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resident 5th March 2007 03:32 PM

pc oscilloscope
 
I'm thinking seriously to buy a pc oscilloscope.
But I'm tottaly newbie on this. Today I have done some google search for the first time.
Do you have any experience with these oscilloscopes?
They're cheap and with spectrum analyzer too.
I allready own an old oscilloscope (Hitachi) but I don't have an analyzer. And as I can see they're too expensive even used. Or I'm wrong?
I'd like to do an upgrade in my test equimpent, so what do you suggest?
Any source with a test btw pc oscilloscopes?
I'm not planning to pay a fortune so low cost equimpent is needed :D

halfgaar 7th March 2007 10:35 AM

I have a Velleman PCS100a (similar to this one). I works reasonably well, but it has some strange problems.

1) it always reads a small 50 Hz component, visible in the spectrum analyzer.

2) Measured values in one sensitivity setting (like 100mV/div), can be something else completely in another, like 1V/div.

3) it's relatively noisy. At least, I think so, because I have difficulty measuring something like a small hum from an amplifier, because I can't differentiate it from the noise. I don't know how this is with other scopes, however.

And, it being a digital scope, it's readout is slow, especially for the lower time/div settings. The best readout is about 15 fps (frames per second), and for the lowest time/div setting, it can be as low as 1 fps.

These are my experiences with this particular scope. It's likely there are better ones.

resident 7th March 2007 01:43 PM

Thanks for your reply. I'm not sure what to do yet!
Also I haven't done any other search on pc scopes.

Anyone else with an opinion? :(

DrDeville 9th March 2007 10:46 PM

PC Oscilloscope Candidate
 
Hi,

I'm interested too.

I don't have any personal experience with this but it looks promising:

http://www.virtins.com/page2.html#Instrument

Anyone have any opinions?

Best,

George

halfgaar 9th March 2007 10:53 PM

I wouldn't trust a sound card oscilloscope. For one, the maximum frequency is quite low. You won't be able to detect oscillation for example, which typically occurs around 500 KHz.

Another important thing is that you don't have the voltage range of a real scope, unless you put in some kind of divider of course. But, anything that is not (optically) isolated from the computer, is not very safe.

And, sound cards can have a pretty high noise factor.

Lastly, I think there are plenty of free packages available which do the same thing.

FastEddy 9th March 2007 11:33 PM

" I wouldn't trust a sound card oscilloscope. For one, the maximum frequency is quite low. You won't be able to detect oscillation for example, which typically occurs around 500 KHz. ..."

I wouldn't trust a parallel port connected oscilloscope. For one, there are going to be serious compatibility issues with any modern PC = no parallel ports.

I would also try for a USB 2.0 'scope as, even if you don't currently have a USB 2 port, these will all be backward and forward compatibile with USB 1.1 and 2.0 ...
....

This is interesting ... a DIY 'scope for USB 2.0 : http://www.usbee.com/index.asp?PageA...PROD&ProdID=17 ... just add your own probes, etc., I guess. ... I was confused until I groked this: http://www.usbee.com/comp.html ... and this: " ... Cypress EZ-USB FX2 Development kit software that you can download for free from Cypress Semiconductor's web site at www.cypress.com. ..." !!

You might also consider: http://www.pc-oscilloscopes.com/ ... their 3000 series is able to do a few MegaHertz which should be good enough for all audio work, even "ultra-sound" medical scanning machines ... I doubt if getting more than two channels is worth the extra bucks. ( http://www.pc-oscilloscopes.com/usb_3224.html )

I kinda like the BitScope: http://www.bitscope.com/ ... the 310 for USB 2.0 is about US$550 or the BS50 "pocket" unit looks like plenty of features for audio. ... I wouldn't bother with the other models unless I was serious about logic analisys.

This looks nice: http://www.tiepie.com/uk/home/ ... the model HS3 should be plenty for audio work. (US / Canadian dealers available)

I have been involved with USB since the beginning and have always wanted a digital 'scope myself. I have seen these as low as US$150 (bare boards w/o probes) and as high as US$1500 (fancy, expensive software does the really cool tricks). I can't really see any differences except noted at the top. Make it USB 2.0 and at least 2 MegaHertz and two channels would be nice. All of that logic analisys stuff is for other purposes than audio ... :whazzat:

halfgaar 10th March 2007 12:02 AM

Quote:

I wouldn't trust a parallel port connected oscilloscope. For one, there are going to be serious compatibility issues with any modern PC = no parallel ports.
My Athlon X2 3800+ still has a parallel port, but you're right, I would prefer a USB one as well. USB 2.0 will probably be overkill, as the sample data can perfectly well be transferred as 1.5 MByte/s.

But, I wouldn't know why you shouldn't "trust" a parallel port connected scope...

FastEddy 10th March 2007 11:27 PM

" ... USB 2.0 will probably be overkill, as the sample data can perfectly well be transferred as 1.5 MByte/s. ..."

Dealing with 8-bit data frames (as many of these 'scopes' A to D converters do) = that's 8 data bits plus 8 bits for the packet address info and check sum & eop data ... times your 1.5 MegaBytes => 24+ MegaBits per second ... so the USB 2.0 being ~ 30+ times faster than the 12 MegaBits per second speed for USB 1.x = a much better performing digital 'scope.

USB 1.x is very good for real time, real world mechanical activity like printers, mice, keybaords, joysticks, turntables, and single or dual channel (stereo) wave forms, etc. ... But when it comes to higher frequency analog data converted to digital format, USB 2.0 is required for anything greater than about 400 K Hertz converted to USB data packets. ... USB 1.x is good enough for the observation of the human hearing range audio (2 to 20K+ Htz. X 2 channels or a full load of broadcast FM radio information w/o the carrier) but not nearly good enough for observing power supply noise or the EMF/noise associated with Class-D audio or switching power supplies as an example. And if you are talking about observiing 6 channels of Dolby 5.1 or 8 channels of, say THX audio, symultaniously, USB 2.0 performance is required :eek:

halfgaar 11th March 2007 12:03 AM

My scope, which uses a parallel port connection, which can transfer at only a few KByte/s, can display 12 MHz signals just fine. There is also a version of this scope, also with LPT connect, which can display several hundred megahertz signals. There is a very simple reason for this: the computer does not get the raw sample data. If it would, it would be a very bad design.

The scope samples the analog signal, normalizes it to values needed for the software to display a waveform, and sends that to the computer.

FastEddy 11th March 2007 03:49 AM

" ... The scope samples the analog signal, normalizes it to values needed for the software to display a waveform, and sends that to the computer. ..."

Yes !! ... in many cases.


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