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EEVblog => EEVblog Specific => Topic started by: EEVblog on June 15, 2019, 12:02:18 am

Title: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: EEVblog on June 15, 2019, 12:02:18 am
Siglent have entered the 1GHz oscilloscope market with the SDS5000X, is it a worthy competitor?

https://www.youtube.com/watch?v=oxu19IFHMgc (https://www.youtube.com/watch?v=oxu19IFHMgc)
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: maginnovision on June 15, 2019, 02:29:13 am
I was cracking up when you wanted to do sequence mode with zone trigger and couldn't. The ONE THING you wanted to do you couldn't. Pretty funny.

Edit: Teardown
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: EEVblog on June 15, 2019, 03:27:32 am
I was cracking up when you wanted to do sequence mode with zone trigger and couldn't. The ONE THING you wanted to do you couldn't. Pretty funny.

It didn't seam unreasonable!
I was shocked when it didn't do it, had no inkling that it wouldn't, just seemed like an obvious practical test and cool combination of features.
I can't really think of any architecture thing that would prevent it, yet the software knows and the has the message a the ready in case you try.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: TheSteve on June 15, 2019, 06:12:32 am
It seems to be a jack of all trades, but a master of none.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: JPortici on June 15, 2019, 07:13:08 am
(Glad you were using 8.2R1 which is indeed the latest firmware available)

I think zone trigger is implemented in software. Trigger -> processor get data, compare with zones -> actual trigger
This would explain why sequence mode is not available with zone

Dave, can you do a teardown of the active probe? I'm really interested in it.. or at least in the communication protocol. The interface on the hardware level is veeeeeery simillar to probus (i measured +12,-12,+5,0 and two 3.3V which may very well be SDA and SCL)
Can't find the thread.. there is one on reverse engineering probus

Re: bugs
cool, didn't know of that one. But i NEVER use gestures. I tried once just to see if they were implemente but after that... knobs or manual entry on the bottom left channel menu.. same for horizontal/vertical adjust.
I'm very fine with no acceleration on the encoders, as i can use the touch screen or manual input for coarse adjustment
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: thmjpr on June 15, 2019, 07:23:38 am
$2,900 the 2ch version is in a bit of a no mans land. Rigol MSO5000: 4 channels, 2 channel sig gen built in (with modulation), better update rate, better intensity/color grading, higher sample rate. Of course, Siglent has a lot of features: histogram charts and zones is unique, 50 ohm, active probe, better responsiveness, front end. And the updates/feature requests via forum is huge too.

For the 4CH model, one of those things has to jump out at you to pay the $3500 vs $1000 price. If 350MHz is hackable to 500MHz, then you've surpassed the rigol spec, and really in another market.
The 350 and 1G have different front ends according to the siglent thread (https://www.eevblog.com/forum/testgear/at-last-siglent_s-sds5054x-touchscreen/), so you may not be able to get the full 1G via unlock.

BTW if you want to clear something thats gone awry, have to hit 'Default' :p. With the Auto button I would just expect it to set horizontal/vertical settings, trigger level, maybe trigger type and leave everything else as-is. Considering the ridiculous number of settings scopes have these days, I wouldn't be surprised if they start implementing profiles to store custom setups.

I think zone trigger is implemented in software. Trigger -> processor get data, compare with zones -> actual trigger
This would explain why sequence mode is not available with zone

Thats not the greatest solution, but may have been a compromise that had to be made given the acquisition structure.
And they call the FFT "Hardware accelerated", but I wonder to what degree, its not wildly fast.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: JPortici on June 15, 2019, 07:44:42 am
mm.. I have the 4 channel 350 MHz and that's 2.9k here
Considering the ridiculous number of settings scopes have these days, I wouldn't be surprised if they start implementing profiles to store custom setups.

Ah, it's already been there for quite some time. I have used a bunch of scopes with this capability
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: 2N3055 on June 15, 2019, 07:46:46 am
Thats not the greatest solution, but may have been a compromise that had to be made given the acquisition structure.
And they call the FFT "Hardware accelerated", but I wonder to what degree, its not wildly fast.

2Mpoints FFT is slow by virtue of gate time. Somebody should try speed on Siglent with 64Kpoints FFT like Keysight has. And usually Keysight doesn't even have full 64K you have to set it so.
So until then , we don't know what the speed is .

Yeah, it's rough around the edges.. We'll see..
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: tautech on June 15, 2019, 08:05:24 am
(Glad you were using 8.2R1 which is indeed the latest firmware available)
Version 8.4R4 has been out with the beta testers for a few days already.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: TurboTom on June 15, 2019, 08:24:25 am
Dave, thanks for the review  :-+

But I've got to place some small criticism here -- your input noise comparison is somewhat dodgy (34:00 into the video): Since the R&S had some visible DC offset of the input signal (round about -300µV), this will clearly contribute to the RMS measurement. Try checking noise with the inputs in AC coupled mode. Depending on the internal processing, the average offset will get subtraced in this mode (not sure if it works this way on the R&S, at least the "mature" Rigol products do it like this).

Then I'm sure you'll find that the R&S is at least on par with the new Siglent scope.

Cheers,
Thomas
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: maginnovision on June 15, 2019, 09:03:22 am
No matter what the RTB is disadvantaged since the Siglent drops to 200MHz bandwidth at small v/div. The only like for like comparison could be done is with both having the 20MHz filter on. However, I would expect the Siglent to have better noise floor anyway.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: Performa01 on June 15, 2019, 12:24:46 pm
Maximum waveform update rate of 110kWfm/s can be reached at 20ns/div in dots mode only. The sin(x)/x reconstruction filter takes its toll in terms of processing time on all the Siglent scopes.

There certainly is a History button on the front panel and it’s even lit when in history review mode.

Zone Trigger is just an addition to any of the existing triggers (so it can be used to refine a complex trigger even further), but not an independent trigger function itself. This is why it doesn’t belong into the trigger selection menu.

BTW, I don’t think Zone Trigger is a software function, as this would be far too slow. It is in the FPGA, like pretty much anything that has to do with triggering.

I cannot know for sure, but I’m positive that History for zone triggered acquisitions could be supported. I guess it could be just like Mask Test in the Zoom window – I’ve long requested that and we’ve got it now on the SDS5000X. I’ll have to check with Siglent R&D.

