about its bigger brother sds2000x-plus?

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 08:20:51 pm
content: Quote from: bdunham7 on December 24, 2021, 06:38:26 amHere I am, I did the test you asked for, please let me know whath do you think about It.Thank you very kind!Photos:1) 1mv/div, no probe, 20Mhz BW limit, 1x2) 1mv/div, probe, 20 MHz BW limit, 1x3) 100mv/div, no probe, all the same4) 100mv/div, probe, all the same

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 08:48:05 pm
content: Quote from: Fiorenzo on December 24, 2021, 08:07:55 pmMe? For that money I'd start with the little brother plus 1000 Euros of other toys(!). When you know more about oscilloscopes and their limitations you can decide if you want to sell it and buy the bigger one.

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 08:51:21 pm
content: Quote from: Fiorenzo on December 24, 2021, 08:20:51 pmLooks flat enough to me. Nothing to be unhappy about.What about 1v/div with 10x probe?

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 08:56:52 pm
content: Also try averaging mode:(image from section 4-5 of the manual)Averaging can be used with any periodic waveform, ie. almost all waveforms where noise might be an issue, eg. measuring ripple.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 09:12:21 pm
content: With 1mv/div It gives about 160mV RMS and 1,2mV peak to peak. Whatching other scopes they seem to have about 4 time less noise.Am I wrong?About me I am not rich, but I would like to buy a quite good oscilloscope.I dislike to spend a lot of money ofcourse, but in my experience with quality instruments you get the best results from what you are doing so maybe a big effort now could be a big help tomorrow, or maybe It Is better that now I spend a little amount of money and wait for more evolute oscilloscopes in the future....If the 1000 series is good for me I take It, if It Is better the Rigol or the 2000 series i will go for It but at the moment I am unsure on which way to take.You speack about other usefull instruments, what could I buy?I have the solder station and some fixed voltage psu and one psu I have made by my self with 4 indipendent regulable output but not very precise....

author: bdunham7
author_rank: Super Contributor
timestamp: December 24, 2021, 09:17:11 pm
content: Quote from: Fiorenzo on December 24, 2021, 08:20:51 pmSo just as a quick apples-to-apples comparison with your first example, I set up an SDS1104X-E with the same no-probe, 20MHz BW, 5us/div and 1mv/div. Then I connected a 1mVrms100kHz signal so you can see the suitability of the scope for viewing such a signal. The noise makes it a bit jumpy and jittery because it affects the trigger point. I have some low-frequency noise that isn't from the scope but is from other stuff that I have around that I can't turn off right now, so I did both a live snapshot and a stopped picture, which is effectively a single-shot. As you can see, the scope is perfectly usable on 1mV signals and your Rigol, which is over 3X as noisy, might have a tough time with the same signal.I also took a snapshot with the input set to GND, which shows you the ADC noise, or so I think. The LSB at this setting is 40uV, so the peak-to-peak noise is 1 bit.I can't tell you what scope works best for you, but if you work at all with small signals, the front-ends of the entry level Siglents is definitely the best for the buck. Features like the ERES acquisition mode and the 10-bit mode of the SDS2000X+ series do make them better, but you shouldn't generally count on multi-capture averaging even though it can look very good, as this can lead to errors.

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 09:37:20 pm
content: Quote from: Fiorenzo on December 24, 2021, 09:12:21 pmIt's not a question of right/wrong, it's a question of whether it makes a difference.There's a whole thread here saying "not as much as you think".Quote from: Fiorenzo on December 24, 2021, 09:12:21 pmOf course.Quote from: Fiorenzo on December 24, 2021, 09:12:21 pmIt's impossible to define "better" when there's almost 50% price difference.Is a car with leather seats "better" than a car which doesn't have them? You can argue that it is but most people still do the shopping with ordinary seats and can fit just as much in the car.Quote from: Fiorenzo on December 24, 2021, 09:12:21 pmWhat multimeters do you own? Do you have space for a bench multimeter? A nice bench multimeter will be far more useful than a Siglent 2000 series vs. a Siglent 1000 series. A good handheld meter is also good (and both together is even better).A good power supply is also more useful. Not so much for providing power but for setting current limits and experimenting with "will this run at XX volts".You can also afford to get the logic analyzer add-on for your Siglent 1000 series. That will be great for your digital work.What solder station have you got? A 100 Euro solder station is much better than a 20 Euro station.Hot air gun for desoldering?Thermal camera? More useful than you might think...

author: tautech
author_rank: Super Contributor
timestamp: December 24, 2021, 09:42:27 pm
content: Quote from: Fungus on December 24, 2021, 09:37:20 pmDon't, it's an abomination get the SDS2104X+ and SPL2016 instead. Totally different and better class of MSO probe.

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 09:47:49 pm
content: Quote from: tautech on December 24, 2021, 09:42:27 pmTautech says something made by Siglent is an abomination? Avoid like the plague.(I haven't actually used one, I sorta assumed it would work for 300 Euros given that the rest of the 'scope is OK)Quote from: tautech on December 24, 2021, 09:42:27 pmAnd ... totally blows the budget. That's the tautech we know and love.Edir: I'm only kidding, OP did mention "2000 Euros" somewhere and it's not quite 2000...

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 10:06:26 pm
content: Hahahaha you all good guys!I like you

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 10:16:52 pm
content: Quote from: Fiorenzo on December 24, 2021, 10:06:26 pmHave you tried averaging mode yet?

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 10:19:40 pm
content: So, I did some test, just to learn and experiment.Same crappy psu, two probes ON in DC mode, one disconnected and the pink one probe on the psu output.First photo 10x attenuation, second photo 1x.The ripple of the psu is about 150mv, now the front end noise seem to make a good part of the noise saw on the ripple wave, high resolution or avarage get rid of a big part of this noise. If I did not be aware of the noisy front end i could think that the noise in the ripple was from the psu itself.Second if i work with the probe in 1x mode the ripple Is now very evident.Is this the right way to check It? I mean in 1x mode.Should i use AC or DC mode?I have read that AC mode get rid of the DC bias so good to work in this way...

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 10:24:16 pm
content: Quote from: Fungus on December 24, 2021, 10:16:52 pmYes many times, and also hi-res mode.I didn't used It in the photos because i wanted to show the real front end noise.Actually i really like this rigol, Is a powerfull scope, but i have never put my hands on the siglents

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 10:34:17 pm
content: Quote from: Fiorenzo on December 24, 2021, 10:19:40 pmRipple can only be at the switching frequency of the PSU, never in the MHz range.Quote from: Fiorenzo on December 24, 2021, 10:19:40 pmYes. 1x mode with 20MHz bandwidth limiter and maximum averaging.Quote from: Fiorenzo on December 24, 2021, 10:19:40 pmAC will center the ripple waveform around zero so you measure RMS, etc.(ie. it's good)

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 10:37:11 pm
content: Quote from: bdunham7 on December 24, 2021, 09:17:11 pmAhhahaah bdunham7 with the same settings i get almost 5 times your noise. The Rigol really like noise....

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 10:40:29 pm
content: Quote from: Fungus on December 24, 2021, 10:34:17 pmThank you fungus you are helping me very well.And also merry Christmas in advance to everyone!!

author: tautech
author_rank: Super Contributor
timestamp: December 24, 2021, 10:41:51 pm
content: Quote from: Fungus on December 24, 2021, 09:47:49 pmIt works fine but it becomes another box on the bench instead of being inbuilt which would be difficult with the very compact SDS****X-E series.Quote from: Fungus on December 24, 2021, 09:47:49 pmSPL2016 with a new scope are on special ATM until at least years end for the unbeatable price of $219 with MSO and FG licensing. That's one hell of a deal unless you want to DIY one with the info from that thread.Christmas midday dinner calls.......

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 10:47:50 pm
content: Quote from: bdunham7 on December 24, 2021, 09:17:11 pmWhat circuits works with such a low intensity signals?Sensors for example?I could think about maybe a shunt, they gives very low output when measuring currents, i use many times shunts in my circuits....Speaking instead about a signal amplifier, as suggested by some one in this thread, It was told that they are a better way to check low intensity signals than giving faith on a low noise front end.Is this true all times?

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 10:52:15 pm
content: Quote from: Fungus on December 24, 2021, 10:34:17 pm...which is of course thewrongway to do it, and was the big error in the now-infamous "Rigol vs. Siglent noise" video.Using AC mode to calculate RMS assumes the 'scope is perfectly calibrated, ie. with zero offset voltage.The correct way to measure RMS is with "Std.Dev", which removes the offset voltage mathematically in both AC and DC modes.You should still use AC mode though because it centers the signal and allows you to crank up the vertical scale without going off screen.

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 10:56:16 pm
content: Quote from: Fiorenzo on December 24, 2021, 10:24:16 pmAveraging mode isn't cheating! It's there for a reason...(And even Siglents have it)

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 10:58:52 pm
content: Watch this photo attached.If i don't ground the probe tip the oscilloscope shows a 50hz sinewave. I have also tried turning off every appliance connected near the scope and also the lights but the sine wave remain unchanged.

author: nctnico
author_rank: Super Contributor
timestamp: December 24, 2021, 11:12:54 pm
content: Quote from: Fiorenzo on December 24, 2021, 10:47:50 pmFor such purposes you better use a pre-amplifier with a differential input. You can easely DIY these using an instrumentation amplifier chip or a specific current sensing amplifier chip. From there feed the amplified signal into your oscilloscope.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 11:26:59 pm
content: Quote from: tautech on December 24, 2021, 10:41:51 pmYes i really need a complete mso now because i am designing an e-bike controller from scratch and also working with the display circuitry and program that i am also designing from the bottom. I did similar things in the past, but without an oscilloscope and had to cope with the problems encountered only with the help of the theory and literature due to the fact that i couldn't check my circuits... But i got to the end fine everytime. Such a satisfaction...Sorry for my bad english...The offer from siglent is very appealing and i don not have the time now to make the probes by my self.But i could instead buy a cheaper scope and an external LA to connect on the computer, maybe this is the best way to proceed at the momentUmmm... But i am not sure what way i will take hahaha....Actually i saw that the AWG of the siglent and rigol are limited and an external signal generator could be better.... But i like that the Rigol has two outputs.I should try a siglent but Amazon don't sell It here in Italy, only the lower models....

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 24, 2021, 11:28:18 pm
content: Quote from: nctnico on December 24, 2021, 11:12:54 pmThank you i will do It

author: bdunham7
author_rank: Super Contributor
timestamp: December 24, 2021, 11:48:31 pm
content: Quote from: Fiorenzo on December 24, 2021, 10:47:50 pmYes--sensors, audio circuit, measuring circuits, even RF circuits. And keep in mind as I said before that you may often want to use a 10X or even 100X probe or custom voltage divider to avoid loading the circuit you are testing and that will magnify the problem.Here's the scope with a 10X probe connected to a 50-ohm terminated signal generator with no signal running, no signal single-shot and then the same 1mV signal as before. Note that I had to use the single-shot to capture the signal as it is so low that the scope won't trigger on it, however it is still clearly visible above the noise.As far as preamplifiers, yes they have a place but they are usually fairly specific and limited, as opposed to being general purpose. For example they typically have a much more limited input voltage range or bandwidth, or both.

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2021, 11:54:09 pm
content: Fiorenzo,Can you post a screenshot of your PSU ripple with 20MHz limiter and maximum averaging?

author: David Hess
author_rank: Super Contributor
timestamp: December 25, 2021, 12:40:56 am
content: Quote from: Fungus on December 24, 2021, 08:03:33 pmI have wondered about that. Preshoot in analog oscilloscopes comes from the delay line implemented as either a lumped-element transmission line or counter braided differential coaxial line. Both have a sharp cutoff frequency and faster propagation of high frequencies than low frequencies, but that sharp cutoff reminds me of the truncated Fourier coefficients which lead to the Gibb's phenomena.Quote from: Fiorenzo on December 24, 2021, 09:12:21 pmIt is possible but as I pointed out, noise is not the only consideration. My preferred oscilloscope has about 120 microvolts RMS input noise because it comes with high input common mode range and differential inputs which are more useful, similar to the AM502 mentioned below.Quote from: Fiorenzo on December 24, 2021, 07:30:31 pmLike I wrote earlier, except for FFTs where noise is a direct limitation, it is not very important. Oscilloscopes are noisy because of the compromises they have to make.When making measurements, other sources of error usually overwhelm noise. Ground loops with single ended probes and the probe ground lead will pick up all kinds of noise in excess of an oscilloscope's front end noise. This suggests that money is better spent on better probes than an oscilloscope with the lowest possible noise which cannot be taken advantage of anyway.Power supply ripple is separate from power supply noise, and a DSO can be triggered and use averaging to remove the noise and keep the ripple. Measuring power supply noise on the other hand will often require a low noise preamplifier which is not difficult to build.In audio applications, an oscilloscope has so much distortion that only gross measurements will be accurate, so noise is not relevant.If you are interested in general purposes low noise measurements within a 1 MHz bandwidth on any oscilloscope, then you might find aTektronix AM502 differential amplifierto be useful. They are easy to repair because unique parts can be sourced from the Tektronix 5A22 and 7A22, and they work well with 1x oscilloscope probes. Using one does mean acquiring a TM500 series power supply mainframe though.QuoteNoise specifications are generally lacking so it is difficult to make a recommendation based on them.Something to consider about the 70 MHz Rigol MSO5072/MSO5074 is that it is bandwidth upgradable to 350 MHz via firmware meaning that it has the higher noise 350 MHz front end whether the bandwidth is limited to 70 MHz or not. So it must have a higher noise than the example I gave of 100 MHz oscilloscopes.What is going on here is that for a given device technology, higher bandwidth yields higher noise density. So for instance a JFET front end which supports a bandwidth of 100 MHz could have a noise density of 3.5 nV/Sqrt(Hz), while a JFET front end which supports 350 MHz would have a noise density several times higher, whether the bandwidth is limited or not. For the same bandwidth, a lower bandwidth oscilloscope can have lower noise than a higher bandwidth oscilloscope.I suspect that is a major part of what is going on with the relatively high noise of the MSO5072/MSO5074. Its noise should be compared to other 350 MHz instruments even though it is limited to 70 MHz.

author: bdunham7
author_rank: Super Contributor
timestamp: December 25, 2021, 01:36:00 am
content: Quote from: David Hess on December 25, 2021, 12:40:56 amI also would put up with a bit of noise to get differential inputs. The isolated scopes that I have are also a bit noisier and I don't complain.As for the Rigols, I really think the issue is how they manage the lowest ranges by using a digital expansion of a higher range. Other scopes would have an additional 10X analog gain. The scope I used for comparison is 200MHz+, the more comparable SDS2000X+ models are 500MHz+ and have slightlybetternoise levels than mine. Comparing 300-500MHz class scopes with the old Tek 2465B that I have--which gets very close to what you said is the ideal noise level-- the better Siglent is maybe 50% noisier (hard to compare because the Tek doesn't have 1mV or 500uV/div settings), the cheap Siglent is 2X as noisy and the Rigol is about 8X. It's like going from a fine-tip ball point pen to a Sharpie and then to a highlighter or magic marker. Of course that is not using ERES or 10-bit or any other DSO tricks.

author: G0HZU
author_rank: Super Contributor
timestamp: December 25, 2021, 11:24:56 am
content: My background is RF so I generally don't use a scope very often but when I do it is nice to look at small signals.I have a really old HP Infinium digital scope with 500MHz bandwidth and it has the noise performance I would expect. At full 500MHz bandwidth and with the input set to 50R termination and 1mV/div it shows about 100uV rms noise when the Vrms measurement is enabled. When fed with noise as the signal under test it can typically measure wideband or narrowband noise signals with acceptable results down to about 200uVrms. This scope is fairly limited in terms of features (and memory depth) compared to modern scopes but it does at least have the noise performance I'd expect from a scope like this.

author: knudch
author_rank: Regular Contributor
timestamp: December 25, 2021, 03:37:57 pm
content: Random Noise is one thing..If you @Fiorenzo would try on your Rigol a thing like this:(done 50ohm termination)Discrete "false signals is something else

author: G0HZU
author_rank: Super Contributor
timestamp: December 25, 2021, 05:43:59 pm
content: Here's my old HP Infinium scope set to 1mV/div with the 30MHz bandwidth limit enabled.The Rigol scope was showing about 1mVpkpk on a 20MHz bandwidth setting which seems really noisy in comparison to my HP scope from the 1990s.My advice to Fiorenzo is to consider something else if the poor noise performance of the Rigol is bothering you. That level of noise would put me off buying a Rigol scope although I doubt I would ever buy one anyway.

author: Fungus
author_rank: Super Contributor
timestamp: December 25, 2021, 06:11:48 pm
content: Quote from: G0HZU on December 25, 2021, 05:43:59 pmWhat's the bandwidth/sample rate of that? The Rigol has 350MHz pathways and is sampling at 8GHz which inherently produces noise, no way around it.Does your HP have waveform averaging mode?At least it looks like your HP can zoom out.

author: David Hess
author_rank: Super Contributor
timestamp: December 25, 2021, 07:19:24 pm
content: Quote from: G0HZU on December 25, 2021, 11:24:56 amWhen a low impedance input is used, higher bandwidth oscilloscopes bypass the high impedance buffer and without that, the input noise can be much lower. The high impedance buffer has to be bypassed because at some point it will not have enough bandwidth.An example of this in old oscilloscopes is the venerable Tektronix 485 which was built at a time when the fastest high impedance buffers were 250 to 300 MHz. In 50 ohm mode, instead of inserting a 50 ohm feedthrough termination before the high impedance buffer, a coaxial relay directs the signal around the high impedance buffer.Later oscilloscopes managed high input impedance up to 500 MHz and I think some now manage 1 GHz.

author: G0HZU
author_rank: Super Contributor
timestamp: December 25, 2021, 07:25:44 pm
content: QuoteI'm not quite sure what info you are asking for but this is a really old HP scope using very dated technology. The basic specs are 2GSa/s and 500MHz bandwidth across 4 channels. Yes it has an averaging mode but it isn't turned on. The 30MHz bandwidth limit is turned on for the screenshot in my previous post.

author: G0HZU
author_rank: Super Contributor
timestamp: December 25, 2021, 07:30:59 pm
content: QuoteIf it helps, I can switch the scope to 1Meg input and attach a 50R load and it looks pretty much the same. There might be a tiny bit more noise but any change is barely perceptible.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: December 25, 2021, 07:41:25 pm
content: some scopes are just badly designed, full of switchmode own noise..the good old Rigol 1054 that we almost all owned ..here i posted a few pictures, look and cryhttps://webx.dk/rigol/

author: Fungus
author_rank: Super Contributor
timestamp: December 25, 2021, 07:51:23 pm
content: Quote from: G0HZU on December 25, 2021, 07:30:59 pmThere's no point. Everybody here knows (and freely admits) that lower noise oscilloscopes exist. They make for pretty screenshots and youtube videos.The questions is: How much advantage does it give you in real life?For digital signals? None at all. For that you need bandwidth and high sample rates which is where the MSO5000 shines.For periodic signals in the mV range? I suspect the answer is "not much if you use averaging", hence me asking if anybody can post a picture of a Rigol MSO5000 showing power supply ripple with 1x probe, 20MHz limiter and waveform averaging. (Prove me wrong!)For non-periodic signals in the mV range? You'd have an advantage there but they're few and far between and you're probably better off looking for them in FFT mode than trying to trigger on them and view them as a trace.nb. Foranysignal in the mV range you can add a signal amplifier. They sell 30dB amplifiers on aliexpress for not much money.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 25, 2021, 08:34:41 pm
content: The x1 probe is not always an option: it is slow (e.g. 5-10 MHz BW) and quite some load (e.g. 100 pF range).With a x1 proble the probe will limit the BW, but it still makes sense to enable the 20 MHz limit to reduce amplifier noise, as there is essentially no signal > 20 MHz anyway.With a non periodic signal the FFT is not an option. It would not give much (if any) useful information.Averaging only works well if one has a good signal to trigger from - so if there is only a small / noisy signal this will not help.Noise in the trigger signal can smoothen out the signal with averaging.With the rigol scope still at hand, one could measure the noise, to see if it is really much worse, or just looking higher noise with higher sampling rate.A point to compare would be with a short (input to GND), a time scale to get a comparable sampling rate (e.g. 1 Gs/s and thus BW limited by the sampling rate to 250 MHz) with only 1 channel active and than a high gain (e.g. 1 mV/div or 5 mV/div before the probe setting).Some digital signals like LVDS are not that large: 400 mV at the input would be 40 mV after a 10:1 probe and thus may want 5 mV/div sensitivity.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 25, 2021, 08:38:19 pm
content: Quote from: Fungus on December 25, 2021, 06:11:48 pmThe picture show 10 Ms/s. So there is anditional BW limit (~ 5 MHz) there. To do a fair comparison one would have the switch the faster scope also a slower hirizontal rate to get the lower sampling rate.

author: Fungus
author_rank: Super Contributor
timestamp: December 25, 2021, 08:42:21 pm
content: Quote from: Kleinstein on December 25, 2021, 08:34:41 pmIf the ripple is too small to trigger from then the power supply is probably OK and there's nothing to worry about.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: December 25, 2021, 08:51:35 pm
content: my siglent, looks like same signal as yours fungusclearly alot less noise, but this is only a 2GS scope :-)

author: Kleinstein
author_rank: Super Contributor
timestamp: December 25, 2021, 08:54:19 pm
content: Quote from: Fungus on December 25, 2021, 08:42:21 pmIt is not just triggering, just a stable triggger to see fast parts too.Often there is a stable trigger available, but one may have to find it. An extra trigger and than looking at the ripply would even separate contricbutions to the ripple if there are multiple asyncronous parts (e.g. mains and a SMPS).It really depends on how much ripple you still care. Sometime 0.1 mV could be too much.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: December 25, 2021, 09:06:44 pm
content: 1mV div, here is where you really see the internal noise :-)

author: G0HZU
author_rank: Super Contributor
timestamp: December 25, 2021, 09:42:58 pm
content: QuoteI'm not sure there will be a 5MHz bandwidth limit. With the 30MHz limiter enabled I think the bandwidth limit for signals is still 30MHz on this scope even at low sample rates. One would have to be wary of aliasing but the signal being viewed here is noise.

