Unit installation

FS70 Trawl Sonar System
72 974-24007001/4.1
A test for slip-ring problems is to slow down the winch (at high
winch speeds you will not see jitter on the current meters) and
check if the current meter is jittering and whether the jitter rate
changes with the winch speed.
Note: The current meter will pulse each time the transmitter pings.
The pulse will be at a constant rate depending on your operating
setting.
2. Increase in Current:
Gradual increases in the trawl unit current may be due to either the
trawl cable or the trawl unit electronics. A higher cable closed loop
resistance, due to cable damage, poor splices, poor winch slip-rings
or water ingress in the cable may reduce the voltage supplied to the
sonar head below the required minimum DC voltage. This will
result in the sonar head drawing more current. Alternatively there
may be a problem in the sonar head that causes additional current
draw.
To diagnose this problem a current reading should be made with the
system running on the test cable. If this value is higher than a
previous value obtained on the test cable or when connected to the
cable simulator then the problem is likely with the trawl unit
electronics. If the current readings are the same on test the cable as
previously obtained, then the trawl cable and winch slip-rings
should be checked.
5.4.4 Trawl Cable Gain
By periodically checking the cable compensation gain obtained
from the system unit and comparing it to a previously recorded
value the condition of the 3
rd
wire trawl cable can be monitored.
Acceptable cable gain values have less than “10, XXX” for the first
gain number. If the first gain value is over “10, XXX” then there
may be a problem with the 3
rd
wire trawl cable and the system
should be checked on the test cable. To facilitate monitoring of the
trawl cable, the cable gain values should be recorded on the test
report.