Siglent SDS800X HD 12 bit DSO's

[Martin72]

Make some movie....

[whodiini]

So now I can compare a store bought PSU to one I made with a wall wart. Mine has a noise peak at 60kHz which I dont understand.  But at least I can make measurements and find out why!   Thanks

If it's a SMPS normal I would say.
60k is a little high as they are normally 20-30 kHz however technology is always changing so recent designs may be operating at those frequencies IDK.

Th
Its a linear regulated supply.  Uses a rohm LDO regulator after a transformer and full wave bridge, filter caps and anti-oscillation caps. That is why it is puzzling. 

[Mechatrommer]

Make some movie....

you dont have to ask, that is his main job... we'll be waiting for it. i hope cover all the functionalities... including FFT plot shown here (if possible downloading data to PC) ymmv.

(Attachment Link)
Purchased wall wart linear regulated.

how can cheap wall wart linear regulated be this good? -80dB is like 100uVpp noise?

[markone]

My fear is that I could find 7" display a bit uncomfortable being nowaday used to 10" DSO screens, so i was considering also the bigger model, but if they share same math performance i would consider the price gap a bit "steep" or, if you want, we can say that the smaller one is to be considered a real bargain

The 1000 series has an RTC, bigger screen, and 100Mpts per channel (compared to 50/ch on the 800). Only you can decide if that's worth the price difference. Either one is a bargain.

Correct me if I'm wrong, but I understood that also the SDS800X HD will gain 100Mpts per channel with the "free upgrade" procedure, so the almost triple price of SDS1104HD starts to be quite bitter to taste.

[2N3055]

My fear is that I could find 7" display a bit uncomfortable being nowaday used to 10" DSO screens, so i was considering also the bigger model, but if they share same math performance i would consider the price gap a bit "steep" or, if you want, we can say that the smaller one is to be considered a real bargain

The 1000 series has an RTC, bigger screen, and 100Mpts per channel (compared to 50/ch on the 800). Only you can decide if that's worth the price difference. Either one is a bargain.

Correct me if I'm wrong, but I understood that also the SDS800X HD will gain 100Mpts per channel with the "free upgrade" procedure, so the almost triple price of SDS1104HD starts to be quite bitter to taste.

No, wrong.

100Mpts is total memory on SDS824xHD.
So 100Mpts for 1 ch, 50Mpts 2 ch and 25Mpts 3 and 4 ch

[egonotto]

Hi

New Siglent SDS804x user here and am embarassed to say, I cant figure out how to transfer a png saved screenshot from the internal memory of the  Siglent to my computer to include in a post.  I read the manual, searched this blog, played with it on the Siglent and havent figured out how to do it.  I have several fft screens I hit the save button so it is a png file on the computer.  How to move that file to my computer?  I can provide a USB stick which I can see on the Siglent.  But when I try to restore or move, cant get it to go to the USB stick.  Many thanks!

Hello,

With my SDS2104X HD I always take the screenshots with the web application on the PC.

Best regards
egonotto

[2N3055]

Hi

New Siglent SDS804x user here and am embarassed to say, I cant figure out how to transfer a png saved screenshot from the internal memory of the  Siglent to my computer to include in a post.  I read the manual, searched this blog, played with it on the Siglent and havent figured out how to do it.  I have several fft screens I hit the save button so it is a png file on the computer.  How to move that file to my computer?  I can provide a USB stick which I can see on the Siglent.  But when I try to restore or move, cant get it to go to the USB stick.  Many thanks!

Hello,

With my SDS2104X HD I always take the screenshots with the web application on the PC.

Best regards
egonotto

And also a network client and server is available to directly share files over the network.

[rf-loop]

Make some movie....

you dont have to ask, that is his main job... we'll be waiting for it. i hope cover all the functionalities... including FFT plot shown here (if possible downloading data to PC) ymmv.

(Attachment Link)
Purchased wall wart linear regulated.

how can cheap wall wart linear regulated be this good? -80dB is like 100uVpp noise?