author: Fungus
author_rank: Super Contributor
timestamp: December 25, 2021, 09:43:36 pm
content: Quote from: Kleinstein on December 25, 2021, 08:54:19 pmYep. No arguments there. That's why I was wondering if OP can actually do it in practice.He already posted a screenshot of his ripplehereso let's see what the 'scope is capable of. It looks like a triggerable signal to me but I don't have an MSO5000 to play with..

author: nctnico
author_rank: Super Contributor
timestamp: December 25, 2021, 09:49:05 pm
content: Quote from: Fungus on December 25, 2021, 07:51:23 pmYou keep taking the wrong turn when only focussing on small signals. Your screenshot clearly shows a wide band of noise where any detail on any signal level is lost. The noise is easely 40% of a division. With 8 divisions and 8 bits you have 32 LSB per division but with 40% noise you might as well have a 5 bit ADC and still get the same result. Needing to use averaging or high-res mode is just a crutch when the noise comes from the DSO itself.There are so many lower noise alternatives out there from GW Instek, MicSig and (if you have the budget) R&S as well that it makes no sense to buy a noisy Rigol at all.

author: Fungus
author_rank: Super Contributor
timestamp: December 25, 2021, 10:04:35 pm
content: Quote from: nctnico on December 25, 2021, 09:49:05 pmExcept for the Pesky Fact that OP says he mainly does digital stuff and nobody else makes a 4 channel, 350Mhz, 8GSample/sec 'scope for only $1000.To me it seems like you're arguing that a car with leather seats will allow people to carry more shopping.

author: Performa01
author_rank: Super Contributor
timestamp: December 25, 2021, 10:10:33 pm
content: I think it’s time to do some myth-busting – and providing some hard evidence instead of presenting just wild guesses.Myth #1: “Noise is only important when using x1 probes. It is irrelevant when using the much more common x10 probes, because the high source impedance will exceed the noise of the DSO anyway.”Nothing could be further from the truth. The only relevant effect is the attenuation of the probe, which requires an appropriate vertical gain on the DSO to compensate for it. And of course this won’t matter much at the low sensitivities, i.e. the noise will be about the same with a x1 probe at 10 V/div, a x10 probe at 1 V/div and a x100 probe at 100 mV/div. But if you happen to work with signals much lower than 80 Vpp, you will notice that 1 mV/div with a x100 probe will be noisier than 100 mV/div with a x1 probe and that in a scenario like this, a proper low noise frontend will be much more pleasant to work with. You sure don’t want the excessive noise of an e.g. Rigol MSO5000 when working with x100 probes (e.g. in vintage tube gear).The output impedance of a x10 probe is dominated by an output capacitance of about 100 pF, therefore the noise bandwidth is only about 1.6 kHz. So except for very low frequencies <100 kHz, we won’t see any significant difference in a properly designed general purpose DSO frontend, whether the scope input is left open, terminated by 1 M or 50 ohms or shorted to ground.For low frequencies, things are a lot more complex than just a FET buffer, because of the split path design of all contemporary wideband frontend designs. The practical consequence is, that general purpose (wideband) oscilloscopes generally aren’t well suited for low frequency tasks below about 10 kHz regardless of the probes used. There are specialized instruments for this.Look at the first two screenshots attached. They show the noise spectrum up to 1 GHz of the Siglent SDS2354X (570 MHz bandwidth). First with the input left open in high impedance mode, then the input internally terminated by 50 ohms. There are minimal changes of the spurious signals (because of the different contributions of voltage- and current effects), but the noise changes by less than 1 dB within the 570 MHz bandwidth of the scope frontend.SDS2354X Plus_FFT_Noise_1M_ BW570M_8bitSDS2354X Plus_FFT_Noise_50_BW570M_8bitBtw: please notice, that up to 1 GHz there are few spurious signals and no spur is exceeding -120 dBV, which is equivalent to 1 µVrms. This is another important aspect, because strong spurs near the signal frequency can be at least as annoying as excessive noise.Myth #2: “Frontends with higher bandwidths are always noisy, even when bandwidth limited.”In any modern DSO, the bandwidth limit is an integral function of the PGA – and it sits at its output. So all the input noise gets filtered before the ADC. Of course this is only a first order RC-filter, because other than some popular believe, there is also no such thing as an effective AA-filter (Anti Aliazing filter) in a serious DSO. The most important property of any DSO frontend that is not a toy is constant group delay, and this rules out any “effective” AA-filter.But even with a humble first order filter, the effect of noise reduction is quite obvious.Next screenshot shows the noise floor at 50 ohms input termination again, but this time with 200 MHz input bandwidth limit. Btw, Siglent scopes show all relevant information on the screen, so screenshots should be pretty much self-explanatory.SDS2354X Plus_FFT_Noise_50_BW200M_8bitCompare this with the previous screenshot. At 110 MHz, we already have a difference of 0.8 dB. At 340 MHz it is nearly 6 dB and 7 dB at 560 MHz. That is a difference, isn’t it?The next screenshot demonstrates what happens if the common 20 MHz bandwidth limiter is activated.SDS2354X Plus_FFT_Noise_50_BW20M_8bitAt 20 MHz, noise is 2.7 dB down, we get -10.9 dB at 110 MHz, -16 dB at 340 MHz and -17.6 dB at 560 MHz.The SDS2000 series has an excellent software enhanced 10 bit mode, which limits the bandwidth to 100 MHz and lowers the noise floor even more. See the next screenshot.SDS2354X Plus_FFT_Noise_50_BW100M_10bitWith this setting, the noise floor fell below the -150 dBV above 200 MHz, so the reference level of the spectrum alanysis had to be adjusted accordingly. Little change up to 110 MHz, but -18.7 dB at 340 MHz and -26.8 dB at 560 MHz make this an excellent low noise mode in applications where 100 MHz bandwidth is sufficient.Of course we can use the 20 MHz bandwidth limiter here as well, as the next screenshot demonstrates.SDS2354X Plus_FFT_Noise_50_BW20M_10bitAt frequencies above 20 MHz, noise drops dramatically: About -13.5 dB at 110 MHz, -28.8 dB at 340 MHz and -31.6 dB at 560 MHz.So this proves that it has nothing to do with the genuine bandwidth of the frontend or any other signal paths. I can easily demonstrate that e.g. a modern 2 GHz DSO like the SDS6204 behaves no different in this regard. The following screenshot shows a noise plot of the 2 GHz scope that can be compared to the very first screenshot in this posting.SDS6204_FFT_Noise_1M_BW2G_D1GThis is in high impedance mode with open input. Once again, the noise with internal 50 ohms termination is very similar. More interesting is the comparison of this 2 GHz scope with the SDS2354X Plus. Even though the high bandwidth scope produces more spurs (but only very few of them slightly exceed 1 µVrms), the noise is comparable or mostly even better than on its 500 MHz counterpart – within the operating bandwidth of the latter, that is. Of course, at 840 MHz the SDS2304X Plus is already in the stopband of the frontend and noise drops significantly, whereas the SDS6000 has not even reached half its bandwidth, so its noise at that frequency has to be in the same ballpark as the other measurements before.What these screenshots also reveal, is that the sample rate does not affect (excessive) frontend noise. If anything, higher sample rate helps to reduce noise. The 5 GSa/s, 2 GHz scope produces less noise than its 2 GSa/s, 500 MHz counterpart.There is the ADC noise itself, which is the granular noise determined solely by the ADC resolution, not the sample rate. A higher sample rate will spread out the noise energy over a wider bandwidth, but the total energy will remain the same. So if only a limited part of that bandwidth is observed (i.e. FFT zoom feature), only a part of the noise is visible, hence will appear lower than the total noise actually is.High sample rates also do not accentuate high frontend noise.If the sample rate is excessive with regard to the bandwidth of the frontend, it will just produce redundant data and pointlessly eat up sample memory with little to no effect on the result.If, on the other hand, the bandwidth of the frontend exceeds half the sample rate, the noise portion above Nyquist will be aliased back into the Nyquist bandwidth, hence we’ll still get all the frontend noise, even with inadequate low sample rates.

author: G0HZU
author_rank: Super Contributor
timestamp: December 25, 2021, 10:38:47 pm
content: QuoteYes, that's what I find with my old HP scope here when the 30MHz bandwidth limit is selected. It still measures the noise level fine even at very low sample rates. It doesn't matter at all because the signal being measured is noise. The same applies if I deliberately feed wideband noise to the scope front end and use a very low sample rate to try and measure the Vrms of the noise. As long as the bandwidth of the external noise signal is less than the 30MHz bandwidth of the scope it should measure the Vrms quite well even at 100kSa/s.

author: bdunham7
author_rank: Super Contributor
timestamp: December 25, 2021, 10:44:12 pm
content: Quote from: Performa01 on December 25, 2021, 10:10:33 pmI think the statement, at least the one I'm thinking of, was that the noisedensitywas higher for higher-BW capable amplifiers. The noise will still be a function of the noise density and the actual bandwidth, so limiting BW will still reduce noise as expected.QuoteI believe that many very-high-BW scopes now have more than a first-order roll off and thus a flatter frequency response but poorer step response. IIRC either Tek or HPAK or both had/have models where you specify which way you want it as a factory option. I don't think this is specifically for anti-aliasing, but it will have that effect. I can't be very specific because stuff like that doesn't get into my hands much--I have to read about it here on EEVBlog.

author: Performa01
author_rank: Super Contributor
timestamp: December 26, 2021, 07:12:27 am
content: Quote from: bdunham7 on December 25, 2021, 10:44:12 pmWell, the FFT plots in my screenshots show nothing but the noise density. Of course, the total noise is actually higher for the 2 GHz instrument at full bandwidth than what it could ever be on the SDS2kX Plus.I strongly suggest that, other than in the seventies of the last century, for modern semiconductors the noise density remains fairly constant over frequency. In my screenshots it can be seen that it gets rather lower at higher frequencies and four times the system bandwidth doesn’t mean higher noise density at all.Quote from: bdunham7 on December 25, 2021, 10:44:12 pmYes, the genuine bandwidth of most scopes is not first order gaussian – unless they are artificially bandwidth limited. This is also why we don’t get ideal pulse response characteristics and vendors have to specify some overshoot.There can be all sorts of filters in high end scopes – mainly for pulse response equalization, but you can have higher order AA-filters as well. But this is limited to filters with Gaussian and Bessel characteristics, where the transition from the passband to the stopband is very smooth, so you still need substantial oversampling in order to get a useful attenuation to fight aliasing. Nothing gained for todays top models within a series, where the bandwidth is not at least five times lower than the sample rate.Furthermore, higher order filters can get tricky with regard to their sensitivity to component tolerances (and their temperature stability) and they might need alignment in the first place. All this increases effort and costs and puts the risk of different frequency/phase response in different DSO channels.This is probably why standard PGAs for “normal off the shelf” instruments have the bandwidth limiter integrated and designers have decided that a first order RC-filter is the best compromise.

author: rf-loop
author_rank: Super Contributor
timestamp: December 26, 2021, 07:19:18 am
content: Quote from: bdunham7 on December 25, 2021, 10:44:12 pmAs is also of course in not-very-high-BW Siglent SDS6k."poorer" step response... what can also turn to "less aliasing" step response.

author: jonpaul
author_rank: Super Contributor
timestamp: December 26, 2021, 10:38:55 am
content: Bonjour just seen this long thread now.Suggest the OP check the many fine books and papers on noise, measurement, reduction, definition.The noise "floor" is a function of the resistance, bandwidth, temperature.Averaging is possible only on repetitive signals.Noise may be irrelevant in some digital systems, but or primary importance in fine instrumentation, audio, etc.Think of microphone preamps, seismic pickups, photomultipliers, etc.A digital scope and analog are "different animals" and have various benefits and downsides.Many options for preamps, diff amps, etc. The best we have seen are the TEK 7000 plugin 7A22.Finally the Chine scopes may have misleading specs and hidden faults, the cheapest implementation.We have used the classic Tektronix scopes since 1967.Just my reflections!Bon Chance,Jon

author: gf
author_rank: Super Contributor
timestamp: December 26, 2021, 11:09:48 am
content: Quote from: Performa01 on December 25, 2021, 10:10:33 pmThe spectrum reminds me on the typical frequency response of a 8-tap moving average filter (possibly in addition to other filters).Is this the well-known HiRes mode, or yet a different mode?

author: David Hess
author_rank: Super Contributor
timestamp: December 26, 2021, 11:34:57 am
content: Quote from: Performa01 on December 26, 2021, 07:12:27 amFor agiven transistor technology and construction, there is a tradeoff between bandwidth and noise density, so for instanced a 2N3822 JFET supporting a bandwidth up to 115 MHz (1) has a noise density of about 3.5 nV/Sqrt(Hz) while a 2N4416 JFET supporting a bandwidth up to 250 MHz has a noise density of about 6 nV/Sqrt(Hz). If the later is used in a 100 MHz amplifier, it results in higher noise than the lower performance part even with the same bandwidth.Further, in general MOSFETs are noisier than JFETs which are noisier than bipolar transistors, which may be an issue with modern instruments which are more likely to rely on RF MOSFETs instead of RF JFETs for their input buffer. It is difficult to make an analytical comparison here even if we know what part is being used because the RF MOSFETs are not as well characterized for noise. This also means that the noise from a bipolar stage following the high impedance input buffer should be of no significance.The above does not apply to higher bandwidth instruments that use exotic and effective unavailable to us technologies. Specialized transistors on exotic processes will have a completely different figure of merit for bandwidth and noise compared to silicon MOSFETs, JFETs, and bipolar transistors, but the general rule about the tradeoff between them still applies. But these inexpensive DSOs up to 350 or maybe even 500 MHz are not using anything like that.And of course none of the above says anything about poor design. Noise could be in excess of the predicted front end noise for lots of different reasons. Empirical measurement is king here and easy to do in this case if the oscilloscope can report peak-to-peak or AC RMS (standard deviation) measurements. (2)(1) As a source follower where Ft = Gm / (2 Pi C); the transistor used for the high impedance buffer needs high transconductance and low capacitance. High transconductance reduces noise, up to a point where other internal noise sources dominate, but the construction for low capacitance increases it.(2) Which reminds me to suggest being a little cagey about Rigol's RMS and standard deviation measurements on a noise waveform, or any instrument which makes measurements on the display record. I have seen evidence in that past that the processing to produce the display record corrupts these measurements when applied to noise.

author: David Hess
author_rank: Super Contributor
timestamp: December 26, 2021, 11:38:41 am
content: Quote from: G0HZU on December 25, 2021, 09:42:58 pmAt low sample rates the noise within the ADC input bandwidth simply gets aliased to lower frequencies. The total noise remains the same.Quote from: Performa01 on December 25, 2021, 10:10:33 pmSplit path high impedance buffers started showing up not long after integrated low input bias current operational amplifiers in the 1970s. The split path actually reduces low frequency noise because even a noisy operational amplifier has lower flicker noise than the RF FET used for the high impedance buffer. Sometimes it is a lot lower.The disadvantage of the split path design is that without careful consideration, overload recovery can be horrible.Quote from: gf on December 26, 2021, 11:09:48 amHigh resolution mode is usually or always implemented as a boxcar averaging filter for simplicity since it must operate at the maximum sample rate during decimation, so it should produce something like a sinc response which is what is shown.

author: gf
author_rank: Super Contributor
timestamp: December 26, 2021, 12:38:08 pm
content: Quote from: David Hess on December 26, 2021, 11:38:41 amIn the screeshot, obviously a 8-tap boxcar averaging filter (or similar) was applied, butwithout down-sampling, otherwise the 3 side-lobes were no longer visible in the spectrum, but already folded down to the first Nyquist zone of the lower sampling rate. So I was just wondering, whether this was really "HiRes" mode (in the sense of LeCroy's definition), or rather a different mode which just applies a post-acquisition filter.Indeed, when it must run in real-time, during acquision, then a boxcar filter has of course the simplicity advantage that it can be implement as CIC filter, not requiring any multiplications.Given the huge memory depths available today, a scope manufacturer may be tempted, though, to renounce capture-time DSP at all, and support only post-acquisition filters, for cost reasons.

author: Performa01
author_rank: Super Contributor
timestamp: December 26, 2021, 12:45:46 pm
content: Quote from: David Hess on December 26, 2021, 11:38:41 amYes, split path input buffer have been invented a long time ago – and it’s all the more baffling that most people don’t seem to be aware of it and make it sound as if an oscilloscope frontend still consists of a cascade of differential amplifiers. Maybe some even think it consists of just a high speed OpAmp…If you actually think the LF noise in a split path design would be reduced, you’re forgetting that the LF path has to be attenuated quite a bit (usually up to 10 times) in order to get the desired input protection and a decent offset compensation range. This has to be compensated for by a corresponding gain in the OpAmp. Together with the high source impedance of the divider (which has to have a total resistance of 1 meg) this can raise the noise floor by more than 20 dB below the crossover frequency.So there is no way around the sad fact, that the usual general purpose DSO isn’t well suited for precision work at low frequencies because of the steeply rising noise floor down there.

author: Performa01
author_rank: Super Contributor
timestamp: December 26, 2021, 12:57:16 pm
content: Quote from: gf on December 26, 2021, 11:09:48 amIt is either HiRes or ERES - I'm not quite sure - but in any case it is a true acquisition mode, in the sense of a real time pre-processing. The sample memory gets halved in this mode, because it is expanded to 16 bits width as the captured raw data now consists of 10 bit samples. All the post processing, measurements and math are now using the 10 bit data. The firmware cannot tell the difference between this resolution enhancement (implemented in the FPGA) or a true 10 bit ADC.

author: David Hess
author_rank: Super Contributor
timestamp: December 26, 2021, 08:12:51 pm
content: Quote from: gf on December 26, 2021, 12:38:08 pmThe implementations I have seen all used a power-of-2 number of samples so the filter could be implemented with only adds and shifts, and if promoting 8-bit acquisitions to a 16-bit record, only adds. Modern low end DSOs usually only produce an 8-bit acquisition record but all of the old Tektronix DSOs promoted 8 and 10 bit samples to 16-bits immediately and did all processing in 16-bits. Tektronix was very scrupulous at one time.

author: David Hess
author_rank: Super Contributor
timestamp: December 26, 2021, 09:13:48 pm
content: Quote from: Performa01 on December 26, 2021, 12:45:46 pmDifferential amplifiers are still routine and the highest performance digitizers have differential inputs. Usually the first stage after the low impedance attenuators converts from single ended to differential, and this stage is convenient for adding the combined position and offset signal is introduced.The various modern PGAs used in oscilloscopes are differential so they follow the same pattern, but since they replace the low impedance attenuators, position and offset are added after. DSOs with a separate offset control will add it before the PGA. Old designs which do this have to somehow add the offset before some of the attenuation stages which means moving some of the attenuators to the differential part of the signal chain which is relatively expensive.QuoteThat is a good point that I had forgotten, but the noise can still be lower even in old designs.Old designs which have two separate x10 high impedance attenuators limit the input range to the buffer to 1/10th the level of new DSOs, so attenuation on the DC path is also lower. The Tektronix 22xx series only attenuates by 1.33.Luckily for the discussion here, low frequency noise is irrelevant because wideband noise at 20 MHz and higher bandwidths dominates.QuoteI agree but if you include older instruments, then some general purposes DSOs are much better than others at low and/or high frequencies. I have not tested enough modern low end DSOs to know if they all have subpar noise performance. Even with older instruments though, I gave up on good low noise performance a long time ago with the exception of anything with the Tektronix 5A22/7A22/AM502.At low frequencies it is relatively easy to make a low noise amplifier, but since oscilloscopes lack the noise marker function for their FFT, I would like to have a low noise dynamic signal analyzer instead.

author: David Hess
author_rank: Super Contributor
timestamp: December 26, 2021, 09:16:42 pm
content: Quote from: Performa01 on December 26, 2021, 12:57:16 pmOld Tektronix DSOs used 16-bit acquisition and processing memory so high resolution mode did not halve the record length.

author: Performa01
author_rank: Super Contributor
timestamp: December 27, 2021, 01:14:52 am
content: Quote from: David Hess on December 26, 2021, 09:13:48 pmIt doesn’t make much sense to get philosophic about obsolete designs. We are talking about general purpose DSOs here, which ranges from entry level (low end) up to the midrange, but excludes high end gear, which is specialized and definitelynotgeneral purpose. At one point, at least after the invention of the digital readout, T&M industry noticed that a minimum of DC accuracy and stability was expected. Users were no longer willing to permanently turn the offset control of their scopes just to center the trace, as they used to do with their ancient CROs, but expected a decently stable offset position and some accuracy. So, the split path design has long become universal for all general purpose DSOs – despite its drawbacks, where the most obvious is the overload recovery issue. And this is unavoidable, even by a good design.Of course we find the cascaded differential stages in almost every HF IC, and in HF instruments like spectrum analyzers it might well be the only amplifier architecture required, but split path has become common in wideband general purpose oscilloscopes since they are supposed to work from DC up to the specified bandwidth.Btw, there are folks who have managed to build a balanced version of the split path input buffer, so you can have this with balanced inputs too.Quote from: David Hess on December 26, 2021, 09:16:42 pmIt’s not “old designs” that utilize two input attenuators. Of course you cannot build a good scope with vertical gain settings from 500 µV/div up to 10 V/div with just one single attenuator. For instance, every contemporary Siglent DSO has two input attenuator stages. Offset compensation voltage has to be added to the input in order to be effective (otherwise the input stage would require a totally unrealistic high common mode range), so this is part of the LF path of a split path input buffer design and topologically sits between the attenuators and the PGA.With low attenuation factors you either need high supply rails (old design) or you get only a very low offset compensation range. But does a Tek 22xx even have a split path design? The specifications of up to one division trace shift for variable gain and trace invert make me wonder. All the more so as the best sensitivity is not particularly high at 2 mV/div. Or maybe they use the cheapest FET-OpAmp with high Offset voltage and -drift without self-calibration in the LF path – but this would somehow scotch the whole idea of the split path approach?Above some 100 kHz the situation eases a lot and at 10 MHz and above we get noise figures in the realm of 2 – 3.5 nV/sqrt(Hz) with proper designs at least from Rohde & Schwarz, LeCroy and Siglent.Quote from: David Hess on December 26, 2021, 09:16:42 pmI do not know what you mean by “low end” DSOs. We are talking about serious instruments here, so low end would be the entry level class. But the problem is not limited to these – all contemporary scopes up to the upper midrange have the very same problem: rising noise at very low frequencies because of the special conditions in a split path input buffer design.If someone needs a superb instrument for low frequencies, then a Picoscope 4262 is one of the few options – apart from a DSA, that is. The 4262 only has 5 MHz bandwidth, but it is true 16 bits, has an SFDR of >96 dB and a near constant noise density from DC to its upper bandwidth limit.Quote from: David Hess on December 26, 2021, 09:16:42 pmI was talking about a Siglent SDS2000X Plus, which provides 200 Mpts memory per channel pair, hence there is some headroom for this. How long was the memory in said old Tektronix DSOs?

