Installation
Seanet SCU v5
0581-SOM-00002-02
Tritech International Ltd.
Page 12 of 35
4.2. Communication Configuration
Fitted inside the SCU, located at the front panel, is the SCU V5 Main Board. This
is a multi-purpose board that houses the bulk of the circuitry from the superseded
AIF PCB. This includes the ARCNET interface, for communications with the subsea
sensor heads, and the RAT interface. The Main Board is also populated with the
Memory Card Reader, Port Status LED's and hardware for COM Ports A to D. The
SCU V5 Main Board will appear in the Setup table as Node 252 which replaces the
Node 255 for the superseded AIF Card.
Full details of all the connections are contained in Appendix B, SCUv5
Communications Setup. Normal communications with the subsea devices is via a
customised version of the ARCNET network system and requires a good quality
balanced twisted pair cable.
An optional RS-232 interface can be provided to allow telemetry connection through
a fibre optic system capable of 115kBaud transmission. The RS-232 interface is
available in the guise of an RS-232 to ARCNET converter PCB that is installed in a
dry pod inside the ROV. Alternatively, an intelligent 4000m pressure rated Junction
Box will provide the RS-232 interface to the network of SeaKing ARCNET devices.
Note
The SeaKing range of Subsea Sensors are designed to work from a
smoothed DC power supply of 18v-36v DC (Absolute Maximum 36v
DC).
If using a rectified transformer PSU, the output of the PSU must have a filter capacitor
of not less than 470µF, for each head being powered. If an unregulated PSU is used,
then make sure that the voltage value measured at the head is in the range 18-36v DC,
both in power off and running conditions. If powering the head(s) down a long lead
or umbilical, the maximum recommended loop resistance of the power line must not
exceed 10ohm for one head, 5ohm for two heads, and 3ohm for three heads. If the
supplied voltage is less than 18v dc the head may not operate correctly.
Caution
Never try to make Tritech International Ltd sonar heads work down a
long cable by increasing the PSU output voltage above the recommended
voltage.
For detail of the appropriate termination requirements for a Tritech International Ltd
ARCNET network please refer to Appendix C, ARCNET Termination
Use with Ethernet Sonars
The motherboard ethernet port is capable of driving a single ethernet device, such as
a Gemini imaging sonar or profiler, or it can be coupled to a network switch to enable
multiple sonars to be operated. A specially designed Gemini Hub unit is available
from Tritech International Ltd which enables multiple Gemini imagers and other
sensors to be attached through the ethernet port.
