hi freq pc based scope

[sss]

hello

i'm thinking of making a pc based scope that is not based on the sound card so the max feq will be higher then 20Khz .does anybody know any related projects ?

[kozak]

I know that velleman is doing such things (pc based scopes) using the parrallel interface.
they also do stand alone little scopes which are quite interesting for audio measure

[gmarsh]

I'd avoid buying a PC based scope.

I know a guy who bought one - he spent something like $600 for a PC scope that has dual channels and the functionality of a $1000 scope.

Now it's a paperweight - It's an ISA card (try finding an ISA slot nowadays), the software only works in DOS, the company went under and obviously isn't releasing any newer drivers, etc... If you buy a PC card scope now, it's probably going to be PCI. But the world's moving in the direction of PCI Express this year, and in a few years you might never see a plain PCI slot again.

And there's other things it won't do - you can't exactly float the ground on a PC based scope.

My 1980's Tek is still nowhere near obsolete.

[apolon34]

velleman sells a 10mhz 1 way kit for 150€

it works on parallel port and is fully isolated from pc.

i own a digital wave generator and it works very well, for a modest price.
with that kind of generator/scope, you can trace a bode diagramm without any effort, or do a fft, or transcient recording, etc...

i will probably buy the scope someday

[Giorgio]

Pico Technology too produces nice virtual instruments, but I have some doubt they are really worth the cost, unless you need to transfer measures to a PC for any reason....

No doubt they are good instruments, with few % precision, rather solid (but I DO NOT dare using mine if there is any relatively high voltage tube around, I know someone that burned its owni that way, the protection limit is 100V), but a 20Msamples unit just provide you a reasonable wawform up to 500K, 1MHz, and then just an hint of what is happening. Newer version overcome this issue for repeating signals by using multiple consecutive acquisitions to build up a precise waveform. Other issue, 8-12 bits for audio are too little, unless you are using only tubes or no feedback circuits, and the scope is not insulated from ground....

It's also true you get hardware and software (continuously upgraded) for a limited amount (500-1000USD range, if I remember correctly).

I do not see any single stop solution either. You need ultra high speed for digtal waveform display, and ultra high dynamics for audio measurements, and these ar not compatible, with today technology (just think: if they were available today, there would be a lot of people screaming that the perceptions of -144dB sound harmonics in the GHz range is fundamental for a correct audio reproduction, isn't it?

The best limited cost solutions package in my view, today, is probably a good 24/96 audio card for audio range FFT measures with a very good 24 bit analyzer sw (more expensive than the card...) and a nice, high frequency (for digital audio) standalone oscilloscope for all the rest. I would suggest to buy all HW second-hand, to spare.

The best overall solution would probably be a 24/192 audio card with some very good software, and a very high speed (1Gs++) digital scope, but this is for sure out of reach for normal diyers.

Kind regards
Giorgio

[fmak]

[QUOTE]Originally posted by Giorgio
[B]Pico Technology too produces nice virtual instruments, but I have some doubt they are really worth the cost, unless you need to transfer measures to a PC for any reason....

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They are too expensive for the money. I agree that a 24/96/192 AUDIO sound card with software FFT like WinAudioMLS with 64 bit FFT is the way to go to add to analogue instruments. My National low D analyser >20 years gives 96-104 dB dynamic range and much better than noisy (fan) HPs.

I get about 100 dB dr on the software system and see all the harmoniocs to 48 kHz, but I would like more.

Can someone tell me how the fan on a HP3445 digital volmeter works? It has 4 connections to some transistorised PS and sometimes doesn't run up to speed properly. Thinking of replacing with a single 12V fan but don't want to burn up the PS citcuit!

[Giorgio]

Yes, indeed, with a good 24/96 card you can already move noise floor to -130dB, and even more if you use high accumulation rates and high number of samples.

Unfortunately both HPW Works and WinAudioMLS seem to be rather good, but for sure are very expensive, even though Win Audio basic version is frequently offered on eBay at very low cost: if you add up all required options to upgrade to 24 bits, you get back to HPW cost again, or even higher...

Kind regards
Giorgio