User Manual

LOGO! functions
4.4 Special functions list - SF
LOGO!
222 Manual, 06/2014, A5E33039675
Timing diagram
The nature, manner and speed with which the AQ changes depend on the parameters KC
and TI. Thus, the course of AQ in the diagram is merely an example. A control action is
continuous; therefore the diagram portrays just an extract.
1. A disturbance causes the PV to drop, as Dir is positioned upwards, AQ increases until PV
corresponds again to SP.
2. A disturbance causes the PV to drop, as Dir is positioned downwards, AQ decreases until
PV corresponds again to SP.
It is not possible to change the direction (Dir) at runtime of the function. The change is
shown here for illustrative purposes only.
3. As AQ is set to 0 by means of the input R, PV changes. This is based on the fact that PV
increases, which on account of Dir = upwards causes AQ to drop.
Functional description
If the input A/M is set to 0, then the special function issues output AQ with the value that you
set with parameter Mq.
If the input A/M is set to 1, then automatic mode commences. As an integral sum the value
Mq is adopted, the controller function begins the calculations.
Note
For further information on the controller basics, please refer to the Online Help for
LOGO!Soft Comfort.
The updated value PV is used to calculate in the formulas:
Updated value PV = (PV • gain) + offset