To get rid of an accidentally placed Histogram region (which automatically enables the Histogram), we need just disable the Histogram function in the Analysis menu. ;)

Intensity Adjust as the default function on the Intensity Adjust knob (as we have it on the older SDS2000X) is on Siglent’s todo list, just like the search for serial triggers.

Finally, I think we can clearly see from the video that the R&S is slightly lower noise despite the higher bandwidth at 1mV/div – but it just so happened to have a far worse DC offset than the Siglent, which didn’t show any noticeable offset at all in this test. So if the proper measurement (standard deviation = RMS without DC component) would have been used, then Siglent would have lost that duel – only by a small margin, but still...
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: nctnico on June 15, 2019, 02:04:12 pm
Regarding reviewing more expensive equipment: I think this is useful. Ofcourse you get a unit on loan but nevertheless it is good to know whether it is worth considering before spending time on getting a piece of equipment in and testing it thouroughly.

Finally, I think we can clearly see from the video that the R&S is slightly lower noise despite the higher bandwidth at 1mV/div – but it just so happened to have a far worse DC offset than the Siglent, which didn’t show any noticeable offset at all in this test.
DC offset is just a matter of running the self-calibration (and/or let the instrument warm up before use).
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: BillB on June 15, 2019, 03:43:15 pm
Good review.  I imagine it must be difficult to cover so much functionality while trying to prioritize what you cover, all while keeping it from being a four hour video. 

Regarding reviewing more expensive equipment: I think this is useful. Ofcourse you get a unit on loan but nevertheless it is good to know whether it is worth considering before spending time on getting a piece of equipment in and testing it thouroughly.

Definitely agree.  Though, I wouldn't want to watch exclusively high-end reviews either.  It would probably bankrupt me.  :)
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: TK on June 15, 2019, 05:26:36 pm
Siglent has a lot of features: histogram charts and zones is unique, 50 ohm, active probe, better responsiveness, front end. And the updates/feature requests via forum is huge too.
Rigol MSO5000 has histogram charts and zone trigger.  It lacks 50 ohm input option.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: JPortici on June 15, 2019, 06:34:47 pm
(Glad you were using 8.2R1 which is indeed the latest firmware available)
Version 8.4R4 has been out with the beta testers for a few days already.
Glad he didn't use that one
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: David Hess on June 15, 2019, 07:07:48 pm
So it has a dedicated roll mode button but not dedicated trigger slope button.  Which one is more likely to be used?

I am not sold on drop down menus combined with a touch screen.  What advantage does that have over using physical menu buttons other than cost when the touch screen is going to be included anyway?

The index graded display looks terrible.

At least they used a non-glare display.  That puts them ahead of many of their competitors and Apple.

Update:

The loss of signal integrity of channel one at about 29:20 looks to me like aliasing of the intermodulation products between the frequency content of the fast edge and sampling clock when the sample rate is reduced to 2.5 Gsamples/second.  Try taking single shot captures in that configuration to see what is going on.  The sample points are correct but the sin(x)/x reconstruction fails when aliasing is present.

The 500 MHz response of the Keysight should not display it as much simply because of lower ratio of bandwidth to sample rate and the same goes for the Rigol.

The shown transient response is not very good.



I would not trust the RMS noise measurement until I confirmed that the DSO measures RMS noise correctly.  Rigol for instance does not.

Better results may be available by measuring the DC standard deviation of a single shot capture and this should agree with the RMS measurement.



I chuckled at the smudged screen of the Keysight toward the end.  Is that a feature?
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: JPortici on June 15, 2019, 08:05:58 pm
I am not sold on drop down menus combined with a touch screen.  What advantage does that have over using physical menu buttons other than cost when the touch screen is going to be included anyway?

There is a looooot of stuff that's not reachable with the buttons because it was added later and/or there wasn't a good place to put them in the buttons, and there's going to be more in the future.
This means that the scope can't effectively be used without the touch screen

I'm fine with it, i use the touch controls a lot more than the knobs these days

Intensity grading, i don't give a shit. I prefer "temperature" color grading a million times over DPO style intensity grading

Incidentally, none of the scope i have and use at work (picoscope, tek TPS, SDS-5035X, lecroy 7200A -the one from the 80s-) have intensity grading, at most they have color grading and in the rare times i need such a thing i prefer it over starndard intensity grading, but that's me
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: genghisnico13 on June 15, 2019, 10:11:15 pm
Just for reference I removed the offset with Math. 1M memory.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: smarteebit on June 16, 2019, 05:03:05 am
Just for reference I removed the offset with Math. 1M memory.
Why not directly use the Stdev measurment?
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: blueskull on June 16, 2019, 05:28:21 am
Intensity grading, i don't give a shit. I prefer "temperature" color grading a million times over DPO style intensity grading

Then how do you implement multi-channel with color conflicts?
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: snoopy on June 16, 2019, 07:46:17 am
It seems to be a jack of all trades, but a master of none.

Plus lots of annoying bugs you don't usually find with the major brands. Looks like a rush job and another re-run of the Rigol MSO7000 :(

Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: genghisnico13 on June 16, 2019, 08:36:33 am
Just for reference I removed the offset with Math. 1M memory.
Why not directly use the Stdev measurment?
I wanted to replicate the measurements as close as possible, but you are right it would have probably been easier, either way the results are the same.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: 2N3055 on June 16, 2019, 08:51:35 am
It seems to be a jack of all trades, but a master of none.

Plus lots of annoying bugs you don't usually find with the major brands. Looks like a rush job and another re-run of the Rigol MSO7000 :(

Keysight Infiniivision 3000T series release notes are 27 pages... R&S RTM3000 is 12 pages, in a year and half after release. Download them and read them.
All of them have bugs. It is about fixing them and how fast.

