>From what I've read dithering is most appropriate on slow moving signals.
Imagine you have a 4bit ADC with a slow moving analog input of 1-16units.
The inputs at say 8.4, you sample it, and get 8. Sample again, 8 again. You
sample 50 times, nothing but 8's, all you know is it's between 8 and 9. Now,
imagine there's noise (say 3LSB p-p (I believe this is somewhere around
1\2LSB noise power)) while you take your 50 measurements. Over those 50
measurements, with the possible 3 LSB's noise you now get values ranging
from say 5 to say 11. Average it out and you should (if the noise is
"random") get about 8.4. Et voila, increased accuracy. If you actually add
known noise you can get even better rsults by then subtracting the added
noise. But, why add noise when you couldn't get rid of it if you tried.

Tom.

-----Original Message-----
From: James Newton [mailto:jamesnewton@PICLIST.COM]
Sent: Thursday, May 04, 2000 2:34 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [OT] [EE] 24-bit A/D. Are We in the Twilite Zone Here?


I don't understand "duplicate numbers slide off the top of one another".

I also can't see how this jittering could have any positive effect. I could
understand shifting it one bit left and then average with previous
readings... The random extra bit makes the reading #.5 rather than #.0. Is
that what we are talking about?

---
James Newton (PICList Admin #3)
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