oscilloscope

[._.]

Originally Posted by tINY

Are you assuming that a 1GS/S, 8 bit converter can only resolve 45dB of dynamic range at 100kHz???

If so, you really need to read up on delta/sigma converters, oversampling, and noise shaping.

You tell me. I just read 2 pdfs about noise in digital scopes written by Agilent. And it seems you can decrease noise by 30dB by oversampling, using bigger buffers, and averaging, but at least one of the methods will essentially remove the noise you are trying to measure so I fail to see how that will be useful.

It also seems like about 190 microvolts is the lowest noise in some good scopes. However that was at almost 300 mhz bandwidth. Not reduced.

And it appears like very good preams have about 1 microvolt of noise, if I understand the measurements correctly. A preamp with -127dBu of noise (3.46e-7 V or 0.000000346 V/ 0,35 microvolts), is not uncommon if you are building some kind of kit, I have seen schematics even better than that.

It looks like a good USB scope is more useful than stand alone one, since you have a real computer doing the calculations for you.

And if you can oversample, average and things like that in a stand alone scope you can surely do just the same with a USB scope to decrease the noise. It looks like a 16 bit scope is better for audio at least.

I think the 16 bit Picoscope looks good, it only takes 20 volts though on 1:1 and its only 5mhz. Maybe one of those special high voltage differential probes could be useful so you can measure mains voltage.

Maybe that and a good multimeter is a good start? Maybe one of those Benchmark interfaces too? Personally I would choose that over a single 500-1000mhz scope costing the same as all those things combined. It just seems more useful.

However (somewhat) good audio gear has been around for at least 50 years so I guess you can do it with only an analog crt scope, analog signal generator and an analog multimeter too if you know how to use them properly.

[The Real MC]

Yeah you thought boutique mic preamps were expensive?

'Scope inputs have a preamp. They have to impart zero nada color on the signal while amplifying it by 60dB - all without any reactive loading on the test point. For digital scopes oversampling is the norm. Signal integrity is imperative on 'scopes.

[robertshaw]

here's a cool use for a scope

[radeng]

That Pong breadboard is insane!

[tINY]

Originally Posted by ._.

You tell me. I just read 2 pdfs about noise in digital scopes written by Agilent. And it seems you can decrease noise by 30dB by oversampling, using bigger buffers, and averaging, but at least one of the methods will essentially remove the noise you are trying to measure so I fail to see how that will be useful.

It also seems like about 190 microvolts is the lowest noise in some good scopes. However that was at almost 300 mhz bandwidth. Not reduced.

And it appears like very good preams have about 1 microvolt of noise, if I understand the measurements correctly. A preamp with -127dBu of noise (3.46e-7 V or 0.000000346 V/ 0,35 microvolts), is not uncommon if you are building some kind of kit, I have seen schematics even better than that....

Are you really concerned with the noise in the 1MHz band on your audio preamp? 10MHz? 100MHz?

It may also be worthwhile to calculate the thernal noise of a 20kHz bandwidth on a 200 or 600 ohm impedance...


Johnson–Nyquist noise - Wikipedia, the free encyclopedia



-tINY

[._.]

No of course not, and even less at 1ghz, 30-40khz is enough fo me. The thermal noise of those resistors should be way down there at -130dBu.

I found some pdfs for those that are interested. Can't link them directly but I can link the searches though.

Search Results: Home | Agilent

"Understanding the Right Metrics to use when Evaluating Oscilloscope Quality"
or "Oscilloscopes and ENOB"

Search Results: Home | Agilent

Evaluating Oscilloscope Vertical Noise Characteristics

Search Results: Home | Agilent

Spectral Analysis Using a Deep-Memory Oscilloscope Fast Fourier Transform (FFT)
or Spectral Analysis Using a Deep Memory Oscilloscope FFT (AN 1383-1))


To the document search page
Document Library: Test & Measurement | Agilent


Haven't read these 3 yet.

Evaluating Oscilloscopes for Best Waveform Update Rates

Evaluating Oscilloscope Bandwidths for Your Application

Evaluating Oscilloscope Sample Rates vs. Sampling Fidelity

[The Real MC]

Originally Posted by radeng

That Pong breadboard is insane!

Yeah I would never breadboard anything 1/3 that size. And it was a college lab project. I wouldn't let anyone NEAR that breadboard for fear of a "misplaced" wire.

They put the 'scope in XY mode and generated the voltages to display the elements of the game. Interesting.

[manzini]

Originally Posted by The Real MC

They put the 'scope in XY mode and generated the voltages to display the elements of the game. Interesting.

Yes, is a tribute as videogames began. Tennis name, I think, near '60, on a oscilloscope, incidentally, not chance only to entertain visitors of any lab.

The only vintage (quad vintage) gear that I have it's my early'70 DIY Tennis kit for CRT screens. Controls made with Telefunken TV spare knobs & pots, into a kodak film case....yehaa I am little oldy

Was my first videogame, pure DIY, and was very inspired to me, to avoid analog electronics and take computer science degree .

EDITED===

I found it!!

Tennis for two, wikipedia... of course:

http://en.wikipedia.org/wiki/Tennis_for_Two

[robertshaw]

Originally Posted by ._.

No of course not, and even less at 1ghz, 30-40khz is enough fo me. The thermal noise of those resistors should be way down there at -130dBu.

I found some pdfs for those that are interested. Can't link them directly but I can link the searches though.

Search Results: Home | Agilent

"Understanding the Right Metrics to use when Evaluating Oscilloscope Quality"
or "Oscilloscopes and ENOB"

Search Results: Home | Agilent

Evaluating Oscilloscope Vertical Noise Characteristics

Search Results: Home | Agilent

Spectral Analysis Using a Deep-Memory Oscilloscope Fast Fourier Transform (FFT)
or Spectral Analysis Using a Deep Memory Oscilloscope FFT (AN 1383-1))


To the document search page
Document Library: Test & Measurement | Agilent


Haven't read these 3 yet.

Evaluating Oscilloscopes for Best Waveform Update Rates

Evaluating Oscilloscope Bandwidths for Your Application

Evaluating Oscilloscope Sample Rates vs. Sampling Fidelity

+1
good links