First just one note. Do you know how much is -80dB...   for hint. Just today in food store milk price was -50%   

But yes I can in this case guess that you mean dBV(rms) what is 0.1mVrms.

I'm too busy (and lazy) to start basic lectures about levels (in time domain and FFT). But I'll put one picture here, the content of which might be good and useful to think about.
(because now you know input signal and  it is not "unknown walmart"





In this picture there is two channels on.
Ch3 no signal (only 50 ohm termination) 5mV/div, full 200MHz BW
Ch4 input random noise 2mV Stdev from generator (and 50 ohm feed thru termination in scope input) Channel set for 5mV/div, full 200MHz BW
Only difference is that for visibility reasons I have adjusted time domain signals vertical position

FFT  both have all same settings, range 250Hz to 25MHz, window FlatTop, trace average 1024 (and even if no average at all, FFT (F4) peak level is roughly about -100dBV in this case. Vertical axis also same.
F1  FFT  Ch3 as base noise reference, all settings same as F2
F4  FFT  Ch4  Start 250Hz  and stop 25MHz

Time domain easurements:  Ch4 V Pk-Pk  and Stdev.  As can see signal is near 2mV AC rms (Stdev) and peak value about 18mV
And there can see Ch4 FFT(4) trace level between -105dBVrms  and -110dBVrms

[markone]

My fear is that I could find 7" display a bit uncomfortable being nowaday used to 10" DSO screens, so i was considering also the bigger model, but if they share same math performance i would consider the price gap a bit "steep" or, if you want, we can say that the smaller one is to be considered a real bargain

The 1000 series has an RTC, bigger screen, and 100Mpts per channel (compared to 50/ch on the 800). Only you can decide if that's worth the price difference. Either one is a bargain.

Correct me if I'm wrong, but I understood that also the SDS800X HD will gain 100Mpts per channel with the "free upgrade" procedure, so the almost triple price of SDS1104HD starts to be quite bitter to taste.

No, wrong.

100Mpts is total memory on SDS824xHD.
So 100Mpts for 1 ch, 50Mpts 2 ch and 25Mpts 3 and 4 ch

 

[Mechatrommer]

Time domain easurements:  Ch4 V Pk-Pk  and Stdev.  As can see signal is near 2mV AC rms (Stdev) and peak value about 18mV
And there can see Ch4 FFT(4) trace level between -105dBVrms  and -110dBVrms

2mV acRms is still -54dBV.. -110dBV is too good to be true. you dont need to do long lecture, enough with providing link. internet is one gigantic lecture hall.. https://www.everythingrf.com/community/what-is-dbv

[ebastler]

But yes I can in this case guess that you mean dBV(rms) what is 0.1mVrms.

I'm too busy (and lazy) to start basic lectures about levels (in time domain and FFT). But I'll put one picture here, the content of which might be good and useful to think about.
(because now you know input signal and  it is not "unknown walmart"

Alright, so Mechatrommer used "dB" instead of "dBV" by mistake. But we all saw the dBV units in whodiini's FFT screenshot he referred to, so I don't think this caused any confusion.

Now, we don't know whether it was a Walmart wall wart or not ,  but it was the output voltage from a cheap linear wall wart which whodiini measured. And I thought the surprise (to Mechatrommer and to me) was that its 60 Hz peak is only at -80 dBV.

That does translate to only 0.1 mV rms of 60 Hz ripple, doesn't it? Or am I missing something FFT-related here?
(Edit: 0.1 mV rms give or take, of course, considering spectral leakage depending on the window function used.)

[rf-loop]

But yes I can in this case guess that you mean dBV(rms) what is 0.1mVrms.

I'm too busy (and lazy) to start basic lectures about levels (in time domain and FFT). But I'll put one picture here, the content of which might be good and useful to think about.
(because now you know input signal and  it is not "unknown walmart"

Alright, so Mechatrommer used "dB" instead of "dBV" by mistake. But we all saw the dBV units in whodiini's FFT screenshot he referred to, so I don't think this caused any confusion.

Now, we don't know whether it was a Walmart wall wart or not ,  but it was the output voltage from a cheap linear wall wart which whodiini measured. And I thought the surprise (to Mechatrommer and to me) was that its 60 Hz peak is only at -80 dBV.

That does translate to only 0.1 mV rms of 60 Hz ripple, doesn't it? Or am I missing something FFT-related here?
(Edit: 0.1 mV rms give or take, of course, considering spectral leakage depending on the window function used.)

Think about what (noise) level there is seen (with this same noise signal level)  in FFT if Bin width is higher..
FFT Processing gain...


And as Mechatrommer said: 2mV acRms is still -54dBV..
Yes I will later give other image where FFT also display it   (nearly because my noise source is not good for this)

[ebastler]

Think about what (noise) level there is seen (with this same noise signal level)  in FFT if Bin width is higher..
FFT Processing gain...

And as Mechatrommer said: 2mV acRms is still -54dBV..
Yes I will later give other image where FFT also display it   (nearly because my noise source is not good for this)

Sorry, that did not help me understand. If there is a 60 Hz hum on that power supply's output, it will show up in the FFT, right? And the peak height should be -80 dBV for 100 µV rms of hum. (Or more, if there is noise on top of the hum.) So, FFT processing gain or not -- doesn't that screenshot by whodiini say that his supply has a maximum of 100 µV rms of mains hum, which is pretty darn good for a cheap wall wart?

[mawyatt]

Think about what (noise) level there is seen (with this same noise signal level)  in FFT if Bin width is higher..
FFT Processing gain...

And as Mechatrommer said: 2mV acRms is still -54dBV..
Yes I will later give other image where FFT also display it   (nearly because my noise source is not good for this)

Sorry, that did not help me understand. If there is a 60 Hz hum on that power supply's output, it will show up in the FFT, right? And the peak height should be -80 dBV for 100 µV rms of hum. (Or more, if there is noise on top of the hum.) So, FFT processing gain or not -- doesn't that screenshot by whodiini say that his supply has a maximum of 100 µV rms of mains hum, which is pretty darn good for a cheap wall wart?

Couldn't one use the 60Hz Mains Trigger and do waveform average feature to revel the 60Hz content and somewhat suppress the other "noises". This should "behave" like synchronous sampling with the benefits of such!!

Best,

[Mechatrommer]

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.

[ebastler]

Couldn't one use the 60Hz Mains Trigger and do waveform average feature to revel the 60Hz content and somewhat suppress the other "noises". This should "behave" like synchronous sampling with the benefits of such!!

I guess you could get even fancier and let the Math function do some synchronous demodulation. 

But there's nothing wrong with using the FFT, I think. I just did a quick test and it very nicely showed some residual -90 dBV hum at 50 Hz next to the -60 dBV at 60 Hz which I sent in from a function generator. I am just confused about rf-loop's messages, which seem to tell me that I am not supposed to trust those peak heights?

[rf-loop]

Think about what (noise) level there is seen (with this same noise signal level)  in FFT if Bin width is higher..
FFT Processing gain...

And as Mechatrommer said: 2mV acRms is still -54dBV..
Yes I will later give other image where FFT also display it   (nearly because my noise source is not good for this)

Sorry, that did not help me understand. If there is a 60 Hz hum on that power supply's output, it will show up in the FFT, right? And the peak height should be -80 dBV for 100 µV rms of hum. (Or more, if there is noise on top of the hum.) So, FFT processing gain or not -- doesn't that screenshot by whodiini say that his supply has a maximum of 100 µV rms of mains hum, which is pretty darn good for a cheap wall wart?

Remember we talk about noise.

If example FFT display 60Hz sinewave 2mVrms its level is displayed as 60Hz peak and level is -53.98dBVrms.
I think this do not need demonstrate. Just same for 3.7MHz sinusoidal continuous signal or example 145MHz signal.

But random (semirandom as was in my previous image)  noise...  it is bit different.

Here image where is same noise. (But far aways from real random white noise... this fake random noise BW is somehere around 60MHz...
But oscilloscope measure its average AC RMS (Stdev Mean) around 1.74 mVrms

But now, I have reduced amount of points in FFT down to 32pts. Now Δf=31.25MHz.  And there is marker what also display level... now roughly -54dBVrms... 
Also FFT start and stop changed because Δf.