So it's not right to hold Rigol or Siglent to different standards. 
Siglent seems to be improving in fixing problems, Rigol could do better but you can't say they are not doing anything...
But SDS5000X is just recently released, and R&S RTM3000 was still fixing serious problems in first few releases.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: 0xdeadbeef on June 16, 2019, 09:34:38 am
Yeah, e.g. there is this Youtube channel "Afug-Info" which seems to focus on finding even the smallest issue in the RTM 3004. While some problems might be fixed already, it's clear that also the RTM 3004 has/had lots of (minor) issues here and there. I fear that's how it is right now. Then again, even the Agilent 7000 series scopes had major (!) bugs in its initial firmware revisions >= ten years ago.
Still, honestly, some aspects of this review have been undermining my enthusiasm for the DS5000X quite a bit. It's also kinda shocking to hear in the 21st century that enabling sin(x)/x interpolation causes a major drop in acquisition (or waveform update) rate and that the specified values are only for dot mode. What about linear interpolation?
Anyway, in direct comparison to the RTM3K directly next to it, I like the (Lecroy-ish) control panel and matte screen of the SDS5000X much better but there's no way denying that everything on the RTM3K looks just sleeker and more polished. E.g. the FFT implementation on the Siglent just looks underwhelming compared to the one on the RTM3K (despite using much less points).
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: Performa01 on June 16, 2019, 10:08:19 am
Still, honestly, some aspects of this review have been undermining my enthusiasm for the DS5000X quite a bit. It's also kinda shocking to hear in the 21st century that enabling sin(x)/x interpolation causes a major drop in acquisition (or waveform update) rate and that the specified values are only for dot mode. What about linear interpolation?
There is no difference. it quite obviously is the additional display points that slow the acquisition rate down, no matter what's the math behind it.
Measurements with an old pre-release firmware (won't be much different today) show that at 20ns/div the trigger rate is 110k with single channel and 100k with both channels in dot mode. It is 23k4 for single channel and 2k8 for dual channel in vector mode.
That sounds bad, but then again we can use dots mode in most situations, because it looks nearly the same on the screen and avoids all the shortcomings of interpolation:
- no graphics processing overhead
- no unstable waveform display in the presence of strong aliasing products
- better intensity grading

Since the interpolation is just a post processing, we can switch it on anytime after the acquisition, e.g. in the history.

Anyway, in direct comparison to the RTM3K directly next to it, I like the (Lecroy-ish) control panel and matte screen of the SDS5000X much better but there's no way denying that everything on the RTM3K looks just sleeker and more polished. E.g. the FFT implementation on the Siglent just looks underwhelming compared to the one on the RTM3K (despite using much less points).
Yes, it is traditional Math FFT right now. Next FW release includes configurable peak and harmonic search with list view as well as configurable FFT length:

(https://www.eevblog.com/forum/blog/eevblog-1220-siglent-sds5000x-1ghz-oscilloscope-review/?action=dlattach;attach=764139;image)
SDS5104X_FFT_Peaks_02_Avg10

A spectrum analyzer package is on the todo list, which should provide a simple and easy setup, similar to a real SA.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: nctnico on June 16, 2019, 10:40:22 am
It seems to be a jack of all trades, but a master of none.

Plus lots of annoying bugs you don't usually find with the major brands. Looks like a rush job and another re-run of the Rigol MSO7000 :(
I don't agree with this. From what I gathered from this forum Siglent is much better at getting a working product onto the market compared to Rigol nowadays (as Dave also notes in his review). Rigol still seems to compete on price where Siglent seems to understand that to enter the professional market succesfully the first priority is a good product and price comes second.

I do agree with 0xdeadbeef. The RTM3004 is way more polished. The next step Siglent needs to take is to look at improving productivity. For starters: let the user select the memory depth. On the SDS2000 (I had the misfortune to own) the automatic (short) memory depth setting was a major nuisance. I never ever ever want to use an oscilloscope which doesn't have a user selectable/fixed memory setting.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: 0xdeadbeef on June 16, 2019, 11:54:53 am
I never ever ever want to use an oscilloscope which doesn't have a user selectable/fixed memory setting.
I'm with you there in principle. But (AFAIK) even e.g. the LeCroy 6Zi I use at work doesn't allow to set a fixed a sample memory size. It allows to set a fixed sample rate though. This allows me to determine if I either prefer a faster update (lower sample rate) or keep the possibility to zoom into details (faster sample rate). This goes so far that if the memory is not sufficient to capture the full screen with the given sample rate, only a part of the screen is updated. This flexibility is missing in all the Agilent/Keysight scopes that I used so far (but I haven't used too many models there).

So I'm concerned that the SDS5000X doesn't seem to allow to set either a fixed memory size nor a fixed sample rate. There's just this "slow" and "fast" acquisition mode which is not really explained in the manual.
Side note: I had a look in the RTM3K user manual and it seems as if there is only a "maximum" record length configurable as well. So it looks like there's neither a fixed memory length nor a fixed sample rate possible. I could be wrong though.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: nctnico on June 16, 2019, 01:56:41 pm
I never ever ever want to use an oscilloscope which doesn't have a user selectable/fixed memory setting.
I'm with you there in principle. But (AFAIK) even e.g. the LeCroy 6Zi I use at work doesn't allow to set a fixed a sample memory size. It allows to set a fixed sample rate though. This allows me to determine if I either prefer a faster update (lower sample rate) or keep the possibility to zoom into details (faster sample rate). This goes so far that if the memory is not sufficient to capture the full screen with the given sample rate, only a part of the screen is updated. This flexibility is missing in all the Agilent/Keysight scopes that I used so far (but I haven't used too many models there).

So I'm concerned that the SDS5000X doesn't seem to allow to set either a fixed memory size nor a fixed sample rate. There's just this "slow" and "fast" acquisition mode which is not really explained in the manual.
Side note: I had a look in the RTM3K user manual and it seems as if there is only a "maximum" record length configurable as well. So it looks like there's neither a fixed memory length nor a fixed sample rate possible. I could be wrong though.
In the RTM3K you can select several memory depths from a few kpts (IIRC) to 80Mpts so you can set a trade-off between memory length, samplerate and update rate. Keysight always uses the maximum memory depth on their Megazoom based scopes.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: 0xdeadbeef on June 16, 2019, 02:51:17 pm
In the RTM3K you can select several memory depths from a few kpts (IIRC) to 80Mpts so you can set a trade-off between memory length, samplerate and update rate.
Hm, OK, I wasn't sure about that, but good to hear.

Keysight always uses the maximum memory depth on their Megazoom based scopes.
I'm not totally convinced that this is totally true in every scenario. Problem here is that the detail behavior is very important. There are scopes which only really sample the full buffer (including the data that doesn't fit on the screen) in single trigger mode and scopes which do that also in normal mode. There are scopes that perform automatic measurements only from the sample buffer and scopes that perform these measurement from intermediate buffers (screen buffer or specialized measurement buffers). At least from my limited experience with 7000 series Agilent and DSOX3000 Keysight scopes I would think that Agilent/Keysight scopes are optimized for fast update rate and short dead times and therefore perform some trickery there.