author: David Hess
author_rank: Super Contributor
timestamp: December 27, 2021, 03:36:58 am
content: Quote from: Performa01 on December 27, 2021, 01:14:52 amThe point is that the designs have not changed much. The PGA has replaced the low impedance switched attenuator but engineers then and now are solving the same problems. Early singed ended input digitizers were replaced with differential input digitizers, and differential signal paths were ultimately kept. Everything is more integrated now of course.QuoteThe move toward the split-path design was not driven by performance; it was about cost. It happened as soon as low cost monolithic low input current operational amplifiers became available. The cost savings came from replacing the discrete dual matched JFET with a single unselected JFET even though the split-path design requires trimming of the compensation or gain or both.QuoteHaha, I am one of those folks, but it was much lower noise, impedance, and bandwidth for low level DC differential amplification. I extended and improved an existing single ended design to fully differential and it worked perfectly on the first try, which pleasantly surprised me.QuoteModern "budget" DSOs use only one input attenuator, which places much greater demands on the input buffer to handle larger signal levels. The mid-tier models I have considered still use two input attenuators. The presence of two input attenuators might be a good way to divide the lowest end budget DSOs from the next level up in performance.QuoteThe Tektronix 22xx series does as shown below, and it might have been the first split-path design from them, but not all stages have balance adjustments in the 22xx series. It is split-path but DC coupled and the operational amplifier controls the source current of the JFET to produce the DC and low frequency output. Steve Roach discussed DC and AC coupled split-path designs in his article about oscilloscope signal conditioning.The offset null is used for balance which is a terrible idea for precision, but probably good enough for an oscilloscope. That might explain why one channel of one of mine has noticeable warmup drift.When I studied the design in detail years ago with an eye toward noise analysis, I got the feeling that the Tektronix engineers paid attention to proper distribution of noise and gain.Sensitivity was limited to 2 mV/div simply because greater sensitivity would require another preamplifier stage and noise was already greater than trace width, which seems funny now that modern oscilloscopes put up with even more noise. It is not shown below but the basic sensitivity is 5 mV/div. 2 mV/div relies on increasing gain by 2.5 times in the preamplifier instead of removing attenuation which was pretty common at the time but has disadvantages.The more modern AC coupled split-path amplifier allows AC and DC coupling to be implemented with the low frequency path instead of a high voltage RF relay which is a major advantage.QuoteThe maximum record length on those old DSOs is tiny by modern standards at only 4k, but even though fast RAM was expensive in both cost and size, they still made it twice as wide as needed. Processing in the modern way would have doubled the record length without increasing the amount of installed memory. Tektronix would later advertise this as a "no compromise" feature.

author: Performa01
author_rank: Super Contributor
timestamp: December 27, 2021, 11:31:39 am
content: Quote from: David Hess on December 27, 2021, 03:36:58 amWell, of course cost might have been a major consideration, even though I cannot see why back then a dual matched FET should have been more expensive than an IC that contains basically the same plus a bunch of additional transistors and other components. Today it’s a different story of course, because these are hard to get and expensive spare parts now, but back in the seventies a dual FET was about as affordable (or rather expensive) as a JFET OpAmp (like LF356) as far as I remember.The discrete differential stages usually did require trimming of the “offset balance”, as far as I remember the old circuit diagrams of up to 300 MHz frontends that did not use a split path topology.Even though your circuit diagram shows three trimmers, I don’t think we’ve seen this in recent designs. Self calibration takes care of the offset error and with modern low tolerance parts in the input and feedback networks the balance between both paths and the transition at the crossover frequency are good enough even without adjustments.Quote from: David Hess on December 27, 2021, 03:36:58 amCongrats – my hat goes off to you! This was (and still is) true design work, not very common anymore…Quote from: David Hess on December 27, 2021, 03:36:58 amThanks for the excerpt from the circuit diagram. It is quite interesting.Yes, I’ve immediately noticed that it’s only DC coupled, which means a number of drawbacks, particularly the fact that the input goes open circuit in AC coupled mode, whereas good designs are supposed to have a constant input impedance regardless of the input coupling, or any other settings for that matter.The LF-path also doesn’t provide the offset control usually found in DSOs – just because it really is best placed here. But yes, with the low division ratio of the LF input network, the compensation range could not be huge anyway. Nevertheless I have to assume that the offset adjustment is done at a later stage, which means that it actually relies on the usable common mode range of the input buffer – which will of course work to a certain degree because of the relatively high rail voltages of +/- 8.6 V.A maximum sensitivity of 2 mV/div means 16 mVpp full scale. Even 5 mV/div is equivalent to 40 mVpp FS. Since this is hardly enough to drive the plates of a CRT, there has to be a lot of amplification after the programmable attenuator. In a DSO, the ADC would require at the very least several hundred millivolts (but usually up to two volts) full scale for proper operation. This is why integrated PGAs do not only provide attenuation, but amplification as well. Consequently, as the signal needs to be amplified anyway, there’s no need to stop at 2 mV/div. With 20 MHz bandwidth limit the total noise in a proper low noise design can be as low as 20 µVrms, so this should not be a problem for the trace width.

author: G0HZU
author_rank: Super Contributor
timestamp: December 27, 2021, 02:40:05 pm
content: QuoteYes, I've seen these and there are also some alternatives. Very tempting. At the moment I sometimes use a Tek RSA3408A 8.5GHz RTSA for looking at low frequency stuff. This has a low noise floor and it has the advantage (for me at least) of having a 50 ohm input impedance. The Picoscope should be a bit better although it is limited to a 5MHz BW. The Tek analyser can capture 40MHz but it is only a 14bit system.

author: David Hess
author_rank: Super Contributor
timestamp: December 27, 2021, 03:27:38 pm
content: Quote from: Performa01 on December 27, 2021, 11:31:39 amMonolithic chips do not require hand grading for precision. The dual matched parts were graded by hand. Note that monolithic dual transistors will not work in this application because of parasitic coupling.Tektronix kept the simpler dual stacked JFET buffer in the trigger circuits where precision was less important.QuoteThe designs Steve Roach shows (attached below) include automated trimming of the gain of the low frequency path. He briefly mentions noise on page 70 where he discusses the shortcomings of RF MOSFETs.QuoteThe part of it that I really liked was adjusting the frequency breakpoint between the fast and slow path for lowest noise using a sampling DC voltmeter. Low noise was my primary design goal. Then I went back and measured the frequency of the breakpoint and it was exactly where the noise curves of the slow and fast path crossed, right where it should be.QuoteI do not know that one way is better than the other and oscilloscopes did it that way for decades without problems except where a DC return path was required. AC coupled designs have to sink the gate current somehow which presents its own complications. The reverse engineered Rigol DS1000Z front end that Dave made shows that the input resistance changes when coupling is switched, which has got to be incorrect, but maybe someone could measure it. The big advantage of the AC coupled split-path buffer is that coupling can be switched on the low frequency side with a solid state switch.QuoteThe stage following the low impedance attenuator does single ended to differential conversion and that is where offset and position are inserted. Since gain is fixed after that point, the scaling of the position control is fixed, but it was still also intended to operate as a limited range offset control.Adjusting offset at the input buffer in this case would alter the transconductance changing the gain and frequency response, but maybe not enough to matter? Later gain stages include first order correction of bandwidth and gain over temperature.QuoteThe worst case input signal range at 50 mV/div, where low impedance attenuation is maximum, is +/- 250 millivolts with overrange. The peak-to-peak noise is only apparent in digital storage mode. At the maximum sensitivity of 2 mV/div, the input noise is only just dominates the noise of the following stages.

author: Performa01
author_rank: Super Contributor
timestamp: December 27, 2021, 05:13:18 pm
content: Quote from: G0HZU on December 27, 2021, 02:40:05 pmI just had a closer look - and sadly my previous statement about near constant noise density isn't true. Even though it clearly is not a split path design and the 1/f corner frequency is significantly lower than for the 500 MHz and 2 GHz scopes that I have here, there is still some significant 1/f noise, slowly starting below some 25 kHz. Well, that's obviously the drawback of an 1 Mohms input impedance, requiring a FET input...Other than the general purpose scopes, there is a major difference between open circuit and 50 ohms termination. Without termination, the noise raises significantly.The noise density stays below 7 nV/sqrt(Hz) at and above 20 kHz, but gets as high as 102 nV/sqrt(Hz) down at 100 Hz. The first two attached screenshots show the noise spectrum at full sample rate up to 100 kHz and at full bandwidth. The noise density is generally higher than in the general purpose scopes (where it is in the range 2-3.5 nV/sqrt(Hz) at and above 1MHz), which might have to do with the higher sensitivity of these scopes. The Picoscope 4262 is limited to 20 mVpp full scale as the most sensitive range.EDIT: Caution! this is for AC coupling with incomplete termination, which results in bad LF performance.Pico_4262_Noise_50_5M_D100kPico_4262_Noise_50_5MNext comes the noise density graph:EDIT: Caution! this is for AC coupling with incomplete termination, which results in bad LF performance.Pico_4262_ND_50_5MA distortion test at 20 kHzSignal_1V_20kHzAnd finally a two tone intermodulation test, demonstrating the SFDR (just look at the cursor measurement; the automatic measurement failed because it obviously isn't intelligent enough to operate on the whole trace):Signal_IMD_40mV_20-21kHzEDIT:The noise measurements shown so far did not show the true performance, because they were flawed for two reasons:1. The input was AC coupled by accident, which of course increases LF-noise significantly.2. The input had a 50 ohm through terminator fitted, but since this scope is sensitive to the source impedance, an additional 50 ohm end terminator should be used to complete the 50 ohms setup.So I've added the correct measurement results for spectral noise and noise density:Pico4262_Noise_25_5MHz_D50kHzPico_4262_ND_25_5M

author: mawyatt
author_rank: Super Contributor
timestamp: December 27, 2021, 05:34:53 pm
content: The two tone IMD looks good as one would expect from a "True" 16 bit system. If you don't mind could you do this test at ~1MHz with the Picoscope 4262?BTW one of the reasons almost everything analogish in complex chips is differential is you can't get a good ground reference on-chip for larger size chips. Later when analog type flip ball bond chips became available the on-chip ground reference was better than with traditional wire bonds since these ball bonds could be located within the chip boundaries as required and thus offered a lower ground impedance.Best,

author: G0HZU
author_rank: Super Contributor
timestamp: December 27, 2021, 06:08:44 pm
content: QuoteThanks. The Tek3408A RTSA can be very laggy and frustrating to use at times but it is very powerful. The front end is 50 ohms and the noise figure at low frequencies is about 20dB. I've not looked to see how noisy it is below 1kHz but it's bound to get a bit noisier here.

author: Performa01
author_rank: Super Contributor
timestamp: December 27, 2021, 06:19:21 pm
content: Quote from: David Hess on December 27, 2021, 03:27:38 pmThanks for the explanation – this makes sense of course.Quote from: David Hess on December 27, 2021, 03:27:38 pmYes, this well known article is brilliant indeed! Yet we can see its age by looking at the first schematic, figure 7-1: the 50 ohms termination is accomplished by just a resistor, that is connected in parallel to the ordinary high impedance input with its high shunt capacitance – a solution that is barely suitable for scopes with a bandwidth exceeding some 100 MHz.Quote from: David Hess on December 27, 2021, 03:27:38 pmIt’s been quite some time, but I think I remember that this reverse engineered Rigol schematic has a number of errors in it. Some are more obvious than others. It is a nice means to get an overview, but certainly not suitable to study any circuit details.Well, just because the AC block has been in the input path for a long time, especially when the bandwidth of a scope was rather low, this does not mean that it is a good thing to have to be prepared for unexpected changes in some major characteristics, when operating a switch that basically just alters the frequency response.Consider a high impedance (100 Mohm), x100 high voltage probe connected to 2kV. If you now switch to AC coupling by accident, the input DC-block capacitor will charge up. Current is limited by the probe resistance, but after 10 seconds the capacitor might be charged to about 1.9 kV and this is equivalent to some 60 mJ of energy. So if the (supposedly) 400 volts rated capacitor doesn’t break down (and suffers damage or at least permanent degradation), it will send a potentially destructive pulse of electric energy into the frontend as soon as someone connects a low impedance source to the input after that incident.Quote from: David Hess on December 27, 2021, 03:27:38 pmFigure 7-3 in your document shows the usual approach where to feed V_offset.In your circuit diagram of the Tek 22xx the offset voltage (delivered from an OpAmp with close to zero output impedance within the LF frequency range) would have to be fed into the lower leg of R98 (after disconnecting it from ground, that is). But with the low division ratio, which clearly is an attempt to keep the LF noise down, there is almost nothing gained, so I can completely understand why it’s done differently in this particular case.EDIT: Sorry, only now i've checked what you mean. Of course, with the transistor output stage the original approach for offset compensation cannot be used.

author: Performa01
author_rank: Super Contributor
timestamp: December 27, 2021, 06:41:52 pm
content: Quote from: mawyatt on December 27, 2021, 05:34:53 pmHere you go - this instrument is not sensitive enough - you can barely see the IM3 products at 990 and 1020 kHz.Signal_IMD_40mV_1000-1010kHz

author: David Hess
author_rank: Super Contributor
timestamp: December 27, 2021, 08:17:11 pm
content: Quote from: Performa01 on December 27, 2021, 06:19:21 pmIt works well with my 150 MHz 2445 and 300 MHz 2440 but they use hybrid construction so the parasitic elements are much less than with a surface mount printed circuit board. I think the later TDS series did it up to 500 MHz but maybe not because the 1 GHz models obviously could not have. As mentioned earlier, the old Tektronix 485 with printed board construction did *not* use a switchable termination but instead an RF relay to direct the input to either the high impedance buffer or a separate 50 ohm input, and the specifications reflect it with lower bandwidth in high impedance mode. At the time I do not think they had a faster JFET high impedance buffer or they would have used it. I consider the 485 to be a "heroic" engineering effort.Based on context, I think Steve Roach worked on the 500 MHz and 1 GHz TDS series of oscilloscopes so his article gives an idea about what was going on in the late 1990s and early 2000s. I believe this makes it particularly useful for emulation in modern amateur designs.QuoteTektronix made high voltage 10x and 100x probes with a built in parallel resistance to avoid that problem. They can be identified by having a lower than expected input resistance. Probes like this are still made but they are difficult to find and come with a premium price.QuoteThe 22xx series also did not need a different method because it is based on a traditional analog design where that was a solved problem. It just represents the last fully documented oscilloscope design along with the 24xx series of analog and digital storage models.Even so, I consider the 2232 to be the first "modern" DSO design with a recognizable user interface. It's predecessor, the 2230, has an archaic albeit interesting user interface and really bridges the gap between analog and digital designs.I do not recommend duplicating the 22xx design, but a lot can still be learned from it.I wish we had better data on available RF MOSFET noise characteristics. What is available is intended for RF amplifier applications.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 27, 2021, 08:28:48 pm
content: I would like to thank you everybody for the many replies.You have been very important and educative to convince me in the decision that in my work It would be better an oscilloscope with a low noise front end than one with a very fast ADC like the Rigol.I am receiving an sds2104x plus in the next two days so I will do a limited comparison with the Rigol mso5000 that I still have.Thank you again.

author: G0HZU
author_rank: Super Contributor
timestamp: December 27, 2021, 08:42:30 pm
content: QuoteCan you measure the noise parameters yourself at audio frequencies? I've done this stuff up at RF and recently measured the s-parameters for the BF998 MOSFET at various bias points across a frequency range of a few MHz up to 3GHz and I also created some noise data for it up at VHF. This noise data gets included in the s-parameter file. I did the same for the old BF981 a few years back with good results when designing amplifiers for low noise figure. I've never tried to do this at audio frequencies though.

author: G0HZU
author_rank: Super Contributor
timestamp: December 27, 2021, 08:46:35 pm
content: Quote from: Fiorenzo on December 27, 2021, 08:28:48 pmSounds good! My first digital scope (Tektronix) was noisy and it spoiled the experience a bit. It is still possible to do good work with a noisy scope but I don't think I'd want to buy another one. Especially if it as noisy as that Rigol.

author: mawyatt
author_rank: Super Contributor
timestamp: December 28, 2021, 12:56:48 am
content: Quote from: Performa01 on December 27, 2021, 06:41:52 pmThis looks good, but the tone levels are -6dBV below the level used at 20KHz so one would expect the 3rd order IMD to be significantly down from the 20KHz case.Anyway, thanks for the test.Best,

author: G0HZU
author_rank: Super Contributor
timestamp: December 28, 2021, 01:34:06 am
content: Note also that the other spurious terms are limiting the spurious free dynamic range on the 1MHz IMD test. A really good (old school swept) microwave spectrum analyser can achieve a typical IP3 limited SFDR of about 112dB with a very narrow RBW on the first frequency range up to a few GHz. However, 105dB is more realistic at (say) 10Hz RBW. I wouldn't expect to see those other spurious terms either when using a conventional spectrum analyser. The Pico will have a much faster refresh rate though!On narrow spans the phase noise will slightly limit the SFDR of the swept analyser so usually stuff like this is done at a wider frequency spacing with a conventional analyser.

author: Performa01
author_rank: Super Contributor
timestamp: December 28, 2021, 02:52:19 am
content: Quote from: mawyatt on December 28, 2021, 12:56:48 amSorry, this was not indended – somehow I did not pay attention to the levels.Please find attached the correct measurement. The result is the same as at 20 kHz.Signal_IMD_80mV_1000-1010kHzQuote from: G0HZU on December 28, 2021, 01:34:06 amOf course you are right – and just for others to put this into perspective, I would like to add:Swept spectrum analyzers only “see” their resolution bandwidth at any point in time (ok, only true for the last IF), whereas the DSO always works at full bandwidth (5 MHz in this particular case). Under these conditions, some 96 dB dynamic is all you can expect from a 16 bit system – everything beyond that is just a lucky incident based on the specific conditions and the results cannot be trusted any longer.In the previous example with the 6 dB lower level, it has been perfectly possible to measure an IMD of 109.6 dBc, since none of the spurs got in the way of this measurement. According to the textbook theory, it should have been 115 dBc though, so the measurement was flawed anyway. As mentioned before, we cannot expect great accuracy once far outside the first order dynamic range of the acquisition system.

author: G0HZU
author_rank: Super Contributor
timestamp: December 28, 2021, 03:39:49 am
content: That really is very impressive from the Picoscope in terms of SFDR.I just turned on the RSA3408A to look at the LF noise floor up to 25kHz and I've added a plot below. This analyser is FFT only and can't do a swept measurement at any frequency. Below 40MHz it feeds direct to a 14 bit ADC and the IMD performance isn't that good. It's much worse than the Picoscope in this respect. However, the LF noise floor is quite good considering this isn't a dedicated AF analyser. I've used it to measure the noise figure of AF amplifiers a few times. As long as I provide enough gain to overcome the noise figure of the 3408A it can make fairly good noise figure measurements. I guess not many people make AF amps with 50 ohm ports but this type of amplifier is popular in direct conversion receivers.You can see the noise floor is a fairly flat -154dBm/Hz across the AF band.

author: David Hess
author_rank: Super Contributor
timestamp: December 28, 2021, 05:05:01 am
content: Quote from: G0HZU on December 27, 2021, 08:42:30 pmUp through audio frequencies would not be sufficient because RF MOSFETs can have a flicker noise corner frequency in the MHz range.I am just not setup to make that kind of measurement easily. I can make spot noise measurements up to 1 MHz but even that would not be high enough. I would have to build something custom and I would prefer a more general solution.

author: Performa01
author_rank: Super Contributor
timestamp: December 28, 2021, 09:28:32 am
content: Quote from: G0HZU on December 28, 2021, 03:39:49 amYeah - bipolar technology, using rf-transistors (with very low intrinsic base resistance) makes for a good noise matching at low impedances like 50 ohms – and a low 1/f corner frequency.High impedance FET input stages are noisy under such conditions. On the other hand, high impedance inputs are much more versatile. We can adapt them to any impedance we like by means of a pass through terminator (at least at low frequencies).Meanwhile I’ve experimented a bit further and detected at least two flaws in my previous noise measurement:1. The input was AC coupled by accident, which of course increases LF-noise significantly.2. The input had a 50 ohm through terminator fitted, but since this scope is sensitive to the source impedance, an additional 50 ohm end terminator should be used to complete the 50 ohms setup.Now look at the screenshot attached.Pico4262_Noise_5MHz_D50kHzI’ve tried to resemble your settings as close as possible but still kept the total FFT bandwidth at 5 MHz in order to keep the high frequency noise out of the LF region. Display units are dBm now for better comparability. Frequency step is 38.15 Hz, which is equivalent to a RBW of 112 Hz with the Flat-Top window – so noise levels will read slightly higher than in your setup.With a noise level of -134.7 dBm this is very comparable to your RSA 3408A above some 30 kHz.At 1 kHz, the FET input goes up by 17.8 dB to -116.9 dBm, but obviously stops at -114 dBm with this RBW.So I’m confident to claim that the Pico 4262 has the same low noise in a 50 ohm system, as long as you keep the input DC-coupled and stay above 30 kHz.EDIT: I have updated my original posting, where you can also see the updated noise density plot.

author: Fungus
author_rank: Super Contributor
timestamp: December 28, 2021, 09:50:30 am
content: Quote from: Fiorenzo on December 27, 2021, 08:28:48 pmStill waiting for the screenshots of your ripple with averaging turned on...

author: gf
author_rank: Super Contributor
timestamp: December 28, 2021, 10:50:02 am
content: Quote from: Fungus on December 28, 2021, 09:50:30 amLooking atthis postagain, I can believe that the first image shows noise from the scope (although it is quite a lot). But I rather cannot believe that the 40mVpp"noise band" on top of the sawtooth in the second image is scope noise as well (apparently scope settings are the same as in the first image). I guess the latter is already present in the input signal. I don't feel able to assess whether it is random noise, or rather a high-frequency oscillation. FFT should help to reveal it.

