Siemens SIMATIC S7-1200 Function Manual page 446

Instructions
9.3 PID_Temp
Config.Output.Cool.PwmPeriode is only effective if the cooling output is activated
(Config.ActivateCooling =TRUE).
When you use PwmPeriode, the accuracy of the PWM output signal is determined by the
relationship of PwmPeriode to the PID_Temp sampling time (cycle time of the OB).
PwmPeriode should be at least 10 times the PID_Temp sampling time.
If the sampling time of the PID algorithm is not an integer multiple of PwmPeriode, each last
period of the PWM within the sampling time of the PID algorithm is extended accordingly.
Example for OutputHeat_PWM
①
PID_Temp sampling time = 100.0 ms (cycle time of the calling cyclic interrupt OB, CycleTime.Value tag)
②
PID algorithm sampling time = 2000.0 ms (Retain.CtrlParams.Heat.Cycle tag)
③
Time period of the PWM for heating = 600.0 ms (Config.Output.Heat.PwmPeriode tag)
446
Function Manual, 03/2017, A5E35300227-AC
PID control