User guide

901-10037001/1.1 FS 20/25 Operators Manual
Page 5.26 Maintenance and Troubleshootin
g
Kongsberg Simrad Mesotech Ltd.
Port Coquitlam, BC - Canada
If the impedance between the cable’s two conductors is too low, then
possible problems are bad splices, water in cable, moisture in slip rings (if
connected during test), or damaged cable. If the impedance between the
cable’s conductors and the vessel’s hull is too low, then possible causes are
damaged outer jacket on cable, bad splice, or bad slip rings (if connected
during test).
• Closed Loop Resistance
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.
To do the test, the conductors at one end of cable should be jumpered together
(shorted). An ohmmeter is then used at the other end of cable to measure the
resistance between the conductors.
• Voltage and Current at Trawl Unit
Further checks of cable losses can be performed by measuring both the voltage and
current at the trawl unit. This measurement requires the trawl unit electronics to be
connected and the FS system powered up. This test is done where the trawl cable
pigtail plugs into the sonar head. Jumpers will be required to breakout the signals
for connection to a handheld multi-meter.
Caution!
There are DC voltages on the trawl cable that are capable of
delivering a lethal electric shock!
The minimum voltage at the trawl unit is 55 Vdc and the current should be
approximately 250 mA with sonar head only connected and 325 mA with both sonar
head and sensor module (current readings will vary depending on operation mode -
i.e., scan speed and range, etc.). This test is recommended more for a service
representative than ship's personnel in the field.
• Test for Water In Cable
When a trawl cable is damaged or there is a poor splice, salt water can get into the
cable. As a result, the cable may act as a battery, producing a small dc voltage
across the conductors of the cable. This is detrimental to the operation of the FS
system and all affected cable should be removed.
To test for this, the trawl cable should be disconnected from the FS system and a
voltage meter connected to the trawl unit end of the cable. If water is present, then