Naturally there is, due to many reasons, errors in measurements including also that this test noise is really poor now for this setup...(look time domain) but still...
Not very far off... theory and this "poor practice" is still in same ballpark..  as can see not anymore -110dBVrms   but now -54

And now again, if we start rise FFT points ... this F4 trace level drops when amount of bins rise... until with 2Mpts FFT (and reduced samplerate) down to this what was in my previous image ( Reply #1182 )  where FFT Δf=59.6Hz and where this FFT trace was around -110dBVrms
But I think no need demonstrate how it behave...

[Mechatrommer]

Couldn't one use the 60Hz Mains Trigger and do waveform average feature to revel the 60Hz content and somewhat suppress the other "noises". This should "behave" like synchronous sampling with the benefits of such!!

FFT doesnt work that way, you only need to capture long enough samples to get higher resolution (smaller bins) doesnt matter where you start, FFT will output the same. but you could get lower noise by averaging FFT to nullify random noises. if you are talking about looking at time domain... uVpp range is not easy to see. but as rf_loop mentioned, the noise range is somewhere 2mVacrms (18-36mVpp?), then i have suspicion in FFT implementation (magnitude calculation) in sds800x scope, ymmv.

[gf]

Alright, so Mechatrommer used "dB" instead of "dBV" by mistake. But we all saw the dBV units in whodiini's FFT screenshot he referred to, so I don't think this caused any confusion.

Now, we don't know whether it was a Walmart wall wart or not ,  but it was the output voltage from a cheap linear wall wart which whodiini measured. And I thought the surprise (to Mechatrommer and to me) was that its 60 Hz peak is only at -80 dBV.

That does translate to only 0.1 mV rms of 60 Hz ripple, doesn't it? Or am I missing something FFT-related here?
(Edit: 0.1 mV rms give or take, of course, considering spectral leakage depending on the window function used.)

Hmm. Sorry, in the referenecd screenshot, I don't see a peak at 60Hz, but only 1/f noise. And it does not look like the PSU were linear, but rather a SMPS, with a switching frequency of ~60kHz (there may be a linear post-regulator, though). And at 60kHz, I don't see a single narrow "peak" either, but it rather looks like a spread spectrum centered at 60kHz.

Note that dBm or dBV units on the FFT scale make only sense for a sine wave or very narrow-band signals (narrower than the RBW).

OTOH, for a spread spectrum, you specify/measure power spectral density, as a function of frequency, using a unit like dBm/Hz, V²/Hz, V/sqrt(Hz), etc. and you need to integrate the power spectral density over a particular frequency range in order to calculate the total power (or RMS voltage) falling into this range. I guess that the total power falling into the (say) 10-100kHz range will be significantly more than -80dBV.

Btw, does anybody know whether the scope supports kind of channel power measurement, i.e. integrate the power between two frequency cursors in the FFT display?

[ebastler]

Hmm. Sorry, in the referenecd screenshot, I don't see a peak at 60Hz, but only 1/f noise. And it does not look like the PSU were linear, but rather a SMPS, with a switching frequency of ~60kHz (there may be a linear post-regulator, though). And at 60kHz, I don't see a single narrow "peak" either, but it rather looks like a spread spectrum centered at 60kHz.

Duh.   Maybe with all the focus on numbers I should not forget to read the letters too, e.g. the little "k"... Thanks for pointing that out.

Since whodiini introduced this as a linear wall wart output, I was totally set on observing a 60 Hz peak. But I agree now, it does look like a switching supply. Ok then, FFT works as expected, whodiini's supply is a pretty decent switcher, but otherwise no unsolved mysteries.

[rf-loop]

Btw, does anybody know whether the scope supports kind of channel power measurement, i.e. integrate the power between two frequency cursors in the FFT display?

Unfortunately not Channel Power function as are in SA:s.

[gf]

Btw, does anybody know whether the scope supports kind of channel power measurement, i.e. integrate the power between two frequency cursors in the FFT display?

