Switching Performance - Limit Contact; Pid-Control; Proportional Behaviour - Ecolab MULTRONIC Notice Technique

8.5.1 Switching performance – Limit contact
8.6

PID-control

To adjust a control exactly to the controlled system, it is
possible to assign each and every controller a unique
action (proportional-integral-differential) as well as mixed
functions resulting from these.
These freely selectable control functions mean that the unit can be adapted for use in a variety
of areas.
All PID controller parameters are calculated from the control variable function y through a rapid
change of the input value x
8.6.1

Proportional behaviour

The P controller has a static characteristic curve. A characteristic feature of the P controller is
the proportional range, X
variable is contained within this range and has an upper and a lower limit.
The lower limit is the controller's response threshold (X
state deviation can have which leads to a measurable control variable. It is the upper limit (X
= 1000 %) which separates the proportional range from the saturation. Beyond this limit it is
not possible for the output signal to increase, even if the input signal is further increased. This
range is known as the controller's regulating range; the control variable may take on any value
whatsoever within this range.
Because of the static characteristic curve the P controller is
unable to reach the setpoint value while in the steady state.
The result is a steady-state deviation; and although this
decreases
increases, it cannot be eliminated entirely with a P controller.
The controller reacts more quickly to larger transmission constants, however there is a limit to
how much the transmission constant can be increased. The controller becomes unstable once
a limit value is exceeded.
Control variable function for pure P-controller: Characteristic value Xp = 1/V
NOTE
417101163_Multronic.doc
at the time of t
W
. The proportional connection between input variable and output
P
as the controller's
For a pure P controller, the proportionality factor should be set at 100%. If the value is
adjusted downwards, the controller reacts more "aggressively". For values above 100%, it
reacts more sluggishly.
In the case of P controllers, the low-delay proportional action causes a very fast
interference. However, the disadvantage is that a system deviation cannot be eliminated
completely.
0.
= 0,1 %). This is the smallest value a
P
transmission constant
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P
R
Rev: 5.07-08