Author Topic: Siglent SDS1104X-E In-Depth Review  (Read 14363 times)

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Offline Performa01

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #50 on: February 22, 2018, 03:43:22 am »
I have updated my review documents  that can be found in the initial posts in this thread.

This includes additional/corrected information on noise, XY mode, differentiate math, various typos and mistakes in the FFT review corrected.

An additional part of the review about segmented memory (history and sequence mode) has been posted there as well.
 
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Offline rigol52

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #51 on: February 22, 2018, 04:41:19 am »
Great review again, Performa01.

Sine max limit is 25MHz. But this is standardized limit and generation probably don't stop at exactly 25MHz.

Curious what would be practical sine limit regarding sine shape (no matter of possible damped amplitude)?

Could it reach 40 or 50MHz and retain sine shape?
« Last Edit: February 22, 2018, 07:12:28 am by rigol52 »
 

Offline Performa01

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #52 on: February 22, 2018, 05:47:39 am »
Sine max limit is 25MHz. But this is standardized limit and generation probably don't stop at exactly 25MHz.

Curious what would be practical sine limit regarding sine shape (no matter of possible damped amplitude)?

Could it reach 40 or 50MHz and retain sine shape?

Well, you were asking for it … now fasten your seat belts.

Of course the SAG1021 can output much higher frequencies at slightly reduced amplitude as has already been demonstrated for the noise “waveform”.

But as I have stated in the review, we don’t get a clean signal anymore above 25MHz.

Here is an example for just 30MHz:


SDS1104X-E_Sine_P10_Play_3MHz_FFT

Yes, the harmonics are even lower at -40dBc, but you should also be able to see the upcoming jitter even in the screenshot. Then there is also that nasty spur emerging at 95MHz with an approx. level of just -25dBc…

You will not be surprised to see how matters get worse if we go even higher in frequency. At 40MHz it looks really bad already:


SDS1104X-E_Sine_P10_Play_4MHz_FFT

This time I did not even try to measure the harmonics, but used the strongest spur at 85MHz instead. It is only 18dB below the carrier and also in the time domain we can see really awful things going on.

You don’t want to know what it looks like at 50MHz output frequency, sure you don’t! ;)

It is only natural, as it is basically the same reconstruction problem as in the scope. But there we have some digital signal processing that can calculate the best possible filter for the data available. For a signal generator on the other hand, we need a real filter, i.e. an analog one. You bet your bottom dollar there is none, otherwise we would not be able to see so little amplitude drop at 1.6 times the maximum sine output frequency. Also look at the noise plot up to 200MHz – barely 6dB amplitude drop at the nyquist frequency of 62.5MHz. Nothing even close to the required brick-wall filter. Consequently, with a 2.5-times oversampling (125MHz to 25MHz) the output looks still reasonable (but not stellar, as the sine distortion tests have shown), but any higher, the lack of a proper reconstruction filter becomes just too obvious.
« Last Edit: April 25, 2018, 12:15:16 am by Performa01 »
 

Offline rigol52

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #53 on: February 22, 2018, 07:07:51 am »
Informative and helpful.
Thanks for all your efforts with subject.

My need with possible new equipment is at least AWG with 40MHz sine.
So it is better to rethink about Siglent SDG1062X in line with SDS1104X-E.


PS: Sorry for typo with your nickname, Performa01, in my previous post.



« Last Edit: February 22, 2018, 07:14:08 am by rigol52 »
 

Offline rf-loop

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #54 on: February 22, 2018, 07:43:33 am »
@Performa01

In sequence mode if I understand right you show average max sapeed. (how much time some amount of segments aka "frames".  But this is not whole truth about speed.  One thing is speed what it can use without missing any trigger.

How to test it. (guaranteed max speed)

It can do using pulse generato and burst.

If scope have max amount of frames example 80000 with some t/div.
Set burst n=80000
Set segments n=80000
Set generator example for 400kHz (0r period 2.5µs)
Set scope for normal trig and sequence mode on.
Start burst.
If scope can capture every pulse it can this speed.
Go to higher speed. And repeat until it can not anymore capture every 80000 segment from one burst.
Go slowly back to slower speed until it start capture full burst. Repeat this enough times, example 10...20... or more. (All t/divs with max segment amount.) If it pass every time without any sigle fail, this is guaranteed maximum speed - minimum trusted trigger period time.

Yes this test take lot of time. I have done it for some previous models including SDS1002X-E. Not for SDS10004X-E
For 2 channel model (note FW) it can find here.
Side text is finnish but  in table there is finchinglish.

But also, this guaranteed speed what do not miss any single trig is not far away from max average speed today with these bit more mature FW's. (some early time there was more differences if I remember right in SDS2k (notX)).

If practice and theory is not equal it tells that used application of theory  is wrong or the theory itself is wrong.
It is much easier to think an apple fall to the ground than to think that the earth and the apple will begin to move toward each other and collide.
 
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Offline Performa01

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #55 on: February 22, 2018, 08:57:02 am »
@Performa01

In sequence mode if I understand right you show average max sapeed. (how much time some amount of segments aka "frames".  But this is not whole truth about speed.  One thing is speed what it can use without missing any trigger.

I see your point - this is certainly a good suggestion for yet another test/measurement. If I got you right, it's pretty much equivalent to a guaranteed max. re-arm time, which in turn determines the guaranteed min. event rate (frequency) that can be captured without losing an event.

