ONLINE ELECTRONICS LTD
2405_5001_A01
Page 6 of 14
3.
OPERATION
As with all acoustic systems, the ambient acoustic noise existing in the environment will have a
significant impact on the performance of the 2405 system. Some of the most common sources
of ambient acoustic noise are vessel engines, water turbulence and rough weather.
Also be aware that there may be nearby acoustic transmitters unexpectedly transmitting at (or
close to) the frequency of interest. These should be disabled if possible. For example any
acoustic beacons on the ROV must be disabled and any support vessels with dynamic
positioning systems should be disabled or configured to work outside of the frequency of
interest if possible.
The typical procedure for detecting an acoustic transmitter is given below. This procedure
assumes the operator knows the expected frequency and pulse rate of the acoustic transmitter
being searched for.
1.
Before each deployment visually inspect all system components to ensure that they are
secure and undamaged. Pay particular attention to the cable and connectors.
2.
Before each deployment ensure that all tests described in section 3.1 SELF TEST and
section 3.2 FUNCTION TEST are repeated.
3.
Before deployment ensure the fishtail is positioned suitably, it can be positioned in several
different positions on the fishtail bracket as required.
4.
Use the control button to select the expected frequency of the acoustic transmitter.
5.
It is recommended that AGC gain is selected as per section 3.5.2 MANUAL MODE / AGC
MODE.
6.
Select a timebase which will display approximately 5 pulses at the expected repetition rate
on the screen as per section 3.4 OPERATING SCREEN.
7.
Ensure the unit is turned on as per section 3.3 TURNING ON and the battery meter shows
more than 50% capacity remaining. If less than 50% is indicated then change the
batteries as per section 4.1 BATTERY REPLACEMENT.
8.
Point the active face of the 2401 hydrophone towards the expected location of the acoustic
transmitter. The active face of the 2401 points out of the tubular frame in the opposite
direction to the 2405 display.
9.
Very slowly scan in different directions while observing the signal received and the AGC
value to try and determine which direction gives the strongest and clearest signal. Move in
this direction to get as close as possible to the transmitter.
10.
Confirm that the FREQUENCY and pulse rate of the acoustic signal are as expected. Be
aware that there may be other acoustic transmitters in the environment (such as ROV
beacons or dynamic positioning beacons). These sources should be disabled if possible
otherwise it should be possible to identify the signal of interest by carefully examining
frequency and pulse rate.