Siemens SIMATIC S7-1200 Function Manual page 498

Instructions
9.4 PID basic functions
Calculation of the parameters:
● PV_FAC = range of PV_NORM/range of CRP_IN;
● PV_OFFS = LL (PV_NORM) - PV_FAC * LL(CRP_IN);
where LL: low limit
The normalization is switched off with the default values (PV_FAC = 1.0 and
PV_OFFS = 0.0). The effective process value is output at the PV output.
Example of Process Value Normalization
If you want to enter the setpoint as a percentage, and you have a temperature range of -20
to 85 °C applied to , CRP_IN you must normalize the temperature range as a percentage.
The following diagram shows an example of adapting the temperature range -20 to 85 °C to
an internal scale of 0 to 100 %:
Forming the control deviation
The difference between the setpoint and process value is the control deviation before the
dead band.
The setpoint and process value must exist in the same unit.
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Function Manual, 03/2017, A5E35300227-AC
PID control