Siglent SDS800X HD 12 bit DSO's

[2N3055]

Since everybody is posting interesting stuff, a bit of contribution from me.
In conversation with my friend, he said that he needs to test VFD drives driver stages to verify proper PWM modulation.
PWM frequency is 20kHz and generated frequency is 50 Hz for instance.

Here an example of SDS824xHD showing filtered PWM generated 50Hz.
Added  amplitude measurements and frequency and period measurement for reconstructed sinewave.

1 Math channel used (so this can be done for 4 channels at the same time), filter set for LP, 10kHz corner freq.
And trigger was set for pulse, carefully set to trigger when PWM had shortest negative going pulse, so display is synchronous with modulation, not carrier.

I guess it really is 50 Hz... 

[Martin72]

10kHz corner freq.

1kHz isn´t possible ?
But still better than nothing.

[2N3055]

10kHz corner freq.

1kHz isn´t possible ?
But still better than nothing.

No 1kHz at 1Msps/s.
But, 10kHz did filter quite nicely. Enough to be able to properly measure frequency of reconstructed signal and phase if it was multi channel.

[ebastler]

10kHz corner freq.

1kHz isn´t possible ?

No, must be >= 0.01 * sampling frequency. There's actually a nice overview in the manual, with diagrams showing the filter constraints, section 19.4.

[Martin72]

That's a shame, because 1kHz would be much better or "closer to reality".
We have a carrier frequency of 10kHz, for example, so the image will no longer look good with a cutoff of 10kHz.
Nevertheless, I will take the 800 to work soon and filter a 3-phase PWM with it.

[gf]

The lower the fc/sample_rate ratio, the more FIR filter taps you need.

[whodiini]

i wonder though if real big heavy transformer wall wart into bridge rectifier and capacitors still exist today for sale... usually what seems to be regular wall wart is actually smps inside. even old psu 5-12V with 50 ohm load you need hefty big capacitors to get -100dBV, if linear reg like LM317 with -60dB PSRR, that means -50dB out of 60Hz bridge rec + cap which is still pretty good components at cheap price. ymmv.

Since there have been several people wondering how a "cheap" wall wart can be this good, let me clarify.  I have been trying to  come up with inexpensive options for a linear regulated power supply for hifi purposes, cheaper than the ~$100+ supplies that are being sold. So I went down the wall wart route.  There are no linear regulated wall warts that are being sold anymore, as they all are SMPS now.  But some older ones 10-20 years old are sold on ebay. I bought 2 models of 5V linear regulated wall warts, one 1200mA and the other 1500mA.  The smaller is big and the larger one huge.  The larger one is so big, I worry it will damage the wall plug!  In any case, they both measure about the same and it is the one I showed as "no name wall wart".  I opened them and they use an obsolete LM317 type linear regulator along with a fairly decent sized filter capacitor 6800µF.   Before I found these, I purchased a unregulated transformer based wall wart, cracked it open and replaced the filter cap with a 10000µF filter and then added a LDO regulator BA50DD0T + extra parts (2 caps for anti-oscillation), diode to protect the LDO.  That is the one I showed that had the puzzling 60 kHz centered peak.  I guarantee you, its not a SMPS, its a linear regulated PS.  I am wondering if the 60 kHz peak has to do with the stability of the regulator - will try replacing cap values and see if anything changes.  Since I am learning about linear PS, this is fun using the Siglent.

[whodiini]

Also, dbV=20log(V2/V1) so -80dB => V2/V1=.0001     5V power supply, so noise is .5mV.  This is pretty standard for a linear regulated power supply so I have read.  -100db => .00001, so noise is .05mV >1kHz.  Thats very good.  Also, you should look not at 60Hz, but at 120Hz for the rejection, since the full wave rectifier operates at  effectively 120Hz. Still -80 dB is pretty good, since the typical linear regulator spec is -60dB. I have no idea why they are so good.  Maybe they built these linear power supplies really well 20 years ago?

[Mechatrommer]

Still -80 dB is pretty good, since the typical linear regulator spec is -60dB. I have no idea why they are so good. Maybe they built these linear power supplies really well 20 years ago?

10mF and LDO might explain it. BA50DD0T's -65dB PSRR @ 120Hz, -78dB from your plot meaning -13dB out of 10mF cap, 200mVrms+ noise is about right... that -80dB 60KHz peak idk, maybe internal regulation of the LDO... ymmv.

...extra parts (2 caps for anti-oscillation), diode to protect the LDO.  That is the one I showed that had the puzzling 60 kHz centered peak.

datasheet says to put 330nF cap, you can experiment different type tantalum or ceramics or elec, ESR can affect stability too... ymmv.

