sound card based sampling oscilloscope

[Glen Walpert]

Looks like a nice cheap hobby project, ~40 MSPS effective sampling rate
on repetitive signals with a 96 kSPS soundcard.
http://www.analog.com/library/analogdialogue/archives/45-11/soundcard.html

 

[Nico Coesel]

That's fun and educational, but one problem is that it's not
triggered. It gets its timebase by heterodyning the signal against an
independent local oscillator. So it only works with repetitive signals
that have very low period jitter.

With the timebase suggested in the appnote, the display time/division
is difficult to figure out, and it's easy to alias the waveform into
something deceptive, like time reversal for instance. In fact, you
have to know the input waveform frequency in advance, otherwise it's
difficult or impossible to know if the timebase divisor is right.

LeCroy did a sampling scope with a free-running, synthesized timebase.
I don't recall it being a successful product.

Maybe they forgot to mention the optional trigger module in the
catalog? Otherwise I don't see how such a scope would produce
meaningfull readings in any situation.