Metrohm tiamo 2.4 (process analysis) - Manual (Page 1654)

7.20 IO controller
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tiamo 2.4 (for Process Analysis)
7.20.8.1.5 General - PID controller
The controller acts as a PID transfer element.
Transfer function
Action diagram
Figure 1 Standard action diagram of a PID controller
The standard action diagram of a PID controller (proportional-integral-
derivative controller) in additive form has been extended to include the
two Boolean inputs (P in feedback and D in feedback) functioning as
switches, so that a modified action diagram can be activated.
The control principle is that setpoint value discontinuities generate large
control values as a result of the differential component of the control
algorithm. This effect causes a strain on the control elements and may
cause an oscillation of the control system. A control algorithm with a dif-
ferential component that is only applied to the controlled variable (D in
feedback = ON) can avoid this problem.
The following transfer functions of the closed control loop can be imple-
mented with the P in feedback and D in feedback inputs:
P in feed-
back D in feed-
back Transfer function
off off
on off
off on