[Performa01]

In a pinch one can utilize the "Track Function" sampling a Measure Frequency Statistic as an FM demodulator. As shown this is a FM Modulated signal at 455KHz (Common IF) at 1KHz with a 10KHz deviation. Modulation shown are Sinewave and Ramp Frequency.

Now we finally have a use case for the earphone connector on the SDS7000A! 😉

Unfortunately, we cannot use advanced measurements in roll mode, consequently a continuous demodulation is not going to happen. But if we can live with very brief drop outs every few seconds, it could still work.

Let’s have a bit more serious look at it.

In the real world, any FM receiver that utilizes a final IF of 455 kHz can only be a narrowband FM receiver, hence an FM-deviation of 2.4 kHz is more likely. With such low FM-deviations, the demodulated signal gets a bit noisy, as you have already demonstrated even with 10 kHz deviation.

Now, real receivers have no problem demodulating such a narrowband-FM signal with good SNR. What’s the difference?

The answer is easy. Every serious receiver has an IF-filter, which has to be a 455 kHz bandpass in this particular case. So let’s fit one!


SDS824X HD_Track_FM_1kHz_Dev2.4kHz_AIM1k

The modulation frequency is 1 kHz and the FM-deviation 2.4 kHz. Both parameters are nicely confirmed by the Track-Plot, which is almost completely noise-free because it uses the filtered IF-data.

[radiohomebrewer2000]

Performa01,
I only have one word for you.  Beautiful! 

The screenshot that is... and what you did to get there creating a math function as an IF filter.


Are we allowed to ask beginner questions in this forum/topic? 

I noticed you are using 1X.  I thought we should use 10X most of the time?

Would a 10.7 MHz IF do better?

[Performa01]

I noticed you are using 1X.  I thought we should use 10X most of the time?

That’s true when using passive high impedance probes. For my demonstrations I’m mainly using signals from my Arbitrary Waveform Generators and for this I’m using direct coax connections of course.

It is just because the SDS800X HD series don’t provide 50 Ω inputs, otherwise you could see it in the channel tab, e.g. “DC50”. As it is, I have to stick with the 1 MΩ inputs and use an external through termination, which cannot be a substitute for a proper 50 Ω input, because accuracy of measurements can be compromised even at rather low frequencies already.

Would a 10.7 MHz IF do better?

Not better, just different.

Here is an example for 10.7 MHz wideband FM with 75 kHz frequency deviation, first without filter:


SDS824X HD_Track_FM_1kHz_Dev75kHz_AIM25k

And now the same exercise with filtered “IF-signal”:


SDS824X HD_Track_FM_1kHz_Dev75kHz_AIM25k_Filter

[nanopico]

Look what turned up.

https://twitter.com/eevblog/status/1777136802262098133

Looks like Dave is extremely busy.

[tautech]

Look what turned up.

https://twitter.com/eevblog/status/1777136802262098133

Looks like Dave is extremely busy.

We will be too making sure he's doing it correctly......his 2000X Plus tangle with the 10bit mode springs to mind. 

[mawyatt]

Here's an example of using the Bode Function to Plot the Injection Locking Characteristics of a 1.6KHz Wien-Bridge Oscillator (or Wein-Bridge if you prefer!!).

This type plot is difficult to perform as the very large oscillator signal essentially becomes a large out-of-band interferer outside the injection locking range, which the Bode function must deal with properly.

Apparently (we don't know the exact algorithm details) the Bode Function has some frequency selectivity (synchronous sampling/detecting maybe) to help deal with the large "out-of-band" oscillator signals. One would expect this to preform well with SMPS as well, since the switching waveform becomes a large out-of-band interferer.

Edit : Think we may have found a "bug", save button doesn't work under Bode Function and save under data is only a csv file not a png type (no selection), so we used the ScreenShot under the LAN Remote feature.

Correction, see below by electronics hobbyist!!   

Best,

[electronics hobbyist]

Edit : Think we may have found a "bug", save button doesn't work under Bode Function and save under data is only a csv file not a png type (no selection), so we used the ScreenShot under the LAN Remote feature.

Best,

I have found the reason and need to set the Utility -> Save Button -> ScreenShot to make the Save button work under BodePlot. Even better, when entering the BodePlot, this should be automatically be set to ScreenShot.

[Kittifix]

no Room on Table  - Tripod can fix ...

@Printables https://www.printables.com/de/model/842637-tripodmount_siglent_sds800x/files

[Martin72]

What the .....

Nice....

[BRZ.tech]

Hey folks just trying to get an idea how to interpret the specs for this scope.  In particular for this scope we have:

Vertical Resolution: 12 bits

and

Effective Number of Bits ENOB: 8.4 bit

What does this mean?  Does it mean we effectively only get 8.4 bits?

