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A mathematical formula is presented which depends on 2 parameters: the sampling period and the filter time constant (Tau). "Tau" relates how far

back in time data are to be averaged. My question is, how to choose an initial value for the filter time constant before to tune a process control

loop where there are noisy process variables? I'd like to get some technical references on that subject (if any) as well.

Thanks,

Miguel Borges

Eng. Miguel Joao Borges Filho

Research and Development Center of Petrobras

Industrial Basic Design Division

Cidade Universitaria - Quadra 7 - Ilha do Fundao

Rio de Janeiro - RJ - BRASIL