Operation
Liquiline System CA80PH
124
Hauser
Disturbance variable
optional, activation code necessary
With "flowing medium" (inline) controls, it can happen that the flow rate is non-constant. In some circumstances, strong
fluctuations are possible. In the case of a settled control system in which the flow rate is suddenly halved, it is desirable
that the dosed quantity from the controller is also directly halved. In order to achieve this type of "flow-rate-proportional"
dosing, this task is not left to the I-component of the controller, but rather one enters the (to be measured) flow rate as
disturbance variable z multiplicative at the controller output.
Strictly speaking, feedforward control involves an open-loop control system, since its effect is not measured directly.
That means that the feed flow is directed exclusively forward. Hence the designation "feedforward control."
For the additive feedforward control that is alternatively available in the device, the (standardized) disturbance variable
is added to the controller actuating variable. This enables you to set up a type of variable base load dosing.
The standardization of the disturbance variable is required both for multiplicative and for additive feedforward control
and is done using parameters Z
0
(zero point) and Z
p
(proportional band): z
n
= (z - z
0
)/z
p
Example:
Flowmeter with measuring range 0 to 200 m
3
/ h
The controller would currently dose 100% without feedforward control.
The feedforward control should be configured such that at z = 200m
3
/h, the controller still doses at 100% (z
n
= 1). If
the flow rate drops, the dosing rate should be reduced, and at a flow rate of less than 4 m
3
/h, dosing should stop entirely
(z
n
= 0).
--> Select the zero point z
0
= 4 m
3
/h and the proportional band Z
p
= 196 m
3
/h.
Function
Options
• Off
• Multiply
• Add
Factory setting
Off
Selecting multiplicative or additive feedforward control
Path: Menu/Setup/Additional functions/Controller 1 or Controller 2
Function
Options
Info
Summary of Contents for Liquiline System CA80PH
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