49
Functions
10.2.5
X.CONTROL
-
control parameter of the positioner
This function sets the parameters of the positioner (dead band and amplification factors).
Dead band: Insensitivity range of the positioner
Input of the dead band in %, based on the scaled stroke range;
i.e.
X.LIMIT
Stroke limitation top -
X.LIMIT
Stroke limitation bottom (See auxiliary function
X.LIMIT
).
This function ensures that the controller does not respond until a certain control difference is reached. This
function protects the solenoid valve in the positioner and the pneumatic actuator.
If, during the execution of
X.TUNE
, the control parameter (
X.CONTROL)
auxiliary function is in
the main menu, the positioner dead band is determined automatically depending on the friction
behaviour of the actuator. The value determined in this way is a guide value. It can be readjusted
manually.
Position set-
point value
Control
difference
Xd1
Actual
position
to the controller
Xd1’
Dead band
Xd1
Xd1’
Fig. 21:
Diagram X.CONTROL
Open/close amplification factor: Parameter of the positioner
Open amplification factor:
Amplification factor of the positioner (for closing the valve)
Close amplification factor:
Amplification factor of the positioner (for opening the valve)
10.2.6
SAFEPOS
-
Definition of safety position
This function is used to set the safety position of the actuator that is approached with defined signals.
The set safety position is only approached if there is a corresponding signal at the digital input
(for configuration see digital input) (
BINARY.IN)
) or when an error occurs.
If the mechanical stroke range is limited with the stroke limit function (
X.LIMIT)
, only safety posi-
tions within this limitation can be approached.
This function is only executed in AUTOMATIC operating state.
Type 8791, REV.2
english
Summary of Contents for 8791 REV.2
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