LowPass Filter

A lowpass filter smooths its input over time. The filter is characterized only by its time constant. Each new sample is combined with the previous output of the filter as follows

New Output = Old Output + dt/tau * ( Input - Old Output)

where dt is the time since the last sample, and tau is the time constant of the filter. You can see that the output approaches the input monotonically, at a rate inversely proportional to the time constant.