(above quote is from Poe)
(yes, tintinnabulation is a word)


I'm sampling a DC voltage with lots O noise.  I've set up a routine that =
takes a sample, waits a few milliseconds, then takes another sample, =
etc.  When 15 samples are taken, it takes the median of the samples as =
the result.  Still get false alarms due to noise pulses every once in a =
while. =20

Now, I am not real sure if I will have 60 hz noise (picked up from the =
air) or 120 hz noise (from a full wave rectified power supply) as the =
major noise component.  It may actually be both, at various times. =20

Does Old Nyquist rule in this situation, should I sample at twice 120 hz =
or more to cancel out the effects of noise?   I'm not interested in the =
frequency of the signal at all, just in an accurate DC level. =20


Let's see: 120 hz =3D 8.33 milliseconds per oscillation.  If I sample at =
twice this, that's 4.33 milliseconds.  sampling at exactly twice is =
cutting it fine, so say we sample at four times that's ~2 milliseconds.  =


I've got enough memory to increase the number of samples, maybe that =
will help as well? =20

-- Lawrence Lile
Sr. Project Engineer
Salton inc. Toastmaster Div.
573-446-5661 Voice
573-446-5676 Fax

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