Before the latest firmware, we could have measured it just by observing the trig-out signal and looking for the widest gap between two trigger events within a sequence (with a sufficiently high input frequency of course). As it is now, we really need to use your suggested method with the burst generator to measure this. I will try to include such a measurement in a future update of the sequence mode review.

EDIT: When looking at your table, I suspect there will not be much difference, as your guaranteed numbers are even a bit higher than my average ones. Most likely because we have used different input signals - mine was a 20MHz sine...
« Last Edit: February 22, 2018, 09:04:44 am by Performa01 »
 

Offline Performa01

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #56 on: February 24, 2018, 06:49:53 am »
I have noticed some folks might be wondering how good the original Siglent probes are and if some other (maybe also more expensive) probes would provide better results, i.e. more bandwidth, faster rise time etc.

I thought it might be beneficial to compare different probes on the 200MHz SDS1202X-E just to give you an idea what can be expected.

Before I’m going to show the results, I feel inclined to remind you that the LF-adjustment found on every scope probe is not the end of the story. The input impedance of a scope channel is a bit more complex than just 1MOhm in parallel with the input capacitance, and the probe cable has some characteristic impedance that is severely mismatched on both ends and the frequency response would be awful if no counter measures were taken – but these depend on the individual scope input channel and its impedance over frequency. This is why the performance of the probes that ship with a decent scope are usually hard to beat, because they are matched with that particular scope input.

More expensive probes provide a separate HF-adjustment and should be more universal because of this. Certain probes have even more adjustments than that. One such probe with separate HF-adjustment has been included for this comparison – just to see if it can outperform the humble little PP215 that ships with the 200MHz SDS1000X-E entry level scopes.

The contenders are:

1.   Siglent no name (300MHz) that came with the SDS2304
2.   Siglent SP2030A (300MHz) that comes with the SDS2304X
3.   Siglent PP215 (200MHz) that comes with the SDS1202X-E and SDS1204X-E
4.   Siglent PP510 (100MHz) that comes with the SDS1104X-E
5.   Pico Technology TA131 (250MHz) that comes with their 200MHz scopes
6.   TesTec TT-MF312 (250MHz) that has a separate HF-adjustment, so should be pretty universal

First comes the probe adjustment, which is straight forward for all candidates except the TesTec TT-MF312, which has the additional HF-adjustment. The instructions tell us to use a 1MHz square wave and adust the edges for virtually no overshoot (just as usual for this kind of probes). But I suspected that my square wave might have a little overshoot (some 5%), so I’ve adjusted the probe accordingly.

The following table shows the frequency response of the Siglent SDS1202X-E with the various probes:


SDS1202X-E_Probe_Comparison 1

The 2nd graph shows the frequency response of the probe alone, i.e. the frequency response of the scope has been subtracted:


SDS1202X-E_Probe_Comparison 2

As can be seen, the differences are not huge, up to 260MHz the probe-only frequency responses match within 2dB. Yet when we look at the first graph, we can see the best probe would be the Pico Tech. TA131, closely followed by Siglent PP215 and PP510.
The Siglent SP2030A has the worst high frequency response above 210MHz.

Now let’s have a look at the pulse test results:


SDS1202X-E_Probe  Siglent NN


SDS1202X-E_Probe  Siglent SP2030A


SDS1202X-E_Probe  Siglent PP215


SDS1202X-E_Probe  Siglent PP510


SDS1202X-E_Probe  Pico Tech TA131


SDS1202X-E_Probe TesTec TT-MF312


Now that’s quite revealing!

The Siglent NN 300MHz probe is a representative of the bulky type and it’s HF-compensation clearly doesn’t match the SDS1202X-E input channel; the transition times are very slow: 2.72ns rise and 3.39ns fall time. We can also see this by the softly rounded pulse corners. Even though the frequency response didn’t look quite as bad, this probe is clearly not suitable for the 200MHz SDS1000X-E series scopes.

The Siglent SP2030A 300MHz probe is a better match, but now we get soft corners and overshoot at the same time, which comes from the +1.5dB peak in the frequency response at around 40MHz. Transition times are still not fast: 2.50ns rise and 2.57ns fall time. This probe is not for the 200MHz SDS1000X-E series scopes either.

The Siglent PP215 200MHz probe is a near perfect match. The top of the pulse is almost flat without overshoot and the corners are reasonably sharp – after all, we’re not talking about a superfast scope here. Transition times are as good as it gets on a 200MHz scope: 2ns rise and fall. There is a reason why this probe is shipping with the 200MHz SDS1000X-E series scopes!

The Siglent PP510 has been a big surprise when we were looking at the frequency response graph; despite being only rated for 100MHz, it performed very close to the PP215 in this regard. But the pulse test reveals the difference as the pulse top and bottom are no longer flat but slanted. Other than that, we still get nice sharply defined corners and the rise and fall times are only 2ns, just like with the PP215.

The Pico Technology TA131 250MHz probe pulse test result looks similar to the Siglent PP215, but corners are even sharper and we see very slight traces of ringing. Top and bottom of the pulse are almost flat and the transition times are the best by far in this comparison: 1.9ns rise and fall times. This probe would be worth a 2nd thought if someone plans to replace the PP215, but I still wouldn’t do that. The TA131 probe is an old-style bulky one with a wire type hook instead of a blade type. The cable is thicker and less flexible. But performance wise it is clearly a winner.

