Products > Test Equipment
Siglent - 11/20 - New SDS1104X-U, 4 channel 100MHz, 1Gsa/s economy oscilloscope
tautech:
New firmware for SDS1104X-U.
Version: V1.1.5R6
8.3MB
https://int.siglent.com/upload_file/zip/firmware/Oscilloscope/SDS1104X-U_1.1.5R6_EN.zip
Release notes
Support EasyScopeX
rf-loop:
--- Quote from: tautech on March 07, 2021, 08:47:34 am ---Talk about cutting it fine :phew: .....finally got around to checking the SDS1104X-U BW after spotting Defpom reporting is as only a little over its rated 100 MHz BW and indeed it just barely makes spec.
Source SDG6022X
Sweep 0-200 MHz
-3dB point ~103 MHz
--- End quote ---
Because oscilloscopes are individuals and also test setups. Here other same kind of test. Note that BW shape looks bit better.
-3dB >110MHz But -1dB point clearly higher.
Used short RG316 and 50ohm feed thru and signal source also some SDG6kX
It is very good BW is rejected to just over 100MHz because fNyq. 125MHz and oscilloscope type of Sinc interpolation need some "free air" before Nyquist wall. Less aliasing = better trusted measurements with unknown signals. Even -6dB point is far over fNyquist leading strong aliasing. But, this is entry level cheap scope and this happen only if 3 or 4 channels simultneously in use. With 2 channels in use fNyq. is 250MHz and 0.8fNyq is 200MHz where attennuation is ok in this class. But still user need know FFT may display quite strong aliases. If need avoid these, then need use external LPF. (and for digital filters fanboys, digital filter do not know if signal after ADC is alias or not, they do not have any label "hey I am alias"... only good (and expensive) place for filter is before ADC. )
(you see small unsymmetry so -3dB is not just as cursor 11.52 (115MHz) reading is. True is bit below.
Sidenote. Why I use this trigger mode and settings. Because it trigs rock solid even when I attenuate signal down to -12dB from sweep start reference level. So I do not need adjust trigger when I change level in wide range.
If this scope BW -3dB point is even bit higher I recommend modify its front end for more narrow BW or Siglent implement to FW some warning message about possible aliasing when 3-4 channels is in use, because its analog BW violates Nyquist-Shannon.
mawyatt:
--- Quote from: rf-loop on May 12, 2021, 11:38:42 am ---If need avoid these, then need use external LPF. (and for digital filters fanboys, digital filter do not know if signal after ADC is alias or not, they do not have any label "hey I am alias"... only good (and expensive) place for filter is before ADC. )
--- End quote ---
This is conventional thinking, requiring an analog antialiasing filter before ADC which can get quite involved depending on how close to Nyquist and what post ADC signal degradation is acceptable. A good example of these analog filters was in the original Sony CD players before oversampling was later introduced. This analog filter had to suppress almost 100dB at 1.1 band transition (22KHz/20KHz) which later oversampling relaxed considerably. Recall analyzing this Sony analog anti-aliasing filter, which used polystyrene precision caps, bobbin wound air-core inductors, and complex active circuitry to keep the aliasing and distortion over 100dB down!! Our interest wasn't for audio, but we were dealing with signals that needed to be preserved with over 100dB fidelity, and aliasing and distortion posed a similar issues. The Sony filter was indeed a work of engineering art :-+
Over a decade ago advanced research work at USC produced a completely new and different type ADC where the waveform being observed creates it's own Nyquist limit. This ADC was called Non-Uniform Sampling (NUS) ADC and had the unique feature of sampling the input waveform in both amplitude and time, which produced a result that was in fact post processed with antialiasing filters in the digital domain, so the waveform did sort of say "hey I am alias"... :)
This was all part of an advanced research project that involved break-thrus in multiple disciplines, and back in ~2012 seeing a 1GHz signal sampled by the NUS ADC with stunningly good results and thinking, "this would make a superb ADC for a RTSA or DSO". Keysight was very interested in this NUS ADC, so maybe we may see these trickle down to our instrumentation world soon ::)
Best,
tv84:
--- Quote from: tautech on May 12, 2021, 05:17:51 am ---New firmware for SDS1104X-U.
Version: V1.1.5R6
8.3MB
https://int.siglent.com/upload_file/zip/firmware/Oscilloscope/SDS1104X-U_1.1.5R6_EN.zip
Release notes
Support EasyScopeX
--- End quote ---
This is PRODUCT_ID 17001.
QuitButton:
Have I got this right or am I missing something here? Timebase of 2ns, I only get 28 samples. (or 14 or 7 with other channels on)
Is that the limit or anyway of increasing the number?
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