11.5 Control parameter [Ti]
The time
[Ti]
is the integral time of the I-con‐
troller (integral controller) in seconds. The time
[Ti]
defines the time integration of the control
deviation from the control variable. The smaller
the time
[Ti]
, the greater the effect on the con‐
trol variable. An infinitely long time
[Ti]
results in
a pure proportional control.
11.6 Control parameter [Td]
The time
[Td]
is the differentiation time of the D-
controller (differential controller) in seconds.
The D-controller reacts to the rate of change of
the measured value.
11.7 Control parameter [Add.
Basic load]
[Add. Basic load]
is the additive basic load. The
additive basic load should balance out a contin‐
uous requirement for feed chemical in order to
maintain the setpoint.
The additive basic load can be set in the range
-100 % … +100 %.
The additive basic load is added to the control
variable determined by the controller and is
effective in both control directions. E.g., if the
control variable calculated by the controller
equals
‘
è
y= -10 % and the add. basic load equals +3
%, then the resulting control variable = Y= -10
% + (+3 %)= -7 %
è
y= 10 % and the add. basic load equals +3
%, then the resulting control variable = Y= 10 %
+ (+3 %)= 13 %
è
y= 0% and the add. basic load equals +3%,
then the resulting control variable = Y= 0 % +
(+3 %)= 3 %’
11.8 Control parameter
[Checkout time]
The
[checkout time]
should prevent overdosing
as a result of a malfunction.
During the
[checkout time]
the control variable
is compared with an adjustable
[threshold]
(=
control variable threshold). Depending on the
control direction, you can set different values
for the
[checkout times]
[Checkout time
up ]
for increasing and
[Checkout time
down]
for
reducing.
The thresholds depend on the concentration of
the metered feed chemical. If the threshold is
exceeded, time recording starts
[(checkout time)]
.
If during the
[checkout time]
the variable again
falls below the threshold, then the time is again
reset to
‘0’
s.
If the control variable remains exceeded for
longer than is permitted by the
[checkout time]
,
then control stops immediately. This function
(Control stop) resets automatically once the
threshold is again undershot.
11.9 Control parameter [max.
ctrl var.]
The
[max. ctrl var.]
specifies the maximum con‐
trol variable to be output. This makes sense if
an actuator is over-dimensioned and must not
be opened to 100 %.
11.10 Interference variable
Steadier control of flow processes using a feed‐
forward control.
Setting the
[Control]
130
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