The TesTec TT-MF312 250MHz probe is mixed bag and rather disappointing overall. The Pulse top is not slanted and the transition times of 1.92ns for rising and 2.0ns for falling edges are even a tad better than the original PP215 (this might be due to the intentional HF-misalignment for 5% overshoot, which has most likely been unjustified after all), but we have to pay a high price for that in shape (literally!) of ugly overshooting, once again due to the +1.5dB peak in the frequency response at 50MHz. At the same time we have a pronounced -1.5dB dip around 175MHz, which makes this probe the worst in the whole contest. There is certainly no reason to use this probe instead of the original one and it’s another “bulky type” on top of that.
« Last Edit: April 24, 2018, 11:59:26 pm by Performa01 »
 
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Offline rigol52

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #57 on: February 24, 2018, 08:51:07 am »
Good work Performa01, thanks.

Very informative. Till yet I was aware a little different, namely:

"Buy your scope-probe, at  least 3x bandpass of your scope."
 

Online nctnico

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #58 on: February 24, 2018, 09:27:46 am »
Several remarks:
- Don't try to measure anything over 100MHz with a high-Z probe. You don't know what you are looking at on the screen because the impedances are all screwed up.
- Probe bandwidths are defined using a source with a 25 Ohm output impedance so you should at least use that doing these kind of tests.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Performa01

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #59 on: February 24, 2018, 10:34:14 am »
Just to make sure no one gets alienated or confused by a couple misleading statements I’d like to assure you that probe manufacturers are no cheats. They don’t sell passive high-Z probes rated up to 500MHz just for fun.

The original PP215 probe deviates by no more than +/- 0.5dB from the direct measurement up to some 260MHz, as can be seen in the 2nd graph (SDS1202X-E_Probe_Comparison 2). That speaks for itself.

I recognize that some context and the reason for this probe test are missing, so here’s the reference:

http://www.eevblog.com/forum/testgear/siglent-sds1204x-e-released-for-domestic-markets-in-china/msg1434294/#msg1434294

The relevant parts:

Quote
The most important (and expensive) part of any scope probe is the cable, that should be low capacitance and needs to have some well defined resistance for the inner conductor (around 200 ohms) in order to damp the resonance effects from the ill-terminated characteristic cable impedance. The optimum cable resistance depends on the circuit details of the scope input and on the SP2030A it quite obviously is just right for the SDS2304X, but a tad too high for the SDS1202X-E.

Some people like to replace their multimeter probes immediately after purchase with “sexier” ones and that is perfectly fine (except that I never did it because I have no use for these impractical probes at all in a lab, be they sexy or not). But for a scope, you should not replace the original probes with random ones without a second thought, just because they look sexier or have a higher bandwidth rating – only inexperienced folks do that. You might end up with an unpleasant surprise if you take the time to actually measure the performance of the probe/scope combination. Of course there’s always a chance that it actually fits well, but you should be able to verify that beforehand.

Quote
As can be seen, the circuit already contains the standard test setup: Signal generator with 50 ohms source impedance and 50 ohms through termination directly on its output, resulting in a total source impedance of 25 ohms, as seen by the probe.
 

Online nctnico

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #60 on: February 24, 2018, 10:41:37 am »
Just to make sure no one gets alienated or confused by a couple misleading statements I’d like to assure you that probe manufacturers are no cheats. They don’t sell passive high-Z probes rated up to 500MHz just for fun.
IMHO they do. Just do the math when taking the probe capacitance at the tip into account. Usually that capacitance is in the 10pf ball park. At 500MHz the circuit is loaded with a 31 Ohm impedance. With an active FET probe or low-Z probe you'll get a way more true representation of the signals you are measuring. One thing people shouldn't forget is that 'to measure is to interfere'. Less interference means you get more accurate results.
« Last Edit: February 24, 2018, 10:47:53 am by nctnico »
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Offline Performa01

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #61 on: February 24, 2018, 11:17:48 am »
Just to make sure no one gets alienated or confused by a couple misleading statements I’d like to assure you that probe manufacturers are no cheats. They don’t sell passive high-Z probes rated up to 500MHz just for fun.
IMHO they do. Just do the math when taking the probe capacitance at the tip into account. Usually that capacitance is in the 10pf ball park. At 500MHz the circuit is loaded with a 31 Ohm impedance. With an active FET probe or low-Z probe you'll get a way more true representation of the signals you are measuring. One thing people shouldn't forget is that 'to measure is to interfere'. Less interference means you get more accurate results.

Of course you are right – it is not at all straightforward to probe high frequencies and people should always keep that in mind. And yes, I agree that 500MHz takes it to the extreme and the number of possible applications is reciprocally proportional to the frequency.

But confirming probe performance up to 300MHz is perfectly possible with 25 ohms source impedance, even though it might appear pointless, given the (low) number of practical uses.

The initial question was about rise time and I always like to check the frequency response too, as it provides additional information helpful for understanding the odd behavior we might see in the time domain.
 

Offline Performa01

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #62 on: February 24, 2018, 11:09:13 pm »
Some of you (any tube aficionados around?) might be interested in the performance of a HV (high voltage) probe, so I wanted to add the TesTec TT-HV250 (x100) to the comparison. This turned out to be much more difficult than expected and inspired me on touching another topic as well: probe performance with the supplied ground leads.

