Chip Weller writes:

> Normally use of a median filter, or rejecting highest and lowest, is
> used when there are very strange "shot" noise problems. If you are not
> having data points which lay outside of 3 sigma of the mean it is
> probably best to use all values.

I think Michael R-J has been getting both Gaussian noise and impulsive
noise. So some sort of non-parametric mean estimator (e.g. the median
estimator) is needed as well as a filter.

> I have had good luck using infinite impulse response filters (IIRF) when
> filtering. You will want to oversample, but that is the case with any
> filtering. Example (in C):
>     FilterX16 -= FilterX16 >> 4;    // add 8 before shift to improve
> rounding
>     FilterX16 += NewValue;

This exponential IIR filter is a great idea for filtering the Gaussian
noise - it is easy, simple and uses little memory.

Mal
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