On Wed, 29 Mar 2000 06:01:10 -0500 Lorick writes: > > while, but are you able to rule out aliasing effects due to sample > > rate? > > I've discounted the possibility but I guess there's always room for > it. I'm > sampling a 330 Hz sine with a 4MHz crystal and I'm just blindly > assuming I'm > way above 2.2x for Nyquist. As I mentioned before, I don't believe Nyquist is a concern unless you are trying to reconstruct the waveform. A RANDOM undersampling of the waveform should be fine. There is a concern over sample time, but I don't think this is a concern at audio frequencies with the PIC A/D. I believe that as long as the sample frequency is not a harmonic of the signal being measured, you'll get a correct RMS with ANY sample rate. You could even take 256 samples at one per second. Harold FCC Rules Online at http://hallikainen.com/FccRules Lighting control for theatre and television at http://www.dovesystems.com ________________________________________________________________ YOU'RE PAYING TOO MUCH FOR THE INTERNET! Juno now offers FREE Internet Access! Try it today - there's no risk! For your FREE software, visit: http://dl.www.juno.com/get/tagj.