The TesTec TT-HV250 is a 300MHz rated 2.5kV x100 probe which means that even with a HF signal source capable of delivering rather high levels like 1.5Vrms into 50 ohms, the scope will still only see 15mVrms. In all my previous tests I had used 400mVrms with x10 probes, hence 40mVrms at the scope input. I would have liked to keep all test conditions equal, but that was just not possible for a x100 probe.

This was still the easy part. This probe does not have a metal shell around its neck, hence the BNC adaptor supplied with that probe cannot make ground contact. Do they even think at TesTec?
Even worse, there is absolutely no means for a ground connection at all, other than the slot where the ground lead is to be clipped in. So I had to use that – for a 300MHz rated probe, take notice please!

The results were as expected – or maybe even not quite as bad as that. Of course you get no chance to ever probe a 300MHz signal with a probe that forces the use of the ground lead – and it shows. But then I though it might be beneficial to demonstrate the performance (or lack of) for an ordinary PP215 with ground lead as well, because this is what many of us will be using most of the time.

First comes the frequency response graph. Dark blue for the TesTec TT-HV250 and orange for the Siglent PP215. As a reference I have included the results for Siglent PP510 (green), which performs very similar to the PP215, as well as Pico Tech TA131 from the last test (with BNC adaptor).


SDS1202X-E_Probe_Comparison GL

We can see that the TesTec TT-HV250 performs quite normal up to 70MHz and still reasonable to about 100MHz, but goes increasingly haywire beyond that. It is quite surprising that it still remains within +/-3dB up to 180MHz – I wouldn’t have expected that. Above that frequency, it really gets dramatic and the 300MHz rating for this “groundless” probe can only be a bad joke.

The Siglent PP215 responds even more allergic to the ground lead and can only be used up to 30MHz without major issues. Hopefully this demonstration helps make users aware of the frequency limit for safe use of the ground lead – “safe” in the sense of still getting reasonable measurement results.

Of course my findings can only be some guide to give you an idea what to expect. Shape and area of the loop antenna formed by the ground lead affect the performance and maybe it would have been possible to tweak it for slightly higher frequencies, But then again, we usually move the probe hence also the ground lead while probing, thus any tweaking would be irrelevant for practical work.

Finally let’s have a look at the pulse responses:


SDS1202X-E_Probe TesTec TT-HV250 GL


SDS1202X-E_Probe  Siglent PP215 GL

The screenshots confirm what we could have predicted from the frequency response graph: the PP215 is much more violent when using the ground lead. The rise times are notably worse than with proper ground connection as well. By comparison, the TesTec TT-HV250 pulse response looks surprisingly benign.
« Last Edit: April 24, 2018, 11:58:10 pm by Performa01 »
 

Offline rf-loop

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #63 on: February 25, 2018, 03:06:31 am »
I have been wondering one thing.

In SDS1000X-E Bandwidth.pdf  there is example this image:

Square_50MHz_BW111MHz_500MSa_Dots

(also some other using dot mode)

I have some intuitio that perhaps there need be some re-thinking what it is or what combination about things leads this shape. This same kind of behavior exist also in SDS2000 series. Is it "aliasing" as we normally think what is aliasing. My hypothese is that not, or least some part is not aliasing.

I do not know how this trigger - fine interpolation - fine positioning system works and what kind of interpolation it do between real sample points for fine adjust this interpolated "imagined" point in signal to trigger time position.
Some very sophisticated scopes may do also there Sinc interpolation but with fast look it somehow looks like that there Siglent do linear interpolation (I do not mean this Sinc what we look in display what interpolate through displayed true samples. I think here fine interpolation between true sample points for fast fine adjust every single acquisition signal on display for minimalize time error in positioning. )
Perhaps this thinking is  meaningless but I'm somehow interested still how it produce these "fun" shapes in dots mode when we go to fast changes in signal related to sample rate. 
I have done some tests with SDS1104X-E and SDS1202X-E (Serial "BB" hardware) but they are not exactly comparable due to different input reactances (example 4 channel nominal input is 15pF and 2 channel model nominal is 18pF what leaads to different mismatch using feed thru termination - with fast risetimes this matters) so it need also bit thinking about what is what when look result images but this is now here quite meaningless.


ETA1:I will later, after test data gathering and organizing, add some images to "Siglent SDS1104X-E and SDS1204X-E Mixed Signal Oscilloscopes" for avoid extra hassle or possible highway to huge O.T. debate in this extremely good deep review thread.
They show well how 100MHz model is bit more protected from some aliasing due to different front end bandwidth before ADC.
ETA2: It takes more time. Problem is some tests made using SDS1104X-E FW .20 where is really some things out of order.  (there is perhaps much more wrong than just trace display disappear in some cases).
« Last Edit: February 25, 2018, 11:03:48 pm by rf-loop »
If practice and theory is not equal it tells that used application of theory  is wrong or the theory itself is wrong.
It is much easier to think an apple fall to the ground than to think that the earth and the apple will begin to move toward each other and collide.
 

Offline Performa01

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #64 on: March 11, 2018, 11:59:09 am »
The first implementation of the MSO option has become available with firmware 7.6.1.20 and I’ve received the SLA1016 digital probe about a week ago. Unfortunately the Sbus cable was missing and even though the connectors are identical, an HDMI cable cannot replace it. So I have to wait until I get the original one.

