Siemens SIMATIC S7-1200 Function Manual page 97

Control mode V1
Physical quantity
Select the unit of measurement and physical quantity for the setpoint and process value in
the "Controller type" group. The setpoint and process value will be displayed in this unit.
Control logic
An increase of the output value is generally intended to cause an increase in the process
value. This is referred to as a normal control logic.
PID_Compact does not work with negative proportional gain. Select the check box "Invert
control logic" to reduce the process value with a higher output value.
Examples
● Opening the drain valve will reduce the level of a container's contents.
● Increasing cooling will reduce the temperature.
Start-up behavior after reset
To change straight to the last active mode after restarting the CPU, select the "Enable last
mode after CPU restart" check box.
PID_Compact will remain in "Inactive" mode if the check box is cleared.
Setpoint V1
Procedure
Proceed as follows to define a fixed setpoint:
1. Select "Instance DB".
2. Enter a setpoint, e.g. 80° C.
3. Delete any entry in the instruction.
Proceed as follows to define a variable setpoint:
1. Select "Instruction".
2. Enter the name of the REAL variable in which the setpoint is saved.
Program-controlled assignment of various values to the REAL variable is possible, for
example for the time controlled change of the setpoint.
PID control
Function Manual, 03/2017, A5E35300227-AC
Using PID_Compact
4.3 PID_Compact V1
97