PMA KS 98, Manual

Page: 199 / 246

Correcting variable processing
The following considerations related to correcting variable processing are applicable to continuous controllers,
two-point, three-point and three-point stepping controllers with position feedback. The
diagram opposite shows the functions and interactions
of correcting variable processing.
Second correcting value
Similar to set-point processing, switch-over to a second preset correcting value
Y2
is possible. Switching over is done
via digital input y/y2 .
Whether Y2 has safety functions, or whether it is only a pre-defined start position in defined process conditions is de-
termined only by the use and integration into an automation concept.
a
Second correcting value
Y2
is evaluated with priority. When switching over to
Y2
is done at one point
(interface or digital control input ‘
y/y2
‘), switching over at the other point is not possible.
Correcting variable limits
Parameters Ymin and Ymax determine
the limits of the correcting variable range
within 0...100 %. With three-point and con-
tinuous controller „split range“, the correct-
ing variable limits are within -100 ... +100
%.
Parameters
Ymin
and
Ymax
are used to
specify fixed correcting variable limits.
9499 040 50611
Controller
199 Process value calculation
x
w
A/M
y-Limitation
Ypid
correcting value
display
1-y
correcting variable
inverted
Ymax Ymin
ED
Y1
Y2
Y0
+
y/y2
Y2
Yout1
sm/hm
Yout2
continu
ous
Yhm
OVC
Yadd
off
0
Fig.: 17 Steps of correcting variable processing
y
t
Ymax
Ymin
100%
0%
Fig.: 18 Fixed limits