Until then, I’ll show some details of the hardware. First the contents of the box (minus the Sbus cable):


SLA1016_Set 01

Top left is the interface box SLA1016 that connects to the SDS1004X-E through the Sbus cable at one end. The other end has a 2x34 connector for the ~80cm long high density flat ribbon cable, which in turn connects to the SPL1016 probe head. It is connected in the picture above, but can easily be detached.
The opposite side of the probe head has two standard 1/10” 2x8 pin male connectors where the supplied probe leads can be connected as well as user specific probes, e.g. with a 16 wire flat ribbon cable on a standard 1/10” 2x8 female header.

The two supplied probe leads consist of a 1/10” 2x8 female header with eight 140mm long digital input leads and two 100mm long ground wires. At the end of each wire there is a metal sleeve that connects to 0.64mm pins on hooks or any other test points/connectors.

Finally there is a bag with 20 cheap hooks.


The picture below shows the SPL1016 probe head. It has the relevant specifications printed on it as well as the connector layout and the color scheme for the supplied probe leads.


SPL1016_Head 01


The next image shows the probe connector side of the SPL1016 head together with one probe lead assembly and a hook.


SPL1016_Head 02


The tip of one of the hooks supplied with the SPL1016 is shown below. The diameter of the plastic sleeve is 1/10”.


SLA1016_Hook


Compare this with the E-Z hook (made in USA) supplied with the SPL2016 digital probe head that is an option for the SDS2000(X) oscilloscopes. The quality is appreciably better and the plastic sleeve has only 1/20” diameter at the tip.


SPL2016_E-Z-Hook


As a consequence the noname hooks supplied with the SPL1016 can only connect every other pin on a SOIC with 1/20” pin spacing, whereas the SPL2016 hooks can connect eight adjacent SOIC pins in a row if required.


Digital_Hooks_Spacing


Thankfully this is not an ultimate limitation for the SPL1016, because the E-Z Hooks (and probably most others) can be used together with the SPL1016 without any problems as shown below.


Digital_Hooks 01

« Last Edit: April 24, 2018, 11:57:26 pm by Performa01 »
 
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Offline 17_29bis

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #65 on: March 11, 2018, 12:30:34 pm »
Thanks for additional info regarding the LA and included hooks.

I don't know what is the point  in including those really cheap test probes but that's disappointing. The total cost of  SLA1016 + 16 Channels MSO Software License here in Canada is 427+141 = 568 CAD (which btw is just 80$ less than the cost of a brand new SDS1104X-E)  - and now to add insult to injury they managed to save extra 40 bucks (the cost of  20 Tektronix  Mini Grabbers 206-0364-0)  by including those 5$ total cheap hooks  >:(
 

Online nctnico

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #66 on: March 11, 2018, 12:40:49 pm »
 :palm: Flatcable... again... really? Any chance to replace the flatcable with something decent which doesn't get damaged very easely and doesn't clutter your desk?
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Performa01

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #67 on: March 11, 2018, 03:34:53 pm »
Bode Plot comparison
The most intriguing new feature of the Siglent SDS1004X-E series is the Bode plotter – others call it FRA (Frequency Response Analyzer). Checking frequency responses belongs to the daily business of analog circuit designers, as it's used for checking transfer characteristics and port impedances of passive and active components as well as circuits such as amplifiers, attenuators, splitters, filters and any combination of them, e.g. control loops.

I’ve not published a review for the Bode plot feature of the SDS1004X-E so far, simply because it is still work in progress and doesn’t quite meet my expectations yet. There are several optimizations and refinements that I’d like to see and also one major issue that prevents the Bode plotter from passing all my tests. I hope this will change with the next update.

Nevertheless several members here have already shown some experiments with the Bode plot feature, so I guess it’s time for me to make up leeway and publish a little teaser as well. My goal is not just to prove that it does exist, but also what level of performance can be expected (once I declare it mature) – at the very least, since I will not stop pushing Siglent really hard to keep improving it.

For now, I’ll just show a little benchmark test between the following contenders:

  • Signal Hound SA44+TG44 – as a representative for the traditional SNA approach.
  • PicoScope 4262 (16 bit) FFT using peak hold with external sweep generator.
  • PicoScope 3206B (8 bit) and its internal AWG driven by the open source FRA4PicoScope frequency response analyzer software.
  • Siglent SDS1104X-E Bode plotter with 7.6.1.20R1 firmware.
For this shootout I have built a simple 455kHz IF filter, consisting of a Kyocera KBF-455R-20A ceramic 6 element filter with two resonant 2nd order L-matching networks for the 50/1500 ohm impedance transformation at both the input and output. This is a rather complex structure with some unwanted responses typical for the ceramic filter, the analysis of which requires high frequency resolution and a wide dynamic range.

  • 50 ohm through terminators have been used for all DSO inputs.
  • For the FRA applications on the Pico 3206B and Siglent SDS1104X-E, a resistive wideband power splitter has been used to tap off the input signal for the reference channel.
  • Only the FRA applications can provide phase information, so this is ignored for the first step of this comparison.
  • The initial goal was to cover the frequency range from 250kHz to 750kHz, but I had to deviate from that on the Pico Scopes for various reasons.

Let’s start with the Spectrum Analyzer as a reference.


IF_Filter_455kHz_Ref 01a

The markers show the amplitude levels of the three major peaks. The speed of just 1.1s for one sweep is second to none, but it shows as the amplitude accuracy below -50dBc is not that great, particularly obvious at the falling flanks of the filter and its unwanted responses. On the other hand, there is little visible noise and the dynamic range of the measured spectrum is about 75dB, which would have been even better on a wider span.


