'William Chops" Westfield ' > S1 + S2 + ... + S(k-1) Sk > ---------------------- + ---- > k k OK so far. That is just a average, as you said. > Now, if you already have an existing average value ("FILT"), this > becomes exactly Olin's earlier equation: > >> (K-1) * FILT NEW >> ------------ + --- >> K K Whoa, that's quite different from above. It is particularly misleading in that (k-1) in the top equation is a iteration number, but in the bottom equation it is a numeric value. The two are totally different, and pretending the two equations are the same because they look largely the sam= e is a very nasty trick on anyone that is not so fluent with this stuff, almost to the point of intellectual fraud. > So you can give it new names, but you're really just computing the > average of the last N samples. You're doing a real disservice to those that don't understand this stuff well, which from previous discussions seems to be most people here. It's hard enough for most people to understand why doing a average on N samples is a dumb way to low pass filter a continuous stream of A/D readings. Now you're throwing more confusion at the heart of the issue. > now, if there's a lot of difference > in samples, you might notice that recent samples have more "weight" > than older samples, but that's just a little detail... It most certainly is not! Again, most people seem to have particular confusion in this area. There are significant differences in frequency response, step response, noise attenuation, state required, and computation required between a box filter and a exponential decay filter. ******************************************************************** Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products (978) 742-9014. Gold level PIC consultants since 2000. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .