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Publication S703E V1.1
Issue 06/09
scanning up to the highest address. All the addresses in the selected range
should be used and gaps in the address range should be avoided. Gaps or
unused addresses cause the system to run more slowly as the unused
addresses are still checked. In addition, unused addresses will generate a
communication failure alarm.
Loop Speed
: This shows the current loop scanning speed (loop baud rate) and the drop-
down box allows a desired loop speed to be selected. The choices are
2400, 1200, 600, 300 and 110 baud. When a new speed is entered it will
take effect as soon as the values are saved. The setting applies to the
Pakscan 2 Loop option card only and the actuators must be changed
individually.
New Loop Speed : The drop down box allows a new data rate speed to be selected for the
field units in the actuators. The new speed will be adopted next time the
loop is reconfigured. A change here should be mirrored by a change in the
loop speed setting above. It is possible to select rates in the range one
step up or two steps down from the current speed.
If the loop communication is not stable it is often necessary to reduce the
speed to improve reliability. If the field units are all in communication with
the master station this is possible with this feature.
Loop Speed
: On a stable loop it is possible to halve the loop scan time by doubling the
Doubling
data speed using this setting. Care is needed to ensure that the loop
continues to be stable, since the use of this feature slightly reduces the
system’s capability to reject interference from pumps and motors.
Retain Data on
: Normally the data base information about an actuator is cleared to zeros if
Loss of
communication with the actuator is lost. This ensures that the false valve
Communication
position information is not transmitted to the host system during the loss of
communication. A single ‘Comms Fail’ data bit is set. This system setting
allows the data to be kept at the last value received from the actuator. Note
that the data is retained indefinitely and does not necessarily reflect the
true actuator status.
DV Convert
: This option can be used to ensure that 100% and 0% Desired Value
outputs to the IQ, IQT, Skil and EH actuators are transformed into actions
to make the actuator run to the fully open (100%) and fully closed (0%)
positions. The message is converted from a DV command to an Open or
Close command respectively. This is useful for positioning actuators,
where it is possible that the valve will not fully shut or open when moved by
only a small amount. When used for tight shut off valves, with analogue
position control only, the setting should be ON; the default is OFF.
Host Port 1
: The drop-down box allows the data base organisation used on this port to
2, Ethernet
be selected. The choices are Generic Modbus, Honeywell PLCG Modbus,
Database
Yokogawa Modbus and Honeywell SI Modbus.
Selection
Port Alarms
: This drop-down box allows port alarm handling to be configured. Alarms
can either operate completely independently (‘separate’) for each port, or
can be linked such that the same alarm information is always reported,
regardless of which port is used.
Alarms must be read and accepted before they can clear and return to
normal. If configured as separate, alarm reading and acceptance must be
done separately for each of the three ports. This ensures that the different
