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| Performa01:
--- Quote from: tggzzz on April 09, 2023, 01:17:36 pm --- --- Quote ---The sample rate on the other hand has to be twice the max. input frequency in order to satisfy Nyquist. --- End quote --- No. Or rather the sample rate has to be at least twice the bandwidth of the signal to satisfy Nyquist[1]. --- End quote --- So you are saying "no", only to use the following sentence to repeat what I said in slightly different words? Oh – did I forget to say "at least"? In a statement where I wanted to stress the fact that oversampling doesn't provide any additional information? And what is the difference between "max. input frequency" and "bandwidth of the signal"? There is only a difference if we presume that we're not interested in the entire input signal, but only a part of it [1] – which certainly would not be a standard use case. --- Quote from: tggzzz on April 09, 2023, 01:17:36 pm ---I have a 1972 portable scope (which can be stored underwater!) which takes one sample every 75µs (i.e. 13kS/s), and has a bandwidth of >5GHz; it measures risetimes of <0.14ns. Back in the 80s I used a top-of-the-range HP 1GHz scope, which sampled at 25MS/s. Nowadays you can see that principle in action in various scopes with modes called various things like Equivalent Time Sampling, and in the mixer of every SDR dongle (multiGHz inputs sampled at ~10MS/s). --- End quote --- And what has this to do with the topic discussed here? The equivalent sample rate has to satisfy Nyquist no matter what. And thankfully, nobody has to resort to the ETS crouch for bandwidths up to a couple of GHz anymore nowadays. --- Quote from: tggzzz on April 09, 2023, 01:17:36 pm --- [1] Standard interview question... You have an audio signal transmitted on a 10MHz carrier. What is the minimum sampling rate you can use? --- End quote --- Funny that you feel like asking that question in reply to my post of all things. [1] I have demonstrated several times, how to analyze narrowband signals by means of down-conversion by undersampling, e.g. here: https://www.eevblog.com/forum/testgear/siglent-sds2000x-hd-12bit-(published-for-chinese-domestic-market-only)/msg4320658/#msg4320658 … so what was the intention of your reply? Just to say "no" … or did you want to add some confusion for those who are less familiar with modern DSOs? |
| nctnico:
--- Quote from: williamlee on April 09, 2023, 04:03:19 pm ---Is it because 99.9% of oscilloscope user doesn`t need the "eye diagram"? so, the sampling rate is quite ok for 1G or 2G? The "real-time" still belongs to the analog scope, right? why does the digital scope need the "sampling rate"? because of the "ADC"? My point of view that MSO5000 is the best C/P value for 90% of applications especially for logic is better value. It makes sure that SDS2000XP also good for the C/P value. ;D ;D --- End quote --- In the end neither a good allround tools though. --- Quote ---If the R/S, Tek, and LeCroy prices are very very close to Rigol and Siglent ... --- End quote --- then the latter would offer you good allround tools like the A brands. Engineering takes time which equates to money and thus their products will cost the same. Just note how Siglent oscilloscope prices keep going up with the number of features they add. While Rigol keeps competing on prices and releases half baked products hoping the revenue might pay for ongoing engineering efforts (or not). The differentiation is all in firmware / software, the hardware costs are pretty much the same for all manufacturers. |
| porter:
Too bad that Keysight and Tektronix oscilloscpes are no longer part of these discussions. |
| Martin72:
A nice short summary/explanation about the different types of sampling in DSOs (or DPOs) we can find here: XYZs of Oscilloscopes from Tektronix (It´s a pdf) |
| Martin72:
--- Quote from: porter on April 09, 2023, 05:30:29 pm ---Too bad that Keysight and Tektronix oscilloscpes are no longer part of these discussions. --- End quote --- In the mentioned pricerange it makes the same sense as talking about lecroy scopes. |
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