Seanet SCU v5
0581-SOM-00002-02
Tritech International Ltd.
Page 31 of 35
Appendix C. ARCNET Termination
The ARCNET communication link requires a termination resistor to be installed at
each end of the umbilical cable. Normally this is supplied fitted within the ARCNET
cable DA-15 connector at the surface and is left for the user to fit at the sub-sea end
in a convenient junction box or by use of the yellow waterblock.
Caution
Fitting the resistor inside the unit is not recommended and may invalidate
the warranty.
The purpose of these terminations is to attenuate any electrical interference or
"reflections" which may occur due to an impedance mis-match and the overall aim
is to improve signal quality and negate any effects which might otherwise be felt by
other sources of impedance such as from the cable itself.
The diagram below shows best practice to use when installing termination resistors
on an ARCNET network of Tritech International Ltd sonar products.
Note
A special yellow waterblock is available from Tritech International Ltd
which contains an in-line impedance of 39ohm which will enable quick
and easy installation of the subsea termination resistor.
Cable length
Termination
Baud rate setting
Less than 100m
Single 39ohm subsea resistor
Normal baud rate
100-1200m
270ohm at surface and 39ohm subsea
Normal baud rate
1200-2500m
270ohm at surface and 39ohm subsea
Half baud rate
Note
If there is more than one sensor connected then the sub-sea resistor should
be fitted at the junction box or splice of the cable.
