Siemens SIMATIC S7-1200 Function Manual page 404

Instructions
9.3 PID_Temp
Tag
Config.Output.Heat.Pwm-
Periode
Config.Output.Heat.PidUpper-
Limit
404
Data type Default
REAL 0.0
REAL 100.0
Description
Period duration of the pulse width modulation (PWM) for
heating (OutputHeat_PWM output) in seconds:
Heat.PwmPeriode = 0.0
•
The sampling time of the PID algorithm for heating
(Retain.CtrlParams.Heat.Cycle) is used as period du-
ration of the PWM.
Heat.PwmPeriode > 0.0
•
The value is rounded off to an integer multiple of the
PID_Temp sampling time (CycleTime.Value) and used
as period duration of the PWM.
This setting can be used to improve the smoothing of
the process value with a long sampling time of the PID
algorithm.
The value must meet the following conditions:
– Heat.PwmPeriode ≤ Retain.CtrlParams.Heat.Cycle,
– Heat.PwmPeriode > Config
.Output.Heat.MinimumOnTime
– Heat.PwmPeriode > Config
.Output.Heat.MinimumOffTime
High limit of the PID output value for heating
The PID output value (PidOutputSum) is limited to the high
limit.
Heat.PidUpperLimit forms a value pair together with the
following parameters for scaling of the PID output value
(PidOutputSum) to the outputs for heating:
Heat.UpperScaling for OutputHeat
•
Heat.PwmUpperScaling for OutputHeat_PWM
•
Heat.PerUpperScaling for OutputHeat_PER
•
If you want to limit the value at the associated output, you
must also adjust these scaling values.
Heat.PidUpperLimit > Heat.PidLowerLimit
Function Manual, 03/2017, A5E35300227-AC
PID control