Author Topic: Siglent SDS1104X-E In-Depth Review  (Read 120590 times)

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Offline Performa01Topic starter

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #200 on: November 29, 2023, 01:26:46 pm »
There has been that DHO800 review video by Dave for quite some time now:



Starting at around minute 29:00, Dave compares the DHO814 FFT with that of the venerable Siglent SDS1104X-E. There have been open questions, misleading speculations and unexpected results. End result was that the usual suspects got ammunition to do some unjustified Siglent bashing.

Only now I got around bringing my SDS1104X-E from the other lab and finally try to do some myth busting. For all those, who are interested in real facts and the true contest of how a good 8-bit DSO is handling the test cases presented in the video, here you go…

First was the 10 MHz carrier with 50 kHz 0.02% AM. The result was not very convincing, and it looked basically the same on both instruments.

This test was quite obviously flawed. Whenever designing a test like this, we have to ask ourselves: What do we want to prove – what are the properties of the DUT (Device Under Test) we want to verify – and: what test signals are required to achieve that. After that, we should make sure that we are able to provide the required test signals with the required accuracy – and should have means to verify that.

Let’s start with the test objects, which are the 8-bit SDS1104X-E vs. a 12-bit DHO814. Since I don’t have a DHO800 here, I’ll be using the well known (to me at least) SDS2504X HD instead. This shouldn’t be a problem for demonstrating the difference between 8- and 12-bit acquisition systems.

8 bit (as in the SDS1104X-E) means a total of 256 steps (aka LSB). At a vertical gain of 200 mV/div, the visible screen height covers 1.6 Vpp. This in turn is equivalent to 200 LSB of the 8-bit ADC (the rest is headroom). If we feed a 1 Vpp signal, this corresponds to 125 LSB of the ADC. Thus, we have already lost some 6 dB of the dynamic range by not exploiting the full scale of the ADC – as is the case in most realistic applications.

At 200 mV/div, 1 LSB corresponds to 1.6 V / 200 = 8 mV;
Full scale would then be 256 * 8 mV = 2.048 V.

8 mVpp is just 42 dB below 1 Vpp. As a consequence, we normally cannot expect the FFT to be accurate below -42 dBc in this particular test case.

For the SDS2000X HD the calculation would be quite different. The visible screen height at 200 mv/div covers 1.6 Vpp as well, but this is equivalent to 3840 LSB. 1 LSB is now only 1.6 V / 3840 = 416.7 µV and full scale is only 4096 * 416.7 µV = 1.7067 V.

416.7 µV is 67.6 dB below the 1 Vpp test signal and we should not blindingly trust to get usable results below that.

Now what about the AM signal? It’s not hard to calculate the sidebands. The lowest signal for reliable measurements is achieved by ~1.6% AM depth for the 8-bit case and 0.083% for 12 bits.

You may notice by now that 0.02% AM depth produces -80 dBc sidebands, hence would require at least 14 bits. So the conclusion from this first test can only be:

The amplitude of the sidebands of an AM signal with just 0.02% depth is much too low even for a proper 12-bit acquisition system. Additionally, the reliability and accuracy of such a an impractical low modulation depth from a standard signal source such as an AWG is questionable at best.

Yet in practice the FFT can deliver more dynamic range than the bare ADC without math and software. So we can at least try and see how far that goes. But first we need to make sure we get a correct signal, and for this I don’t like to rely on AM with an AM-depth so low that it requires at least 14 bits, but a proper signal mix instead, from well-defined sources with the help of a power combiner and precision attenuators. This way we can get two signals whose amplitudes are 80 dB apart – and even a proper SA isn’t terribly accurate at such ridiculously low levels, as the delta is measured almost 1.5 dB too high.


Ref_-80dBc

Now let’s see what this signal looks like on a true 12 bit DSO with a proper FFT implementation:


SDS2504X HD_FFT_D80dB

Remember? Careful thinking led us to the conclusion that the physical resolution of the 12 bit DSO (the SDS2000X HD particularly) is some 417 µV @ 200 mV/div, hence this would be only 67.6 dB below a 1 Vpp carrier. Nevertheless we were able to measure -80 dBc with still reasonable accuracy. In fact, the error is less than 0.75 dB, hence way more accurate than the SA.

