Unit installation

FS70 Trawl Sonar System
74 974-24007001/4.1
Signal Attenuation Through Cable:
<40 dB (1/100 signal amplitude) @ 55 kHz
<20 dB (1/10 signal amplitude) @ 12 kHz
The cable closed loop resistance determines the maximum voltage
drop along the trawl cable. For proper operation the FS 70 trawl
unit electronics require a supply voltage of 60 to 200 VDC. For
typical operation, the current is approximately 195 mA to 250 mA
with peaks to 450 mA. The equations for calculating the voltage
drop along the trawl cable are described in the next paragraph.
There are two methods to check the closed loop resistance of the 3
rd
wire:
Method 1
To do the test the conductors at one end of cable should be shorted
together. An ohmmeter is then used at the other end of cable to
measure the resistance between the conductors.
Method 2
An estimate of cable losses and resistance can be done by
measuring 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.
The cable closed loop resistance determines the maximum voltage
drop along the trawl cable. For proper operation, the FS Trawl
Sonar System requires between 120 VDC or 200 VDC @ 1 A
maximum depending on the type of sonar head you are using. For
typical operation, the current is approximately 195 mA to 350 mA
with peaks to up to 450 mA.
The equation for calculating the resistance of the 3
rd
wire trawl
cable from the TTM to the sonar head is:
Cable Resistance =