Now compare this with the excellent 16 bit PicoScope 4262. A signal generator with a sweep time of 120 seconds has been used to cover the frequency range from 100kHz to 1MHz. This span has been chosen because the FFT only offers a limited choice of analysis bandwidths and it makes no difference for this test setup anyway. Either linear or logarithmic frequency axis is supported; for filter analysis we typically choose linear. An FFT with just 8kpts registers the peak amplitudes for the entire frequency span, but at least two generator sweeps are required to get a reasonably nice plot. A total of 10 minutes for 5 sweeps were required to create the plot shown in the screenshot below. More FFT points would have significantly increased the sweep time without any additional benefit. For 8kpts, the frequency step is 244Hz and resolution bandwidth is about 710Hz using the Flat Top window.


IF_Filter_455kHz_Ref 02_FTZ

While this test setup is certainly anything but fast, it has high frequency resolution and >90dB dynamic range which is the best in this comparison by a clear margin. So this measurement can be considered to be the true reference with regard to amplitude levels. On the downside, this solution cannot provide a phase plot and works up to 5MHz only, as this is the bandwidth limit of the 16 bit PicoScope 4262.


Now for the dedicated frequency response analyzer, which I would have loved to try with the 16 bit PicoScope 4262, but unfortunately the FRA4PicoScope does not support external waveform generators and the integrated low distortion AWG of the PicoScope 4264 has an upper frequency limit of only 20kHz. As a consequence, the 8 bit PicoScope 3206B had to be used. The phase plot has been disabled for visual comparability with the previous measurements.


IF_Filter_455kHz_Ref 03

The frequency span had to be 100kHz to 1MHz because otherwise we wouldn’t get any annotation on the frequency axis. The application supports logarithmic frequency axis only, the grid does not look particularly nice and no cursors for precise measurements are available. There’s a lot of visible noise below -68dB and the dynamic range of the displayed spectrum is just about 66dB because of this. This is the worst dynamic in this comparison, particularly obvious at and below 250kHz. This is mainly because of the PicoScope 3206B ‘s mediocre sensitivity of 10mV/div and the rather low output level of its internal AWG of just 2Vpp.

Even more importantly, the AWGs in the PicoScopes have an output impedance of 600 ohms, which makes the level drop by another 22dB. So the dynamic range can be phantastic in high impedance networks, but it is nearly unusable for the widespread 50 ohm standard. Since we are constricted to the internal AWG of the scope when using the FRA4PicoScope, the upper frequency limit is only 1MHz and the practical applications are very limited because of this as well.

The limitation to 1000 frequency steps/decade rules out more extreme narrowband analyses.

On the positive side, there is the pretty fast sweep time of only 11.7s for 500 data points – the screenshot above shows 1000 data points (19.5s) because of the frequency span which is twice as wide as has been planned initially.


Finally we take a look at the Bode plotter in the Siglent SDS1104X-E and its current state with firmware version 7.6.1.20R1. It gives us the choice between linear or logarithmic frequency axis and for filter analysis, linear is what we want. For the first test, the phase plot has been shifted out of view to maintain visual compatibility with the other contenders. Center frequency and span are both 500kHz in accordance with the spectrum analyzer measurement.


SDS1104X-E_BP_455_500kHz_BP_500_nophase

We get a rather nice low noise trace and about 75dB dynamic range for the displayed spectrum. This looks quite usable in my book, even though the unwanted responses appear a bit too low in amplitude compared with the results from the spectrum analyzer or the 16 bit DSO. I have confirmed that this does not change the least bit with higher frequency resolution.


If we want a phase plot, then there are only two opponents left, the FRA4PicoScope and the Siglent SDS1004X-E. Let’s have a look at the PicoScope first.


IF_Filter_455kHz_Ref 03_Phase

Well, that certainly doesn’t look right and the phase plot is pretty much useless. But there is also an option to “unwrap” the phase plot, and that looks like this:


IF_Filter_455kHz_Ref 03_Phase_unwrap

It looks a lot clearer now, yet the phase plot shows only street numbers except for the filter pass band and the unwanted response. It looks like the system attempts to measure the phase of the noise, which is of course not going to lead anywhere. All in all, this solution is not useful for analysing 50 ohm systems.


Finally the complete Bode plot including phase for the Siglent SDS1104X-E. There is no “unwrap” option (yet), so it looks a bit confusing, especially at the spots where the phase jumps between -180° and +180° (which is the same of course) because of noise and/or minor inaccuracies, but at least it is much closer to the truth than the FRA4PicoScope Result.


SDS1104X-E_BP_455_500kHz_BP_500_2

Anyway, this screenshot already hints on a number of desirable improvements, like dynamic adaption of the threshold for the wrap-around when the phase plot is shifted, then of course the “unwrap” option as well as the possibility to completely hide the phase plot, as it isn’t always needed and for complex structures like this, the picture is much clearer without. In fact, nobody really cares for the phase when analyzing a high order narrowband filter like this.
It can also be seen that the phase plot overwrites the amplitude trace, particularly obvious for the 2nd unwanted resonance at 650kHz; this flaw needs to be resolved as well.


Finally, the table below summarizes the general features and the results from this test.


Bode Plot Comparison

The SDS1004X-E shines with its three analysis channels and offers a fairly complete feature set by providing a phase plot and giving the choice of linear or logarithmic frequency axis. It covers a wide frequency range up to 120MHz (a limit that is most likely to be further expanded in the near future) and offers convenient tracking cursor measurements.

