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From: "Walter Harley"
Subject: Re: generating calibration voltage
Date: Fri, 10 Jan 2003 11:59:04 -0800
Organization: Posted via Supernews, http://www.supernews.com
Reply-To: "Walter Harley"
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
"Tom Torfs" wrote in message
> > How square must the square wave be? (What rise and fall times do you
> > require?)
> Rise/fall times can be upto a few ms. I'm only interested in the
> amplitude. The reason I can't just use a DC signal is that there is a
> highpass filter with fc=0.1Hz after that (and also a lowpass filter
> with fc=70Hz).
Umm, if you take a 30Hz signal (square or otherwise), and lowpass filter it
at 70Hz, you get the first and second harmonics only. And a square wave
doesn't have any even harmonics, so if you start with a 30Hz square wave all
you get is a 30Hz sine wave, with a bit of distortion depending on how sharp
your lowpass cutoff is. Is that going to be good enough to meet your needs?
There's a nice little Java applet at
http://www.clubi.ie/amhiggins/fourier1.html that will help visualize
waveforms with different harmonic content.
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