Siemens SIMATIC S7-1200 Function Manual page 482

Instructions
9.4 PID basic functions
The following diagram illustrates two-step control with a unipolar manipulated variable range
(0% to 100%):
Minimum pulse or minimum break time (P_B_TM)
Short on or off times hinder the lifespan of actuators and fine controlling units. These can be
avoided by setting a minimum pulse duration or minimum break time P_B_TM.
Small absolute values at the input variable LmnN that could otherwise generate a pulse
duration shorter than P_B_TM are suppressed.
Large input values that would generate a pulse duration greater than
PER_TM - P_B_TM are set to 100%. This reduces the dynamics of pulse generation.
Set values of P_B_TM ≤ 0,1 * PER_TM are recommended for the minimum pulse duration
and the minimum break duration.
The "knees" in the curves in the diagram above are caused by the minimum pulse or
minimum break times.
The following schematic illustrates the switching response of the pulse output:
482
Function Manual, 03/2017, A5E35300227-AC
PID control