Three evaluated values have clear physical meaning: static gain, delay and reaction time. They are obtained from the first three moments of the system response. The parameters of the PID regulator are then calculated according to these evaluated values. There are other several self tuning methods implemented in PLCs. EXACT method (Expert Adaptive Controller Tuning) is an out of date method developed and implemented in older versions of Foxboro PLCs. A principle of this method is the monitoring of changes of the set point, of the disturbance value and of the process value. Design or redesign of the regulator parameters is made according to the evaluated responses. Latzel method, implemented in out of date PLC SIPARD DR21 by Siemens, uses evaluation of the step response to design regulation parameters by optimum module. There are many other methods for self tuning function including fuzzy logic, neural networks, genetic algorithms and their combinations.