The original idea behind the ripple voltage measurement was assuming
that the 5V supply was a switcher, in which case the ripple would
probably be between 50kHz and 300kHz or so. The soundcard would not
show such high frequencies due to its audio-frequency anti-aliasing
filters on the input.

Sean


On Sat, Sep 5, 2009 at 4:57 PM, Gerhard
Fiedler<lists@connectionbrazil.com> wrote:
> Carl Denk wrote:
>
>> Thanks for the quick reply. The closest thing to a o-scope I have is
>> the PC sound card plus Zeitnitz's software
>> http://www.zeitnitz.de/Christian/index.php?sel=3Dscope_en Would have to
>> make a voltage divider to get the 5 volt down below 1 volt, but
>> that's no problem. Do you think that will work.
>
> You can use the soundcard for AC -- which is what it is designed for
> anyway :) =A0Just block DC by sending the signal through a capacitor. This
> will create a highpass filter; make sure the cap is big enough so that
> the cutoff frequency is low enough (far enough below the 60 Hz you want
> to see).
>
> Gerhard
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