In the video above, this cannot even be called a “test”; nobody cared for the results, tried to measure the level of the sidebands and to judge the accuracy. It was just “oh, there are some spectral lines visible”, which might please some Rigol fanboys, but not an engineer.

Now for the 8-bit SDS1104X-E:


E_FFT_10MHz_D80dB_Avg10

The SDS1104X-E can do the job quite nicely. The error is just about 1 dB, so even the 8-bit DSO can be more accurate than the spectrum analyzer in such borderline situations, where extreme dynamic ranges are required.

Yes, the Siglent offers the FFT averaging mode, which is about equivalent to the VBW (View Bandwidth) setting on a dedicated spectrum analyzer. This makes for a much clearer view and allows us to see low level signals. Without that goodie, we have to dig in the mess to get the correct measurement every now and then:


SDS1104X-E_FFT_10MHz_D80dB

Peak #9 is the correct one, and I think few people would prefer that mess over a cleanly averaged spectrum view. Yet it apparently must be sexy, as the DHO don’t provide this and nobody complains.


And now for some strange speculations about ERES in FFT math mode. Base line is:

Without appropriate dither, the ADC will just sit at its DC output value as soon as the input signal drops below 1 LSB.

If the ADC doesn’t produce any data, then no software trick in the world can make something useful of it. ERES can only enhance the resolution if there is a dither signal. The FFT itself is a resolution enhancement technique, (buzzword “process gain”) and ERES severely limits the bandwidth, so it would be completely useless for general FFT use anyway.

The truth is, that even on a low noise instrument like the SDS1000X-E, input noise is usually high enough to act as a dither. Only the 100 mV/div (hence also 1 V/div and 10 V/div) ranges are so electrically quiet on an SDS1104X-E, that I’ve seen resolution enhancement techniques fail at times.

At this occasion we noticed that the FFT was processed a lot faster in the DHO800. Yes, that’s impressive and of course we would want that for every DSO. But it’s not really a surprise either: a 6 (or even 8?) core processor at 2 GHz should certainly be more powerful than a Xilinx Zync with 2 cores and some 800 MHz. Now if only Rigol made good use of it – the fastest FFT doesn’t help much if the results are as it were shown in the video. By comparison look at the SDS1000X-E screenshots: even without peak table you can clearly see the spectral lines (and not some spurs) and know the amplitude with reasonable accuracy.

Now for the “30 mVpp signal at 10 V/div” test. Yes, this is a clear case where a low-noise 8-bit scope has to give up. In the AM test, the carrier acted as (almost full scale) dither, hence the accuracy of level measurements far below the 8-bit dynamic range was still pretty good. But now we have to rely on the input noise as dither, which will barely exceed 1 LSB at 200 mV/div. Consequently, the accuracy is completely gone, but the signal itself is still clearly visible:


SDS1104X-E_FFT_10MHz_-40dBV_Avg10

Yes, this appears to be the advantage of a 12-bit DSO, but it is nevertheless pretty much meaningless in practice: whenever we have to measure an isolated (single) signal that low, then we just select an appropriate vertical gain. If, on the other hand, this is not possible because there are other stronger signals present at the same time, then we can happily use a less sensitive input range and let those stronger signals act as dither. All in all, the rather high 1 LSB threshold of an 8-bit ADC isn’t really a concern particularly for FFT.

Now finally the great mystery, how Dave managed to get a completely screwed-up picture of the FM modulated signal on the SDS1104X-E. I just could not reproduce it:


SDS1104X-E_FFT_10MHz_FM50k_1kHz

By the way, I‘ve often stated that for emulating an SA, Flattop is the correct window to use. The only alternative in desperate situations would be Blackman, which has a little narrower RBW and still bearable amplitude error. Yet I’ve sticked to Hanning, just to precisely match Dave’s settings. And meaningful results or even accuracy didn’t seem to be a topic in this review anyway…

As always, display averaging gives a clearer picture:


SDS1104X-E_FFT_10MHz_FM50k_1kHz_Avg10

This screenshot shows the expected result and reveals a dynamic range of almost 80 dB. Of course there’s nothing wrong with the Siglent. I’ve known it from the start, because I’ve done extensive tests back in 2017 already, when I wrote my review. The FFT has been improved since then, yet it never failed to display the correct spectrum.

