Siemens SIMATIC S7-1200 Function Manual page 422

Instructions
9.3 PID_Temp
Tag
PIDSelfTune.TIR.Output-
OffsetHeat
422
Data type Default
REAL 0.0
Description
Tuning offset heating of the PID output value
TIR.OutputOffsetHeat is added to the value that results
from PidOutputSum for the heating branch.
To receive a positive offset at the outputs for heating,
define a positive value for TIR.OutputOffsetHeat.
The resulting values at the outputs for heating are the
result of the configured output scaling (Struktur Con-
fig.Output.Heat).
This tuning offset can be used in controllers with activated
cooling output and PID parameter switching (Con-
fig.ActivateCooling = TRUE, Config.AdvancedCooling =
TRUE) for fine tuning cooling. If the outputs for cooling are
not active at the setpoint that is to be tuned (PidOut-
putSum > 0.0), fine tuning cooling is not possible. In this
case, define a positive tuning offset heating which is
greater than the PID output value (PidOutputSum) at the
setpoint in the steady state before you start tuning. This
step increases the values at the outputs for heating and
activates the outputs for cooling (PidOutputSum < 0.0).
Fine tuning cooling is now possible.
When fine tuning is complete, TIR.OutputOffsetHeat is
reset to 0.0.
Major changes at TIR.OutputOffsetHeat in one step can
result in temporary overshoots.
Config.Output.Heat.PidUpperLimit ≥ PIDSelf-
Tune.TIR.OutputOffsetHeat ≥ Config
.Output.Heat.PidLowerLimit
Function Manual, 03/2017, A5E35300227-AC
PID control