Evoqua WALLACE & TIERNAN SFC, Original Instruction Manual

Page: 89 / 288

SFC
Functions
4.
89
Control direction
Meaning:
Direction of the control
Display:
Direct/inverse (e.g. for pH)
Explanation:
Defines which medium is used to perform the correction.
Example:
pH:
Control direction "inverse": Lowering pH-value by
adding acid
pH: Control direction "direct": Adding alkaline to raise
the pH value
Setpoint
Specified value at which the control variable can be maintained by
the controller. The setting range corresponds to the respective
measuring range.
Control variable 2
This parameter activates and deactivates a second control
variable during the single feed forward (only with application 2).
If „Control Variable 2“ = measured value X is selected, this
influences the actuator output. The „Off“ setting indicates that this
control variable is inactive (factory setting) (see 4.5.2.1 “Single
feed forward with process measurement”).
T
Sampling time T is the time after which a change controlvariable or
setpoint is responded to. This value must be adjusted in the case
of delayed feedback signals.
Tconst
Defines the constant dead time in the compound loop. Consists of
the sample water line dead time and the dosing delay time (for the
calculation, see 4.5.2.3 “Compound loop with process
measurement”).
Tn
Meaning:
Integral action time (I-element)
Display:
Minutes (min)
Explanation:
On the basis of the integral action time Tn, the dosing capacity
changes constantly until the setpoint is reached. The higher the
value of Tn, the longer it takes until the controller increases the
dosing rate.
Tn higher: Control response becomes slower
Tn lower: Control response is faster
Setting range:
The parameter Tn can be set from 0 – 100 min (Tn = 0 means that
the "I-element" is deactivated, i.e. a pure P-control response
applies). It may not be possible to reach the setpoint value.