Siemens SIMATIC S7-1200 Function Manual page 228

Using PID basic functions
7.3 TCONT_CP
The tuning manipulated variable (LMN0 + TUN_DLMN) is activated by setting the start bit
TUN_ST (transition from phase 1 -> 2). When you modify the setpoint value, the new value
will not take effect until the point of inflection has been reached (automatic mode will not be
enabled until this point has been reached).
The user is responsible for defining the output excitation delta (TUN_DLMN) according to the
permitted process value change. The sign of TUN_DLMN must be set depending on the
intended process value change (take into account the direction in which the control is
operating).
NOTICE
Safety off at 75% is not available when you excite the process via TUN_ST. Tuning is
ended when the point of inflection is reached. However, in noisy processes the point of
inflection may be significantly exceeded.
Manual fine-tuning in control mode
The following measures can be employed to achieve an overshoot-free setpoint response:
● Adapting the control zone
● Optimize command action
● Attenuation of control parameters
● Modifying control parameters
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Function Manual, 03/2017, A5E35300227-AC
PID control