Input and Output Signals
Publication
PUB091-004-00_0918
55 of 64
7.9.1
Action on Loss of Comms (Register 7)
This register is used with register 13 (Comms Lost Position) and 21 (Comms Fault Timer).
The Action on Loss of Comms register defines the actuator action that will result after the time set for
the Comms Fault Timer (register 21) if there is no network communication activity detected by the
MFU.
The action may be
Nothing
(0)
No action; the actuator will complete any command in process (default
setting)
Open
(1)
The actuator will open the valve
Close
(3)
The actuator will close the valve
Stop
(5)
The actuator stops
Position
(7)
The actuator will move the valve to the position set in the Comms Lost
Position (register 13).
7.9.2
Limited Range Position Minimum and Maximum (Registers 8 and 9)
These parameter registers are used to define the positions in the range of valve travel that will be
reported as 0 to 100% if it the whole travel from the closed position to the open position is not used. In
addition, the position demand setpoint output value will also be modified to follow this limited range.
It is possible to make the position data reported and the position controller relate to a reduced span of
actual valve travel. In this mode the position data relates to the reduced portion of the valve stroke.
This is sometimes used where the valve is required to have a 0% position (or 100% position) that is
not the same as the fully closed position (or fully open position). These parameters define the actual
limited range of valve travel that will be used for the position reporting and control by the positioner.
Fig 18:
Limited Range Position Control and Reporting
Note that the digital open and close commands will still make the valve travel over its full stroke. The
special case analogue commands of 0% and 100% that would otherwise cause the actuator to travel
to the limit switch or torque off positions are inhibited if values other than 0 and 100 are set in these
parameters.
The values inserted relate to the maximum total valve travel between closed and open and represent
the point in the full stroke which will now be used for the limited stroke 0 and 100 values.
7.9.3
Deadband and Hysteresis (Registers 10 and 14)
When using position control by sending a value to the Actuator Position DV setpoint there are a
number of parameter registers used to tune the position controller and reduce the possibility of
damage to the actuator. These two registers are set to prevent hunting around the setpoint due to high
0% ----------------- Reported Position --------------------- 100%
Valve Stroke
CLOSED
OPEN
Position Minimum Setting
Position Maximum Setting
