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| Siglent SDS2000X Plus Bandwidth & Aliasing Application Note |
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| Performa01:
I've only very lightly touched the topic of probing in my document: --- Quote ---High bandwidth can also have its drawbacks. We need better probes alongside with better probing techniques, better cables and connectors – which all sums up in additional cost and effort. This deserves more and more attention at increasingly higher frequencies. --- End quote --- The article was not intended as a tutorial for high-speed probing, but to show the capabilities as well as the limits of a modern upper entry level instrument like the Siglent SDS2000X Plus series. We need to know what our tools can do for us in the first place, then we can look into a proper probing solution. For me personally the 50 ohms probing is quite a natural thing. It is far better to design some 50 ohms test ports into the prototype in order to get easy access to the strategic important signals and limit the fiddling with probes to the less important signals that need not be accessed that often. One goal was to establish some basic understanding what really dictates the required bandwidth – after all I've experienced "professionals”, also here in the forum, who seriously claimed that digital oscilloscopes are crap, because a 50 MHz square wave didn’t look square at all on a 100 MHz DSO… (…and then there’s also the fact that this of all things would not be any different on their beloved old CRO) Taking this one step further, the fundamental frequency is almost completely irrelevant if a close representation of the real signal is of any importance. This has been demonstrated by using a 10 MHz pulse, which requires at least 1 GHz bandwidth (a hundred times the fundamental frequency!), just because it has fast 500 ps edges. Of course, the spectrum extends to even higher frequencies, but everything below some -40 dBc becomes irrelevant – at least for an 8-bit DSO. In the vast majority of applications, it should not matter whether a pulse overshoot is measured as 2 % or 1.5 % - or even 3 % for that matter, so the -40 dBc figure should give plenty of margin, even on a 12-bit DSO. We just don’t want to see a significant overshoot from the scope itself when fed with a signal spectrum within its bandwidth. Regarding my 500 ps tests, other than for 1 ns and above, I do not have a perfect signal available; all overshooting came from the signal source, as is confirmed by the reference measurement on the 2 GHz scope. |
| mawyatt:
Something useful for those without a proper fast edge sub-nanosecond pulse generator is the inexpensive RF Signal Source based upon the ADF4351 chip. This is much better than the kludge avalanche transistor junction we were using before!! Someone else posted this on another thread which I can't locate, so maybe they'll spot this post and take credit. These are handy little sources than operate from USB, shown below being USB battery powered. Here's the response of an "Enhanced" SDS2104X+, enhanced to 500MHz which also has the 500ps/div sweep extension. Note the screen capture is shown as SDS2504X Plus. Best, |
| blurpy:
Since there is some confusion about the model name, it's been discussed before: https://www.eevblog.com/forum/testgear/siglent-sds2000x-plus-coming/msg3088181/#msg3088181 Performa01 likely has an old configuration file from before Siglent officially added 500MHz model name. |
| trp806mo:
--- Quote from: 2N3055 on January 06, 2022, 10:43:09 am --- Now support, services and consulting is the primary product. Equipment is only there so they have an object as an anchor to sell you the services for it. That will (and already has) mean that they will ignore all market segments (customers and products) that does not have potential for large volume of services and paid support. That means all low and mid range equipment, small business etc etc.. --- End quote --- +1 and more when you read the topic https://www.eevblog.com/forum/testgear/keysight-officially-lost-the-plot-dont-buy-if-youre-a-hobbyist/msg3865562/#msg3865562 Currently if I'm not able to spend at least 50K€ of"service/hardware" every year I have the same service as 10 years ago when I were a private person with a 1K€ old stuff. |
| Johnny B Good:
--- Quote from: tautech on January 05, 2022, 08:54:56 pm --- --- Quote from: knudch on January 05, 2022, 08:18:37 pm --- --- Quote from: Performa01 on January 05, 2022, 07:08:11 pm --- --- Quote from: bdunham7 on January 05, 2022, 06:24:47 pm --- --- Quote from: Performa01 on January 05, 2022, 05:59:10 pm ---There is no such thing as an SDS2504X Plus: --- End quote --- What does your scope identify itself as in the system menu? --- End quote --- Unsurprisingly it says: "SDS2354X Plus". The model name in the screenshots also comes from the scope itself. --- End quote --- My SDS2104X+ with "features" say SDS2504X plus in system menu --- End quote --- Yes, AFAIK SDS2354X+ with the 500 MHz BW SDS2000XP-4BW05 option applied should display SDS2504X+ in the system menu. Maybe other members need also confirm this. --- End quote --- I upgraded my SDS2104X+ to the 500MHz BW option over a year ago (mid 2020), initially landing up with the serial number showing a series of xs in place of the original and I think the displayed model number showed as SDS2354X+ (I'd done the upgrade in steps) until a couple of the forum members provided the required keycode to restore my 'scope's original serial number which also changed the displayed model number to correctly reflect the 500MHz BW upgrade (or not - see edit below). The xxxxx serial number was, iirc, a Siglent testing mode. If you've upgraded to the 500MHz BW but the model number isn't being displayed as SDS2504X+, I'd expect your 'scope would be displaying a series of xs in place of the original SN (or not - see below). [EDIT] I may be conflating the destroyed SN issue with a different issue to the one relating to the failure of the 500MHz BW update to correctly update the model number. This was seemingly a typographical error in a cfg file which Siglent corrected in a later version as reported by tv84 here: https://www.eevblog.com/forum/testgear/siglent-sds2000x-plus-coming/msg3088181/#msg3088181 |
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