Products > Test Equipment
Siglent SDS1104X-E In-Depth Review
<< < (9/48) > >>
Performa01:

--- Quote from: maxwell3e10 on February 18, 2018, 12:44:47 am ---Thanks, Performa01, for a very detailed review. I am trying to figure out the input noise of the scope from your data, section 3 of the review.

When I look at figure on page 64 I would estimate that +/-2 sigma level is about 1 division, so the RMS noise is 125 uV. When I look at RMS noise on the plot on page 67, 16 LSB corresponds to 16*0.5mV*10/250 =  320 uV.

I am wondering if the RMS noise estimate on page 67 comes from the RMS measurement on the scope? In that case it can include the offset as well. It would be interesting to find the standard deviation of the data with shortened input.


--- End quote ---

You are perfectly right that RMS measurements always include the DC offset error, which has been around 10 LSB at that particular time, as can be seen in the graphs on page 66. Unfortunately, I tend to forget that and the data in the graph on page 67 comes from the automatic RMS measurement indeed.

Thanks a lot for the hint!

Here is an example for 1µs/div with the correct measurement included:


SDS1104X-E_Noise_1us_500uV

Regarding the scope input termination, it makes no difference whether it is shorted or left open. A high voltage tolerant amplifier with its clamp protected high impedance input network cannot be low noise anyway, so the noise of the source impedance is absolutely negligible. Yet I’ve fitted a 50? through termination just to make the input insensitive to electrical noise that might be generated within my lab.

I will update the noise graph for the next revision of my review document, but here is a preliminary version as an immediate “hot fix”:


SDS1104X-E Noise_vs_time BW_full


So we’re actually talking about a noise level of 39µVrms @ 1ns/div slowly increasing up to 68µVrms @ 1ms/div. I’ve also taken more time to determine the exact mean pk-pk noise level and as can be seen, it is a much smoother trace now.

Finally, I’d also like to show the absolute horror scenario for any general purpose scope input, i.e. 100ms/div, which should be equivalent to a lower noise bandwidth limit of <1Hz:


SDS1104X-E_Noise_100ms_500uV

Now we have 705µV pk-pk noise, but rms noise is even lower (compared to 1ms/div) at 64µV. That’s most likely because the sample rate has now dropped to 10MSa/s (whereas it still was 1GSa/s at 1ms/div) and quite obviously the aliasing caused by the noise above 5MHz does not have much impact for a number of reasons.
maxwell3e10:
Thanks for quick measurements!

I wouldn't trust the rms noise for very short time scale (1 ns/div), because its beyond the bandwidth of the scope, so the data are largely correlated. The flat level of 60 uV rms is more representative of true noise.

As tautech points out, its also important to compare the BW. On many scopes the 1 mV/div scale is BW limited by default to 20 MHz, so for fair comparison it would be good to know the noise level on 20 MHz BW setting.
Performa01:

--- Quote from: rigol52 on February 16, 2018, 12:31:28 pm ---Thanks.
Not really happy with such facts which lead to changing lab equipment (seems along with my nick name),
bu what to do - world is not perfect.
Still very impressed with capability of here reviewed scope taking into account its price/performance outcome.

--- End quote ---

Yes, I know it’s a pity and I also don’t like to change an instrument that does the job and that I’m used to. But you just cannot expect instruments from different manufacturers to remote control each other.

There is no universal standardized protocol to remote control signal generators (or any other instruments). It is sometimes not even the same for all instruments of the same class within one brand. So it’s no big surprise that T&M companies don’t make an effort in supporting instruments from competing brands, except when they have been established as a (quasi) industry standard.

You can only combine devices from any brands you like when you write your own application (on a PC) and remote control all instruments involved. By doing this, the many pitfalls associated with controlling instruments for a more complex application like network analysis will become clear quite quickly – apart from the fact, that it is way more efficient if that application runs directly on the instrument that has to do the majority of the work, i.e. the DSO in this and most other cases.
Performa01:

--- Quote from: maxwell3e10 on February 18, 2018, 06:02:15 am ---Thanks for quick measurements!

I wouldn't trust the rms noise for very short time scale (1 ns/div), because its beyond the bandwidth of the scope, so the data are largely correlated. The flat level of 60 uV rms is more representative of true noise.

As tautech points out, its also important to compare the BW. On many scopes the 1 mV/div scale is BW limited by default to 20 MHz, so for fair comparison it would be good to know the noise level on 20 MHz BW setting.

--- End quote ---

Well, even though the SDS1104X-E is only a 100MHz scope, the figures get much better with the 20MHz bandwidth limit. Here’s the graph:


SDS1104X-E Noise_vs_time BW_20M


And here’s a screenshot for 1µs/div:


SDS1104X-E_Noise_1us_500uV_BW20M
tautech:

--- Quote from: Performa01 on February 18, 2018, 06:49:49 am ---Well, even though the SDS1104X-E is only a 100MHz scope, the figures get much better with the 20MHz bandwidth limit.

--- End quote ---
Dots or vectors ?
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod