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PC based Oscilloscopes that use sound cards — Parallax Forums

PC based Oscilloscopes that use sound cards

Steve JoblinSteve Joblin Posts: 784
edited 2007-01-10 17:08 in General Discussion
I would like to start experimenting with oscilloscopes, but don't want to spend the money for the Parallax USB Oscilloscope (although at $140, it seems very reasonably priced!) just yet...

I found several freeware oscilloscopes that use the PC's sound card (winscope and BipScope).· Both make warnings about potential damage to the PC's sound card if used incorrectly.

Couple questions:

If I just want to get started and play around a bit, will these freeware packages work for electronic circuits?· That is, could I complete the "Understanding Signals" curriculum using these freeware packages?

Is there any circuitry that could act as a "buffer" and protect me from potential damage to my soundcard?

Comments

  • boeboyboeboy Posts: 301
    edited 2007-01-06 18:25
    You could use a optoisolator to bufer the input.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    lets see what this does... KA BOOM (note to self do not cross red and black)
  • T ChapT Chap Posts: 4,249
    edited 2007-01-06 20:34
    www.virtins.com/

    I have virtins on a PC that I use rarely since I have another real scope, but I really like this Virtins PC scope! It is a dual trace with some nice features.

    One thing to keep in mind for a sound card based scope: They are usually AC coupled, which means the signal passes through a cap getting into the ADC. That is no big deal for many applications including looking at signals, clocks etc. But if you intend to stare at a DC voltage it is not going to happen. What you will see with DC will look like a saw tooth, the inital rise will be perfect on the ON, but even if the signal stays on, the line will drop very rapidly and looki like this fine ascii art:


    

          ' ' ' ' ' '  
          '           '
          '             '  
..........                 '  .................




    So, they work great for most all non-critical applications, but they will never have a flat top to any fixed voltage. There are cheap interfaces that will eliminate the problem, such as the Parallax scope.

    I have abused this PC scope like you wouldn't believe, ran way more voltage into than they rate it at, and it never has had a problem If you care about the PC, just use a sound card you can buy anywhere for $20. If you don't card about the PC sound input, just use that as you will probably not hurt it if you follow the guidelines which I never do.
  • PLJackPLJack Posts: 398
    edited 2007-01-07 18:08
    I researched this a couple of years ago. I posted my results on these forums for just such an occasion.
    Read it here:
    http://forums.parallax.com/showthread.php?p=542285

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    - - - PLJack - - -


    Perfection in design is not achieved when there is nothing left to add.
    It is achieved when there is nothing left to take away.
  • SteelSteel Posts: 313
    edited 2007-01-10 17:08
    You do need to be careful hardware-wise with using your sound card.·· Depending on the soundcard, it is expecting specific line-in voltage and current levels.· If those levels are exceded, you are going to experience some major problems.

    The Parallax OScope is·a GREAT deal, and I use it for testing products that have been released to market.

    You may not want to bother with the $140 now...but if you blow your soundcard, you'll wish you had.
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