author: Fungus
author_rank: Super Contributor
timestamp: December 28, 2021, 11:46:11 am
content: Quote from: gf on December 28, 2021, 10:50:02 amI'm just interested in what an MSO5000 can do with a signal like that when a user really uses all the provided features.

author: Fungus
author_rank: Super Contributor
timestamp: December 28, 2021, 11:52:00 am
content: Also... the color gradient mode as mentionedon the first page. How would the ripple appear if you enable that?

author: nctnico
author_rank: Super Contributor
timestamp: December 28, 2021, 12:06:35 pm
content: For color grading to be usefull you need a perfectly repetitive signal. After all color grading is a form of averaging. Power supply ripple isn't perfectly repetitive so color grading won't help at all.Just face it: you will want to use an oscilloscope with the least amount of internal noise to look at any signal. After all the purpose of an oscilloscope is to look at the shape of a signal and the less an oscilloscope distorts that signal, the better. It seems Rigol dropped the ball where it comes to noise reduction and at some point cheap doesn't make up for poor performance.

author: Fungus
author_rank: Super Contributor
timestamp: December 28, 2021, 12:28:32 pm
content: Quote from: nctnico on December 28, 2021, 12:06:35 pmI'd still like to see a screenshot of it.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 28, 2021, 04:42:52 pm
content: I am going to do the photos you asked, maybe this evening or tomorrow

author: David Hess
author_rank: Super Contributor
timestamp: December 28, 2021, 09:25:39 pm
content: Quote from: Performa01 on December 28, 2021, 09:28:32 amIf I did my math right, that comes out to 3.9 nV/SqrtHz so similar to a well designed 100 MHz JFET input, and consistent with the specified 15 picofarad input capacitance. (1) For a lower frequency singled ended JFET input instrument, 1 nV/SqrtHz is possible (LSK170) but the input capacitance would be 2 or 3 times higher. So why is the input capacitance low and noise high for such low bandwidth?Given their dynamic range and distortion requirements for 16-bits, a simple FET source follower would have too much distortion; feedback is required to lower the distortion. So they probably used a JFET operational amplifier, and that would be consistent with higher noise, 5 MHz bandwidth, and a 15 picofarad input capacitance.That also places this instrument into a different class than an oscilloscope, although similar to the old Tektronix oscilloscopes which used the 5A22 or 7A22 differential amplifier.(1) There is a close relationship with input capacitance, bandwidth, and input noise. Lower bandwidth FETs have lower noise and higher input capacitance.

author: David Hess
author_rank: Super Contributor
timestamp: December 28, 2021, 09:34:08 pm
content: Quote from: Fiorenzo on December 27, 2021, 08:28:48 pmHopefully the discussion was of some help.QuoteI do not think low noise and high sample rate are mutually exclusive because the digitizer's input noise should be insignificant compared to the noise from earlier stages and especially from the amplified noise of the high impedance input buffer. The instruments in question seem to suffer from higher noise in general rather than because of sample rate.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 28, 2021, 09:57:59 pm
content: So i did a lot of photos.First two comparison: no probe, 1mv/div, 20mhz BW limit. There is a huge difference

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 28, 2021, 10:01:03 pm
content: Same no probe

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 28, 2021, 10:03:35 pm
content: 4x avarage no probe

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 28, 2021, 10:05:33 pm
content: Eres 3db on siglent and hi-res on rigolno probe

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 28, 2021, 10:06:46 pm
content: Normal modeProbe connected 1x and grounded

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 28, 2021, 10:08:00 pm
content: Ripple same settings on both oscilloscopeAC, normal mode, 1x probe

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 28, 2021, 10:13:42 pm
content: There is a huge difference between this two scopes.The Rigol has a faster update of the image, almost double... and the quality of the rappresentation, i mean the graphics, of the signal is a lot better than the Siglent. It seem like the Siglent had a lower resolution. There is not a huge difference in the speed of the user interface and also the Rigol appear to have a better quality of the material of the scope. But the front end noise is a lot different.Judge by your self from the photos attached.

author: David Hess
author_rank: Super Contributor
timestamp: December 28, 2021, 10:15:02 pm
content: Quote from: Fiorenzo on December 28, 2021, 10:06:46 pmShorting the probe tip can be tricky. For lowest noise it is not sufficient to simply clip the probe's ground lead to the probe's tip because the loop will pick up ambient noise. Best is to short the tip out with a coaxial probe tip to BNC adapter plugged into a BNC short or 50 ohm termination, but winding wire around the probe tip also works.

author: nctnico
author_rank: Super Contributor
timestamp: December 28, 2021, 10:19:06 pm
content: This is even worse than I expected (). I don't care about the open / shorted inputs at the most sensitive V/div (Rigol does digital zoom there so it is not an apples for apples comparison) but I do care about the display of an actual signal. On the Siglent you can clearly see spikes on the signal which are completely obscured on the Rigol.

author: Fungus
author_rank: Super Contributor
timestamp: December 28, 2021, 11:11:03 pm
content: Quote from: Fiorenzo on December 28, 2021, 09:57:59 pmIrrelevant. Only real signals count.Quote from: Fiorenzo on December 28, 2021, 10:03:35 pmAveraging only works when there's a periodic signal.Quote from: Fiorenzo on December 28, 2021, 10:08:00 pmNo averaging?That's the only thing that counts - if averaging mode can better show the underlying signal or not.Quote from: David Hess on December 28, 2021, 10:15:02 pmYep. Connecting the ground clip to the probe actually creates an antenna.

author: Fungus
author_rank: Super Contributor
timestamp: December 28, 2021, 11:14:05 pm
content: Quote from: Fiorenzo on December 28, 2021, 10:08:00 pmI disagree that there's ahugedifference in useful information. Sure, the Siglent line is thinner but The Rigol is showing the ripple just fine.You should also be able to change the displayed part of the signal (the red bit) by twisting the selection knob on the Rigol (ie. intensity setting).And again: What does averaging mode do if you turn it on in this situation? Why is this being avoided?

author: Fungus
author_rank: Super Contributor
timestamp: December 28, 2021, 11:32:30 pm
content: Quote from: nctnico on December 28, 2021, 10:19:06 pmI dunno what those "spikes" are but they're not ripple. To me it seems liek the Rigol is perfectly capable of showing the ripple from that power supply. Is there anybody here who can't see the ripple in this image or thinks that the 14.003mV displayed value is somehow massively different than the 14.048mV displayed by the Siglent?(and this is without averaging, apparently, averaging can only improve this)Is the Siglent display or the number displayed by the Siglent worth400 Eurosmore? I dunno. It's all relative, but I could buy all sorts of useful stuff for 400 Euros.However you look at it: You'll have a hard time convincing me that the Rigol is adisaster. Sure the Siglent's line is thinner but the Rigol is perfectly capable of showing the ripple on screenandmeasuring it. That's what really counts, and is the subject of this thread.

author: nctnico
author_rank: Super Contributor
timestamp: December 29, 2021, 12:30:05 am
content: Just stop trying to make right what is clearly wrong. The small spikes that the trace shows on the Siglent (or any other modern DSO other than Rigol mentioned in this thread) can point to other problems. An FFT will tell more but again, on the Rigol the HF component riding on the lower frequency ripple likely gets drowned in the noise. The Rigol MSO5000 is outright horrible. Claiming anything else is delusional. Edit: pay close attention to the excellent example G0HZU posted below. It may save your bacon one day trying to find an illusive problem in a circuit.At some point cheap doesn't make up for poor performance.In the end you'll need to buy an extra instrument to make the measurement cheaper gear can't do. Been there, done that and wasted enough money on cheap gear which in the end didn't deliver.

author: G0HZU
author_rank: Super Contributor
timestamp: December 29, 2021, 12:38:06 am
content: QuoteOK I'll bite...If you want to see the effects of averaging then see the example below.I've just set up a couple of function generators and summed the waveforms into my old HP Infinium scope. I've set the scope to 50R input and done everything in x1.The scope is set to 1mV/div and I've turned on the 30MHz bandwidth limit. Waveform 1 is a triangle wave at about 500Hz and it is about 5mV pkpk. Waveform 2 is a series of narrow positive pulses each of amplitude 1mV and they occur every 768us. The plots below show the low noise performance of this old scope and also show how averaging can cause information to be lost.See below for a single shot capture and see also for what happens with averaging. The information about the pulses is totally lost in the averaged screenshot because the period of the triangle wave and the pulses is different. I hope this helps?

author: bdunham7
author_rank: Super Contributor
timestamp: December 29, 2021, 01:09:08 am
content: Quote from: Fungus on December 28, 2021, 11:32:30 pmWhat are you going to do when the ripple is even smaller? For example, here is a ~150uVrms10MHz signal being clearly triggered and displayed. This signal was displayable--triggerable and above the noise threshold on a Tek 2465B (shown), a Tek 2221A (digital and analog) and the Siglent 1104X-E (although just barely and not as reliably). I was able to do the same thing with a 1MHz and 100Hz signal of approximately the same amplitude. What would it look like on the Rigol?You can't average your way out of this when you are looking for noise--possibly non-periodic--in the first place. On the Tek 2221A and the Sig 1104X-E, averaging made the signal look nicer but I'm not convinced that means better.

author: bdunham7
author_rank: Super Contributor
timestamp: December 29, 2021, 04:05:33 am
content: Quote from: Fiorenzo on December 28, 2021, 10:13:42 pmCould you try the ripple and maybe no probe (like the first photos) with the Siglent in the 10-bit acquisition mode?

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 29, 2021, 06:10:52 am
content: Quote from: David Hess on December 28, 2021, 10:15:02 pmYes I have put the wire of the probe in the less noisy position

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 29, 2021, 06:16:54 am
content: Quote from: Fungus on December 28, 2021, 11:11:03 pmI know but i put the probes in the same manner with the lowest noise captured, i also did the photos with avarage on the signal of the ripple i didn't had the time to upload

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 29, 2021, 06:23:48 am
content: Quote from: bdunham7 on December 29, 2021, 04:05:33 amYes i will do. The 10 bit more reduce the noise as i checked yesterday evening. I will post some photos.In regard of the Rigol It Is in my opinion a very good scope but It has the problem of the noisy front end

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 29, 2021, 08:11:57 am
content: Quote from: Fungus on December 28, 2021, 11:14:05 pmThe spikes you can clearly see in the Siglent i think are switching noise coming from the next stage of this psu. I am going to do some test about It to check if the front end noise of the Rigol is covering such interference

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 29, 2021, 08:32:56 am
content: As asked some photos with the avarage mode4x averageIn my opinion the avarage, even if It conserve almost the shape of the signal, destroys "the low intensity" informations

author: Fungus
author_rank: Super Contributor
timestamp: December 29, 2021, 10:22:10 am
content: Quote from: Fiorenzo on December 29, 2021, 08:11:57 amThanks for the photos! This is all very useful information.The one remaining test is to see the effect of turning up the display intensity on the Rigol to see if it reveals those spikes better (without averaging).

author: 2N3055
author_rank: Super Contributor
timestamp: December 29, 2021, 10:22:45 am
content: I 'm reading some of these posts andIt is obvious MSO5000 has much more noise, and that it is a problem, unless you only look at digital signals and just want to look at general shape and some timing information.It is shame, really, because new Rigol scopes are much more powerful processing wise than the old ones, and generally held great promise but analog front end/ADC noise performance is not very good.Scope with low noise is always going to be better instrument than the one with high noise. Why is that even a discussion?Is this some audiofool discussion how this huge noise is pleasant to look at because it's pretty?I don't use bandwidth limiting, averaging or any "signal cleanup" features when I'm looking into a signal I want to understand. You would want to look at this switcher signal with a full 1GHz bandwidth and with as low noise scope you can.To really see what is there... Switching ripple is most of the time least interesting part of switching PSU. We expect it to be there, and most of the time it will be roughly what we calculated. Other, higher frequency stuff (those little hairs on top) is much more problematic and most of the time those will give you headaches.. Nanovolts of those will already be seen on any EMI test...You filter, limit and "cleanup" signal in circumstances where you understand your signal and you want to ignore noise and other parts of signal on purpose. If your signal is buried inside the noise, you average.But is that noise part of signal you're measuring or your scope is not irrelevant. If it comes from DUT I want to know that. I want to see it..Only way to do that is to have low noise scope.Of course, like OP correctly asked, there is a point of diminishing returns..Is scope with 5 uV of RMS noise so much better than one with 50uV RMS noise for measuring this switcher signal from this example? Probably not.It would be definitely better but probably not usefully so in this case. But one with 50uV of RMS noise is definitely better than one which has trace that is whooping 20 mV wide... On a signal that is 60mV P-P...On this test I would call MSO5000 from Rigol useless for this measurement. And averaging thisnot autocorrelatedsignal ( it doesn't repeat cleanly and doesn't retrace it's waveform exactly but varies slightly all the time) willnotextract more detail but will hide even more information about signal..OTOH Siglent shows pretty much perfect representation of the signal, big peaks, ripple AND little hairs. That is your switcher output. That isusefulinformation..Little Micsig STO1104C/E, or Siglent SDS1104X-E could do equally good job here.Sad part is that little Rigol DS1054Z would be much better for this signal than MSO5000.. DS2000A had excellent low noise front end .. But new series of Rigol scopes is very powerful in processing power but analog performance is worse than older series. Shame really, otherwise they are very nice scopes.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 29, 2021, 10:29:23 am
content: Quote from: Fungus on December 29, 2021, 10:22:10 amSorry fungus i have been very busy. I have more photos. Check in the next messages

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 29, 2021, 10:30:13 am
content: 16x average

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 29, 2021, 10:32:04 am
content: Max average possibile

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 29, 2021, 10:36:03 am
content: Fungus actually i think in my modest opinion that the Rigol is a greate scope, for sure i will miss it due to its graphics and fast acquisition, comparing both the scope you see the difference a lot. But It has also a lot more noise.... I have an idea to show you how much the signal degrade due to this problem.

author: tautech
author_rank: Super Contributor
timestamp: December 29, 2021, 10:42:11 am
content: Quote from: Fiorenzo on December 29, 2021, 10:36:03 amStudy the screenshots you've just posted to see just how fast it actually is with averaging engaged.Which initiates another question; what would the MSO5000 sampling drop to if one more channel was activated ?

author: Fungus
author_rank: Super Contributor
timestamp: December 29, 2021, 11:07:21 am
content: Quote from: nctnico on December 29, 2021, 12:30:05 amI'm not trying to make anything "right", I'm just trying to see if the Rigol would prevent somebody from doing their job with this signal.Questions:(1) Can the Rigol display/measure the ripple? It clearly can.(2) Can the Rigol see the high frequency spikes? Maybe not as well as the Siglent but they're clearly visible.(and the jury is out until we know the effect of turning the intensity up/down to enhance them - just like you had to do on old Analog 'scopes to see artifacts like that)Bottom line: The Rigol can see what's going on in that signal.Quote from: nctnico on December 29, 2021, 12:30:05 amGet an amplifier?Does ripple/noise/electronics magically stop at 1mV? There's plenty of signals that the Siglent can't see either...

author: Fungus
author_rank: Super Contributor
timestamp: December 29, 2021, 11:11:48 am
content: Quote from: tautech on December 29, 2021, 10:42:11 amIt's not difficult: With two channels you get 4GHz/channel, with three or four channels you get 2GHz/channel.At no point is it less than the Siglent with just a single channel.

author: Fungus
author_rank: Super Contributor
timestamp: December 29, 2021, 11:40:23 am
content: Quote from: Fiorenzo on December 29, 2021, 10:36:03 amAll 'scopes degrade the signal, none are perfect.The real problem with this Rigol vs. Siglent comparison is that you're comparing two devices side by side where one of them happens to work better at 1mV then the other one does.ie. When you turn the Siglent's vertical control to "max" then it makes the Rigol look badat that level. If you were comparing 1V signals or 5V signals in your screenshots then you wouldn't see the same difference between them.Guess what? Electronics doesn't magically stop at the exact place where the Siglent's vertical control does. There's plenty of signals below 1mV. You'll need an amplifier to see them and the exact same same amplifier would work with a Rigol, too.Plus: You originally said you do digital stuff, so...

author: tautech
author_rank: Super Contributor
timestamp: December 29, 2021, 11:40:55 am
content: Quote from: Fungus on December 29, 2021, 11:11:48 amIt is when you overlook the full picture of each scopes acquisition system.With channels 1 and 3 of each scope activated a very different picture may emerge at some timebase settings.

author: 2N3055
author_rank: Super Contributor
timestamp: December 29, 2021, 11:46:37 am
content: Quote from: Fungus on December 29, 2021, 11:07:21 amThis not a stupid debate club where we debate whether it is more appropriate to say "apply the law" or "apply the letter of law"..This is physics and measurements and math. There is no negotiation with these guys.You are wrong and stop being a spoiled child. You. Are. Wrong. Take it as an adult.Worse is worse, and if you can chose, chose better. Why on Earth would you take worse device and then spend years "figuring out" how to deal with fundamental shortcomings (that you really can't fix because of it's nature) than simply take something that actually works much better.Nothing does anything magically. Usually more than good enough is when we know scope contributes less than few percent of the error. That also coincides with what can be easily seen with naked eye and 8 bits of a scope.When scope shows 20 mV noise on top of 65mv P-P signal that is definitely bad. Unusable for that measurement. Fact that it showssomethingis not that useful. It needs to show it accurate enough so person looking into scope can make something with it..Also you keep repeating about some magical amplifiers. Amplifiers that have DC-100 Mhz bandwith and less noise as even a little Micsig or Siglent SDS1104X-E cost as much as a good scope from Keysight. There are amplifiers for audio frequency range that can be used for low noise measurements. Those are useless for measuring a things mentioned here.. So no, some mythical preamps are not a solution.

author: Fungus
author_rank: Super Contributor
timestamp: December 29, 2021, 11:48:21 am
content: Quote from: tautech on December 29, 2021, 11:40:55 amYes, because if you enable to adjacent channels the Siglent only has 1GS/sec to look at 350Mhz signals, ie. it's getting uncomfortably close to Nyquist.Turning a channel off can bump the sample rate to 2GS/sec and give a different picture.The Rigol MSO5000 series is one of the few oscilloscopes which can maintain a comfortable Nyquist margin with any combination of channels.

author: Fungus
author_rank: Super Contributor
timestamp: December 29, 2021, 11:51:05 am
content: Quote from: 2N3055 on December 29, 2021, 11:46:37 amYes, but amplifiers from DC to 1MHz are incredibly cheap (ie. a $2 OP-amp plus power supply) and would be perfectly adequate for audio work and looking at power supply ripple.Amplifiers from 10kHz to 2GHz are also incredibly cheap.

author: 2N3055
author_rank: Super Contributor
timestamp: December 29, 2021, 11:55:50 am
content: Quote from: Fungus on December 29, 2021, 11:40:23 amYour thinking:Siglent that has 5-10X times better noise and performance and sensitivity but cannot measure properly something at 200uV levels,Rigol MSO5000 cannot measure something properly even at 10mVThat makes them equal. Because they both havesomethingthey cannot measure.By the analogy:You are same as a gorilla. You both have eyes.. Let's ignore other, irrelevant, details..Get a grip..

author: 2N3055
author_rank: Super Contributor
timestamp: December 29, 2021, 11:59:33 am
content: Quote from: Fungus on December 29, 2021, 11:51:05 amSwitching power supplies are measured by convention in DC-20MHz range. And that was for old switchers switching at up to some 100ths of kilohertz. Today switchers are in MHz range, and you better be looking at them up to 300-400 MHz range because of EMI problems...Also those RF amplifiers are not replacement for a proper scope front end.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 29, 2021, 12:07:28 pm
content: Quote from: 2N3055 on December 29, 2021, 10:22:45 amThank you for the great explenations, I also agree with you

author: Vestom
author_rank: Regular Contributor
timestamp: December 29, 2021, 12:09:00 pm
content: The lower sampling frequency of the SDS2000X+ is much less of a problem than it sounds due to the excellent ETS-like trigger implementation. There are plenty of examples showing the Leo Bodnar pulse with very good fidelity on the SDS2k+.However frame-by-frame averaging is really a kludge one should be careful about using, since it hides transients, glitches etc. Also with modern low-amplitude digital signals measured using x10 probe, low noise performance has become more important for digital signals than you might think...Of course you can add external amplifiers - but why not buy a proper scope instead?

