Technical data

Table Of Contents
System Software for S7-300/400 System and Standard Functions - Volume 2/2
A5E00739858-01
27-1
27 SFBs for Integrated Control
27.1 Continuous Control with SFB 41/FB 41 "CONT_C"
Introduction
SFB/FB "CONT_C" (continuous controller) is used on SIMATIC S7 programmable
logic controllers to control technical processes with continuous input and output
variables. During parameter assignment, you can activate or deactivate sub-
functions of the PID controller to adapt the controller to the process. You can
assign this easily by using the parameter assignment tool (Menu path: Start >
Simatic > Step7 > Assign PID Control parameters). The online electronic
manual is found under Start > Simatic > Step7 > Assign PID Control English.
Application
You can use the controller as a PID fixed setpoint controller or in multi-loop
controls as a cascade, blending or ratio controller. The functions of the controller
are based on the PID control algorithm of the sampling controller with an analog
signal, if necessary extended by including a pulse generator stage to generate
pulse duration modulated output signals for two or three step controllers with
proportional actuators.
Note
The calculation of the values in the control blocks is only correct if the block is
called at regular intervals. For this reason, you should call the control blocks in a
cyclic interrupt OB (OB30 to OB38). Enter the sampling time in the CYCLE
parameter.