West Control Solutions KS98-1 - Manual (Page 265)

Controller parameter “a” can be used to define at which distance to the final setpoint the target orientation should be
switched over to the final setpoint. The target line-out function is activated under the following conditions :
1. W < Wend
2. W > Wend-2a
3. X > Wend-a
Marginal conditions / restrictions:
With internal setpoint ramps, the controller knows the future target setpoint. When using external setpoints with ramp
function (programmer), the ramp end value must be bound to input X3 of the controller block. When the internal ramp
is active, line-out to the target setpoint is always related to the internal ramp end value, and the value at X3 is ineffec -
tive.
Target line-out is activated only, if the external ramp setpoint changes continuously. The function can be used both
with differentiation of control deviation (XW) and differentiation of process value (X). With 3-element control, target
line-out is omitted. The signification of parameter “a” is different and connection of an external end setpoint is not
possible. With ratio control, target line-out is only restricted with fixed distance (1 in units of the physical quantity).
The signification of parameter a is different.
III-16.13 Process value calculation
Standard controller
The process variable measured via analog input X1 is
used as process value by the controller.
Ratio controller
Process control frequently requires various components to be mixed into a product. These components must be mixed
according to a given ratio.
The main component is measured and used as reference for the other components. With increasing flow of the main
component, the flow of the other components will increase accordingly. This means that process value x used by the
controller is determined by the ratio of two input variables rather than being measured as one process variable.
9499-040-82711
Process value calculation III-265
x - w
+
-
X1
weff
Fig. 83
Fig. 84