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 29, 2021, 12:18:04 pm
content: Quote from: Fungus on December 29, 2021, 11:48:21 amNo. Actually i did many experiment about It. If you set the Rigol so it has a lower sampling speed the noise doesn't become lower.I checked It in many ways.For example if you turn on all the channels together the noise stay the same.If you lower the memory buffer the sampling rate becomes lower but the noise stay again similar until you force It to work with a very very little Memory like 20k or so.I have tried all i could think to get a better sampling from the Rigol and It was not possible.In regard of me now I am doing digital stuff but i am going to work a lot with analoge signals and circuits so i preferred to switch to the Siglent.As i said i think the Rigol is a very great scope but noisy

author: Fungus
author_rank: Super Contributor
timestamp: December 29, 2021, 12:19:46 pm
content: Quote from: 2N3055 on December 29, 2021, 10:22:45 amFiorenzo originally said his main work was digital.Quote from: 2N3055 on December 29, 2021, 10:22:45 amBecause: "Price"(ie. This isn't a 100% technical discussion, if it was we'd all be driving 10-bit R&S 'scopes)Quote from: 2N3055 on December 29, 2021, 10:22:45 amThe Rigol displayed "14.003mV" on screen and the Siglent displayed "14.0482mV"That's 0.3% difference between them.Quote from: 2N3055 on December 29, 2021, 10:22:45 amYep. My original recommendation was to save 1000 Euros and get the SDS1104X-E.

author: Fungus
author_rank: Super Contributor
timestamp: December 29, 2021, 12:25:42 pm
content: Quote from: Fiorenzo on December 29, 2021, 12:18:04 pmThat's because it won't actually change the ADC clock speed, it just discards samples.What's being discussed is the sample rate to bandwidth ratio. When it approaches a ratio of 2 you'll start to see artifacts in the display.The Siglent has 350Mhz bandwidth and can drop to 1Ghz sample rate if you enable all channels. This can produce visibly different results at maximum zoom. You'll see it most on digital signals.The Rigol doesn't drop below 2GHz sample rate so it should never have a problem.

author: nctnico
author_rank: Super Contributor
timestamp: December 29, 2021, 12:35:40 pm
content: Quote from: Fungus on December 29, 2021, 12:25:42 pmIn the end neither is suitable for looking at 350MHz signals using 4 channels. The Siglent SDS2k due to low samplerate, the Rigol MSO5000 due to excessive noise. Also note what David Hess wrote: Rigol typically performs math on decimated data which can give the wrong results when doing measurements on noise.All in all, if you venture into the HF arena, you'll need to look at more expensive scopes. For a general purpose daily driver scope, low noise is king all day long.

author: 2N3055
author_rank: Super Contributor
timestamp: December 29, 2021, 12:38:56 pm
content: Quote from: nctnico on December 29, 2021, 12:35:40 pmMSO5000 actually can use all data.it has propper implementation of math but it is let down by noise.. Shame.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 29, 2021, 12:48:20 pm
content: Yes fungus I think so.In regard of your suggestion to buy a cheaper scope my thinking was in line with you but i needed some function that are only in the Siglent sds2000.About this topic my need was to understand how more important is sample rate against front end noise.Because of my bad english maybe i could not explain well my doubts.In the end if you or other have suggestions i can do some other test with the limited equipment i have until I have both the scopes at home..... because i am going to send back the Rigol as soon as possible.

author: Fungus
author_rank: Super Contributor
timestamp: December 29, 2021, 12:49:52 pm
content: Quote from: nctnico on December 29, 2021, 12:35:40 pmProbing a 350MHz signal with passive probes is also a minefield, the artifacts from the probe will usually be bigger than the signal.I wouldn't buy either of these for the bandwidth, I'd buy them for the big touch screens, large memory, etc.

author: Fungus
author_rank: Super Contributor
timestamp: December 29, 2021, 12:52:24 pm
content: Quote from: Fiorenzo on December 29, 2021, 12:48:20 pmWhat function?Siglent has added more functions to the SDS1104X since launch. Maybe they added it but you're looking at an old manual.Quote from: Fiorenzo on December 29, 2021, 12:48:20 pmThe only other interesting test is the effect of intensity on the color-graded display.For that a photo of the screen isn't really good enough though. You'll need to put in a USB stick and press the 'print' button.

author: Martin72
author_rank: Super Contributor
timestamp: December 29, 2021, 02:01:54 pm
content: I´ve changed from MSO5354 () to the sds2k+ - After I did the very first ripple-measurement with the mso.The noiselevel is "horrible", useless for doing low noise measurements - By the way, Dave mentioned it also in his first rigol mso 5000 video.I got the sds2k+ over a year now, before the rigol over a year, there is nearly nothing the rigol can do better.Display is worser, much worser ( same resolution btw), UI is mickey mouse style and sometimes really confusing, the response itself is slower...It´s a shame, because the hardware itself is powerful, except the noisy frontend.And as I´ve asked the rigol support, if there is a chance to get it better by buying the 7000, their answer to me kills everything.Frontend are the same and that was it, I´ve changed to siglent without any regrets so far, except the missing of 4 math-traces at the same time..

author: mawyatt
author_rank: Super Contributor
timestamp: December 29, 2021, 03:53:23 pm
content: We had to sift thru all this a year and half ago. After a few months decided to "listen" to those that had actual experience with the scopes and for comparisons actually had used various brands. Dave's videos are a great resource, and should be reviewed many times.Couple folks here (think 2N3055 & Martin72) have actually used and worked with both the Rigol and Siglent scopes, so value these experiences and responses.BTW we decided on the Siglent SDS2000X+, the deciding factor was the Rigol noise. Now have 2 Siglent scopes and maybe getting a 3rd, so that alone says enough about our experiences.Best, and Happy Scope Hunting

author: mawyatt
author_rank: Super Contributor
timestamp: December 29, 2021, 04:20:30 pm
content: Not to discredit Rigols' attempt and deployment of integrating the entire front end and ADC, actually we should applaud themComing from a career that often involved low noise, wide bandwidth and high dynamic range requirements, designing such at the discrete level is extremely difficult, and speaking from experience, at the Integrated IC level, this becomes exceedingly difficult and quite expensive. Things that work at the discrete level may not work so well on an IC, and an entire different design approach is often required. Modern IC processes that feature amazing small devices, and very fast, are dictated by the digital requirements. The analog use of such is "you get what you get" and you must figure out how to achieve the analog performance goals, which often means a complete departure from a conventional discrete approach.Anyway, hopefully Rigol (Siglent, maybe some other mid-level players) will continue with an integrated scope front-end and ADC solution because we'll all benefit from this integration.Best,

author: Performa01
author_rank: Super Contributor
timestamp: December 29, 2021, 05:47:54 pm
content: Quote from: 2N3055 on December 29, 2021, 11:55:50 amAre you sure? See reply #130 in the following threadhttps://www.eevblog.com/forum/testgear/suggestions-for-a-dmm/msg2766948/#msg2766948

author: Fungus
author_rank: Super Contributor
timestamp: December 29, 2021, 06:10:48 pm
content: Quote from: 2N3055 on December 29, 2021, 11:55:50 amThis, in a thread full of screenshots showing the Rigol measuring things to sub-millivolt resolution with the same accuracy as a Siglent.

author: Performa01
author_rank: Super Contributor
timestamp: December 29, 2021, 07:01:39 pm
content: Quote from: Fungus on December 29, 2021, 06:10:48 pmIt appears hard to understand for some (well, actually I know only one), but even though the amplitude measurement for the ripple is correct - which doesn't come as a surprise since noise averages out to zero - engineers still want to see the details apart from the very predictable ripple, which includes switching noise and other potential RFI components, as well as any other glitches that might hint on hidden problems with the circuit.EDIT: And the result is only equal for the Vrms measurement. Has anyone noticed the huge difference in the Vpp measurment, where the noise does not average out to zero?

author: 2N3055
author_rank: Super Contributor
timestamp: December 29, 2021, 08:18:23 pm
content: Quote from: Fungus on December 29, 2021, 07:36:42 pmNow let's see ifyoucan understand this:Rigol cannot see anything less than 10mV.Siglent users will see this, with stable triggering:That's almost two orders of magnitude better.I rest my case. You're trolling now, nothing else... Stop wasting our time. Please.

author: nctnico
author_rank: Super Contributor
timestamp: December 29, 2021, 08:50:02 pm
content: R&S owners are equally blessed with low noiseAnd the option to use a filter on the signal.

author: gf
author_rank: Super Contributor
timestamp: December 29, 2021, 09:01:14 pm
content: Quote from: nctnico on December 29, 2021, 08:50:02 pmCompared to the previous Siglent screenshots, the sine wave looks a bit distorted, though. Or is the signal generator to blame here?

author: nctnico
author_rank: Super Contributor
timestamp: December 29, 2021, 09:10:24 pm
content: Quote from: gf on December 29, 2021, 09:01:14 pmThere is some noise riding on top and keep in mind the bottom trace is not averaged but filtered.

author: David Hess
author_rank: Super Contributor
timestamp: December 29, 2021, 09:24:48 pm
content: Quote from: bdunham7 on December 29, 2021, 01:09:08 amI have run across that problem a couple times, where only a lower noise oscilloscope would do when looking for subtle anomalies. The usual solution is to use averaging or high resolution mode and trigger off of a different channel from a signal which is synchronous to the signal of interest, but this is not always possible. See below about differential probes.My 10 bit digitizing but not a DSO Tektronix 400 MHz 7854 can reveal signals that my 40 uV RMS over 100 MHz 2232 or 2230 cannot even see in digital storage mode, and do it with an RF sampling front end if needed, but an equivalent instrument today would be 10s of thousands of dollars and we are not discussing those.Quote from: tautech on December 29, 2021, 10:42:11 amLower cost DSOs do that because they either have only one bank of acquisition memory with limited bandwidth shared between 4 digitizers, or because the digitizer is interleaved between the 4 channels. The later is practically universal in lower cost DSOs.Either can be seen as a cost saving measure or a way to maximize performance when only a single channel is used, and more expensive instruments may use completely separate digitizing and storage for each channel so sample rate, and usually record length, does not depend on the number of channels. Tektronix used to refer to a DSO as being "real time" if its maximum sample rate, and record length, did not change with the number of channels and for many years they maintained a separate line of DSOs which worked this way because some applications demand it.Quote from: Fungus on December 29, 2021, 11:51:05 amWhat is not cheap or easy are getting good flatness and settling time over the bandwidth of interest. However the high noise is a problem of design and not cost. Up to 350 MHz, there is no excuse for such a noisy implementation and obviously Siglent is doing something right that Rigol is not. The noise on the Siglent is high compared to what it could be, but that makes the noise on the Rigol much worse than high.Quote from: nctnico on December 29, 2021, 12:35:40 pmIt is not the decimated data which is the problem but performing math on the display record which has already been processed for the display. More expensive instruments maintain a separate full resolution record for processing what is essentially the "raw" data, that is separate from the processed display record.Quote from: Fungus on December 29, 2021, 12:49:52 pmPassive high impedance probes are more difficult to use at higher frequencies than active probes, but if this is taken into account, the usual problem is noise from the ground loop with a singled ended probe, which even an active probe does not solve. A differential probe solves this but at the expense of greater noise, and this tradeoff is almost always worth it if their higher cost can be accepted. Several times I have probed signals approaching the limit of the input noise of my oscilloscope where differential probing was a solution because it removed common mode noise.QuoteI was thinking that about the Rigol MSO5000 series before I saw how much better the Siglent is for noise. They are both noisier than the general state of the art of more than 2 decades ago, but for most applications that is good enough. By preference I do not even use the lowest noise oscilloscope that I have available. Fiorenzo did the right thing by inquiring.

author: Fungus
author_rank: Super Contributor
timestamp: December 29, 2021, 09:30:58 pm
content: Quote from: David Hess on December 29, 2021, 09:24:48 pmAnd has provided some valuable data.

author: masterx81
author_rank: Frequent Contributor
timestamp: December 29, 2021, 09:36:33 pm
content: How did you get so low noise waveforms? Did all you live in a faraday cage?I can't go so low with my 1104x-e as it pickup always random noises also with all things turned off in the room except the scope. It get also noises from the cooking gas sparks for starting the flame two rooms away from me (kitchen). I get the 34khz from the fluorescent lamp on the desk when powered on. The scope itself send a decent ammount of noise from the lcd panel (i think the lcd backlight buck is causing it), and you need to be very careful to the routing of the wire of the probe. Also if i connect the output of a battery powered signal generator, i can't reach those so low level of noise (still better than the fg fy6900, correctly grounded and with all-linear psu). In any case before the siglent i had an owon 7102... and hell, that thing was horrible in noise.

author: bdunham7
author_rank: Super Contributor
timestamp: December 29, 2021, 10:26:25 pm
content: Well if we're having a noise contest, the new models are going to have to answer to the antiques.In the DSO category, here's a Tek 2221A with a 150uVrmssignal:And to take the cake in the CRO category, here is a Kikusui COS5100A with a20uVrms(-81dBm)signal at 1mV/div. You can barely see it, but amazingly the trigger locks on steady. I've never seen another full-bandwidth scope (100MHz in this case) that can do this.

author: 0culus
author_rank: Super Contributor
timestamp: December 29, 2021, 10:30:10 pm
content: Piece of cake for a 7A22 amplifier. 10 µV/div, adjustable bandpass from DC-1 MHz.

author: 2N3055
author_rank: Super Contributor
timestamp: December 29, 2021, 10:48:03 pm
content: Quote from: masterx81 on December 29, 2021, 09:36:33 pmGood question..Everything coaxial, 50Ohm, attenuators.. And relatively quiet lab. No WiFi or phones within 5 meters... And signal source was Picoscope 4262 internal low distortion AWG.

author: 2N3055
author_rank: Super Contributor
timestamp: December 29, 2021, 10:53:52 pm
content: Quote from: bdunham7 on December 29, 2021, 10:26:25 pm20uV RMS at full 100 MHz BW ? That is good!Quote from: 0culus on December 29, 2021, 10:30:10 pm7A22 is special no doubt..Picoscope 4262 has noise floor of 8uV if we talk 5 MHz BW max..It can come close to 7A22.But original discussion was for at least 20MHz BW...

author: tautech
author_rank: Super Contributor
timestamp: December 29, 2021, 10:56:39 pm
content: Quote from: David Hess on December 29, 2021, 09:24:48 pmYet this is not the case for the 2 Siglent models that have been brought to this discussion whereas for the MSO5k AFAIK its 8GSa/s is shared by all 4 channels. OTOH SDS1104X-E and SDS2104X+ both have dual ADC's that give the user the opportunity to maintain high sampling rates when 2 channels are active by assigning them to each ADC that BTW each have their own memory support.In the case of the screenshots previously posted with asinglechannel active the MSO5k is displaying 500MSa/s at the timebase selected whereas the SDS2104X+ displayed 400MSa/s.Therefore activating any other channel should drop the MSO5k to 250MSa/s whereas if a second channel was assigned the the 2nd ADC on the SDS2104X+ its sampling rate and memory depth will remain unchanged.As yet nobody has provided this info for MSO5k.

author: David Hess
author_rank: Super Contributor
timestamp: December 29, 2021, 11:11:20 pm
content: I duplicated your test as best as I could on my 2232. Note that front end noise dominates digitizer noise at 2mV/div. The third example shows peak detection with noise reduction applied. I think the noise reduction algorithm is a noise gate.

author: David Hess
author_rank: Super Contributor
timestamp: December 29, 2021, 11:18:53 pm
content: Quote from: 2N3055 on December 29, 2021, 10:48:03 pmI did the same but of course my 2232 has no 50 ohm input. My signal source was a Tektronix FG502 11 MHz function generator set for minimum output with 50 dB of attention attached to its output.If you look carefully, my examples show a discontinuity in the sine function output from common mode noise which I should have removed by using a higher output level and more attenuation.

author: normi
author_rank: Regular Contributor
timestamp: December 29, 2021, 11:35:57 pm
content: @FiorenzoYou face the common issue most new scope buyers face; you want a scope that will do as much as possible for the amount of money you spend, unfortunately that is not the case. The MSO5000 will do things the Siglent can't and visa versa, although the Siglent is 40-50% more expensive. So lets look at the difference, noise floor Vs Sample rate.Sample Rate:It is horizontal resolution, it allows you to see finer details horizontally (time). It is an invisible feature, meaning that if your sample rate is low and causing an issue most cases you won't know. Aliasing is a visible issue if you are experienced enough to see it, but other critical flaws will be hidden. (You won't know that you don't know)When most needed:If there is a non repetitive and infrequent glitch in a signal that would not be sampled by the scope because the spacing between the samples is too wide (AKA low sample rate).Impact:You could go weeks trying to figure out a problem and will not realize that your circuit's failure is caused by the glitch that your slow scope is unable to find, this can be very costly in time.Work around:1. Obtain a high sample rate scope, all are very expensive (except the MSO5000).Noise floor, small voltage scales:It is the vertical resolution (volts). It is very visible, which is why you came to this forum, so unlike sample rate you will be fully aware of what you can't see.When most needed:Looking at very low voltage signals.Impact:If your system is susceptible to very small noise signals or you work with tiny signals then you want as low noise as possible. Since you can clearly observe your scopes noise level you won't spend as much time searching as you would be aware that you can't see signals cleanly below a certain level. So not likely to have a dramatic impact as the unseen glitch, because you can quickly proceed to a work around if you want to investigate low noise.Workaround:1. Use averaging to clean up noisy signal2. use an amplifier - some a very cheap and can be modified for Oscilloscopes or Spectrum analyzers, or can be built. Professional ones are very expensive but are usually used for differential measurements and are needed by even the scopes with low noise floor to see much smaller signals.3. Obtain a scope with lower noise, in some cases these lower noise scope can be cheaper than the MSO5000Outside of the fact that the RIGOL MSO5000 has a much lower price than the Siglent SDS - Plus, you could still buy a cheaper Siglent scope which would have the same noise performance as the SDS -Plus, however it is impossible to find another non Rigol 8G/S scope for under a $1000, or under $2000. This is the reason why the scope is attractive to many buyers.

author: gf
author_rank: Super Contributor
timestamp: December 29, 2021, 11:58:34 pm
content: To challenge Rigol, here are 1.5mVppon a real toy scopeRelatively clean trace despite no averaging (not supported), but admittedly just 2MHz BW.Frontend buffer seems to be just an off-the-shelf JFET opamp like LF356 or LF357, or similar.

author: nctnico
author_rank: Super Contributor
timestamp: December 30, 2021, 12:07:48 am
content: Quote from: normi on December 29, 2021, 11:35:57 pmBuuzzzzz wrong! As I wrote before: noise floor simply scales along with the V/div settings. In that perspective using low level signals is not representative for regular scope usage. The Rigol MSO5000 also sucks for higher level signals because the noise will still drown details of the signal. Averaging won't help because that also obscures the details that you want to catch.And having a higher samplerate gives you nothing if it is far beyond the bandwidth of your scope; it only wastes valuable memory. It just becomes a ridiculous number like having an 8000kW engine in a go-kart.

author: gf
author_rank: Super Contributor
timestamp: December 30, 2021, 12:45:16 am
content: Quote from: nctnico on December 30, 2021, 12:07:48 amIt helps insofar, as you can you turn on HiRes acquisition, and still end up with a relatively high decimated sample rate.E.g. 8-tap HiRes boxcar averaging @ 8GSa/s gives a decimated sample rate of still 1GSa/s, and noise is reduced by a factor of ~2.8.If the primary sample rate were only 1GSa/s, then the decimated rate were already as low as 125MSa/s.Edit: And enabling more than 1 channel reduces the sample rater further.

author: David Hess
author_rank: Super Contributor
timestamp: December 30, 2021, 05:28:15 am
content: Quote from: nctnico on December 30, 2021, 12:07:48 amIn most cases, the noise of the high impedance buffer at the input will dominate at the highest V/div sensitivities where attenuation immediately after the high impedance buffer is lowest. For this not to be the case, their must be a gain stage following the attenuators which has higher noise. This is not impossible, and could even be likely if the following gain stage is integrated CMOS instead of bipolar.For the Rigol MSO5000 we could learn something from measuring the noise at all V/div settings. If the high impedance input buffer noise is greater than the following stages, then there should be a jump to higher noise at about 0.1 V/div where the input attenuator is switched in, and the low impedance attenuators are switched out.

author: Performa01
author_rank: Super Contributor
timestamp: December 30, 2021, 07:47:05 am
content: While we would like the noise at low frequencies (<100 kHz) to be lower, yet it is certainly not high at 1 MHz and above. Very comparable with old analog scopes.Here's a demonstration, what an SDS2000X Plus can show with an emulated ripple with asynchronous spikes riding on it if optimal probing (without additional noise pickup) is applied. 2.5 mVpp 1 MHz ramp with 300 µV 6.000001 MHz 10 ns wide spikes riding on it.DSO Sensitivity is 500 µV/div, 10 bits mode, 100 MHz bandwidth. No averaging of course, in order to keep the spikes clearly visible.SDS2354X Plus_Ramp_2.5mV_1M_Pulse_300uV_6000001Hz

author: Fungus
author_rank: Super Contributor
timestamp: December 30, 2021, 09:02:38 am
content: Quote from: gf on December 30, 2021, 12:45:16 amThe Rigol doesn't do HiRes mode though.(unless they've added it and missed the memo)

author: gf
author_rank: Super Contributor
timestamp: December 30, 2021, 09:30:53 am
content: Quote from: Fungus on December 30, 2021, 09:02:38 amI don't remember that I had seen a HiRes screenshot from the MSO5000 in this thread.But the MSO5000 User Guide claims that it does:QuoteEdit: It does not tell the actual decimation factor or the number of averaged neighbor samples, though. A boxcar filter with 16 taps had a -3dB cut-off of ~fs/35, with 8 taps it were ~fs/17, and in order to get the documented fs/32, the closest number of required taps were 15. But this is pure speculation now and I think the "truth of the actual implementation" can only be determined experimentally by an owner.Btw: One disadvantage of a boxcar averaging filter (and thus disadvantage of HiRes, if based on boxcar averaging) is that its sinc frequency response starts rolling off already beyond DC, i.e. the passband has no pronounced "flat top". If this matters for a particular use case, the filter cut-off should be rather chosen several times higher than the highest frequency of interest.

author: Fungus
author_rank: Super Contributor
timestamp: December 30, 2021, 09:56:13 am
content: Quote from: gf on December 30, 2021, 09:30:53 amSTOP THE THREAD!I just downloaded the latest manual from Rigol and it says they've now added "High Res" mode.HiRes will make a huge difference to the noise level by leveraging that massive 8Ghz sample rate.Fiorino, we need another test with "HiRes" mode enabled.

author: 2N3055
author_rank: Super Contributor
timestamp: December 30, 2021, 10:46:13 am
content: Quote from: Fungus on December 30, 2021, 09:56:13 amYes, please, stop...He already did it. It didn't help, it simply low pass filtered out signal of interest. It hid it.First thing, HiRes on MSO5000 has been around for some time now, and it's not big help...They had to downsample 32 times to get something and then not much. HiRes makes it 250Msps/s single channel, down to 62.5Msps/s 3 or 4 channels enabled. 32 MHz max bandwidth at max sample rate, and if you grab longer sequences even lower.You keep ignoring one fact (probably deliberately by now, because to you it's not about facts but about winning the argument even with lies and misdirection, apparently) that it isnot about small signals per sebut aboutdetailsin signal that can be quite large.High noise makes ENOB (effective number of bits) even less than already not very big 8 bits. So you see thick big sinewave on MSO5000, and a sinewave with a small squarewave superimposed on top on other scope that had low noise and had retained it's resolution better. Hi res scope would do even better, and that is why every manufacturer now is trying to go 10 or 12 or even more bits. It is not irrelevant.MSO5000 is not useless. It's a scope that you can do work with. There are some usage scenarios when it's high noise won't stop you from doing your job. For some people that might be good enough. Mostly because if you don't know you have a problem, you cannot worry about it..But, putting head in a sand doesn't make it better or equally good as some other equipment that actually have better specifications and can show signals MSO5000 cannot. Other instruments are literally much better for this kind of measurements. If you only need scope to decode 4 decodes at the same time, yeah, then MSO5000 will be better because other scopes mentioned don't have 4 decode channels. But mediocre analog performance didn't go away and suddenly became perfect. No, it is still mediocre but you don't care. Which is OK if you are FULLY AWARE of all pros and cons.But fanboying like yours tries to make it like MSO5000 is equally good in EVERY parameter as other scopes. It is NOT.If you're doing analog,there are better choices.