The frequency resolution might appear a little on the low side, but it is certainly adequate, especially since this is the only device in this test restricted to a small 7” TFT, whereas all other contenders are essentially PC applications.

The speed is slow but bearable and I hope we’ll see some improvements in this regard.

Amplitude accuracy appears a bit off at the lower level resonance peaks in this test, but that is not conclusive yet and needs further investigation.

EDIT: Max. vertical sensitivity for PicoScope 3206B corrected to 10mV/div.

EDIT 2: Added some important information on the FRA4PicoScope: the AWGs are 600 ohm output impedance, which explains the very poor dynamic when used in a 50 ohm system. The 1000 poits/decade limit makes extreme narrowband analysis impossible.

« Last Edit: April 24, 2018, 11:46:52 pm by Performa01 »
 
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Online tautech

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #68 on: March 11, 2018, 03:45:47 pm »
500 frequency steps, low res mode ?
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Offline rf-loop

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #69 on: March 11, 2018, 08:50:24 pm »
First thank this SFRA test and compare with these PC scopes and what  have very highly limited frequency range.
Unclear (for me) is: when they say some amount of points for decade... is it really what I think...
SFRA from 999000 Hz to 999500 Hz how many steps...  or  just normal IF channel filter and SFRA example from 21.375000 MHz to 21.425000 MHz (oops, there was some PC scope limited to 1MHz "audio" so that only somehow usable for 455kHz IF filters).  So how these points per decade things...

For IF filters tests of course this is very very limited due to very low dynamic  so we do not know "anything" about good filters stop band characteristics. But this is not designed for these. Still many things can do - up to 120MHz depending generator in use.

Only roughly this price class stand alone scopes what have SFRA is Keysight and some chinese GoodWill.
It looks like Kysight have nothing but just feature listed in advertisements (least data sheet what I have seen tell that 10 points/decade)

I think SFRA may rise later more discussion (also about possible performance and UI improvements) but now this:




Top left is the interface box SLA1016 that connects to the SDS1004X-E through the Sbus cable at one end. The other end has a 2x34 connector for the ~80cm long high density flat ribbon cable, which in turn connects to the SPL1016 probe head. It is connected in the picture above, but can easily be detached.


This SPL1016 looks like exactly same SPL1016 what is used with SDS1002X+ models.
Only what I can not see enough clear in images is SLA1016 connector. (ribbon cable between SPL1016 head and SLA1016)
SPL1016 head include electronics, all comparators etc. After this head, in ribbon cable, signal is buffered.
I have used it with SDS1102X+

Now, because this kind of cables wear and damage quite easy in use it is nice if parts can buy separately and not need buy whole set including SLA1016 and SPL1016 together.
 
But question is: Is this SPL1016 head really same and cable with connectors also exactly same what is used in SDS1002X+ MSO.
If so, only new part is this SLA1016 control and converter box.
If practice and theory is not equal it tells that used application of theory  is wrong or the theory itself is wrong.
It is much easier to think an apple fall to the ground than to think that the earth and the apple will begin to move toward each other and collide.
 

Offline Performa01

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #70 on: March 11, 2018, 09:44:46 pm »
500 frequency steps, low res mode ?

I’m not sure if I quite understand your remark/question…

Anyway, it might do no harm to give some additional information on the frequency resolution topic.

The Bode plotter in the SDS1004X-E has three different resolution modes, that provide a total number of frequency steps as shown below:

Low          20
Medium   100
High        500

The number of measurements, hence data points, is the number of frequency steps plus one.

The above scheme has been chosen in order to get a full resolution sweep (high), where each horizontal screen pixel corresponds to a measurement or a fast sweep (low) for a quick overview and also wideband structures that don’t require high frequency resolution. The medium resolution is just a compromise between the two and might be universal for pretty much everything that does not contain any high-Q resonant structures.

Still the 501 data points in high-res mode might not be enough for the following two scenarios:

1.   Detecting narrow resonance peaks in a wideband scan.
2.   Gaining additional detail when zooming into a Bode plot after the measurement has been made.

The first scenario is not very common and would be pretty similar to using peak detect in Y-t mode at a slow timebase in order to capture narrow spikes. While this is a realistic use case for a DSO, it isn’t very common for the frequency response of a circuit. It is only possible if the circuit includes high-Q resonant structures, which should not happen by accident, at least not in the frequency range up to 120MHz. For high-Q resonant structures, we are usually only interested in the frequency span around the resonance frequency, just as for the IF-filter in my previous example and then the frequency resolution is perfectly adequate.

Getting additional detail by zooming into a Bode plot after the measurement on the other hand was just not a design goal for the bode plotter in the SDS1004X-E. We rather have to repeat the measurement (or even take more than one measurement) with a narrow span. This is also a question of measurement speed. If Siglent engineers manage to significantly improve the sweep speed and come anywhere close to the FRA4PicoScope in this regard, then we could always add a “Super High” resolution mode or just increase the number of frequency steps for the existing ones.
« Last Edit: March 13, 2018, 08:34:45 am by Performa01 »
 
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Offline Performa01

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #71 on: March 12, 2018, 09:06:17 am »
First thank this SFRA test and compare with these PC scopes and what  have very highly limited frequency range.
Unclear (for me) is: when they say some amount of points for decade... is it really what I think...
SFRA from 999000 Hz to 999500 Hz how many steps...  or  just normal IF channel filter and SFRA example from 21.375000 MHz to 21.425000 MHz (oops, there was some PC scope limited to 1MHz "audio" so that only somehow usable for 455kHz IF filters).  So how these points per decade things...

