Sartorius DCU 3, Operator'S Handbook Manual

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Operators Handbook DCU3 – System
6., Main function „Control Loops“
BAEDCU3 - Rev. 4.6 - 0504 6 - 4
6.4 Parametrization of Controllers, in General
For optimum adaptation of the DDC controllers to the control loops of the fermentor, the operator can
change important control parameters of individual controllers via the parametrization displays:
MIN, MAX : Minimum and maximum limits for the controller output
DEADB : Deadband adjustment (only for PID controllers)
XP, TI, TD : PID-Parameter (only PID controllers)
The parametrization display combined with a controller display is only accessible by entering a pass-
word. On delivery a DCU3 - system is configured with such control parameters that ensure a stable
control of the fermentor system it is designed for. For details about the parameters preset in the fac-
tory see the corresponding table in the supplement or in the documentation delivered extra for custom-
ized configurations of the DCU3 – system.
Changing the preset control parameters is not necessary under normal use. An exception are control
loops which vary with the fermentation process, such as for pH- and pO
2
-control.
6.4.1 Output Limits
For setpoint controllers and PID controllers the controller outputs can be limited (MIN and MAX). Thus
unintended high actuator changes can be avoided and, for cascade controllers, the setpoint for the
servo controller can be limited.
The limits must be entered at MIN for the „minimum output“ and MAX for the „maximum
output“. All settings are in terms of [%].
For full controller output range the following limits must be entered:
– single controller output : MIN = 0%, MAX = 100 %
– splitrange controller output : MIN = -100 %, MAX = 100 %
6.4.2 Deadband
For PID controllers a deadband can be adjusted. If the control deviation is within this deadband the
controller output remains constant or is set to zero (specific feature of the pH controller). By means of
the deadband a more stable control with minimized actuator changes can be achieved for actual val-
ues which vary stochastically. Furthermore, this will avoid oscillating of the controller output for spli-
trange controller outputs (e.g. continuously alternating acid-alkali dosage by the pH - controller).
The deadband is adjusted in the entry DEADB as percentage [%] of the measurement span
of the corresponding actual value. It is symmetrical to the adjusted setpoint.
example for pH controller: - measurement range pH = 2 - 12 pH
- measurement span 10 pH
- adjusted deadband ± 0.1 pH
- adjusted setpoint 6.0 pH
Then the pH-control is inactive at an actual value of 5.9 pH - 6.1 pH