Products > Test Equipment
Building my own scope
tggzzz:
--- Quote from: Mechatrommer on October 24, 2022, 09:13:42 pm ---because generally when a person want to build a diy dso implicitly means the real-time one. a person will come with building a "sampling" scope in the topic when he knows what he is talking about. and nobody will recommend newbies asking about buying a new scope to buy a "sampling" scope.
--- End quote ---
Er, newbies are routinely recommended to buy a sampling scope.
You, at least I think it was you, previously ignored the point that all modern scopes (e.g. the Rigol DS1054) tale samples of the input signal. You can even look and see the individual samples on the display, presuming you can navigate the menu system to find the right config parameter.
rob77:
--- Quote from: tggzzz on October 24, 2022, 10:53:46 pm ---
--- Quote from: Mechatrommer on October 24, 2022, 09:13:42 pm ---because generally when a person want to build a diy dso implicitly means the real-time one. a person will come with building a "sampling" scope in the topic when he knows what he is talking about. and nobody will recommend newbies asking about buying a new scope to buy a "sampling" scope.
--- End quote ---
Er, newbies are routinely recommended to buy a sampling scope.
You, at least I think it was you, previously ignored the point that all modern scopes (e.g. the Rigol DS1054) tale samples of the input signal. You can even look and see the individual samples on the display, presuming you can navigate the menu system to find the right config parameter.
--- End quote ---
just stop it , seriously... twisting everyone's words and spreading bullcrap....
now you suggest that every DSO is a sampling scope because they take samples ? :-DD
it's you who spreads half truth statements and derails the discussion in this thread.
it was you who stated sample rate and bandwidth are independent without context , which is half true
it was you who stated that cheap sdr dongles are sampling 2GHz... that's a misinformation... those have have a tuner outputting a much lower IF and that IF is sampled...
it was you who suggested to delete a FPGA and do discrete control for ADC and let the computer take data on it's convenience...when i asked you how exactly you would implement your "idea".. you just mumbled some generic stuff and steered away...
you might be a knowledgeable expert but that doesn't mean you can't be an trolling a-hole at the same time :-DD
tggzzz:
--- Quote from: rob77 on October 24, 2022, 11:32:58 pm ---
--- Quote from: tggzzz on October 24, 2022, 10:53:46 pm ---
--- Quote from: Mechatrommer on October 24, 2022, 09:13:42 pm ---because generally when a person want to build a diy dso implicitly means the real-time one. a person will come with building a "sampling" scope in the topic when he knows what he is talking about. and nobody will recommend newbies asking about buying a new scope to buy a "sampling" scope.
--- End quote ---
Er, newbies are routinely recommended to buy a sampling scope.
You, at least I think it was you, previously ignored the point that all modern scopes (e.g. the Rigol DS1054) tale samples of the input signal. You can even look and see the individual samples on the display, presuming you can navigate the menu system to find the right config parameter.
--- End quote ---
just stop it , seriously... twisting everyone's words and spreading bullcrap....
now you suggest that every DSO is a sampling scope because they take samples ? :-DD
--- End quote ---
You do realise how stupid that sentence is, don't you?
Could you please point us towards a DSO that doesn't sample the inputs?
--- Quote ---it's you who spreads half truth statements and derails the discussion in this thread.
it was you who stated sample rate and bandwidth are independent without context , which is half true
--- End quote ---
They are independent, in theory and in practical instruments and products that you can go out and buy. I've given examples.
--- Quote ---it was you who stated that cheap sdr dongles are sampling 2GHz... that's a misinformation... those have have a tuner outputting a much lower IF and that IF is sampled...
--- End quote ---
The "tuner" (as you call it) is a mixer and that is doing the sampling. That's precisely how the Tayloe/PolyPhase mixer in SDR dongles work!.
The output of the Tayloe/PolyPhase mixer is then sampled (and digitised) at a much lower rate, usually a few MHz.
You appear to be confusing the sampling in the mixer with the digitisation sampling rate.
