Products > Test Equipment
Should I buy a Rigol MSO5000?
Anding:
For making VLF antennas it's basically just a case of adding or removing capacitors until resonance is found at the desired frequency, typically 20-100 kHz. And you only do it once. As long as an amplifier is stable then relative readings are enough. Granted it's a different amplifier module though.
2N3055:
--- Quote from: Fungus on October 27, 2022, 10:15:59 am ---
--- Quote from: Martin72 on October 27, 2022, 05:25:32 am ---Reminder.....
--- End quote ---
Here's a picture of what your sock puppet says is too complicated/fiddly/generally impossible to do:
All the guy did was insert the cheapest, cheap-ass $3(plus shipping) Aliexpress amplifier into his signal path and the pink trace turned into the yellow trace.
There was no fiddling or messing around, just connect it up and it works. In this case it was inserted in the path of an AWG.
I don't know what more "proof" anybody could ask for.
--- End quote ---
Dear Fungus,
Now I see you don't understand what we are talking about. I apologize for not being clear enough.
Yes we can see some scope screen and some waveforms.
But that is exactly the point: you see something on a screen.
And if all you need is to see if, for instance, you have clock on some pin it is fine like that.
But in that case even the original signal representation by noisy MSO5000 would be enough for GO/NoGO check.
But scope is not just used for scope art. We need to measure things. We need to see if signal is distorted.
We need to verify amplitude.
For that amplifier needs to be calibrated, it needs to have standardized input and output impedance. We need to have it
characterized for bandwidth, distortion, phase distortions..
When that "amplifier" is part of scope itself all that stuff is already done by scope manufacturer and included in scope specifications and calibrated.
Also since when you have a scope that has minimum 5mV/div, from that to 500uV there are 3 amplification steps missing (2mv, 1mv, and 500uV div). Are you going to have 3 different amplifiers? For what bandwidth? What input imepedance? Those 5 USD amplifiers are RF amps. They are 50Ω (they should be but nobody know if they are and what it's real impedance is, you need a VNA to measure it). They don't go to DC. You might find an amplifier that is high impedance (1MΩ//some pF) but with what BW? Is that one DC too?.
So, if you have a lab with several thousands worth of other equipment you might characterize and use your own preamps for specific purpose. And that is actually done all the time. People make custom preamps for specific purpose too.
But none of that is "replacement of fix" for scope limited range. It is an application specific thing that takes a lot effort and knowledge to be done right. None of it is "just throw in a preamp". And you might need dozens of different preamps and all the stuff that goes with it.
Fact is, and that is what I said before but it was not registered, there are oscilloscope preamplifiers. Basically those are scope front ends (the high sensitivity low noise ones, some even differential) with all the needed parameters already sorted out. Those can be (and are) used to purpose you are advocating. Problem with those is they cost so much, it is cheaper to buy SDS2354X HD (12 bit low noise one) than one of these fancy preamps.
Fungus:
--- Quote from: 2N3055 on October 27, 2022, 11:58:40 am ---And if all you need is to see if, for instance, you have clock on some pin it is fine like that.
--- End quote ---
Are you seriously saying I'm telling people to use an amplifier to see if there's a clock on a pin?
--- Quote from: Anding on October 27, 2022, 11:19:39 am ---All I want to say is that I found the relentless presentation / implication of the ADC noise as a “fatal flaw” to be unhelpful
--- End quote ---
Yep. The Siglent fanboys are a constant nuisance.
--- Quote from: Anding on October 27, 2022, 11:19:39 am ---nobody says “the noise is likely a problem if you doing X but will be no issue if you want to do mainly Y and occasionally Z”
--- End quote ---
I say things like that all the time.
I say things like "Digital use: Not a problem." and "Looking at mV signals? Problem."
--- Quote from: dietert1 on October 27, 2022, 11:41:58 am ---When we use a scope, we want to measure something, like signal shape, amplitude, noise..
Nothing of this will be possible with that cheap amplifier in the signal chain, using it out of bandwidth and with its low input impedance. That recommendation was misleading to say the least.
--- End quote ---
You're all batshit insane. Seriously.
Every single time I mention an amplifier I make a point to qualify it with "for occasional use" or "in a pinch".
I even tell people not to use them, eg. here's a post on the previous page of this thread where where I say: "The proposed solution would only be for occasional use. If looking at mV signals is a central part of what you're planning to use your oscilloscope for then maybe you need to look at a 12-bit "HD" oscilloscope."
Link: https://www.eevblog.com/forum/testgear/should-i-buy-a-rigol-mso5000/msg4481770/#msg4481770
gf:
I wonder whether the mV ranges really need to be used at full bandwidth, or whether a lower bandwidth (say 20MHz or even less) would suffice for many low-voltage use cases?
Of course, if the ADC noise is the dominant contributor to noise, then it won't suffice to limit the bandwidth in the frontend, but the bandwith reduction from the 4GHz noise bandwidth of the ADC to (say) 20MHz needs to be done by applying a low-pass filter in the digital domain, after sampling at full 8GSa/s. The seems to exist a lowpass filter math function.
Fungus:
--- Quote from: gf on October 27, 2022, 02:15:29 pm ---I wonder whether the mV ranges really need to be used at full bandwidth, or whether a lower bandwidth (say 20MHz or even less) would suffice for many low-voltage use cases?
--- End quote ---
The depends on whether you're using a probe or 50 Ohm coax.
If you're using a probe then it will be switched to 1x mode and it's almost compulsory to use the 20MHz bandwidth limiter.
--- Quote from: gf on October 27, 2022, 02:15:29 pm ---20MHz needs to be done by applying a low-pass filter in the digital domain, after sampling at full 8GSa/s. The seems to exist a lowpass filter math function.
--- End quote ---
Aka "hires" mode.
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