Products > Test Equipment
True analog scopes
2N3055:
--- Quote from: Sherlock Holmes on December 13, 2022, 01:10:17 pm ---
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1st: on CRT scope you can only see what you see on a screen with your eyes. Noise that is too small to see cannot be seen..
2nd: noise is noise. Digital, analog, periodic, stochastic. It is garbage added to our signal in process of measurement.
3rd: if noise is smaller than what you can resolve on screen it doesn't exist for that particular purpose.
4th: no, you cannot see to more than 8-9 bit of resolution on analog scope. It doesn't have perfect focus, and screen is too small
5th: no you cannot see 16bit quantization noise while looking at screen with full range signal on it (as analogous to CRT scope). You don't have screen with 65536 pixels vertically. 12 bit is 4096 pixels vertically.
Only reason you can "see" quantization effects is that you have digitized data in numeric format where you can easily look at 5th decimal and say "look there is a step".
Make an experiment: create 8, 10, 12 and 16bit sinewave as an array (in any software) and then plot them on screen.
You will see what I mean.
precaud:
Besides familiarity and ease of use, there are two main reasons why I still keep a Tek analog scope on the bench:
7CT1N curve tracer plugin
7A22 diff amp
I'm still waiting for a DSO maker to offer anything remotely as useful as these two plugins.
Mechatrommer:
--- Quote from: Sherlock Holmes on December 13, 2022, 12:13:56 pm ---Yes, really. Didn't you know? if you convert an analog voltage to a digital representation of that voltage, you'll introduce quantization noise. If you actually watch that video, you'll see he's not talking about quantization noise.
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agree it is there, but i mean on which part quantization noise is visible there on the screen? or when it matters?
Sherlock Holmes:
--- Quote from: Mechatrommer on December 13, 2022, 01:50:03 pm ---
--- Quote from: Sherlock Holmes on December 13, 2022, 12:13:56 pm ---
--- Quote from: Mechatrommer on December 13, 2022, 10:34:13 am ---
--- Quote from: Sherlock Holmes on December 12, 2022, 09:59:30 pm ---Well, there's zero quantization noise, so I was wandering if some applications find that important?
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oo weally? can you differentiate white noise vs black noise? analog vs digital noise? english noise vs asia noise? have you heard about sinc(x)?
https://www.tek.com/en/support/faqs/why-does-my-digital-oscilloscope-have-more-noise-then-my-analog-oscilloscope
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Yes, really. Didn't you know? if you convert an analog voltage to a digital representation of that voltage, you'll introduce quantization noise. If you actually watch that video, you'll see he's not talking about quantization noise.
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agree it is there, but i mean on which part quantization noise is visible there on the screen? or when it matters?
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That's the question I'm asking! That's what the OP is asking, when/why/if would an analog scope ever be preferable to a digital one, try answering rather than asking me my own question!
tggzzz:
--- Quote from: JPortici on December 13, 2022, 01:03:39 pm ---
--- Quote from: tggzzz on December 13, 2022, 12:43:05 pm ---Spectrum analysis and allied measurements are a good counter-example.
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but we're talking about scopes here :) correct me if i'm wrong, but in the frequency domain we use intruments that downconvert a portion of the spectrum so it can be acquired with low samplerate / high resolution converters (unless the bandwidth of interest is low enough that direct sampling can be used such as in audio analyzers) so in theory the quantization noise can be lowered enough to be lower than the noise
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That's one type of spectrum analyser; there are others. One keyphrase used by HPAK is "dynamic signal analyser", e.g. https://www.keysight.com/us/en/product/35670A/fft-dynamic-signal-analyzer-dc1024-khz.html
Many scopes now have an option to post-process captured samples using an FFT. Limitations (compared with "RF" SAs) are linearity and quantisation leading to spurious spurs.
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