For IF filters tests of course this is very very limited due to very low dynamic  so we do not know "anything" about good filters stop band characteristics. But this is not designed for these. Still many things can do - up to 120MHz depending generator in use.

Only roughly this price class stand alone scopes what have SFRA is Keysight and some chinese GoodWill.
It looks like Kysight have nothing but just feature listed in advertisements (least data sheet what I have seen tell that 10 points/decade)

Your thinking is absolutely correct. The FRA4PicoScope can handle up to 1000 steps per decade, which may sound like a lot in wideband applications, but makes it unusable for extreme narrowband analysis. For your frequency span examples, it would be just one step (and/or an error message).

I should have pointed this out more clearly in my comparison and I’ve edited my posting in the meantime to include some additional information on the FRA4PicoScope.

Just now it occurred to me that the internal AWGs in the Picoscopes are not only limited to 1MHz and 2Vpp, but have 600 ohms output impedance on top of that, which also explains the high noise floor and poor dynamic of the measurements. We’d need a booster amplifier for proper usage in a 50 ohm system – and then the dynamic would most likely approach 90dB (and up to 100dB if the booster could deliver 10Vpp into 50 ohms).

When talking about just 10 steps/decade, this is clearly a joke and would not even remotely cover my test scenario. Here’s the same 455kHz IF filter plotted with the FRA4PicoScope using only 10 steps/decade:


10 points per decade

« Last Edit: April 24, 2018, 11:44:35 pm by Performa01 »
 

Offline Performa01

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #72 on: March 12, 2018, 09:14:20 am »

Top left is the interface box SLA1016 that connects to the SDS1004X-E through the Sbus cable at one end. The other end has a 2x34 connector for the ~80cm long high density flat ribbon cable, which in turn connects to the SPL1016 probe head. It is connected in the picture above, but can easily be detached.


This SPL1016 looks like exactly same SPL1016 what is used with SDS1002X+ models.
Only what I can not see enough clear in images is SLA1016 connector. (ribbon cable between SPL1016 head and SLA1016)
SPL1016 head include electronics, all comparators etc. After this head, in ribbon cable, signal is buffered.
I have used it with SDS1102X+

Now, because this kind of cables wear and damage quite easy in use it is nice if parts can buy separately and not need buy whole set including SLA1016 and SPL1016 together.
 
But question is: Is this SPL1016 head really same and cable with connectors also exactly same what is used in SDS1002X+ MSO.
If so, only new part is this SLA1016 control and converter box.

I've never had a SDS1000X+, so I cannot comment on it. However I happen to have a picture of the SLA1016 connectors:


SLA1016_Interface
« Last Edit: April 24, 2018, 11:45:10 pm by Performa01 »
 

Online tautech

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #73 on: March 12, 2018, 09:33:33 am »

Top left is the interface box SLA1016 that connects to the SDS1004X-E through the Sbus cable at one end. The other end has a 2x34 connector for the ~80cm long high density flat ribbon cable, which in turn connects to the SPL1016 probe head. It is connected in the picture above, but can easily be detached.


This SPL1016 looks like exactly same SPL1016 what is used with SDS1002X+ models.
Only what I can not see enough clear in images is SLA1016 connector. (ribbon cable between SPL1016 head and SLA1016)
SPL1016 head include electronics, all comparators etc. After this head, in ribbon cable, signal is buffered.
I have used it with SDS1102X+

Now, because this kind of cables wear and damage quite easy in use it is nice if parts can buy separately and not need buy whole set including SLA1016 and SPL1016 together.
 
But question is: Is this SPL1016 head really same and cable with connectors also exactly same what is used in SDS1002X+ MSO.
If so, only new part is this SLA1016 control and converter box.

I've never had a SDS1000X+, so I cannot comment on it. However I happen to have a picture of the SLA1016 connectors:


SLA1016_Interface
Do you happen to have a SCSI drive cable and can maybe check if it's the same 68 pin/plug format ?

A cable such as this could then offer a better solution to the gawd awful ribbon cable:
https://www.ebay.com/itm/SCSI-3-Ultra-Cable-68-pin-HD68-Male-to-68-pin-HD68-Male-HP-166298-038-AF-0-60m/391907302964?hash=item5b3f7ede34:g:6GkAAOSwNsRZ41iJ
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Offline rf-loop

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #74 on: March 12, 2018, 03:31:48 pm »

I've never had a SDS1000X+, so I cannot comment on it. However I happen to have a picture of the SLA1016 connectors:


Physically connector looks same as SPL1016 used with SDS1102X+. At this point I´m quite sure SPL1016 including cables is same. Interface with scope is of course different, outside of scope SLA1016 with Sbus. SPL1016 price alone without license and SLA1016 interface box is around 189 Eur (VAT0). This is what need buy if you have full MSO set and later want new probe if it is damaged or want more than just one probe.
« Last Edit: March 12, 2018, 04:34:57 pm by rf-loop »
If practice and theory is not equal it tells that used application of theory  is wrong or the theory itself is wrong.
It is much easier to think an apple fall to the ground than to think that the earth and the apple will begin to move toward each other and collide.
 


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