BTW: Automatic measurements are one reason why defining a fixed sample rate can be more desirable than defining a fixed memory width as the sample rate directly defined the measurement resolution. Scopes that choose the sample rate automatically to optimize the update rate are somewhat problematic regarding resolution of measurements.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: 2N3055 on June 16, 2019, 03:56:32 pm
Keysight 3000T doesn't always use whole memory.

From fastest timebase 500ps/div to 20us/div it samples in such way that if you sample at 500ps/div and stop, you can "zoom out" to 20us/div.
So if you running from anywhere from 500ps/div to 20 us/div and  stop it from run, you get 1 MPoints of data after trigger (minus pre trigger time).
In single mode you get to expand out to 50 us/div, which gives 2,5 Mpoints of data.

If you are running slower timebase than 20us/div in RUN and 50us/div in single, you get only data that you see on the screen, plus minus 150us before and after so 650us altogether, at 2.5GS/s, which gives 1,625 MPoints.  In SINGLE mode all the same, except 5GS/s which gives 3,25 MPoints.

And it changes as you go through timebases. 
So I would say that Keysight has a strategy to maximize memory used when you go to STOP or SINGLE mode. But memory length is nor fixed nor maximum all the time.

And in a run mode it is not running full memory but some sort of circular buffer, and uses only one frame worth of data, to maximize waveforms per second rate..
When you stop it, it reassembles all the buffers in one full capture.
It is actually quite clever, but not very simple to understand.

Other strategy is one that is used by LeCroy, Picoscope and some others, that you can set  MAX sample size, but it will fetch exactly and only length of data that you set it to. So for instance 50us/div, at 10 div horizontal, will result in 500us of data being captured. Not a point more or less. And also it will try to sample with as quick sample rate as it will try to maximize sample points to achieve max set size. Meaning if you set for 10MPoints MAX, at 1GS/s, you will get 1MPoints in a capture that is 1ms long.  In capture 1us long (100ns/div, 10div) you will get only 1000 points.  Because it is ruled by capturing exact time interval. Max sample size will be in effect only when time base is slow enough that with highest sample rate it would want to acquire 2 Gpoints of data. So, you decide how much is too much, and then it starts slowing down sample rate..

It's really two schools of thought, optimized for different usage patterns. I think both are useful. What bothers me is that scope could be made to be able to do both but nobody does it..
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: nctnico on June 16, 2019, 04:44:15 pm
Keysight 3000T doesn't always use whole memory.

From fastest timebase 500ps/div to 20us/div it samples in such way that if you sample at 500ps/div and stop, you can "zoom out" to 20us/div.
So if you running from anywhere from 500ps/div to 20 us/div and  stop it from run, you get 1 MPoints of data after trigger (minus pre trigger time).
In single mode you get to expand out to 50 us/div, which gives 2,5 Mpoints of data.

If you are running slower timebase than 20us/div in RUN and 50us/div in single, you get only data that you see on the screen, plus minus 150us before and after so 650us altogether, at 2.5GS/s, which gives 1,625 MPoints.  In SINGLE mode all the same, except 5GS/s which gives 3,25 MPoints.
But this isn't due to speed but due to double buffering and memory sharing. In normal mode the memory is divided between an acquisition and display buffer so you effectively get half the memory depth. There are other factors at play as well like reference traces and digital input memory which also eat away from the available memory. In short: on a Keysight Megazoom scope it is tricky to get use of the full memory depth. It is not a feature but a limitation.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: David Hess on June 17, 2019, 12:35:25 am
Dave, the tests I would like to see include:

1. RMS noise measurement of a calibrated source - many DSOs do not do this correctly.  This should be done at different sample rates and with and without aliasing.  The result should be invariant.

2. Transient response - this could require verification of your signal source on a trusted oscilloscope.

3. Trigger after delay - to see if it even exists.  Many DSOs do not support this and in some cases the documentation is deceptive.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: EEVblog on June 17, 2019, 12:54:46 am
I never ever ever want to use an oscilloscope which doesn't have a user selectable/fixed memory setting.

The Keysight X series doesn't let you select memory depth and I've never found it a problem in practice.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: EEVblog on June 17, 2019, 01:08:15 am
Dave, thanks for the review  :-+

But I've got to place some small criticism here -- your input noise comparison is somewhat dodgy (34:00 into the video): Since the R&S had some visible DC offset of the input signal (round about -300µV), this will clearly contribute to the RMS measurement. Try checking noise with the inputs in AC coupled mode. Depending on the internal processing, the average offset will get subtraced in this mode (not sure if it works this way on the R&S, at least the "mature" Rigol products do it like this).
Then I'm sure you'll find that the R&S is at least on par with the new Siglent scope.

AC coupling makes no difference.
But you are right, the DC offset matters.
Just powered it up again and it happened to have almost no DC offset and a I got 107uV RMS, and it's 87uV in standard deviation mode.
After a bit the offset rose and the standard deviation gets rid of it, still around 87uV
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: TheSteve on June 17, 2019, 06:20:06 am
I never ever ever want to use an oscilloscope which doesn't have a user selectable/fixed memory setting.

The Keysight X series doesn't let you select memory depth and I've never found it a problem in practice.

The newest 3000t firmware does now let you select memory depth and as a result also lets you see the current memory it is using. I don't know when you'd want to lower the memory but it is nice seeing how much it is actually using.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: Smokey on June 17, 2019, 06:59:12 am
Say you are a company that has a long reputation for making inexpensive buggy questionably specced stuff, but you want to get into the higher end market with a new expensive product and sell it internationally to compete with major players.  At what point do you just change your name or spin off another company with a new name under which to sell the higher end stuff and drop the baggage of all the previous toy products? 
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: nctnico on June 17, 2019, 08:39:56 am
I never ever ever want to use an oscilloscope which doesn't have a user selectable/fixed memory setting.

