West Control Solutions KS98-1 - Manual (Page 260)

III-16.12 Setpoint functions
Terminology
w internal setpoint
we external setpoint
w2 second (internal) setpoint
Weff effective setpoint
xw control deviation (x-w r process value - )
General
Several possible setpoints are available. For the priorities, see the
drawing shown opposite. "Safety setpoint " w2 is given priority
over the other setpoints. Switchover between setpoints is possible
via interface or via the digital inputs of the conroller block.
If gradient control was activated, a change will be made effective
continuously instead of being made effective by a step r gra-
dient control page 261.
By activating digital input w stop , the instantaneously effec-
tive setpoint is maintained. In this case, neither a setpoint change
nor switchover to another setpoint becomes effective.
Setpoint / setpoint / cascade
Configuration word WFunc can be used to select, if switch-over to the external setpoint (setpoint / cascade) is also
possible in addition to the internal setpoint.
Setpoint
( WFunc = Setpoint) Setpoint control means that the setpoint is firmly predefined by the internal setpoint W.
Setpoint/cascade
( WFunc = Fest/Folg) Setpoint /cascade control permits switchover between internal setpoint W and external
setpoint We . Switchover is via digital input we/wi or via the interface.
Unless this input is connected, or if a 0 signal is applied, the external setpoint is used as effective setpoint. Unless di -
gital input
we/wi as well as analog input wext are connected, the controller invariably uses the internal setpoint.
W2 - safety setpoint
The second setpoint W2 can be activated at any time and has highest priority. The change-over between internal set -
point and W2 can be triggered via interface or the digital control input
w/w2. In order to make the W2 effective, on
w/w2 is a logic 1 to be attached. If the internal setpoint is to be active, a logic 0 must be given on we/wi.
In the past
W2 was designated as "safety setpoint". Whether W2 takes over safety functions or only a pre-defined
starting position in certain process conditions, becomes determined only by the kind of the use and integration into an
automation concept.
9499-040-82711
III-260 Setpoint functions
x - w
+
-
Weff
W2
xeff
w/w2
we/wi
w
Wext
Fig. 77