Modbus Option Card Properties
Publication
PUB091-004-00_0918
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2
MODBUS OPTION CARD PROPERTIES
2.1 Mechanical properties
The Modbus module option card differs from all previous versions in that it interfaces directly between
the Modbus RTU network and the communication protocol used within the actuator. There is no
intermediate circuit board that it plugs into. We refer to it as the Modbus Field Unit, MFU.
The MFU is a single rectangular printed circuit board that fits inside the actuator electrical housing. It
connects directly to the Control Module PCB of the actuator by a ten pin connector (10 way header,
SK2). The field unit should be carefully fitted so that the connectors mate correctly. The actuator
internal wiring harness connects the field unit at SK3 to the Modbus highway via the actuator terminal
bung. The connector is polarised to prevent incorrect connection.
In the IQ3, the field unit can be fitted directly to the Control Module PCB using either one of the 2 slots
available, or can be fitted on top of another option module that may already be fitted in one of these
slots. There are 4 available slots for option cards to be mounted either directly or indirectly behind the
Control Module PCB.
Fig 2:
The Modbus Field Unit
SK3
– Field
connections.
Control board
connection. SK2
connector fitted on
underside of MFU.