The Keysight X series doesn't let you select memory depth and I've never found it a problem in practice.
That is because you always get the maximum depth (which isn't much to begin with) on a Keysight and Keysight uses some trickery to make the update rate independent of the memory depth. But the way Siglent does it (only sample enough to fill the screen) is really annoying; you have to change the time/div setting all the time.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: EEVblog on June 17, 2019, 10:17:47 am
The newest 3000t firmware does now let you select memory depth and as a result also lets you see the current memory it is using. I don't know when you'd want to lower the memory but it is nice seeing how much it is actually using.

Ah, didn't know that, will have to update. Yes, it's always handy to know.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: EEVblog on June 17, 2019, 10:19:26 am
Say you are a company that has a long reputation for making inexpensive buggy questionably specced stuff, but you want to get into the higher end market with a new expensive product and sell it internationally to compete with major players.  At what point do you just change your name or spin off another company with a new name under which to sell the higher end stuff and drop the baggage of all the previous toy products?

Isn't that when you sell it with a Lecroy badge?  ;D
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: thm_w on June 17, 2019, 08:04:45 pm
Intensity grading, i don't give a shit. I prefer "temperature" color grading a million times over DPO style intensity grading

Incidentally, none of the scope i have and use at work (picoscope, tek TPS, SDS-5035X, lecroy 7200A -the one from the 80s-) have intensity grading, at most they have color grading and in the rare times i need such a thing i prefer it over starndard intensity grading, but that's me

Sure,  but something is odd with how they are calculating/displaying it. Almost as if the number of gradients is too low or something.
But this could have been due to another setting Dave had on at the time (mem depth, etc.).
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: Performa01 on June 17, 2019, 08:38:33 pm
Sure,  but something is odd with how they are calculating/displaying it. Almost as if the number of gradients is too low or something.
But this could have been due to another setting Dave had on at the time (mem depth, etc.).
No, it wasn't Dave's fault. I tried to reproduce it and was quite baffled to find the SPO engine broken (didn't notice it before, as I've mostly tested other features like new measurements, FFT and Bode Plot lately).

So the SPO issue has been confirmed and Siglent R&D is working on a fix.

I for one do value an intensity grading that is actually working all the time, independent of memory and other settings, because it provides additional information about the signal, just like analog scopes did. It makes the difference between a true color display and a pen plotter ;)

Even though I use (and like) Picoscopes a lot, I don't see any value in special modes that provide intensity and color grading exclusively together with high waveform update rates, but a lot of limitations otherwise. It's quite obviously the USB bottleneck that forced Picotech to copycat Tek in this regard.

Siglent also has a special mode, called Sequence Recording, but only for waveform cature rates up to 500kWfm/s and no  limitations other than screen update rate, whereas intensitiy grading has to work all the time without the need for a special mode.


On this occasion I'd like to clarify another misconception in the video: the [Roll] button is there to enable or disable Auto-Roll mode. I for one don't like auto-roll at all, but for those who want it, it is still available, no problem.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: rf-loop on June 18, 2019, 10:21:16 am
Since the interpolation is just a post processing, we can switch it on anytime after the acquisition, e.g. in the history.

 :-+

This is one of very good thing in all Siglent X series oscilloscopes - even when it slows wfm/s. (wfm/s is many times bit overvalued salesmen advertising value). In all cases there is true sample points available in runtime and afterwards and it draw Sinc perfectly via true sample points (No violation of rule.)
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: Smokey on June 18, 2019, 11:55:02 am
Say you are a company that has a long reputation for making inexpensive buggy questionably specced stuff, but you want to get into the higher end market with a new expensive product and sell it internationally to compete with major players.  At what point do you just change your name or spin off another company with a new name under which to sell the higher end stuff and drop the baggage of all the previous toy products?

Isn't that when you sell it with a Lecroy badge?  ;D

Ya, but if you think you are ready to go at it alone on your own name it might help to have a name that isn't immediately (and not unfairly) associated with software bugs and questionable quality. 
Also it's not like when people find out their Lecroy Wave-whatever was made by Siglent that they feel better about it.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: JPortici on June 18, 2019, 12:33:08 pm
And yet, to be fair, hardware quality has always been increasing in scopes, SA, power supply, signal generator, ..
Software quality is also constantly increasing. The 5000X is a very good example. While there are still bugs and more advanced features are not yet implemented the user interface is already beyond anything they had done before and if we put aside what i think are quirks (encoder acceleration, traces don't move as smoothly as i would like, some menus are missing in the firmware release he used, some touch actions that i would take from granted are missing in the firmware release he used) it is actually very good and what i would expect from any mid range product. Lecroy style. The effort in making a good quality product there.
Then i don't know if you have used the newer spectrum analyzer series but the user interface is very good there as well and i would consider the firmware to be in a mature state.

but i don't expect everyone to see it, we all have different expectations in how an instrument should operate, and whenever it doesn't it's easy to blame it on the manufacturer

if i "found out" that my lecroy is actually a siglent i wouldn't feel good because i would wonder WHY i spent double the money, and that's it. Altough i don't know yet if the rebadge of the 5000x will be actually done and if it will use lecroy's os (like the WS3K) or the siglent firmware, but with lecroy's logo
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: 0xdeadbeef on June 18, 2019, 04:51:50 pm
This is one of very good thing in all Siglent X series oscilloscopes - even when it slows wfm/s. (wfm/s is many times bit overvalued salesmen advertising value). In all cases there is true sample points available in runtime and afterwards and it draw Sinc perfectly via true sample points (No violation of rule.)
Maybe I didn't get the point but I can't imagine that any scope on the market isn't interpolating the displayed waveform from "true" sample points. At least in single shot mode there simply isn't any choice, or is it? And in the "digital phospor" / intensity grading modes. I would assume the samples of previous acquisition are not really existing anymore, just the previous waveform(s) must be stored somewhere to process the grading.
Anyway, I still find it puzzling that any kind of interpolation divides the acquisition rate by a factor of four (or more).

