Deep Sea Electronics Plc DSE8660 MKII

Specification
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2.10.3 RS485 PORT
NOTE: For a single module to PC connection and distances up to 6 m (20 feet) the USB
connection method is more suitable and provides for a lower cost alternative to RS485 (which
is more suited to longer distance connections).
The RS485 port on the controller supports the MODBUS RTU protocol and is for connection to a
single MODBUS master device only.
The DSE MODBUS register table for the controller is available upon request from the DSE Technical
Support Department.
RS485 is used for point-to-point cable connection of more than one device (maximum 32 devices)
and allows for connection to PCs, PLCs and Building Management Systems (to name just a few
devices).
One advantage of the RS485 interface is the large distance specification (1.2 km when using Belden
9841 (or equivalent) cable. This allows for a large distance between the module and a PC running the
DSE Configuration Suite software. The operator is then able to control the module, starting or
stopping the engine, selecting operating modes, etc.
The various operating parameters (such as coolant temperature, oil pressure, etc.) of the remote
engine are viewed or changed.
Many PCs are not fitted with an internal RS485 serial port. DSE DOES NOT recommend the use of
USB to RS485 convertors but can recommend PC add-ons to provide the computer with an
RS485port.
2.10.3.1 CABLE SPECIFICATION
NOTE: DSE recommend Belden 9841 (or equivalent) cable for RS485 communication. This
is rated to a maximum cable length of 1.2 km. DSE Stock Belden 9841 cable, DSE Part Number:
016-030.
Description
Specification
Cable Type Two core screened and shielded twisted pair
Cable Characteristics
120 Ω impedance
Low capacitance
Recommended Cable
Belden 9841
Belden 9271
Maximum Cable Length
1200 m (¾ mile) when using Belden 9841 or direct equivalent.
600 m (656 yards) when using Belden 9271 or direct equivalent.
RS485 Topology “Daisy Chain” Bus with no stubs (spurs)
RS485 Termination
120 Ω. Not fitted internally to module. Must be fitted externally to the ‘first’
and ‘last’ device on the RS485 link.