Yes, the reality is that those waveforms assume a steep cutoff filter.
 The waveforms you'll see will actually look a lot more like square
waves with rounded corners.

-Adam

On Wed, Nov 18, 2009 at 12:18 PM, Alan B. Pearce
<Alan.B.Pearce@stfc.ac.uk> wrote:
>>This is what you can expect to see if you cut
>>a square wave off at 10 times its frequency:
>
> Umm, maybe, but that graph only has a subset of the harmonics in it. In
> practice, the cut off frequency will normally be at -3db, and so there will
> be some higher harmonics at a lower amplitude than they would otherwise be.
> The result is that on an analogue scope you don't tend to see the ringing
> except at the edges.
>
> However I guess the device in question is using an A/D to digitise the
> signal, so whatever filter is in there will have a much steeper slope with a
> true filter going down to a notch, so that graph may well be closer to what
> one would see.
>
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