author: Fungus
author_rank: Super Contributor
timestamp: December 30, 2021, 10:52:41 am
content: Quote from: 2N3055 on December 30, 2021, 10:46:13 amI never said that.The title of this thread is "How much...?", you're the one burying your head and refusing to answerthatquestion by fanboying the Siglents.

author: tv84
author_rank: Super Contributor
timestamp: December 30, 2021, 11:01:39 am
content: Quote from: Performa01 on December 30, 2021, 07:47:05 amNice example (pic worth a thousand words). How did you generate such signal?

author: Martin72
author_rank: Super Contributor
timestamp: December 30, 2021, 11:13:02 am
content: Quote from: gf on December 30, 2021, 09:30:53 amHi-Res mode was implemented by the second firmware update, AFAIK.I´ve did some measurements, in one of them you could see that hi-res was active because of the reduced bandwith (squarewave measurement), the pics are somewhere in the rigol 5000 thread..

author: Fungus
author_rank: Super Contributor
timestamp: December 30, 2021, 11:33:06 am
content: Quote from: Martin72 on December 30, 2021, 11:13:02 amYep, you're right.So...And, yes, Fiorenzodidpost a screenshot of his test signal in Hires mode, my bad:The manual says "In "High Res" mode, the signal bandwidth does not exceed 1/32 of the sampling rate" so it sounds like they do 32x oversampling with no user control. Not ideal.You'd probably see the spikes on that signal if you zoom in a bit. They'd be much more visible in "peak" mode, too. I wish I had one here to fiddle with.

author: Fungus
author_rank: Super Contributor
timestamp: December 30, 2021, 11:58:15 am
content: Quote from: tv84 on December 30, 2021, 11:01:39 amAny half decent signal generator will do it, including the one built into the Rigol. Just generate the two waves described above and modulate them. The trick is is in the "optimal probing".Is there anybody here with a Rigol who can do generate the same test signal and optimize all the display settings to see how good it can be?

author: 2N3055
author_rank: Super Contributor
timestamp: December 30, 2021, 12:06:38 pm
content: Quote from: Fungus on December 30, 2021, 11:33:06 amNo you wouldn't see anything because it was filtered out.And in Peak Detect mode you would see 10 mm thick solid wall of noise.. You don't seem to understand exactly how these acquisition modes work.And I agree. We ALL would like if you could just maybe borrow one and play with it for a while. You would soon understand what we all are talking about.I can't (or want to) speak for other people, but for me it is not about bashing Rigol. I have DG1062Z and it is very nice little AWG. I had DS1054Z too, and loved the little thing. Best thing after sliced bread at the time.When Rigol announced new DS5000/7000 series, I was waiting at the door to buy DS7000. Looked sooo good on paper. After it was released, I tried it and month after I gave twice as much money for Keysight 3000T.R&S RTM3000 was too expensive and had it's own share of problems. LeCroy was my first choice but I could not get good deal. Keysight was simply much better at business. They actually took effort to find something for me.Big plus for Keysight then. Nowadays, it seems they would be same as LeCroy, and not care about small fish..If SDS2000/5000/6000 from Siglent were available then, those would be my first choice, even compared to Keysight 3000T for many things..Today, they would definitely be my first choice in their respective classes.If Rigol releases MSO7000 MarkII with as low noise as Siglent, then I would be willing to reconsider.. Until then, that is my opinion.

author: 2N3055
author_rank: Super Contributor
timestamp: December 30, 2021, 12:11:50 pm
content: Quote from: Fungus on December 30, 2021, 11:58:15 amNo, that signal was created by combining two signals, either with digital combiner (Siglent AWGs have one) or by simple resistive combiner, that will serve as attenuator at the same time.I use two two pass trough terminators to 1k resistors from siggen, other side connected together, and grounded with 100 Ohm resistor. I have that one because we had some previous discussion about two tone testing, and someone did it with that one so I made it exactly like that so we can compare results...

author: mawyatt
author_rank: Super Contributor
timestamp: December 30, 2021, 03:25:40 pm
content: Quote from: 2N3055 on December 30, 2021, 12:11:50 pmThat might have been me since I was interested in the scopes DR performance. The 1K series R is to isolate the two AWG outputs from each other so they don't "see" the other signal as much with the ~26dB reverse isolation looking back from the shunt 100 ohm resistor. Was concerned about how the AWG output behaves in the presence of another signal and how this might affect the AWG output amp linearity. With this high an isolation the AWG output amplifier effects should be minimal and the resultant two tone IDM representing the scopes performance. BTW using the digital combining isn't as good, since the signal is created and then passed thru the AWG amplifier chain to the output, thus exposing the signal to the chains linearity effects. However may be OK since we are only looking at 65~75dB IMD with these scopes, but with Performa01 Picoscope results of ~100dB some of the AWG amplifier chain effects may contribute if using the AWG digital combining for the two tones.Thanks to you, and a few others for pointing out the various features/limitations of the DSOs under consideration by means of actual "hands on" experience & usage rather than delusional speculation. Also don't think anyone is bashing Rigol, just pointing out features/limitations, seems not the case for Siglent which always seems to get bashed by some, especially when compared to the Rigol.Personally feel bad for the OP and those that seek informative answers about these instruments, they shouldn't have to read and sift thru multiple threads and many hundreds of posts to get informative information.Anyway, maybe a "Special Informative Instrument/Equipment Section" could be created where only those with actual "hands on" experience could comment, this would be highly beneficial to those seeking information to help decide on a purchase.Best,

author: Fungus
author_rank: Super Contributor
timestamp: December 30, 2021, 03:33:12 pm
content: Quote from: 2N3055 on December 30, 2021, 12:11:50 pmOh, I checked the manual and the MSO5000 AWG can only do AM, FM and FSK. No "add" function.(sorry, "combine")Quote from: 2N3055 on December 30, 2021, 12:06:38 pmI wonder why they don't, you'd think they'd have had time to tweak their ASIC by now. All their expensive devices are based on it so it must be costing them a lot of lost sales.(or maybe not, Batronix' bestseller list puts theRigol ahead in sales)That amount of noise is difficult to defend.

author: Fungus
author_rank: Super Contributor
timestamp: December 30, 2021, 03:40:18 pm
content: Quote from: mawyatt on December 30, 2021, 03:25:40 pmStrongly disagree.Who would be the arbiter of truth? You? Not everybody in the world does the same job as you or has the same needs or the same budget as you.The Rigol could even be the better choice in many situations.(I even suspect that hardly anybody in this thread actually sits all day looking at mV signals. All these Siglents probably spend far more time at 1V/div than at 1mV/div).

author: mawyatt
author_rank: Super Contributor
timestamp: December 30, 2021, 04:13:40 pm
content: Quote from: Fungus on December 30, 2021, 03:40:18 pmNo arbitrator, just only those with actual "hands on" experience with the equipment/instrument under consideration should comment. This way one can get information related to actual experience with such equipment.In the case of this thread I wouldn't comment because I've never had "hands on" with a Rigol.Best,

author: bdunham7
author_rank: Super Contributor
timestamp: December 30, 2021, 04:16:30 pm
content: Quote from: Fungus on December 30, 2021, 03:40:18 pmWell I do, and I don't mean just responding to this thread. I may not be looking at 1mV signals, but I often use 100X probes to minimize circuit loading. So I'm right back in that 1-10mV/div area. In fact, on occasion even the slightly higher noise of the Siglent is annoying.I got a box delivered yesterday and I find that the SDS2000X+ is only very slightly better--if at all--than the SDS1104X-E as far as noise and minimum trigger. It isn't able to match the Tek 2221A, but it gets pretty close--200uVrmsvs 150uVrmsfor a stable display.

author: 2N3055
author_rank: Super Contributor
timestamp: December 30, 2021, 04:36:30 pm
content: Quote from: Fungus on December 30, 2021, 03:40:18 pmI would be very happy with Mike as arbiter of that.. He is supremely qualified to do so.. Unlike some others..Not that I want to push that burden on him. Just saying. Not everybody's opinion has same weight, despite size of their egos...Some people simply know more..In the end your "democratic choice" argument is useless and doesn't hold. Those without knowledge are not capable of making educated decisions, because of lack of knowledge. Nobody is contesting their freedom of choice, they simply don't know enough to make good decision. At one point you have to trust the doctor and not the fear, rumors and your preferences.Giving patient raw CT, MRI and X-ray images without doctors diagnose for them is not useful. All they can do go to another doctor with them.Rigol would be better choice in some situations, which I already pointed out before. SDS2000X+ is better rounded scope overall. Excellent for analog, competent for digital. Rigol OTOH is one show pony, it is quite good for decoding and that is it. You can do analog stuff with it but not well.MSO8000 OTOH is quite good scope for the price, because it has some more options, and 2 GHz bandwidth. It's noise is good FOR the bandwidth. MSO5000 is just weird. It could have been so much better.Again, like Nico and others told you, it is not all about uVolts. Rigol shows finger thick trace all the time. It is only exacerbated even more when using 10x probes, where you are really at 100mV div (noise wise) doing digital stuff at 1v/div. It is not about microvolts, it is about details in the picture. Or shall I say the lack of them...

author: nctnico
author_rank: Super Contributor
timestamp: December 30, 2021, 04:39:38 pm
content: Quote from: mawyatt on December 30, 2021, 04:13:40 pmThat way you only get mostly information from people who are still on their -what I call- buyer's 'high'. On top of that, not everyone's needs are the same. What is a great tool for one, totally sucks for someone else. It would be a lot more useful to asses equipment using standarised testing but that takes a lot of time. All in all having a mix of owners and people who (based on experience with a wide range of equipment) know what works for a certain use case and what doesn't is a good compromise.

author: Fungus
author_rank: Super Contributor
timestamp: December 30, 2021, 04:54:22 pm
content: Quote from: 2N3055 on December 30, 2021, 04:36:30 pmInsults are still coming thick and fast I see.I seem to recall telling Fiorenzonot to use 1x probe without 20Mhz limiter. I even posted a link to Dave's video on that.I also suggested trying color gradient mode and averaging mode to see what happens.I evensuggested the SDS1104X-Eas a way of saving money, because I know the noise is pretty much the same as the 2000 series and it seemed like it would cover his stated needs perfectly well.At no point was he in any danger of being tricked into buying a Rigol because of fanboyism (imaginary).Seems like the only people here being "hurt" here are the curmudgeons.(...and it's only beenonethread, which nobody was forcing you to read anyway. Was the sky really falling?)

author: Fungus
author_rank: Super Contributor
timestamp: December 30, 2021, 04:57:00 pm
content: Quote from: nctnico on December 30, 2021, 04:39:38 pmYep. The Rigol MSO5000 is cheaperandit's a better choice for some percentage of users.

author: David Hess
author_rank: Super Contributor
timestamp: December 30, 2021, 05:03:22 pm
content: Quote from: Fungus on December 30, 2021, 03:33:12 pmThe noise is likely a characteristic of the process used to make the ASIC. It is unlikely any available circuit change would fix it. Many digital CMOS processes, which can still be used to make fast ADCs, are incredibly noisy, like 100s of nV/SqrtHz and MHz noise corners.As you pointed out, most applications do not involve inspecting millivolt level signals so the Rigol's high level of noise is irrelevant to most users.Quote from: bdunham7 on December 30, 2021, 04:16:30 pmI suspect higher noise is a major reason x100 probes are not very popular despite having better high frequency performance than x10 probes. My own experience is that the difference in noise is very noticeable.

author: nctnico
author_rank: Super Contributor
timestamp: December 30, 2021, 05:09:42 pm
content: Quote from: David Hess on December 30, 2021, 05:03:22 pmNo, the problem is not in the milli-volt level signals but the overall high noise which obscures details in the signal and makes the traces much thicker. I have owned a very noisy (high end) DSO myself (from a different brand though) and it was very cumbersome to work with due to the high noise level. Hi-res and averaging can clean up a signal to some extend but you'll also lose the details. And I wasn't even using it to look at particulary special signals; just getting measurements on analog signals in the range of a few Volts already proved difficult.

author: Fungus
author_rank: Super Contributor
timestamp: December 30, 2021, 05:18:15 pm
content: Quote from: David Hess on December 30, 2021, 05:03:22 pmKeysight's ASIC isn't as noisy and that's quite old now. Is that a different process?Even if the ASIC can't easily be fixed, you'd think there would be more ways to improve the signal in software.eg. Their HiRes mode seems to be fixed at 32x which is a bit heavy-handed. I'd have preferred a user-selectable setting, eg. 4x, 8x, 16x, 32x... to preserve some detail.Or even implement a programmable FIR filter on the 8Ghz incoming data.

author: bdunham7
author_rank: Super Contributor
timestamp: December 30, 2021, 06:02:11 pm
content: Quote from: David Hess on December 30, 2021, 05:03:22 pmThe main reasons I'll use a 100X probe are HV (not an issue here) and low circuit loading. For the latter, obviously there are issues with low signal levels and higher frequencies where the capacitive loading takes over. So usually I'll be looking at some rather mundane medium-level signal, like a crystal oscillator or CMOS logic circuit, and I just want a halfway decent reading with minimal loading. It never looks really great, but a 100X probe often gets the job done. More noise? I'm sure there is, but I don't think it overwhelms scope input noise.Here are three examples of 100mV/1MHz, 100mV/100Hz and 20mV/100Hz. This results in a 1mVrmsor 200uVrmsinput to the scope. I find this sort of setup to be very useful in troubleshooting random stuff.

author: 2N3055
author_rank: Super Contributor
timestamp: December 30, 2021, 06:33:00 pm
content: Quote from: Fungus on December 30, 2021, 05:18:15 pmKeysight has access to state of the art processes.Also Keysight has years of experience of making massively parallel ADC.Your comments about Hi Res are valid. Except, Rigol initially didn't filter so heavily, and problem was that people were saying HiRes is not working. They had to go all the way up to 32x to make it show..Rigols chipset consists of two components AFE ASIC (Beta Phoenicis) and Signal processing (Ankaa) that contains ADC block. Problems are that both chips were designed for MSO8000 and have up to 4 GHz bandwidth.AFE ASIC is fully contained, including amplifiers and solid state switches for attenuators. I don't know exact internal architecture. Also SP chip with ADC also has full bandwidth (4GHz) driver buffers to drive ADC cluster. That can be source of noise too. And also noise might be from ADC, quantization noise. If ADC is massively parallel type, there are all kinds of things that can go wrong.. intercalibration, clock distribution, crosstalk etc etc..One interesting thing would be to disconnect/short input directly into Rigol ADC chip. That would give a better clue where the noise comes from.

author: Performa01
author_rank: Super Contributor
timestamp: December 30, 2021, 06:53:58 pm
content: Quote from: tv84 on December 30, 2021, 11:01:39 amIt is a two channel AWG (SDG6052X in this particular case), both channels combined by means of a resistive wideband (DC-12.4 GHz) power combiner/splitter. This will provide 6 dB attenuation for each channel.Channel 1 generates a 5 mVpp ramp with 5% symmetry at 1 MHz.Channel 2 generates a 10 ns wide pulse with 3 ns rise/fall times at 6.000001 MHz with 60 mVpp amplitude and this signal is fed through a 1 GHz precision step attenuator, set at 40 dB.The output of the power combiner is what you see.Quote from: 2N3055 on December 30, 2021, 10:46:13 amThe manual says that thebandwidthcannot exceed 1/32 the samplerate, so this sounds like 16 times oversampling to me.This would be roughly equivalent to ERES 2.0 bits on a Siglent, where the resolution enhancement in ENOB can be set from 0.5 to 3.0.In 10 bit mode together with ERES 2.0, we get a total resolution enhancement to 14 bits (and a theoretical ENOB of 11 bits). The trace gets very thin with this, see attached screenshot.SDS2354X Plus_Ramp_2.5mV_1M_Pulse_300uV_6000001Hz_ERES2.0Quote from: mawyatt on December 30, 2021, 03:25:40 pmFor the high 3rd order dynamic range on the Picoscope 4262 I did not need to use any additional attenuators apart from the power combiner itself, which only provides 6 dB isolation between its ports. At frequencies as low as 1 MHz, an SDG6000 amplifier output quite obviously cannot be intermodulated that easily. But maybe I should try one more time with additional attenuation – who knows, maybe the Picoscope can do even better…EDIT: Done - and found no difference. The SDG6052X performs well enough for this test at 1 MHz, even without additional isolation between the outputs.The integrated digital combiner does indeed generate some IMD products on its own, so it is not suitable for reliable 3rd order dynamic tests. IMD can be as bad as 45 dBc at high output levels.EDIT: Using the internal digital combiner, the third order intermodulation intercept point is about +21 dBm at an output level of +9 dBm and a frequency of ~50 MHz.EDIT2: Unsurprisingly (since it's done in the digital domain), the third order intermodulation intercept point is nearly the same (+21.5 dBm) for a -18 dBm output level at 1 MHz.Quote from: bdunham7 on December 30, 2021, 04:16:30 pmThere is almost no difference indeed. If anything, the SDS2000X Plus might show less or lower spurious signals, but the noise level should be about the same. In fact, the little SDS1000X-E even has a slight edge here, because it provides a true full resolution 500 µV/div sensitivity, whereas the SDS2000X Plus is limited to 1 mV/div. Yet the 500 µV/div gain setting is not useless there either, because of the 16 bit display interface. This means you can make use of it in 10 bit mode (which becomes 9 bit at 500 µV/div) and also the results of math functions, especially ERES of course.

author: 2N3055
author_rank: Super Contributor
timestamp: December 30, 2021, 07:07:55 pm
content: Quote from: Performa01 on December 30, 2021, 06:53:58 pmYes, that makes sense.Quote from: Performa01 on December 30, 2021, 06:53:58 pmI tried with 1k/100Ohm combiner and got roughly the same numbers as you for two tone test...And both are better than spec.. Love that little guy.And SDG6000 too, it is much better than spec for signal distortion, and digital combiner keeps surprising me...

author: normi
author_rank: Regular Contributor
timestamp: December 30, 2021, 07:11:34 pm
content: Quote from: nctnico on December 30, 2021, 12:07:48 amI disagree, the noise on the MSO5000 is about 2mv at the lowest 4mv level, so if that scaled as in your example it would mean that at 10V/div the noise would be 5v. What appears to be the issue is this Phoenix chipset which no one has information on how it works has a noise component which is added in but it does not scale proportionally with V/div, the scope would also have the regular scope noise which scales with the V/div.It is arguable whether the MSO5000 has more sample rate than it needs but the fact is that it is better than having barely enough. With all channels on it has 2G/S per channel.

author: mawyatt
author_rank: Super Contributor
timestamp: December 30, 2021, 07:12:41 pm
content: Quote from: Fungus on December 30, 2021, 05:18:15 pmCMOS comes in many flavors, the modern versions feature very fast and small featured devices. Because MOS devices exhibit more noise than bipolar, we often oped for a SiGe BiCMOS process where we had access to superb bipolars and good CMOS. However as time marched on the BiCMOS couldn't keep up with the SOTA mainly because there's not enough market to justify the enormous foundry costs, so BiCMOS is becoming an orphan. Wise folks realized this long ago and began to move designs to pure CMOS and leverage off the almost unlimited finances of CMOS driven by Smart Phone and Laptop/iPads.I suspect Rigol's attempt at a fully integrated front end didn't turn out as well as expected, especially noise-wise, and maybe done in pure CMOS. The cost of improving this is likely moving to another CMOS process, and the expense of a complete redesign in a newer CMOS process is very high....maybe too high for Rigol to invest at this time. Hopefully they will produce at better performing ASIC, and I admire them for taking on the ASIC design challenge in the first place.Keysight has much deeper pockets and experience than just about anyone in the instrument field, and have been developing full custom ASICs for AWGs and DSO for some time. The Griffin AWG ASIC was an absolute masterpiece of engineering (see image), done in a SiGe BiCMOS process back in ~2009, however the next generation is all CMOS. The Stingray ASIC from ~2011 is an ADC and part of the front end of a developmental high performance DSO (see images) and all CMOS. So Keysight has been moving towards CMOS for custom ASICs for a decade now, and likely others too.Custom ASIC designs in any process are expensive, and may not fit the financial model for all companies. So, at the moment seem relegated to a few A player levels in instrumentation field, except for Rigol.Best,

author: David Hess
author_rank: Super Contributor
timestamp: December 30, 2021, 10:38:41 pm
content: Quote from: Fungus on December 30, 2021, 05:18:15 pmGiven the age difference, it almost has to be a different process.QuoteThe only way to remove noise is to limit the bandwidth or synchronously demodulate the signal with averaging over multiple triggers. And limiting the bandwidth does not reduce the noise density.QuoteThat is how Tektronix used to do it. Bandwidth was variable since the adjustment was tied to sweep speed with a fixed maximum sample rate. It was certainly effective. I do not know what they do now.QuoteThat is not impossible but it has high cost. Some high end DSOs manage it if you want to buy a DSO instead of an expensive new car.Quote from: 2N3055 on December 30, 2021, 06:33:00 pmThat explains at least part of the problem. A signal chain with 4 GHz performance will always have higher noise density than one designed for a much lower frequency. I gave an example of this earlier.QuoteThe attachment I included earlier about signal conditioning in oscilloscopes written by Steve Roach gives some idea of how such a design is possible, although he thought an alternative using MEMS switches was more likely.QuoteMeasuring the noise at every volts per division setting would reveal some of what is going on.

author: Fungus
author_rank: Super Contributor
timestamp: December 31, 2021, 12:46:28 am
content: Quote from: David Hess on December 30, 2021, 10:38:41 pmIt's only 8 bit numbers and trivially parallelizable.If the FPGA is capable of triggering on incoming serial data then it might be able to do it.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 31, 2021, 12:13:16 pm
content: Quote from: normi on December 29, 2021, 11:35:57 pmThank you normi, very interesting and usefull explanation.And also thank you again to everybody, you are super kind to support this thread

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 31, 2021, 12:19:32 pm
content: Quote from: gf on December 30, 2021, 09:30:53 amThe Rigol has hi-res mode but many times It was ineffective.... I don't know whyI have some photos but i should search for those.

