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Very low frequency/slow response filters

Question asked by J3627 on Jun 27, 2014
Latest reply on Jun 27, 2014 by KJBob

I would like to make a system that responds very slowly to an RMS measurement, like rising to full value over several minutes.  Setting the RMSTC to 1 isn't slow enough, so I thought I could follow it by a LPF (also the envelope block has a linear decay which I don't want, while the LPF would have the correct log decay), but none of those can be set to a low enough frequency either.  State-variable filters are supposed to be numerically stable at low frequencies?  But the lowest SigmaStudio lets me set it is 0.1 Hz with 0.5 Q, and this still rises to full value within 20 seconds (and the 0.5 Q still allows a little overshoot, which I don't want).  Any advice on making a lower frequency filter with no overshoot?