Remember when the DHO800 showed weird things on the screen? Dave tried hard to find the cause – which in the end was just a flaky cable connection. He made even a separate video on it. Yet when the Siglent showed implausible results, Dave just wrote it off as “it doesn’t like it at all” – and Rigol fanboys had a party, even though it should be very clear that such an obvious major bug would not have gone unnoticed for an instrument that’s been on the market for almost 6 years now and numerous examples of its (still) superb FFT have been posted in this forum already.
« Last Edit: November 29, 2023, 04:58:36 pm by Performa01 »
 
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Online Martin72

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #201 on: November 29, 2023, 08:34:04 pm »
Hi,
With the help of the wave combine function I was able to reproduce the signal without an attenuator, with 10Vpp and 1mVpp (thanks to Performa01).
I get almost the same result, see pictures.
I would also like to recreate the FM thing, but I don't know the settings for it.
Then I fed the signal into the dho and also set it to "flat top", but the result I won´t post here.
"Comparison is the end of happiness and the beginning of dissatisfaction."
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Offline 807

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #202 on: November 30, 2023, 05:25:39 pm »
Re the FM tests. Dave didn't say what the deviation was for the first test, just that it was a frequency of 500HZ. Looking at the settings on the Rigol, it looked like he set a deviation of 30kHz. Applying those to my 1104X-E, I got a result similar to the Rigol. Same for the second test using 15kHz at 20kHz deviation.

I don't know how Dave managed to get those wonky displays.  :-//
 
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Offline GnomeZA

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #203 on: November 30, 2023, 05:42:51 pm »
Remember when the DHO800 showed weird things on the screen? Dave tried hard to find the cause – which in the end was just a flaky cable connection. He made even a separate video on it. Yet when the Siglent showed implausible results, Dave just wrote it off as “it doesn’t like it at all” – and Rigol fanboys had a party, even though it should be very clear that such an obvious major bug would not have gone unnoticed for an instrument that’s been on the market for almost 6 years now and numerous examples of its (still) superb FFT have been posted in this forum already.

Dave regularly hand waves away things that don't match his cognitive model.
ie. when he opens a cheap multimeter everything other comment is "<shows part>. Part <part> here but is it the genuine article?  I don't think so/I don't know".
There are no technical reason he can fault it on its performance (ie. it is meeting its stated performance) so then it gets to nit picking about things that simply don't matter or completely unsubstantiated by any evidence whatsoever.

Whereas the likes of Fluke and so on get comments like "you know it is going to work, it is Fluke"  :-DD

I'm not sure he can be taken seriously as a reviewer, entertainer is possible more appropriate.

I appreciate a lot of the way he has paved for electronics early days, but I rarely watch any of his videos anymore.
I watched the DHO video and gave up half way through.
 
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Online ebastler

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #204 on: November 30, 2023, 06:04:31 pm »
"No script, no fear, all opinion", as it says on the label.  8)
 
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Offline sylvandb

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #205 on: November 30, 2023, 06:12:47 pm »
Dave regularly hand waves away things that don't match his cognitive model.
ie. when he opens a cheap multimeter everything other comment is "<shows part>. Part <part> here but is it the genuine article?  I don't think so/I don't know".
...
Whereas the likes of Fluke and so on get comments like "you know it is going to work, it is Fluke"  :-DD

I'm not sure he can be taken seriously as a reviewer, entertainer is possible more appropriate.

I find every reviewer has biases and oversights.  I appreciate Dave's reviews because he makes it easy to identify his perspective, which makes it easier for me to weight or discount his observations to fit my concerns.
 
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Online Martin72

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #206 on: November 30, 2023, 07:28:08 pm »
Today I also managed to get the FM-Mod pictures, once without average, once with.
So "my" 1104X-e is the third one here. ;)



"Comparison is the end of happiness and the beginning of dissatisfaction."
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Siglent SDS800X HD Deep Review
 
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Offline tautech

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #207 on: November 30, 2023, 07:29:47 pm »
Today I also managed to get the FM-Mod pictures, once without average, once with.
So "my" 1104X-e is the third one here. ;)

Menu = Off ?  :-//
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Online Martin72

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #208 on: November 30, 2023, 07:32:49 pm »
Why not?
This always bothers me, but if you still want menus, I can submit them later. ;)
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Offline tautech

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #209 on: November 30, 2023, 07:34:13 pm »
Why not?
This always bothers me, but if you still want menus, i can submit them later. ;)
Showing menu helps those with lesser skill to setup correctly.  ;)
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Offline core

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #210 on: November 30, 2023, 08:02:54 pm »
I've tried too. So, another SDS1104X-E in test  ;D

Signal generator is Siglent SDG2000X

HiZ, no 50 Ohm terminator on scope.

