Posts

Showing posts with the label Process inertia

Autocorrelation: How to Manage it

Image
When a process variable has only random variation, each output is independent of the previous ones.This is what happens in a lottery. In some processes this independence does not happen.   If we control our daily weight, for instance, our weight today is correlated to the weight of the previous days: it has autocorrelation . Weight Autocorrelation One common case of autocorrelation is shown by our body weight.  Our weight today is correlated with: Yesterday's weight:      53% The day before:           39%    Body weight has inertia: you don't expect sudden changes. A similar effect happens when you control a heavy aircraft or a ship: its masive weight prevents you from making a sharp turning or make a sudden stop.  This opposing force to change is what is called Inertia . This inertia definition applies to moving objects and it is proportional to the object mass.  Inertia also applies to fluids: a tank accumulating ...