Siemens SIMATIC S7-1200 Function Manual page 433

State / Mode Description of operating mode
1 The more stable the process value is, the easier it is to calculate the PID parameters and the more precise
the result will be. Noise on the process value can be tolerated as long as the rate of rise of the process
value is significantly higher compared to the noise. This is most likely the case in operating modes "Inac-
tive" or "Manual mode".
The setpoint is frozen in the CurrentSetpoint tag. Tuning is canceled when:
Setpoint > CurrentSetpoint + CancelTuningLevel
•
or
Setpoint < CurrentSetpoint - CancelTuningLevel
•
The method for calculation of the PID parameters can be specified separately for heating and cooling with
PIDSelfTune.SUT.TuneRuleHeat and PIDSelfTune.SUT.TuneRuleCool.
Before the PID parameters are recalculated, they are backed up in the CtrlParamsBackUp structure and
can be reactivated with LoadBackUp.
After successful pretuning, the switch is made to automatic mode.
After unsuccessful pretuning, the switch to the mode is determined by ActivateRecoverMode.
The phase of pretuning is indicated with PIDSelfTune.SUT.State.
PID control
Function Manual, 03/2017, A5E35300227-AC
Instructions
9.3 PID_Temp
433