Siemens SIMATIC S7-1200 Function Manual page 462

Instructions
9.4 PID basic functions
Block diagram
Accuracy of the manipulated value
With a "Sampling ratio" of 1:10 (CONT_C calls to PULSEGEN calls) the accuracy of the
manipulated value in this example is restricted to 10%, in other words, set input values INV
can only be simulated by a pulse duration at the QPOS_P output in steps of 10 %.
The accuracy is increased as the number of PULSEGEN calls per CONT_C call is
increased.
If PULSEGEN is called, for example, 100 times more often than CONT_C, a resolution of 1
% of the manipulated value range is achieved.
Note
The reduction ratio of the call frequency must be programmed by the user.
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Function Manual, 03/2017, A5E35300227-AC
PID control