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At 12:51 AM 6/12/2004, Alex Matulich wrote:
>At first glance, this might be tough to implement. I know enough that an
>RC lowpass filter is identical to an exponential moving average (actually
>any RC filter can be implemented as a pile of EMAs). I know the time
>constant of an RC filter is RC, the time constant of an RL filter is L/R,
>but what's the time constant for an LC filter having no R? sqrt(LC)?
The inductor actually has resistance, which is not shown in the schematic, and has hysteresis losses as well if the inductor has an iron core. The capacitors have small losses as well.
>Trouble is, my _SMA3 is an FIR filter. Doing something similar with an
>IIR filter would be nice, because I have another application that requires
>using the previous value as an input.
There is a modification of the T3 filter that is critically damped. There is a variable called "Hot" in the T3 code I wrote and you can change the damping by changing that. As I recall, the value Hot = 0 is critically damped but I am not sure. You can easily find the correct value.
Bob Fulks
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