if i "found out" that my lecroy is actually a siglent i wouldn't feel good because i would wonder WHY i spent double the money, and that's it. Altough i don't know yet if the rebadge of the 5000x will be actually done and if it will use lecroy's os (like the WS3K) or the siglent firmware, but with lecroy's logo
At least currently, rebranded entry level scopes are white, while "real" LeCroys with ProBus are black (wasn't always like this though). The WS3000(Z) is obviously considered a "real" LeCroy even though it's the result of a cooperation with Siglent. Since the WS3000(Z) doen't have the bandwidth limitation for the lower ranges, I would think that things like the frontend are (at least partly) designed by LeCroy. Anyway, as long as the WS3000Z (aka SDS3000X) marks the entry point for black LeCroy scopes, it doesn't make much sense to rebrand the SDS5000X which is superior to the WS3000Z at least in some aspects (e.g. memory depth).
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: JPortici on June 18, 2019, 07:33:47 pm
AFAIK the WS3000 is all siglent built on specifications given by lecroy, the only lecroy IP is the software. The reason why the new frontend is limited for the 1GHz model (is not in my scope, which is the 350MHz model) was explained somewhere by Performa01 (i don't remember which thread exactly)

the 5000X is superior in many aspects: more memory, more grunt, better screen.
Lacks the integrated AWG, which in the lecroy is stupidly limited for which i prefer
- No generator
- Control of external generator from the scope
- External brick (forget the SAG1021.. there's going to be the SAG1021I where "I" stands for isolated, +/-42V of isolation according to http://www.saelig.com/supplier/siglent/sds5000x-datasheet-0519-saelig.pdf (http://www.saelig.com/supplier/siglent/sds5000x-datasheet-0519-saelig.pdf))

The firmware from lecroy is of course more flexible as in multiple math channels, more advanced math on math, more advanced math.

But I have used both and there is no comparison. It would make way more sense to drop the WS3000 and replace it with the 5000X
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: nctnico on June 18, 2019, 07:36:40 pm
This is one of very good thing in all Siglent X series oscilloscopes - even when it slows wfm/s. (wfm/s is many times bit overvalued salesmen advertising value). In all cases there is true sample points available in runtime and afterwards and it draw Sinc perfectly via true sample points (No violation of rule.)
Maybe I didn't get the point but I can't imagine that any scope on the market isn't interpolating the displayed waveform from "true" sample points.
The Rigol DS1054Z seems to be the only exception. But otherwise the sample points are including in sin x/x reconstruction by definition. All in all rf-loops statements makes it look like Siglent is more special then what it is in reality.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: tautech on June 18, 2019, 08:53:23 pm
This is one of very good thing in all Siglent X series oscilloscopes - even when it slows wfm/s. (wfm/s is many times bit overvalued salesmen advertising value). In all cases there is true sample points available in runtime and afterwards and it draw Sinc perfectly via true sample points (No violation of rule.)
Maybe I didn't get the point but I can't imagine that any scope on the market isn't interpolating the displayed waveform from "true" sample points.
The Rigol DS1054Z seems to be the only exception. But otherwise the sample points are including in sin x/x reconstruction by definition. All in all rf-loops statements makes it look like Siglent is more special then what it is in reality.
I wouldn't be so sure..........
.............
I have both and there is something I don't really like in the DS1000Z series: when you select "dots" mode it doesn't display actual samples, but interpolated data which, in my opinion, is a big mistake. Rigol developers seem to favor some cosmetic criteria when deciding how to display data (non transparent handling of sin(x)/x interpolation, no real dots mode, etc).
..................
...............
6. In Dots mode you don’t see dots; even at small time base (2 ns) dots are connected with lines.
[FW v00.01.01.04.04] / [FW v00.01.01.04.04]
..................
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: nctnico on June 18, 2019, 09:03:39 pm
@tautech: As I wrote in my previous post: so far the Rigol DS1054Z seems to be the only exception. Pehaps you should include the oscilloscope model  WinnieThePooh is testing (the Rigol MSO5000 series) and the problem he describes in you short (likely out of context quote) has nothing to do with sin x/x reconstruction. Don't make the same mistake rf-loop made in his eagerness to make things prettier than they are or make standard features look special. It sounds like a clueless salesperson; 'Look, this Siglent calculator is showing 2 when I punch in 1+1'. Real engineers will be put off by those kind of tactics.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: rf-loop on June 18, 2019, 09:13:18 pm
And in the "digital phospor" / intensity grading modes. I would assume the samples of previous acquisition are not really existing anymore, just the previous waveform(s) must be stored somewhere to process the grading.

I do not fully understand what you mean here.

Do you perhaps mean that after acquisition data is handled  for add to display memory (to digital phosphor) for produce gradation but after then it - older than last one - do not really exist except in display map.
This is not how Siglent works.
"I would assume the samples of previous acquisition are not really existing anymore" No, in Siglent, they still really exist.

Example, if think one display frame. It do acquisition to memory (and interpolate (this  can see when look trigger out signal with other scope, depending interpolation also every single acq. time change, not only time gap when it update new display frame, if 5000X works like previous models) and map it without decimation also to display memory map and then next and next and so on until is time to show display, all accumulated acquisitions overlaid,  but still every acquisitions also separately in wfm  fifo, not only mapped to display memory, even if there is 100 or thousands of individual acquisitions in one display frame producing also one part of intensity gradation.
Also when it produce display frame it do not decimate, it maps every sample. Siglent keep still also all these separate acquisitions in data memory (wfm fifo), not only in display map. Also these every individual acquisitions what one display frame include (or more) are available for user. User can look these separate acquisitions (user can example break last screen back into individual acquisitions and afterward change interpolation or turn interpolation off). There is always background working waveform history buffer (fifo) where are least last frame individual acquisitions every original sample.

How much it do work for produce one screen. It can somehow see when use sequence mode (what is nearly 5 times more fast than normal mode) In this mode it do not produce display screen (and do not interpolate) at all until whole sequence is captured. If capture example 50000 waveforms sequence. After these 50000 are all captured it stops and start produce display frame. If there is example sinc interpolation instead of dots alone, it  takes more time before all these are interpolated and mapped to display memory and displayed with intensity gradation (all 50000 overlaid at once, perhaps over 100M sample points where every single point to point need interpolate and draw )

----
About Dave's video. There can see SDS5000X intensity gradation is somehow broken and need urgent repair. It looks terrible. Also it looks other way terrible because very unstable trig to  AM modulating freq (but this is imho user intentional error)
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: tautech on June 18, 2019, 09:18:06 pm
@tautech: As I wrote in my previous post: so far the Rigol DS1054Z seems to be the only exception. Pehaps you should include the oscilloscope model  WinnieThePooh is testing (the Rigol MSO5000 series) and the problem he describes in you short (likely out of context quote) has nothing to do with sin x/x reconstruction. Don't make the same mistake rf-loop made in his eagerness to make things prettier than they are or make standard features look special. It sounds like a clueless salesperson; 'Look, this Siglent calculator is showing 2 when I punch in 1+1'. Real engineers will be put off by those kind of tactics.
Which is why I included a link to the post, so you can check the context and model.
Yes it seems the 5k series is afflicted by incorrect Dot mode implementation too and this info is from other sources other than rf-loop.  :P
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: David Hess on June 19, 2019, 07:03:49 am
But I've got to place some small criticism here -- your input noise comparison is somewhat dodgy (34:00 into the video): Since the R&S had some visible DC offset of the input signal (round about -300µV), this will clearly contribute to the RMS measurement. Try checking noise with the inputs in AC coupled mode. Depending on the internal processing, the average offset will get subtraced in this mode (not sure if it works this way on the R&S, at least the "mature" Rigol products do it like this).
Then I'm sure you'll find that the R&S is at least on par with the new Siglent scope.

AC coupling makes no difference.
But you are right, the DC offset matters.
Just powered it up again and it happened to have almost no DC offset and a I got 107uV RMS, and it's 87uV in standard deviation mode.
After a bit the offset rose and the standard deviation gets rid of it, still around 87uV

Looking at their incomplete manual, at least Siglent included Stdev to compute AC RMS and RMS to compute AC + DC RMS.  But the multimeter has separate AC RMS and DC RMS selections.  Is Siglent always so consistent?

Calculating AC + DC RMS when AC coupling is selected must be a dumb oversight.

87 microvolts RMS over 1 GHz is respectable; many DSOs are much worse.  The lowest noise oscilloscopes I have tested have a slightly lower broadband spot noise than that, about 25% lower.  But with a lower bandwidth, that is expected because higher spot noise comes with higher bandwidth devices.

Maybe I didn't get the point but I can't imagine that any scope on the market isn't interpolating the displayed waveform from "true" sample points. At least in single shot mode there simply isn't any choice, or is it? And in the "digital phospor" / intensity grading modes. I would assume the samples of previous acquisition are not really existing anymore, just the previous waveform(s) must be stored somewhere to process the grading.
Anyway, I still find it puzzling that any kind of interpolation divides the acquisition rate by a factor of four (or more).

Interpolation might be used for the display but not to fill in the acquisition record.

The original DPO mode of operation generated a 3D histogram of the data in hardware at the maximum sample rate with no interpolation.  Modern DSOs tend to generate the histogram (for display or measurement) from the acquisition record with the processor instead of in hardware and the record length then limits the sample rate.  This makes sense when less than the absolute maximum performance is required because processor performance is so much better now than 20 years ago and it makes for less expensive high performance DSO.

But this creates a conundrum.  If interpolation is used, then it corrupts the histogram and any measurements which rely on it like RMS, peak, or whatever if aliasing is present.  I suspect Rigol does something like this explaining various odd measurement behaviors.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: Performa01 on June 19, 2019, 09:25:23 am
Maybe I didn't get the point but I can't imagine that any scope on the market isn't interpolating the displayed waveform from "true" sample points. At least in single shot mode there simply isn't any choice, or is it?
Yes, it's hard to believe, yet rumours have it that such scopes do exist. You can always calculate something completely new from a number of original samples, which then just get replaced by the result of the computation (like most modern digital cameras do).

And in the "digital phospor" / intensity grading modes. I would assume the samples of previous acquisition are not really existing anymore, just the previous waveform(s) must be stored somewhere to process the grading.
Yes, there are some scopes that use only the screen (or some small secondary) buffer for intensity grading.

For Siglent X-series scopes there is one irrevocable standard: In normal mode, it will always show all original sample data from within the last 40ms (if available) on the screen at once. In Sequence recording mode it will even show the complete history buffer, i.e. up to 100000 records  and/or a total of 440 Megasamples at once. This way you can detect any anomaly at a glance.

This is true for normal acquisition mode; Peak Detect might, Average and Eres will replace the original sample data by the corresponding processed data, i.e. min/max data pairs in case of Peak Detect, the sliding average of corresponding samples over a number of subsequent records in case of Average and the result of a FIR lowpass filter operation within one record for Eres. Nevertheless, the number of samples doesn't change though and we still get all the data displayed.

This is by the way the major difference to LeCroy scopes, which never ever manipulate the original sample data, thus cannot have peak detect and implement Average as well as Eres as Math functions.

Now for the mystery of intensity grading, which some confuse with persistence (of course we can have persistence as well, but that has absolutely nothing to do with intensity grading):

It is simply a matter of the number of samples falling into the exact same position on the screen – similar to an analog scope, where intensity is determined by the speed of the electron beam moving over the screen. Since each sample represents a certain time step (1/samplerate) the accumulation of these results in a total time which in turn determines the trace intensity.

For this process, a lot of data is involved in the display mapping. It is the record length multiplied by the number of acquisitions within a span of 40ms (which is the display refresh period).

Anyway, I still find it puzzling that any kind of interpolation divides the acquisition rate by a factor of four (or more).
With the explanation given above, we could measure/calculate the data rate for different timebase settings:

200ps/div => 120kpts/s => 4.8kpts/frame;
20ns/div => 110Mpts/s => 4.4Mpts/frame;
1ms/div => 950Mpts/s => 38Mpts/frame;

So while at even slower timebases we can exceed 1Gpts/s, there seems to be no dedicated graphics processor to handle such an amount of graphic data in a fast and efficient way.

The amount of additional dots required for interpolation depends on the signal amplitude, waveform and frequency. This can easily lead to a multiple of the original data to be drawn on the screen. This seems to be the bottleneck and both position mapping and interpolation require additional processing time.

