Instruction Manual

Ratio = Type 2
W
XN
X X SFact
=
+
+×
10
12()
In this example, water (x1) must be batched as a percentage of
the total (paste; x1+x2). As the paste quantity is not available
directly as a measurement signal, the total is calculated inter
-
nally from x1 and x2. N0 = 0 must also be adjusted in this case.
Ratio = Type 3
W
XXN
X SFact
=
-+
×
210
2
Unlike the previous examples, yoghurt (x2) and the final product
(x1) are measured in this case.
Three-element control
With three-element control, process value calculation is accor-
ding to equation
xXaXX
eff
=+×123(\ )
whereby term
(\ )XX23
is
the difference between the steam and water flow rates. Factor
b for flow range matching used so far is omitted, because the
mA signals are converted directly into physical units during in-
put value conditioning (x0, x100). The calculated process value
is displayed on the process value display.
For selecting a three-element controller, ‘CFunc =
3-elem.‘ must be entered in the configuration.
Correcting variable processing
The following considerations related to
correcting variable processing are appli
-
cable to continuous controllers,
two-point, three-point and three-point
stepping controllers with position feed
-
back. The diagram opposite shows the
functions and interactions of correcting
variable processing.
9499-040-82711
Process value calculation III-267
Flour
X1
X2
x1
x2
Water
w = (x1+N0) / (x1+x2) SFacw
Dough
Fig. 87
x1-x2
x2
w = (x2 - x1) / (x2 SFac)w
Fat
Yoghurt
x2
x1
X2
X2
Fig. 88
Setpoint w
Water
Steam
Fd
Level L
Fw
+
Process valuex = x1 +a (x2 - x3)
y + dFd/dt
_
X3
X1
X2
Fig. 89
x
w
Ypid
Ymax
Ymin
Y2
Y0
+
OVC
a/m
y/y2
Y
Fig.: 90 Steps of the output signal processing