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 31, 2021, 12:28:22 pm
content: Quote from: Fungus on December 30, 2021, 09:56:13 amMy name Is Fiorenzo ahahah....In regard of the photos I have some, give me some time and i will post them.Also, I cannot do more of them because i sent back the Rigol.I experimented a week with the hi-res mode.My thought was: well if It has 8GSa/s It should give good results with the hi-res mode but It was not many times.... unfortunately.... Most times It gave only a reduction in the visibile noise of about 10-20%.... some time nothing, and free times not more than 50%....So I came to the conclusion that hi-res was not the solution for the noise problem...

author: Fiorenzo
author_rank: Regular Contributor
timestamp: December 31, 2021, 12:38:31 pm
content: Quote from: 2N3055 on December 30, 2021, 12:06:38 pmYes that Is right. I have seen that many times on the Rigol. Also hi-res mode seemed to me more of an avarage than a bit resolution improve...

author: Fungus
author_rank: Super Contributor
timestamp: December 31, 2021, 12:54:40 pm
content: Quote from: Fiorenzo on December 31, 2021, 12:28:22 pmMy impression from the manual is that it would depend a lot on the horizontal zoom.It's not a "solution for the noise" but it might make the spikes more visible when you zoom in a bit.

author: gf
author_rank: Super Contributor
timestamp: December 31, 2021, 01:33:49 pm
content: Quote from: Fiorenzo on December 31, 2021, 12:38:31 pmWhen I look at your 20mV/div screenshot showing 815µV RMS of noise (w/o HiRes and w/o 20MHz BW limit), this is a SNR of only ~36.8dBFS, or ~5.8 ENOB.Assuming white noise, the theoretical noise voltage reduction with 16x HiRes is factor 4 = sqrt(16), or ~12dB, leading to a SNR of ~48.8dBFSthen, or ~7.8 ENOB.So the result is not at all an enhancement beyond 8 ENOB, but HiRes just helps to bring 8 ENOB almost back, at the cost of limiting -3dB bandwidth to ~230MHz, and a sampling rate reduction to 500MSa/s. That's only 1/2 the sampling rate of a 1GSa/s scope then.[ I don't know whether the same applies to other V/div settings, too. To get evidence, each one would need to be evaluated indiviually. ]QuoteTwo points that come into my mind:1) If the initial noise (w/o HiRes) happens to be low, then the iprovement can possibly only be seen on the screen when zooming in vertically.2) The amount of noise reduction achievable by HiRes depends on the spectral power distribution of the noise. The theoretical factor of sqrt(N), where N is the number of adjacent samples being averaged, only applies to white noise. If the noise power is already concentrated at low frequencies, then the HiRes low-pass filtering can't help much. To assess this, it were necessary to do a FFT of the captured signal (w/o HiRes processing applied). E.g. if you already apply a 20MHz BW limit in the AFE, then an additional low-pass with a cut-off at ~230MHz won't make too much difference, but it can only reduce any additional noise originating after the AFE's 20MHz filter (e.g. noise from the ADC).Edit: Changed some phrasing in order to be hopefully more clear.Edit: Attached the frequency response of a 16-tap boxcar moving avarage lowpass filter, when running at a sample rate of 8GSa/s. Maybe it helps to understand what kind of filtering is happening when HiRes is enabled.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 31, 2021, 02:39:42 pm
content: The high res mode averaging helps with the white noise, like much of the noise behind the amplifier. With a BW limit of 70 to 350 MHz much of the noise below this would not be reduced from 2 to 16 times averaging and 32 fold averaging only just starts to reduce the input noise.In this respect it makes some sense that they did not provide less averaging. The lower averaging steps may still help with the otherwise more favorabel settings (maybe 100 mV/div), where input noise is no such a factor.

author: gf
author_rank: Super Contributor
timestamp: December 31, 2021, 04:57:59 pm
content: Quote from: Kleinstein on December 31, 2021, 02:39:42 pmYou are right, and this should not be neglected: An implicit analog BW limit of 70 to 350 MHz is always present in the AFE, depending on the model.Edit: Possibly one should really measure the noise floor SPD at different settings, likePerforma01 did for the Siglent.

author: mawyatt
author_rank: Super Contributor
timestamp: December 31, 2021, 05:27:39 pm
content: Quote from: nctnico on December 30, 2021, 04:39:38 pmMaybe on a "buyers high", or maybe on a buyers remorse, all depends on how well the the item behaves, and maybe long after the purchase which is good indicator. Not all purchases turn out as expected!!Regarding the requesters "needs", that would be up to the requestor to indicate such and the responses should be from folks with actual "hands on" experience with the equipment & the perceived "needs".In the end, it's up to the requestor to sift through the fanboys/girls and chicken little responses for a reliable equipment assessment. However, this would be orders of magnitude easier for the requestor than through the countless pages and posts we've all experienced."Been there done that" when we wanted to consider a modern MSO/DSO, and it took some time and effort to figure out where the posts were coming from, who's behind them, what experience was involved and so on, and I personally feel that others should not have to suffer thru all thisBest,

author: normi
author_rank: Regular Contributor
timestamp: December 31, 2021, 11:02:12 pm
content: The OP had already made up his mind when he made the post, he just wanted some reassurance. If someone thinks something matters then it matters even if it does not matter to others. And that basically applies to everything in life.Most posters had no experience with the scopes and are just debating ideas, and yes all the information on the scopes have been posted many times in other threads.Unfortunately there are no clear cut choices when buying and there are numerous parameters to consider, so the debates will continue.

author: David Hess
author_rank: Super Contributor
timestamp: January 01, 2022, 03:41:50 am
content: Quote from: gf on December 31, 2021, 04:57:59 pmAs I pointed out earlier, any bandwidth limit, including high resolution mode, lowers the spot noise (1) but does nothing for the noise density. For lower noise density, better or more suitable devices are required.(1) Above the flicker noise corner frequency, RMS Spot noise = Noise Density * Sqrt(Noise Bandwidth)

author: Fiorenzo
author_rank: Regular Contributor
timestamp: January 01, 2022, 06:01:01 am
content: So, here we have a photo of the ripple with and with out ERES 3bit.It seem that ERES avarages the signal removing all the visible spikes that was possibile to see with the Siglent due its lower noise front end.Some information about the signal Is lost.

author: bdunham7
author_rank: Super Contributor
timestamp: January 01, 2022, 06:22:29 am
content: Quote from: Fiorenzo on January 01, 2022, 06:01:01 amTry increasing the memory depth to get the sample rate up, or else speed up the timebase to 1ms/div. ERES shouldn't be averaging out your noise, but it will reduce the bandwidth.

author: rf-loop
author_rank: Super Contributor
timestamp: January 01, 2022, 07:17:32 am
content: It is also "averaging" but not simplest "boxcar" filtering as is in HiRes. ERES have "bell shape" filtering.Also it acts like LPF as @bdunham7 told. (same but bit different happen with HiRes where it is used)In @Fiorenzo last image LPF -3dB corner is at around 3.2MHz.Before this and that wild stories or wondering about ERES, it is good to understand basic fundamentals about it (and HiRes)Here (Teledyne LeCroy and it is enough compatible for also Siglent)@FiorenzoFor what is reason you display these horrible photographs instead of direct scope TFT screenshots in png format.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 01, 2022, 09:08:19 am
content: Quote from: David Hess on January 01, 2022, 03:41:50 amSkipping samples to reduce the data rate instead of averaging (or a similar filter with slightly different weights) adjacent samples will cause some aliasing and this way also the measured noise density. It depends of the noise of the input stage on how important the later stage and ADC noise is.In case of the Rigol sope it looks like most of the noise comes from the input stage, even though the ADC part is way higher BW than actually needed.Especially for the lower BW versions a more conventional input stage would be a much better choice and not necessary that expensive.

author: David Hess
author_rank: Super Contributor
timestamp: January 01, 2022, 08:34:35 pm
content: Quote from: Kleinstein on January 01, 2022, 09:08:19 amAnother way to say that is aliasing folds the noise bandwidth over below the Nyquist frequency increasing the noise density so that the spot noise remains the same. This does not apply to ADCs in DSOs from Tektronix and Keysight and other high end manufacturers which perform noise shaping, but that does nothing for the noise from earlier stages.QuoteIn an integrated CMOS design, it would not surprise me if the noise of the preamplifier following the input buffer is as high or higher in some cases. Companies like Tektronix and Keysight can rely on exotic processes to achieve much better noise performance for a given bandwidth than available with CMOS. Otherwise JFETs provide the lowest noise but are limited to lower bandwidth.I wonder what the fastest available JFET is these days. My Tektronix notes list the 2N5397 at 260 MHz but that was as of 1982, and faster JFET front ends even in 1984 used hybrid construction.On the other hand, a Toshiba 3SK293 dual gate MOSFET comes out to 1.5 GHz so if someone wants to home build a faster front end, or an active probe, the parts are available.QuoteI hope they considered it and decided that their intended market did not require lower noise so it would have been an unnecessary expense. Otherwise it is just bad design.The best solution with the existing Rigol ASIC would be a separate input buffer with lower bandwidth and lower noise followed by a preamplifier with enough gain to overcome the noise of the following stages, but doing this would make the lower bandwidth models cost more to produce than the higher bandwidth models? Rigol is making these things incredibly cheap.

author: nctnico
author_rank: Super Contributor
timestamp: January 01, 2022, 08:48:08 pm
content: Quote from: David Hess on January 01, 2022, 08:34:35 pmIMHO too cheap. This thread is one of many examples where people returned their Rigol MSO5000 scope and bought something else. If they can bypass the problem with a different frontend then it would save Rigol's bacon because it is a relatively easy fix. But at this point it is unknown where the majority of the noise is coming from (fronted or ADC).

author: Martin72
author_rank: Super Contributor
timestamp: January 01, 2022, 10:55:50 pm
content: QuoteLike me..And we shouldn´t forget, the much more expensive 7000 series is not better in this case.And since more than 3 yrs it is crystal clear, that the noise is the showstopper - But no reaction from rigol, no improved hardware fix, nothing.Why..

author: Kleinstein
author_rank: Super Contributor
timestamp: January 02, 2022, 07:57:23 am
content: Quote from: David Hess on January 01, 2022, 08:34:35 pmThere are some pretty fast FETs available for sat LNAs. As an example CE3512: they give a gain of 13 dB at 12 GHz.Not sure if they are silicon or maybe some other material. The voltage is limited and they may not be suitable for a high impedance input stage, but fast JFETs are available.The main ASIC in the Rigol scope seems to be OK and good for the price. The small front end ASIC seems to be more of a problem.For the lower BW models even a front end like in the 1054 may be an improvement, and I doubt it would be much more expensive.One may still need mode gain steps, as some of the Hitite ADCs are quite good and include some gain adjustment, that may not be available in the RIGOL ADC.

author: David Hess
author_rank: Super Contributor
timestamp: January 02, 2022, 08:36:51 am
content: Quote from: Kleinstein on January 02, 2022, 07:57:23 amI think I checked those out 20 years ago with that idea in mind. They are gallium arsenide and among other deficiencies, have a gate leakage 100s to 1000s of times too large to be used for a 1 megohm input. The highest performance active probes use them with an input divider to get a useful input voltage range, which explains why some active probes only have a moderate input resistance. The same thing was also sometimes done with RF bipolar transistors in active probes.

author: gf
author_rank: Super Contributor
timestamp: January 02, 2022, 09:29:01 am
content: Quote from: Kleinstein on January 02, 2022, 07:57:23 amBut BW were not upgradable then. Who buys a 8GSa/s scope with only 70MHz BW? I guess that many (most?) who buy the cheaper 70MHz model have the intention in mind to do a "free upgrade" to full 350+ MHz BW.

author: David Hess
author_rank: Super Contributor
timestamp: January 02, 2022, 10:09:00 am
content: Quote from: gf on January 02, 2022, 09:29:01 amI assume Rigol is grading their custom modules and placing the lower performance ones which would otherwise go to waste in their 5000 series, so 8 GS/s is essentially free.

author: 2N3055
author_rank: Super Contributor
timestamp: January 02, 2022, 10:39:32 am
content: DS2000A had good 350MHz front end. That would be one to put into MSO5000, together with 50 Ohm path it doesn't have now.That would make it a good scope, provided AFE is dominant source of noise.But as it was pointed out, it is not clear where does noise come from exactly. Looking at architectural diagram from Rigol, there is some buffering and amplification in ADC chip. Which is not a simple ADC chip, but like MegaZoom, it has some other functions inside too. Also some of the noise could come from ADC itself.. In diagram they claim some DSP capability on ADC chip itself. Maybe there is some digital correction for equalization and linearization? Are they loosing bits there?We don't know..I'm sure there must be a sweet spot in input settings where input is not attenuated and not heavily amplified. There must be a sweet spot where SINAD and corresponding ENOB is maximum. Measure that and ADC cannot be worse that that. It still can be a bit better if there are funny choices made in architecture, but cannot be worse. If those numbers are respectable for a 8 bit ADC, then you know actual front end before it is to blame..

author: tv84
author_rank: Super Contributor
timestamp: January 02, 2022, 11:07:12 am
content: This forum lacks Rigol insiders...One day we'll understand the delay on a major FW update for the MSO5000. Maybe they are trying their best to correct via software the HW shortcomings or the HW is a lost cause and may only serve as a "recycle bin" (as David Hess basically hypothesized) for their less performant ICs.

author: Martin72
author_rank: Super Contributor
timestamp: January 02, 2022, 11:19:26 am
content: QuoteRemember the thing, as there were no hi-res mode on both series, 5000 and 7000...That was already somehow suspicious.

author: tv84
author_rank: Super Contributor
timestamp: January 02, 2022, 11:28:22 am
content: Quote from: Martin72 on January 02, 2022, 11:19:26 amI'm going out of my confort zone here but I suspect that is another consequence of the software uniformization between models... A feature not intended for this specific device got NOPed to make it work and, as such, little or just some psychological effect is visible.

author: 2N3055
author_rank: Super Contributor
timestamp: January 02, 2022, 12:09:57 pm
content: Quote from: tv84 on January 02, 2022, 11:07:12 amWell, as many will agree, you can "improve" some things with software. But mostly it is more of "hiding" it with software, or extracting partial data by ignoring the rest.There is no software algorithm that can "improve" noise on wideband signal and retain all of it's characteristics.I would happily make measurements, but I don't own Rigol scopes in question and I'm NOT going to buy one just out of curiosity. Not that curious or rich.As for chip binning I wouldn't call it "recycle bin" exactly. Binnig for bandwidth is standard practice for high value chips.Of course, unless you use chips "rejected" for high noise...

author: mawyatt
author_rank: Super Contributor
timestamp: January 02, 2022, 02:00:29 pm
content: Quote from: David Hess on January 02, 2022, 08:36:51 amGaN devices might be an alternative today, haven't looked into them for anything like a scope front end tho. Believe Keysight uses a InP front end on their higher end scopes, the Keysight InP process we designed some test circuits with some time ago were 600GHz, today likely >1THz. Northrup Grumman developed a 1THz communication system over a decade ago with InP, so there's definitely some very fast 3/5 compound processes available. CMOS is also very fast today, but the breakdown*speed product isn't as good as InP or GaN, and of course there's SiGe.Best,

author: David Hess
author_rank: Super Contributor
timestamp: January 02, 2022, 04:56:58 pm
content: Quote from: mawyatt on January 02, 2022, 02:00:29 pmWith the exception of active probes, the existing high speed MMIC (monolithic microwave integrated circuit) processes are used at 50 ohms. In general none of the advanced processes are used to make improved small signal discretes, at least not ones mere mortals have access to, which would replace the small signal silicon JFETs and depletion mode MOSFETs which are currently on the endangered list. All of the action is with high power switching and RF.I noticed yesterday that NXP is discontinuing practically all of their small signal JFETs and MOSFETs leaving one chopper JFET, one RF JFET, and two RF dual-gate MOSFETs.I found a faster JFET, but it is an old one that is still nominally available. Calogic, On, and InterFET have the J308–J310 which could be good to 500 MHz.

author: mawyatt
author_rank: Super Contributor
timestamp: January 02, 2022, 10:28:54 pm
content: Quote from: David Hess on January 02, 2022, 04:56:58 pmBelieve you can get discrete GaN devices, these would be depletion mode types and maybe a "drop in" replacement for a JFET.Best,

author: David Hess
author_rank: Super Contributor
timestamp: January 03, 2022, 05:47:06 am
content: QuoteI was only able to find power devices. Do you have a link?

author: mawyatt
author_rank: Super Contributor
timestamp: January 03, 2022, 06:50:27 pm
content: Quote from: David Hess on January 03, 2022, 05:47:06 amHad some discrete GaN devices from Nitronix and Raytheon over 15 years ago, also had some from Cree but these were higher power types (~1A), recall the Nitronix & Raytheon were ~ 0.5A. These were utilized as a proof of concept for the GaNsistor and DD2A (Direct Digital to Antenna) which culminated in patents 7939857 and 7903016. We didn't have direct access to a GaN fab, so used Raytheon, Cree and Nitronix. A few researchers were delving into GaN MMW MIMICs like mixers, LNAs and such back then, so discrete devices were available to help characterize the GaN MIMIC processes which were plagued with memory issues, but don't know if any made it into the COTS world.Recall these small signal GaN devices were extremely ESD sensitive, likely because of the very thin gate region & low capacitance. The power devices were more ESD hardened tho, and maybe why no discrete small signal GaN devices are readily COTS.Best,

author: Fungus
author_rank: Super Contributor
timestamp: January 17, 2022, 06:20:35 pm
content: Take a look at the screenshots in this thread? Where's the famous "thick traces"?https://www.eevblog.com/forum/testgear/rigol-mso5000-artifacts/msg3947554/#msg3947554

author: 2N3055
author_rank: Super Contributor
timestamp: January 17, 2022, 06:45:59 pm
content: Quote from: Fungus on January 17, 2022, 06:20:35 pmYou weren't happy with the answer there or ?

author: Performa01
author_rank: Super Contributor
timestamp: January 17, 2022, 08:45:44 pm
content: Well, if I were a Rigol fanboy and was to defend the MSO5000, I would certainly not point to a thread that strikingly demonstrates the excessive noise of this instrument and how this can ruin measurements even at low sensitivities like 50 mV/div (which would be 500 mV/div when using a x10 Probe).If the trigger level is placed close to the peak amplitude, then it picks up the noise and triggers on the peak noise level, thus highlighting it.Siglents can do this as well – to a far lesser degree, that is. And they need to be at a 1 mV/div sensitivity to show an effect that is still not as ugly (with a kink that cannot exist in reality, hence we have reconstruction errors despite the high sample rate) as on the Rigol at 50 mV/div. See first screenshot:SDS2354X Plus_Sine_120MHz_4mVpp_T3.3HzMind you, for this, we need to use the full bandwidth (580 MHz measured) and highest sensitivity (1 mV/div). The trigger event occurs about 3.3 times per second, so that’s 27.5 ppb of the rising edges in the input signal.Things are almost back to normal again if we use just a little bit less sensitive range, like 5 mV/div:SDS2354X Plus_Sine_120MHz_20mVpp_T2HzThe peak value occurs only 2 times per second, that is 17 ppb of the total potential trigger events.On an SDS2000X+, we also have a HiRes mode, that is actually working. So, if we can make do with just 100 MHz bandwidth, we don’t have a problem even at 1 mV/div:SDS2354X Plus_10Bit_Sine_100MHz_4mVpp_T6.37HzThe peak value occurs only 6.37 times per second, that is 63.7 ppb of the total potential trigger events.

author: ozkarah
author_rank: Regular Contributor
timestamp: March 20, 2022, 12:54:11 am
content: Quote from: Fungus on December 23, 2021, 02:51:59 pmNot true. The amplifier designed here is working between only 10Hz-100KHz bandwidth. After 100 KHz there is a big gain roll-off.

author: OverBugg
author_rank: Newbie
timestamp: April 11, 2022, 06:02:01 pm
content: Hi All,I know this subject is grinded to death between the Siglent SDS2k+ and Rigol MSO5000 but I'd love if you gurus could answer a couple of questions to a beginner considering getting one of the two (SDS2104X Plus or Rigol MSO5104).I'll use a scope mainly for testing power glitching and decoding high speed digital signals for known/unknown protocols and on occasion will do analog stuff just for learning so analog is a second priority, I've read endless reviews/posts and got all pros/cons for each, but since I'm a beginner I have no clue whether:1. Will the noisy front end for the Rigol will prevent me from achieving my goals (currently I don't know what steps I'll use for glitching) if you have experience here I'd love your advice2. Will the higher sample rate of the Rigol 8Gb/s will be an advantage against the Siglent 2Gb/s all channels or will not make a difference for probing unknown high speed digital signals? (knowing the Rigol's sample rate is for one channel and splits for 2/4, its acceptable by my needs).My two options currently are:1. Rigol MSO5104 with Logic Probes2. SDS2104+ with some generic 1Gb/s Logic analyzer (i.e. dslogic U3pro32 or if you have a better option..)3. -=Add your dream setup here=-Thank you so much...

author: Fungus
author_rank: Super Contributor
timestamp: April 11, 2022, 07:58:05 pm
content: All you'll get is a repeat of people pointing out the large numbers of people happily doing analog work with their Rigols and people saying it's completely unusable for any sort of work whatsoever.The only conclusion to be drawn is that the truth is somewhere in between soyouwill have to decide how much you'll be using the 'scope for analog work in the mV range and buy accordingly.If they cost the same then the decision would be easy but they don't. As noted you can have a Rigol plus logic probes for the same (or less?) money as a Siglent without them.