I would strongly recommend this video

Hi,
Dear @pdenisowski
I frequently watch the videos on the R&S YouTube channel.
I think they are excellent THEORETICAL videos.
In my opinion, they need to be completed with practical videos, with real instruments, and without cuts and editing in the videos. It's you connecting the cables, the attenuators, pressing the buttons on the signal generators and the DSO/MSO, and showing the results “On Screen” from the DSO/MSO.
The idea is: if @pdnisowski does it, the user can also reproduce the tests step by step. It is in this condition that a “newbie” learns and keeps something in his mind.
Who watches your theoretical videos?
Maybe the “newbies” like me. Perhaps an “expert” does not have the patience to watch these videos considered “boring and long” and with lots of details. But “newbies” will really appreciate it. And the R&S concept will become much more popular, beyond the professional market.
This is not a personal criticism of you or R&S, it is a suggestion for consideration.
All the best.

[KungFuJosh]

Maybe the “newbies” like me. Perhaps an “expert” does not have the patience to watch these videos considered “boring and long” and with lots of details. But “newbies” will really appreciate it. And the R&S concept will become much more popular, beyond the professional market.
This is not a personal criticism of you or R&S, it is a suggestion for consideration.
All the best.

I don't think people that fit in the category you're talking about purchase 6 figure scopes. R&S isn't a school, they make high-end TE.

[pdenisowski]

Dear @pdenisowski
I frequently watch the videos on the R&S YouTube channel.
I think they are excellent THEORETICAL videos.
In my opinion, they need to be completed with practical videos, with real instruments, and without cuts and editing in the videos. It's you connecting the cables, the attenuators, pressing the buttons on the signal generators and the DSO/MSO, and showing the results “On Screen” from the DSO/MSO.
The idea is: if @pdnisowski does it, the user can also reproduce the tests step by step. It is in this condition that a “newbie” learns and keeps something in his mind.

About half of the 200+ videos I've made are about how to do things on our instruments.  I spent the first 20 years of my career in T&M demonstrating things on real instruments using real DUTs in real labs with real customers, so I like to think I'm pretty comfortable doing that   That said, I use the "narrated PowerPoint" method even for the practical videos for a number of reasons, one of which being that the "slides" can be used for in-person, classroom training and reference, whereas a video typically has to stand alone. 

Who watches your theoretical videos?
Maybe the “newbies” like me. Perhaps an “expert” does not have the patience to watch these videos considered “boring and long” and with lots of details. But “newbies” will really appreciate it. And the R&S concept will become much more popular, beyond the professional market.

The "theoretical" videos (I call them "technology" videos) are literally ten times more popular in terms of views, likes, and comments compared to the "product videos"  And as of last week, the "theoretical" videos had over 3 million total views. So somebody is watching them

And again, from my experience working with thousands of T&M customers: even people who are experts in one field often want a brief (~10-15 mins) explanation of a technology or measurement they may be unfamiliar with.  And they want it without chit-chat, advertising, jokes, a flashy intro/outro, etc.  That's my target audience.

This is not a personal criticism of you or R&S, it is a suggestion for consideration.

Not at all!  I very much appreciate any and all feedback.  Although my "formula" seems to work, I'm always looking for ways to improve and expand, so your post is very helpful.  Thanks!

[pdenisowski]

I don't think people that fit in the category you're talking about purchase 6 figure scopes.

(laughs)  We make plenty of things with six-figure price tags, but we also make plenty of things with four-figure price tags  

The "technology" videos are very deliberately made to be product-agnostic: my video on third order intercept applies to both our FPC1000 spec an (entry level) or our flagship FSW spec an.  In fact, many of the technology videos in the Test and Measurement Fundamentals playlist were originally made for introductory training on our basic products.

I don't think people that fit in the category you're talking about purchase 6 figure scopes. R&S isn't a school, they make high-end TE.

Education / training is really important for us here at R&S:  we want our customers to be successful using our instruments!

[KungFuJosh]

(laughs)  We make plenty of things with six-figure price tags, but we also make plenty of things with four-figure price tags  

I know. I really want an MXO 5 with lots of options. I'm six figures short right now though. lol

I don't think people that fit in the category you're talking about purchase 6 figure scopes. R&S isn't a school, they make high-end TE.

Education / training is really important for us here at R&S:  we want our customers to be successful using our instruments!

Your videos are excellent, I'm a fan of your work. The point I was getting at though, is that (probably) nobody is going to take a mortgage out to buy a scope if they don't know how to use it. 😉😉

On a side note, it probably helps your video production quality that none of your gear competes in price range with the scopes in this thread (which are excellent in their own right).

[BillyO]

We make plenty of things with six-figure price tags, but we also make plenty of things with four-figure price tags

I'm more a three-figure guy myself. 

[Mechatrommer]

Xxx.xx promotion price, in reality 999.99