Products > Test Equipment
buy a better oscilloscope than the Siglent SDS1104X-E
rf-loop:
Here is one quite old image. At this time I own one Rigol 1074Z (mod to 1104Z)
In upper part of image (Rigol) there is also note about data used to measurements, today we know more also about this and it really use very extremely tiny intermediate buffer for measurements when Siglent use full acquisition data.
And then bottom part of image Siglent SDS1104X-E. Settings as same as possible what was used with Rigol for fair compare.
1mV/dif used because Rigol did not have 500uV/div. (also 1mV/div in Rigol is not true full resolution, it is some kind of production from 5mV/div)
Around 60uV AC RMS (Stdev) is quite good for 100+ MHz bandwidth with 1Mohm inputs.
Typically it is much better than service manual "go to repair" limit.
This is many years old..
Also I have measured several SDS1104X-E and I really can say that common value at 500uV/div is between 50 - 65uV/div Stdev (AC RMS)
Performa01:
--- Quote from: uargo on August 18, 2023, 08:47:52 pm ---I have put the FFT in the table, look well,
--- End quote ---
Well, yes, I've overlooked it in this messy table. FFT is normally characterized in points, not bytes and there are still some other parameters to consider.
Btw, your table contains a Siglent SDS1104X HD - a scope which doesn't exist outside China. Currently, nobody will be able to tell you what exactly we (the rest of the world) will be getting. However, I can assure you that it will be worth waiting for - if you really need a high resolution oscilloscope and don't mind a clumsy solution for the digital channels, like on the SDS1104X-E.
--- Quote from: uargo on August 18, 2023, 08:47:52 pm ---I have been researching on the internet to obtain the background noise of the SDS1104X-E and the only thing I have found is that it is:
Table 8 Noise Floor Limited Range for 2-Channel
Volt/Div Stdev Limited Range
500 uv ≤ 250 uv
link:https://int.siglent.com/upload_file/user/SDS1000X-E/SDS1000X-E_ServiceManual_SM0101E-E01A.pdf
--- End quote ---
This is a generic tolerance window for all SDS1000X-E series scopes, including the 200 MHz models, which have an actual bandwidth of ~240 MHz (SDS1104X-E: 110 MHz). The margins are wide; even though the SDS1000X-E are low noise like all contemporary Siglent scopes, Siglent quite obviously isn't willing to guarantee this for their bottom entry level scopes.
--- Quote from: uargo on August 18, 2023, 08:47:52 pm ---and where do you get that it has 56uVrms ( better even than the $4,600 12-bit 350Mhz SDS2354X HD which has 70uVrms)
--- End quote ---
Quite simple. I've measured it.
--- Quote from: uargo on August 18, 2023, 08:47:52 pm ---It is clear that my oscilloscope and yours, even though they are the same model, have different characteristics.
--- End quote ---
No. In theory, there could be slight differences, but since it's an easy task, many people have measured the noise of their SDS1000X-E and there never has been any significant discrepancy.
Hint: a 200 MHz device should show about 50% more noise, i.e. about 84 µVrms.
Martin72:
--- Quote from: Martin72 on August 18, 2023, 10:02:36 pm ---At the moment I let the SDS1104X-E warm up for it...
--- End quote ---
Did it now, "yesterday" it was too late...
@uargo:
Important is to make a selfcal before, pic 1 shows the traces after switching the scope on.
Then warmup for appx 30min, then let the scope performing the selfcal, pic 2 show the result after.
Took channel 2, 500µV/div., 1ms/Div., no shielding at all, no averaging.
Performa01:
--- Quote from: Martin72 on August 19, 2023, 12:25:56 pm ---
--- Quote from: Martin72 on August 18, 2023, 10:02:36 pm ---At the moment I let the SDS1104X-E warm up for it...
--- End quote ---
Did it now, "yesterday" it was too late...
--- End quote ---
A few remarks:
* Even more important than the total bandwidth is the lower bandwidth limit, due to the 1/f noise characteristics. At 1 ms/div the lower bandwidt limit is ~70 Hz on an SDS1000X-E. This will of course yield significantly worse results than a measurement at e.g. 1 µs/div and ~70 kHz lower bandwidth limit. We can also take the current record length as a criterion (and 1.4 Mpts is a massive amount of data), but specifying the lower bandwidth limit is a much more robust statement.
* It has been mentioned over and over again: RMS is the wrong measurement for noise. If we use Stdev instead (on some DSOs it's called AC-RMS), then we need not worry about DC offsets and neither have to wait half an hour nor do a self-cal just because we want to measure noise. Apart from that, even with a fresh self-cal there will still be some remaining offset error which will be erroneously interpreted as noise when using the RMS measurement.
* Many scopes do not have 500 µV/div sensitivity (some even have only 4 or 5 mV/div and use digital zoom to fake higher sensitivity). So I recommend to use 1 mV/div throughout. It's a more fair comparison because of a near identical dynamic range for all contenders and it is visually better comparable as well.
* Your measurement appears to be in the right ballpark (61 µVrms) for full bandwidth, which could easily drop to 56 µVrms once you use the right measurement (Stdev).
* Your measurement with 20 MHz bandwidth limiter appears much too high (55 µVrms), where I have no other explanation than that is caused by an DC offset error. It would be nice to see a Stdev measurement to confirm my theory.
* Finally I want to repeat what rf-loop already mentioned: The Siglent always measures the entire record, hence 1.4 Mpts is this example. "Measurements" that only use decimated (screen) data will just provide street numbers, because decimation alters the bandwidth.
Martin72:
--- Quote ---A few remarks:
--- End quote ---
;)
Can repeat it with the wanted parameter.
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