For AM : 1 ch 10MHz, 10Vpp; 2 ch 10.05MHz, 2mVpp. Mixed with wave combine.
For FM : 1Vpp, 10MHz, FM dev 50kHz, FM freq 1kHz.

FFT settings:
1M, Hanning, Center freq 10MHz, 100kHz/div for AM and 50kHz/div for FM

Same results.
« Last Edit: November 30, 2023, 08:40:58 pm by core »
 
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Offline tautech

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #211 on: November 30, 2023, 08:05:45 pm »


The blue Print (to USB) button is more useful to keep menus displayed.  ;)
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Offline core

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #212 on: November 30, 2023, 08:09:13 pm »


The blue Print (to USB) button is more useful to keep menus displayed.  ;)

Of course, yeah. I was in a hurry ... forgot about the blue button ...
 
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Re: Siglent SDS1104X-E In-Depth Review
« Reply #213 on: November 30, 2023, 08:18:53 pm »
So, here again in a little more detail...
"Comparison is the end of happiness and the beginning of dissatisfaction."
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Siglent SDS800X HD Deep Review
 
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Offline Performa01Topic starter

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #214 on: December 03, 2023, 11:52:33 am »
There has already been a two tone test for exploring the 1st order dynamic range of the SDS1104X-E in mid 2019, where an 80 dB dynamic range could be demonstrated (reply #1386):

https://www.eevblog.com/forum/testgear/siglent-sds1204x-e-released-for-domestic-markets-in-china/msg2454291/#msg2454291


Now for the “30 mVpp signal at 10 V/div” test. Yes, this is a clear case where a low-noise 8-bit scope has to give up. In the AM test, the carrier acted as (almost full scale) dither, hence the accuracy of level measurements far below the 8-bit dynamic range was still pretty good. But now we have to rely on the input noise as dither, which will barely exceed 1 LSB at 200 mV/div. Consequently, the accuracy is completely gone, but the signal itself is still clearly visible:


SDS1104X-E_FFT_10MHz_-40dBV_Avg10

Yes, this appears to be the advantage of a 12-bit DSO, but it is nevertheless pretty much meaningless in practice: whenever we have to measure an isolated (single) signal that low, then we just select an appropriate vertical gain. If, on the other hand, this is not possible because there are other stronger signals present at the same time, then we can happily use a less sensitive input range and let those stronger signals act as dither. All in all, the rather high 1 LSB threshold of an 8-bit ADC isn’t really a concern particularly for FFT.
Now let’s prove that assertion as well.

When using the low vertical ranges, like 1 mV/div or even 500 µV/div, the input noise acts as a dither just nicely. This enables us to make accurate measurements down to -110 dBm (2 µVpp = 707 nVrms)!


SDS1104X-E_FFT_10MHz_-110dBm_500uV

The measurement results from -40 dBm down to -110 dBm can be found in the following table:


SDS1104X-E_FFT_10MHz_LL

The maximum error was 0.2 dB or 2.33% respectively for -100 dBm @ 10 MHz.
« Last Edit: December 03, 2023, 01:36:50 pm by Performa01 »
 
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Offline core

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #215 on: December 23, 2023, 08:12:20 am »
I've tried too. So, another SDS1104X-E in test  ;D

Signal generator is Siglent SDG2000X

HiZ, no 50 Ohm terminator on scope.

For AM : 1 ch 10MHz, 10Vpp; 2 ch 10.05MHz, 2mVpp. Mixed with wave combine.
For FM : 1Vpp, 10MHz, FM dev 50kHz, FM freq 1kHz.

FFT settings:
1M, Hanning, Center freq 10MHz, 100kHz/div for AM and 50kHz/div for FM

Same results.


I was playing around with DHO1074 and some modulated signals and by mistake (bad contact terminator) I've found an explanation about the wrong FFT plot regarding SDS1104X-E.