FFI you can enlighten yourself with the info in this thread: https://eevblog.com/forum/rf-microwave/polyphase-or-n-path-mixer/ Be warned that it isn't easy reading, and many people find it is counter-intuitive. Alternatively the "ARRL Handbook for radio communications 2014" has a brief description and a practical circuit in section 10. I imagine it is also in other ARRL Handbooks.
--- Quote ---it was you who suggested to delete a FPGA and do discrete control for ADC and let the computer take data on it's convenience...when i asked you how exactly you would implement your "idea".. you just mumbled some generic stuff and steered away...
--- End quote ---
Well, I certainly haven't got time to (poorly) explain the basic theory here; a textbook will do a much better job.
As for designing an implementation, I doubt the OP wants that. If he did then I would discuss the commercial terms.
--- Quote ---you might be a knowledgeable expert but that doesn't mean you can't be an trolling a-hole at the same time :-DD
--- End quote ---
Can I suggest your being a little less sure that you know and understand the theory and practice.
Mechatrommer:
--- Quote from: rob77 on October 24, 2022, 11:32:58 pm ---just stop it , seriously... twisting everyone's words and spreading bullcrap....
--- End quote ---
i know the problem now. he is a literalist and want to stick with terminology when it was first appeared some 80 years ago. let the old man give his point of view, we only need to know his dictionary to come to an agreement.
David Hess:
--- Quote from: rob77 on October 24, 2022, 06:35:04 pm ---synchronous sampling ... isn't that called logic analyzer ? ;)
--- End quote ---
Logic analyzers can operate synchronously or asynchronously.
--- Quote from: tggzzz on October 24, 2022, 10:53:46 pm ---
--- Quote from: Mechatrommer on October 24, 2022, 09:13:42 pm ---because generally when a person want to build a diy dso implicitly means the real-time one. a person will come with building a "sampling" scope in the topic when he knows what he is talking about. and nobody will recommend newbies asking about buying a new scope to buy a "sampling" scope.
--- End quote ---
Er, newbies are routinely recommended to buy a sampling scope.
You, at least I think it was you, previously ignored the point that all modern scopes (e.g. the Rigol DS1054) tale samples of the input signal. You can even look and see the individual samples on the display, presuming you can navigate the menu system to find the right config parameter.
--- End quote ---
DSO stands for digital storage oscilloscope distinguishing it from digital sampling oscilloscope. The later term was almost never used, but does refer to a specific type of instrument which is not a DSO.
Nothing requires a digital storage oscilloscope, or any ADC or digitizer, to use sampling, and when they do use sampling, it is *not* the same type of sampling that a sampling oscilloscope uses. Datasheets tend to no longer distinguish them, but ADCs are available in sampling and non-sampling varieties. Going back to the beginning of DSO evolution, the Tektronix 468, 2230, and 2232 all use non-sampling ADCs, however the 2230 included a discrete sampling unit before its 20 MHz flash ADC, and the 2232 included integrated samplers before each of its 100 MS/s flash ADCs. None of these worked the same way as the sampler does inside of a sampling oscilloscope. These were digital storage oscilloscopes.
The sampler in a sampling oscilloscope operates with a strobe which is *shorter*, often a lot shorter, than the acquisition time needed to charge the storage element. This means that either the storage element must be reset between samples or the output is based on both the old and new value, which is where sampling gain come into play. By requiring only a fraction of the charge to be transferred, the "sampler" has gain which can be applied to increase its bandwidth. (1) (2)
The distinguishing feature of a sampling oscilloscope is that sampling occurs first in the signal chain. Gain is applied after sampling in the analog domain. This means that bandwidth is determined entirely by the the sampling strobe width, which also produces a non-linear frequency response, so the 0.35 rule does not apply. One advantage of this besides predictable frequency response, is instant overload recovery. Overload never gets past the sampler so nothing needs to recover.
(1) Nobody is saying how modern integrated ADCs do their sampling for high bandwidth. An internal 50 ohm termination results in a 25 ohm source impedance to charge the sampling storage element which sure doesn't seem like enough for the bandwidth they achieve.
(2) I am describing the sampler needed for random sampling which is the more general case. The sampler in a sequential sampling oscilloscope can operate with a gain of 1 by repetitively sampling the same point of a waveform.
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