West Control Solutions KS98-1 - Manual (Page 238)

Continuous controller / Split range
Continuous controller
An analog value is provided as correcting variable by output
Yout1, e.g. temperature control with electrical heating
and thyristor power regulator.
A continuous controller in ‘split-range’ operation is comparable with a three-point controller. The neutral zone is also
separately adjustable.
Within limits Xsh1 and Xsh2, the control deviation for calculation of the controller reaction is set to zero. A pure P
controller does not change the correcting variable within these limits. A PID controller has a dynamic behaviour which
has not always decayed, also when reaching “control deviation = 0”. Both D and I action can still have an effect accor -
ding to the characteristic determined by Tv due to a preceding disturbance or a setpoint step change. This effect can
be strong enough to cause the control deviation to leave range Xsh1/Xsh2, i.e. the P action is activated again for rea -
ching the neutral zone.
Selection from the following continuous controllers is possible:
1. CFunc = continuous r continuous controller
2. CFunc = splitRang r continuous controller with split-range operation
The continuous output is split on outputs Yout1 and Yout2 .
3.) CFunc = continuous Yp r continuous controller w ith position feedback.
The actually flowing positioning current can be displayed via input Yp .Yp is not included in the control operation.
Controller 9499-040-82711
III-238 Control behaviour
Process value
Process value
Controlling variable Yout1
Setpoint
Setpoint
Controlling variable Yout1
100%
0%
Â
Xn100 Xn0 W0 Weff W100
Xeff
Xp1=Xp'+Xp''
Xp' Xp''
Xsh1 Xsh2
actual
working point
Fig.: 59
Operating principle of the
proportional part of the continous
controller