I've used a 10MHz, 2Vpp signal, FM modulated, mod freq 500Hz, Deviation 50kHz (and 30kHz in the following examples).
If the input stage is not overloaded, it can't measure the frequency - see the hw counter in the up-right corner.
If the input stage is overloaded, the counter works. In the Dave's review the counter works, so we can presume that the SDS was overloaded, may be because of a bad contact terminator.

An overloaded DHO have an even more funny FFT plot for 30kHz deviation.
 
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Offline core

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #216 on: December 23, 2023, 08:44:57 am »
By mistake, the DHO was with 20MHz filter activated.
Below the same FFT, overloaded, full BW. Still more funny with limited BW  :)
 
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Offline Performa01Topic starter

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #217 on: December 23, 2023, 08:51:13 am »
I was playing around with DHO1074 and some modulated signals and by mistake (bad contact terminator) I've found an explanation about the wrong FFT plot regarding SDS1104X-E.
...
An overloaded DHO have an even more funny FFT plot for 30kHz deviation.
Thank you very much for solving this puzzle. I honestly could not figure how a flacky cable connection could cause such an implausible spectrum, yet the overload explanation makes a lot of sense.

Yet the damage is done. Some of the "experts" out there could yell out that the Siglent FFT is broken or the user interface is so awkward that Dave couldn't get it right.  :palm:
 
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Offline core

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #218 on: December 23, 2023, 10:24:53 am »
For me, the SDS1104X-E is the reference I check when something looks suspicious with another oscilloscope. After numerous tests, I have come to the conclusion that it is a truly finished product, at least for my usual needs.
Even though I've bought better ones in the meantime, it will remain here if only as a collector's item. I like it very much.

That's why I remembered the problem and immediately made the connection when it happened.
 
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Re: Siglent SDS1104X-E In-Depth Review
« Reply #219 on: December 23, 2023, 12:13:08 pm »
Quote
Yet the damage is done. Some of the "experts" out there could yell out that the Siglent FFT is broken or the user interface is so awkward that Dave couldn't get it right.

This was said after we were able to disprove it here, that something was wrong with the FFT.
Let's see what comes out of that corner now.
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Siglent SDS800X HD Deep Review
 
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Offline tautech

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #220 on: December 23, 2023, 02:08:33 pm »
 :popcorn:
Quote
Yet the damage is done. Some of the "experts" out there could yell out that the Siglent FFT is broken or the user interface is so awkward that Dave couldn't get it right.

This was said after we were able to disprove it here, that something was wrong with the FFT.
Let's see what comes out of that corner now.
:popcorn:
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Offline cichmen

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #221 on: January 12, 2024, 05:42:07 pm »
Hi,

I would like to ask if other users of this scope (SDS1104X-E, latest FW, no hacks) are also seeing this strange behavior:
Input signal is square wave 10Hz, 2Vpp, scope has DC coupling, connected with coax cable, external 50ohm load, 1x mode:


If I want to focus on the upper flat part of the signal (change the offset and vertical amplification) like this:

I can see ringing of the scope vertical amplifier there. It gets worse with more offset.

I double-checked with another scope (RTM3004) and it is quite flat as expected:


Cichmen
 

Online bdunham7

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #222 on: January 12, 2024, 06:54:46 pm »
I would like to ask if other users of this scope (SDS1104X-E, latest FW, no hacks) are also seeing this strange behavior:
Input signal is square wave 10Hz, 2Vpp, scope has DC coupling, connected with coax cable, external 50ohm load, 1x mode:

Yes, the low frequency 'wrinkles' in low frequency square waves is a known feature.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline cichmen

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #223 on: January 12, 2024, 07:06:13 pm »
Yes, the low frequency 'wrinkles' in low frequency square waves is a known feature.
Good to know. Thanks. Do you have some link where it is referenced?
 

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Re: Siglent SDS1104X-E In-Depth Review
« Reply #224 on: January 12, 2024, 07:12:19 pm »
Good to know. Thanks. Do you have some link where it is referenced?

If you mean "official word" or something, no, but here is an example of a previous discussion.  This my reply, go back a page to see how the question came up.

https://www.eevblog.com/forum/testgear/dmmcheck-plus-multimeter-calibration-reference-experiences/msg4955995/#msg4955995
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 


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