author: nctnico
author_rank: Super Contributor
timestamp: April 11, 2022, 08:10:57 pm
content: Quote from: OverBugg on April 11, 2022, 06:02:01 pm3.-=Add your dream setup here=-R&S RTB2004

author: bdunham7
author_rank: Super Contributor
timestamp: April 11, 2022, 08:41:08 pm
content: Quote from: OverBugg on April 11, 2022, 06:02:01 pmI have the Siglent with the logic probes and I can look at 16 digital channels plus look at 4 of them with the analog channels just by connecting to the second pin on the grabbers. That's the true utility of having both functions in one unit--you can trace a glitch in one domain with one in another. So whichever you get, even if you do get a separate PC-based logic analyzer, the logic probes for the scope are worth the money. So, if money is tight and you aren't overly concerned with low-level analog, perhaps the Rigol is for you.To answer your specific questions, you won't know if the noise issue will be a problem until one day it is. And perhaps that day may be never. For me, it would be intolerable. But I'm not doing what you're doing and I'm not sure what you mean by 'glitching'. The sample rate will probably be a non-issue for 99.9% of use cases. I think you'd have work pretty hard to demonstrate why the Rigol is better because of the sample rate.QuoteFully loaded Tek MSO68B with 4 Iso-Vue fiber probes and 4 logic probe modules.https://www.testequipmentdepot.com/tektronix/oscilloscope/8-flexchannel-mixed-signal-oscilloscope-mso68b6bw10000.htm?ref=gbase&gclid=CjwKCAjwo8-SBhAlEiwAopc9W8lJoVoqUW9D8yJ7PC7Z4WjSFinuHNkxyGz1nXVdtFSy93NMdIppRxoCHxcQAvD_BwEhttps://www.tek.com/en/products/oscilloscopes/probes/isovu-isolated-probeshttps://www.testequipmentdepot.com/tektronix/accessories/oscilloscope-probe/logic-probes/8-channel-flexchannel-general-purpose-logic-probe-tlp058.htm?ref=gbase&gclid=CjwKCAjwo8-SBhAlEiwAopc9W_bJBrnhzfK_PiGpB_1BhEzqroBQIiHfAjJfWQ2ADK5B1DITeFGxZhoCdoYQAvD_BwE

author: Fungus
author_rank: Super Contributor
timestamp: April 13, 2022, 08:17:49 pm
content: Quote from: bdunham7 on April 11, 2022, 08:41:08 pmIf we follow that logic to the end we should all buy 4x4 pickup trucks just in case we ever need to take bales of hay up the hill to the horses in winter.Some peopledolive on ranches and own horses so the logic holds for them. Other people live in the city and could buy things they actually need with the difference in price between a monster pickup and a Honda Civic.

author: bdunham7
author_rank: Super Contributor
timestamp: April 13, 2022, 08:32:37 pm
content: Quote from: Fungus on April 13, 2022, 08:17:49 pmIf you had only read a little bit further...

author: OverBugg
author_rank: Newbie
timestamp: April 16, 2022, 07:53:50 am
content: bdunham7 and all, Thank you for your elaborated response, that was extremely helpful (tending to the Siglent atm), to be more specific regarding the power analysis I want to perform testing on power like described in this paper:https://mdpi-res.com/d_attachment/cryptography/cryptography-04-00015/article_deploy/cryptography-04-00015-v3.pdf, my concern is that the noise will prevent me "seeing" uV/mV changes in this resolution, if the Rigol can do that then I prefer it over the Siglent since I'll use the 8Gs/s more often later on with other testing scenarios, but if not then the Siglent + Logic probes as you suggested is the next lineup.Thanks again,

author: David Hess
author_rank: Super Contributor
timestamp: April 17, 2022, 01:40:38 am
content: Quote from: OverBugg on April 16, 2022, 07:53:50 amWhat you need is an amplifier which allows a "slideback" measurement, as they used to call it. This is also known as a differential comparator. Essentially it is a differential probe with a variable reference voltage applied to one input, so a precision DC offset can be subtracted from the signal to be measured. The classic examples of this type of oscilloscope input amplifier are the Tektronix 7A13 and 7A22 but there were earlier ones. The 7A22 supports 10 microvolt/div measurements with up to 1 volt of offset, but bandwidth is limited to below 1 MHz. Modern DSOs implement this as an "offset" function but without as much performance as old instruments.Even with the low noise 7A22, achieving 10 microvolt/division sensitivity is questionable at its full bandwidth of 1 MHz. A modern implementation could do better because there are some better parts available finally, but not by a lot.Since you are measuring a current, there are some better ways. Use a transimpedance amplifier to make a virtual ground (or supply) for current measurement and produce a low noise fast voltage output proportional to supply current. Then do a subtraction with an adjustable reference voltage and use the DSO of your choice. Performance will be limited by the transimpedance amplifier implementation but that is a well researched topic.

author: Fungus
author_rank: Super Contributor
timestamp: April 17, 2022, 07:11:14 am
content: Quote from: OverBugg on April 16, 2022, 07:53:50 amWhy do you assume the Siglent can do it?At some point you're going to need an amplifier to see tiny signals. The Siglent just delays that moment a bit longer than the Rigol.

author: 2N3055
author_rank: Super Contributor
timestamp: April 17, 2022, 07:40:12 am
content: With side channel attack current analysis, probing solution is the most important one.I recommend @OverBugg to do some research on that. There are many ways to do it, including non-contact probes (take a look at Little Bee magnetic probe, for instance..)

author: 2N3055
author_rank: Super Contributor
timestamp: April 17, 2022, 07:46:56 am
content: Quote from: Fungus on April 17, 2022, 07:11:14 amAnd World War II didn't happen because you don't like Siglent...His presumption comes for the fact that one piece of equipment has 10X more sensitive input amplifiers and more than 4-5X less noise...I would say that delaying that moment 10 times is VERY relevant.If you need that kind of analog performance, Siglent is outperforming Rigol MSO5000 by a very large margin.Siglent SDS2000X+, literally HAVE 10X amplifier built in , compared to MSO5000.Full range, propper oscilloscope front end amplifier...If you don't need very best analog performance, then it doesn't matter.

author: Fungus
author_rank: Super Contributor
timestamp: April 17, 2022, 12:25:47 pm
content: Quote from: 2N3055 on April 17, 2022, 07:46:56 amIf somebody comes in and says they want to look at uV signals then it seems like the question should be asked. Signals don't magically stop where Siglents say they do.

author: bdunham7
author_rank: Super Contributor
timestamp: April 17, 2022, 03:05:42 pm
content: Quote from: OverBugg on April 16, 2022, 07:53:50 amOK, interesting. I think the Siglent will be anorder of magnitude betterat this particular job, but I don't have the Rigol to test directly so perhaps someone else can, using the signal I explain below?David Hesshas pointed out that for the general case, you need an amplifier or probe that can provide or accept a DC offset--some differential and single-ended FET probes do have this feature but you'll have a hard time finding one that is 1X, let alone amplified. So you might need to solve that issue if the built-in capabilities of the scope aren't enough. You also just might be able to use AC coupling in this sort of setup, but that would take more getting into the specifics.So to be specific, I looked at Fig. 2 on p. 33 of your link, this is showing a few-millivolt signal on a 600-ish millivolt offset with some detail. I sort of replicated this with an AWG set to put out a 5mVp-p1 kHz 8-step staircase signal with a 650mV offset. Then I set up the SDS2354X+ at 1ms/div, 1mV/div and a -650mV offset (which takes a bit of doing) and was pleasantly surprised to find thatin this case, the scope was perfectly capable of making the reading directly. Eventually you run out of offset, but that's in the manual. I noted a little less than a 1mV apparent error in the offset, or ~0.15%, which seems very good to me. I captured these two screenshots--one in 10-bit with 20MHz BW and one with ERES @ 3.0 bits. As the document you linked stated, further methods like averaging can be used in some cases. As you can see, the signal appears to be fairly clear, but you certainly wouldn't want more noise.

author: bdunham7
author_rank: Super Contributor
timestamp: April 17, 2022, 03:14:18 pm
content: Quote from: Fungus on April 17, 2022, 12:25:47 pmWhat question? If the signal is lower than can be readily observed directly on the Siglent, than you need to consider amplification. But AFAIK there's no readily available amplification product that will render the differences between the two scopes moot. You will always be much better off starting with the quieter, more sensitive scope and using less amplification. I think you'd have a serious and expensive challenge just making a preamp that would get the small-signal performance of the Rigol to merely equal what the Siglent already has.

author: OverBugg
author_rank: Newbie
timestamp: April 17, 2022, 03:21:45 pm
content: @fungus I don't assume anything because in reality I don't actually know the level of precision needed for a specific use case, I have worked mostly with logic analyzers in the digital domain in the past (reverse engineering several devices) but never in the "analog" side of things which I would like to explore more and learn, my use case is very simple: get a microcontroller with encryption, pull one leg with 1k/10/100k resistor and measure voltage while its doing its computation to extract the key, I have seen and read cases using oscilloscopes such as the Rigol DSO2072A and Keysight DSO-X 2004A, my thought was getting an MSO with a bit more "pawa.." to be able to learn analog stuff as well as my primary usage which is mostly digital (decoding/capturing), that is itso the only question remains, will one of the two(SDS2k+/MSO5000) will do the trick in regards to precision/sample rate/etc., I am also open to get a DSO if you can recommend one that will be a better option for these things.Thanks for your time helping a noob

author: OverBugg
author_rank: Newbie
timestamp: April 17, 2022, 03:27:09 pm
content: AMAZING bdunham7.... thank you for taking the time for this. I'll look into your results, Beers on me when we meet..

author: SpacedCowboy
author_rank: Frequent Contributor
timestamp: April 17, 2022, 03:41:42 pm
content: Quote from: bdunham7 on April 11, 2022, 08:41:08 pmI’m somewhat interested in getting one of the two scopes under discussion (my current scope is a Rigol 1102D, so due an upgrade) - but somewhat torn on the options available. They both seem like pretty good scopes, but while a low noise floor seems like a great property for a scope to have, modding the license code seems a lot more difficult on modern Siglent scopes than Rigol, and I’d hate to be stuck with the low-end model, however hard that is to ethically justify In reference to the above quote, though, I *do* own aSalaea Logic Pro 16analyzer (bought when it was about half its current price) and for digital work it’s pretty awesome - and it will (more slowly) do analogue sampling as well as digital. You don’t necessarily need a scope for mixed work, the lines are blurred in both directions these days - plus you can write your own protocol analyzers relatively trivially with the Salaea - I did one for PECI a year or so back. For digital signals, I’m not even sure the scope is the better option…

author: ozkarah
author_rank: Regular Contributor
timestamp: April 17, 2022, 08:17:16 pm
content: I’ve been at the same place with you. My options were MSO5104, SDS2104X+, and R&S RTB2004. Thanks to contributors here I read a lot, and I learned a lot. Let me share my experience with you.I don’t have a large budget. Price/Performance was important for me. First I eliminated RTB2004. Because it is more expensive (considered with options and upgrades) and not possible to hack it in the future. Then I had 2 options left:RIGOL MSO5104:Pros:+ 8 GSa/sec sample rate (it is great if you need high freq) (4 Gsa/sec with 2 channels enabled, 1GSa/sec with 4 channels enabled) (Siglent: 2 Gsa/sec with 1/2 channels enabled, 1GSa/sec with 3/4 channels enabled)+ Easy to upgrade(or hack) for all options (including 500MHz bandwith)+ Comes with 4 x 350 MHz probes (Siglent comes with 200 MHz probes)+ 1 GSa/sec digital channels sampling rate. (Siglent has 500 MSa/sec)+ 2 Channel AWG (option) (but up to 25 MHz. Siglent comes with 1 Ch 50 MHz option)+ Better price. (and some very attractive promotions with bundle options)+ HDMI output (but 1024x600 not scaled to fullscreen)+ Web viewer.+ 4 Math functions at a time (Siglent has 2)Cons:- The most popular one is the noisy front end. Bad for analog signals. I considered adding an amplifier. The most effective types of signal amplifiers are active/diffferantial probes. However, they are too expensive, even more expensive than the scope itself. There are also very cheap low-noise signal amplifiers. However, their problem is nonlinearity. Their gain cannot stay at the same level as the frequency changes. So you can see the shape of the signal, but cannot trust to the measurements. It depends on your requirements. If just seeing the waveform is enough no problem.- Buggy UI and firmware. Rigol used its own ASIC chip on this model. And users report that software bugs are less now but still there.- 100 mega points (analog) standard memory. 100 mp is a good value but less compared to Siglent. (Siglent has 200 Mp out of the box. 200 Mp/ch when 2 ch enabled. 100 mp/ch when 4 channels are enabled. Rigol has 100 Mp/ch when a single channel is enabled. 25 Mp/ch when 4 channels are enabled. However, Rigol has a 400 USD upgrade option to 200 mp/ch, MSO5000-2RL, which doubles the numbers in the previous sentence. Still half of the Siglent, even with the deep memory option purchased.)- 25 mega points per digital channel memory (Siglent has 50 Mp/ch)- You have to buy separately the 16 channel logic probes and to use them and it is not cheap (probes: ~400 USD). But no sw license is needed.- You have to pay (or hack) for all protocol decoding options (sometimes there are free bundle promotions. at Siglent basic protocols are included for free)- There is no 50 Ohm input setting. You have to use 50 ohm terminator when your source impedance is 50 Ohms.- 1 mega points FFT-----------------------------------------------------SIGLENT SDS2104XPros:+ Very low noise floor (It is around 70 microvolts which is really great fun when working with low amplitude signals)+ 500 microvolt/div range setting (which is not pixel doubling as it is in Rigol)+ Easy to upgrade(or hack) for all options (including 500MHz bandwith)+ Astonishing 10.1 display with 256 level intensity grading (Rigol has 9”). Touchscreen and gestures work smoothly (I saw some videos in which Rigol has some problems with that).+ 50 MHz signal generator (optional) (but 1 channel)+ 10-bit mode is really working fine (also you can add ERES filter to increase the effective bits on top of it)+ If you have a signal generator from Siglent (SDG2042X I have) scope can communicate and command it flawlessly (through the local area network) to calculate the Bode plot.+ DIY digital logic probe schematics are available in the forum. (not sure if Rigol also has)+ Decoding for basic (UART, I2C, SPI, … ) protocols is included for free. You have to pay for some additional protocols (I2S, Manchester, CAN FD, FlexRay, MIL-STD 1553B, SENT)+ Stable UI/UX.+ Web control with full screen viewing option. (There is a VNC server running on the device. From any client you can connect and view scope UI)+ 50 Ohm input setting is there.+ 2 mega points FFTCons:- In high frequencies, 2 GSa/sec per channel might be limiting (It is 1GSa/ch when 3 or4 channel is used).- When upgraded to 500 MHz bandwidth it is up to 2 channels at a time. If you need 3 or 4 channels simultaneously, bandwidth limit is 350 MHz.- 200 MHz probes come with 100MHz and 200 MHz models.- Price level is higher than Rigol. (Sometimes, also very attractive bundle promotions are there but usually still higher)- You have to buy separately the 16 channel logic probes and a sw licence to use them and it is not cheap (probes: ~380 USD sw:~175 USD).- No HDMI/VGA output. (You have to use web viewer or VNC)+ Only 2 Math functions at a time (Rigol has 4)-----------------------------------------------------SUMMARY:• Both scopes are really good. You shouldn’t expect the best scope of the world at this price level.• Both scopes are open to liberation (hack). R&S RTB2000 is not as I know.• If you will mostly work with digital signals which don’t need more resolutions but higher sample rates Rigol has a 2 times sample rate compared to the Siglent. (2 GSa/sec when 4 channels are used compared to 1 GSa/sec). Also when you need 1 channel only 8GSa/sec should be very great at high frequencies. So with digital signals at high freq Rigol looks great.• Having a low noise floor, effective 10-bit mode, and ERES filter Siglent is much better at analog signals (or when probing digital signals with analog probes).• Siglent has 4 times of memory of Rigol’s in most cases. (2 times when Rigol’s deep memory option is purchased)• Siglent is more expensive.• Siglent has a less buggy and better UI/UX (my opinion).• If you need BODE PLOT analysis and already have a signal generator from Siglent or Rigol you would want to consider the integration benefits of having a scope from the same brand.Which one we should choose?It really depends. You should consider your requirements and check the pro and con conditions above. If you only work with digital signals Rigol beats with a high sample rate and attractive price. If analog is also important and especially you need a good resolution then Siglent is better.I usually work with digital signals but analog signal probing is also a must for me, and I didn’t wanna struggle with the noise problems when going analog. So, I went with Siglent. I bought it under a promotion price; bundled with AWG, 16 channel logic probes, and a logic probing software license. Sometimes I wonder how fun it would be if it had an 8 GSa/sec sample rate, but in common I am very happy with the Siglent.

author: Fungus
author_rank: Super Contributor
timestamp: April 18, 2022, 10:20:32 am
content: Quote from: ozkarah on April 17, 2022, 08:17:16 pmGood summary.Just a nitpick: Both scopes are probably going to be hacked so the Rigol's deep memory is "standard".

author: ozkarah
author_rank: Regular Contributor
timestamp: April 18, 2022, 10:20:07 pm
content: Quote from: Fungus on April 18, 2022, 10:20:32 amThanks. Till you liberate it is still an option. However, you are right too. Most probably it is not a big issue if you are not afraid of warranty validity risks.

author: Fungus
author_rank: Super Contributor
timestamp: April 19, 2022, 07:29:57 am
content: Quote from: ozkarah on April 18, 2022, 10:20:07 pmThe hacks can be easily removed, leaving no trace.

author: ozkarah
author_rank: Regular Contributor
timestamp: April 19, 2022, 12:56:59 pm
content: Quote from: Fungus on April 19, 2022, 07:29:57 amThat's good to know. I read a lot of discussions about that but not a clear answer or description.Can you pls elaborate on how it is done for Siglent SDS2000X Plus series?I have an SDS2104X Plus and I didn't hack any option yet.I succeeded in backing up all configuration files from the scope. Is that enough?

author: Fungus
author_rank: Super Contributor
timestamp: April 19, 2022, 02:22:44 pm
content: Quote from: ozkarah on April 19, 2022, 12:56:59 pmhttps://www.eevblog.com/forum/testgear/siglent-sds2000x-plus-hack/msg3526524/#msg3526524

author: ozkarah
author_rank: Regular Contributor
timestamp: April 20, 2022, 03:06:38 am
content: Quote from: Fungus on April 19, 2022, 02:22:44 pmCouldn't find any info on reaching that menu. Does anyone know?

author: 2N3055
author_rank: Super Contributor
timestamp: April 20, 2022, 04:42:16 am
content: Quote from: ozkarah on April 20, 2022, 03:06:38 amIt's in a Utility menu. Download the manual and spend some time just browsing around on the scope. It will help you remember where things are. It is like music, you need to play basic scales first to memorize where things are...EDIT: Wasn't paying attention. I thought it was normal info menu.. Sorry..

author: tautech
author_rank: Super Contributor
timestamp: April 20, 2022, 07:47:15 am
content: Quote from: 2N3055 on April 20, 2022, 04:42:16 amWell not quite.The menu shown is added to with a magic USB stick that permits resetall options to Nil and resettimes of free option uses to the standard 30.This is distributor only stuff and from those that discovered it buried deep in Siglent code.Even the Siglent scope product manager was quite shocked I had a copy as it's reserved for EU and NA service centers.However for those that buy these scopes and plan to hack them the Python code is the simplest way to get all the options and BW upgrades.

author: Fungus
author_rank: Super Contributor
timestamp: April 20, 2022, 11:38:48 am
content: Quote from: ozkarah on April 20, 2022, 03:06:38 amJust be happy that itcanbe done!(and cross fingers that you never need to...)

author: cdev
author_rank: Super Contributor
timestamp: April 20, 2022, 01:26:56 pm
content: That "noise" may be naturally present and you may simply not be used to having instruments with high input impedance's.Roll that around a bit in your mind, and experimentally, determine if its the case.Don't sour on a perfectly good instrument because its input is showing you occasional high voltages present in your environment. The fact is, often, they are there.On the other hand, sometimes noise isnt there and if an instrument shows annoying amounts of noise, obscuring real measurements then its a problem. How to differentiate? Dave or others here who have lots of experience testing instruments should answer that.I could show you however that when turned on my (quite decent) Uni-T multimeter set to voltage or the input on my Tek scope, both show lots of voltage is present when the input is not connected to anything. I.e. floating. In my kitchen for some reason, there always is a lot. It just varies, randomly. I could make a video to show how nuts it acts.Whats cooking? Nothing, right now. I actually often use my kitchen table as a workbench. The situation is never a problem for me.Quote from: Fiorenzo on December 23, 2021, 12:00:05 pmI have a bitscope with an MSO function. Here at my workbench, plugging it in, you might think it was defective.But if I connect it to electronics, usually the measurements make sense.its actually just what it picks up normally.They all only pick up this stuff when a probe is connected to the input and extended out a bit. Yes, that kind of is noise, as I complain about it with reason when I am trying to receive radio signals. It is noisy.I live in New Jersey, near all sorts of activities. My fellow residents, industrial activities. Lots of people have wifi. Internet. various appliances, home workshops.

author: 2N3055
author_rank: Super Contributor
timestamp: April 20, 2022, 05:28:13 pm
content: Quote from: cdev on April 20, 2022, 01:26:56 pmNope, not that kind of "noise".We are talking about noise inherent into scope, that will show even if you put a short BNC plug right at the BNC input.Not the work environment noise.. That is a whole different can of worms...

author: tautech
author_rank: Super Contributor
timestamp: April 20, 2022, 07:31:59 pm
content: Quote from: 2N3055 on April 20, 2022, 05:28:13 pmWell yes, not everybody gets that when you connect a probe to a scope suddenly there is noise displayed especially at high input sensitivities.Then when they connect to a DUT and the noise goes away they think there's something wrong with the scope.Recently we had a customer send a scope back when he couldn't get his head around these basic principles and even when screenshots sent him from a different model displayed similar noise.We'll not have a customer that isn't happy with one of our instruments so refunded his money and insisted any further instrument he collected in person and tried before he purchased.Another more experienced customer was almost tearing his hair out however he had a clearer mind and after some insistence the scope was not faulty he finally found a unknown wallwart behind a curtain spewing all manner of EMI/RFI out and corrupting his measurements.The more enlightened of us use this EMI/RFI input sensitivity to advantage especially when tuning a small motor such as a chainsaw where it's hardly a demanding task for a scopes frequency readout that needs to read 200 Hz for an equivalent 12,000 RPM.

author: ozkarah
author_rank: Regular Contributor
timestamp: April 21, 2022, 04:12:44 pm
content: Quote from: tautech on April 20, 2022, 07:47:15 amIn some screenshots, I saw that after the hack scope serial and scope ID are lost/empty. Is this issue still happening? And is there a procedure to follow both to have this issue ?

author: ozkarah
author_rank: Regular Contributor
timestamp: April 21, 2022, 09:40:14 pm
content: Quote from: ozkarah on April 21, 2022, 04:12:44 pmNever mind. The upgrade worked like a charm. No issues at all.