Looking at their incomplete manual, at least Siglent included Stdev to compute AC RMS and RMS to compute AC + DC RMS.  But the multimeter has separate AC RMS and DC RMS selections.  Is Siglent always so consistent?
Well, these are different worlds, I suppose. Experienced DSO users should be familiar with the Stdev measurement (even though I’ve come across “experts” who confuse it with the standard deviation in the measurement statistics), whereas on a DMM the terms AC RMS (often just RMS) and AC+DC RMS are common. But that’s irrelevant, because other than a true scope meter, a pseudo DMM is just a marketing gimmick in my book, that doesn’t belong into a DSO – not in the midrange class anyway. Yet since it was introduced by one of the big boys, every manufacturer feels the need to offer one as well. I think Siglent is the last one to follow that trend.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: nctnico on June 19, 2019, 11:55:33 am
Another option could be that Siglent is making the intensity grading actually useful. There is not much use to hide a small glitch in 255 shades of yellow because you won't see it (just like on an analog scope). 8, maybe 16 shades is more than enough to distinguish between often and more rarely occuring signals.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: rf-loop on June 19, 2019, 12:17:34 pm
Another option could be that Siglent is making the intensity grading actually useful. There is not much use to hide a small glitch in 255 shades of yellow because you won't see it (just like on an analog scope). 8, maybe 16 shades is more than enough to distinguish between often and more rarely occuring signals.

Let's hope master of magicians protect us from this devastation of performance.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: David Hess on June 20, 2019, 05:19:04 am
Looking at their incomplete manual, at least Siglent included Stdev to compute AC RMS and RMS to compute AC + DC RMS.  But the multimeter has separate AC RMS and DC RMS selections.  Is Siglent always so consistent?

Well, these are different worlds, I suppose. Experienced DSO users should be familiar with the Stdev measurement (even though I’ve come across “experts” who confuse it with the standard deviation in the measurement statistics), whereas on a DMM the terms AC RMS (often just RMS) and AC+DC RMS are common. But that’s irrelevant, because other than a true scope meter, a pseudo DMM is just a marketing gimmick in my book, that doesn’t belong into a DSO – not in the midrange class anyway. Yet since it was introduced by one of the big boys, every manufacturer feels the need to offer one as well. I think Siglent is the last one to follow that trend.

The documentation does not even discuss the difference and then of course there is the standard deviation calculation of the measurements so that is three different names for the same calculation on different data.  I think standard deviation for automatic measurements and AC RMS and DC RMS for acquisition record measurements by both the DSO and digital multimeter would be less confusing.  As evidence I present Dave having to go back and make the noise measurement a second time.

Some old oscilloscopes had a real digital voltmeter coupled to the vertical inputs with real digital voltmeter performance.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: Performa01 on June 20, 2019, 07:03:12 am
The documentation does not even discuss the difference and then of course there is the standard deviation calculation of the measurements so that is three different names for the same calculation on different data.  I think standard deviation for automatic measurements and AC RMS and DC RMS for acquisition record measurements by both the DSO and digital multimeter would be less confusing.  As evidence I present Dave having to go back and make the noise measurement a second time.
You're right, the documentation could certainly be improved.

Apart from that, it should be obvious that Siglent is heading more in the direction of LeCroy (and R&S), so we certainly shouldn't confuse professionals by arbitrarily changing names of measurements they have long been familiar with. Not after all that time anyway.

I take it that professionals would know that standard deviation is the same as RMS without the DC component and that RMS includes DC by definition.

The misleading terms have been widespread for DMMs as well, with names like "True RMS". What's a "true" RMS (as opposed to just RMS)? Well, I remember at least one company that used RMS for Standard Deviation and "True RMS" for RMS.

Some old oscilloscopes had a real digital voltmeter coupled to the vertical inputs with real digital voltmeter performance.
Yes, we know that.

But these options used to be separate devices in a special housing, bolted on top of scopes that were prepared to display the DMM measurements. I think I've even seen some with their own display, back in the days when scopes didn't support alphanumeric readout on the CRT. In any case they had individual 4mm sockets. So pretty much the same as a scope meter, the latter with good portability for service technicians - and that certainly makes sense.

Apart from students on a tight budget, who would like to have as many features for as little money as possible in a single device, I cannot imagine anyone wanting a bolted-on or even integrated solution in a scope over a proper separate and independent device in a lab.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: tinhead on June 20, 2019, 09:23:13 am
- External brick (forget the SAG1021.. there's going to be the SAG1021I where "I" stands for isolated, +/-42V of isolation

giving the problematic offset with SAG1021, Siglent should replace all already sold devices by SAG1021I.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: EEVblog on June 20, 2019, 09:45:47 am
The misleading terms have been widespread for DMMs as well, with names like "True RMS". What's a "true" RMS (as opposed to just RMS)? Well, I remember at least one company that used RMS for Standard Deviation and "True RMS" for RMS.

"True RMS" came about because all meters on AC are calibrated to display an RMS value, but one without "True RMS" are only valid for pure sine waves.
Title: Re: EEVblog #1220 - Siglent SDS5000X 1GHz Oscilloscope Review
Post by: David Hess on June 20, 2019, 04:57:16 pm
Some old oscilloscopes had a real digital voltmeter coupled to the vertical inputs with real digital voltmeter performance.

Yes, we know that.

But these options used to be separate devices in a special housing, bolted on top of scopes that were prepared to display the DMM measurements. I think I've even seen some with their own display, back in the days when scopes didn't support alphanumeric readout on the CRT. In any case they had individual 4mm sockets. So pretty much the same as a scope meter, the latter with good portability for service technicians - and that certainly makes sense.

No No No!  I am referring to oscilloscopes where the DVM was coupled directly into the vertical input and measurements are made through the oscilloscope probe!

The example below is from the Tektronix 2236.  Coupling to the DVM occurs immediately after the high impedance buffer through R20 as marked.  Further, the state of the input attenuators, probe coding (x1 or x10), and input coupling (AC or DC), are also forwarded to the DVM as marked.  (1)

Tektronix produced a special x10 probe for this model to preserve the accuracy of the DVM since standard oscilloscope probes are typically no better than 1% and are often worse.  Tektronix also made probes which could be trimmed for DC accuracy but except for the ones LeCroy inherited from Preamble and is discontinuing, I know of no such thing being made now.

(1) The vertical input coupling selection literally determines whether the DVM makes an AC RMS or average DC measurement and the schematic is even marked to indicate this.  Ambiguity was not a virtue back then.  The RMS converter is AC coupled to remove any DC offset from the internal circuits.

"True RMS" came about because all meters on AC are calibrated to display an RMS value, but one without "True RMS" are only valid for pure sine waves.

I would have said this if you had not.

"AC" makes sense, "RMS calibrated" makes sense, and "True RMS" makes sense.  But "RMS" alone sometimes confusingly could mean either or even AC + DC RMS as we have discovered.