Unfortunately not Channel Power function as are in SA:s.

I guess a Y scale in power spectral density units (like dBm/Hz, V²/Hz, V/sqrt(Hz), etc.) is not supported either, is it?
Or "noise markes", which specify density units?

[mawyatt]

Couldn't one use the 60Hz Mains Trigger and do waveform average feature to revel the 60Hz content and somewhat suppress the other "noises". This should "behave" like synchronous sampling with the benefits of such!!

I guess you could get even fancier and let the Math function do some synchronous demodulation. 

But there's nothing wrong with using the FFT, I think. I just did a quick test and it very nicely showed some residual -90 dBV hum at 50 Hz next to the -60 dBV at 60 Hz which I sent in from a function generator. I am just confused about rf-loop's messages, which seem to tell me that I am not supposed to trust those peak heights?

Technique mentioned above seems to work well, and is straight forward.

Best,

[mawyatt]

Any serious analytical scope should be able to do this, yet there are quite some instruments, even very expensive ones, that can not. The special feature of DSOs that I’m regularly recommending, like the ones from Pico and Siglent, is that you get such midrange features even in their low-end devices. Yet this task can be a bit tricky, see the comments below…

Regarding the speed, there are two aspects:

1. Signal Acquisition.

In order to capture enough data to properly analyze a 5 Hz modulation frequency, we need to capture more than 200 ms of the PWM signal. I have chosen one full second (100 ms/div) to capture five full modulation periods; yet I’ll only be able to display 2.5 periods because of some limitations in the Track plot implementation I did not set the correct horizontal track plot position.

2. Horizontal Parameter Measurement.

The number of measurements within a single record (AIM-limit) is 1000 by default and can be set to a maximum of 25000. For my example to work, we need to set it to at least 10000. The time for this is only a small fraction of the total acquisition time.


SDS824X HD_Track_PWM_20kHz_5Hz

The modulation is retrieved quite accurately; the update speed is 0.914 Hz ≈ 1.1 seconds per frame.

The automatic measurements show the statistics count of more than two million, which already hints on the 10000 measurements per record – it is exactly 10000 times the statistic count of the amplitude measurements, since the AIM-parameter was set to 10000.

The pulse amplitude is measured 608 mV (should be 600 mV), hence the combined tolerances of waveform generator and SDS824X HD (and cabling) are 1.33%.

The peak-to-peak measurement of 615 mV hints on negligible over/undershooting at the pulse edges.

The average positive pulse width is measured as 25.0019 µs (should be 25 µs), hence the combined tolerances of waveform generator and SDS824X HD are ~0.0076%.

The average positive duty cycle is measured as 49.99924% (should be 50%), hence the combined tolerances of waveform generator and SDS824X HD are ~0.01%.

From the Track Plot diagram, we can see that the duty cycle deviation is about 96% (should be 96%) and the modulation period is about 200 ms, corresponding to 5 Hz modulation frequency.

EDIT: Track Plot works as expected and displays the full number of modulation periods if set up correctly.

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.

Not going to replace a proper Demodulator, but handy in a fix

Edit: Added another plot showing an FSK signal centered at 455KHz with a 100Hz rate at 10KHz deviation. This plot shows the Time Domain Signal, FFT and Frequency vs Time plot all on the same screen at the same time!! Also another with 100Hz Sine & Triangle Wave FM Modulation.

Note the SD(rms) for the Square, Sine, and Triangler Wave modulations which should ideally be 1, 1/rt(2), 1/rt(3) times peak FM deviation (10KHz), or 10KHz, 7.07KHz and 5.77KHz respectively!!

Impressive little DSO/Instrument

Best

[2N3055]

Btw, does anybody know whether the scope supports kind of channel power measurement, i.e. integrate the power between two frequency cursors in the FFT display?

Unfortunately not Channel Power function as are in SA:s.

I guess a Y scale in power spectral density units (like dBm/Hz, V²/Hz, V/sqrt(Hz), etc.) is not supported either, is it?
Or "noise markes", which specify density units?

No unfortunately not, at the time. No PSD type of display or noise markers.