Unit installation
Troubleshooting and Maintenance
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5.4.5 Testing the Trawl Cable
If after testing the FS system the trawl cable is suspected to be
faulty, then troubleshooting is needed to determine what and where
the problem is. For problems that are not obvious, however, this
can be quite difficult to do and may require someone experienced
with testing trawl cables. This following paragraph provides some
basic tips in troubleshooting trawl cables but is in no way a
complete and comprehensive guide.
5.4.5.1 Trawl Cable Insulation Measurement
The use of a Mega-Ohmmeter to check the impedance of the trawl
cable may be the most useful test. It can be done with or without
the slip-rings connected and readings should be taken between the
cable’s two conductors and also from each conductor to the fishing
vessels hull. Typically the impedance should be greater than 2 MΩ,
and preferably over 6 MΩ and lower readings may be indicative of
potential problems with the third wire cabling.
Caution: The FS system MUST be disconnected from trawl cable
during Mega-Ohmmeter tests to prevent possible damage to the
electronics!
If the impedance between the cable’s two conductors is relatively
low then the cable should be inspected for possible problems with
splices, water ingress, and moisture in slip-rings (if connected
during test).
If the impedance between the cable’s conductors and the vessel’s
hull is relatively low then inspect the cable for any visible damage
to the cable armour/jacket. Other possible causes are bad splices or
bad slip-rings (if connected during test)
5.4.5.2 Closed Loop Resistance, Voltage and Current at Trawl
Unit
As previously mentioned, the closed loop resistance must be less
than 100 Ohms for proper operation of the FS system.
This test should be done with the FS system disconnected but with
the winch slip-rings included. For whatever cable type and length
used the following specifications must be met for operation with the
Simrad FS trawl Monitoring system:
Cable Closed Loop Resistance <100 ohms