5 – Operational Considerations
DPN 402197 Issue 7.1
© Teledyne Limited
5- 5
Reduce the potential errors caused by a sloping seabed by operating the ROV as close as possible to
the seabed.
5.2.2 Electrical Interference
The 350 system is unaffected by the following factors:
❐
Changes of ROV heading
❐
Any local static magnetic field
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Acoustic noise
❐
The presence of platforms, rigs or other vessels in the vicinity
This sub-section describes the sources of interference that might affect the 350 System.
You may estimate the level of background noise by examining the Scope and Spectrum Analyser
Window. If the noise level is so high so that it masks the tone frequency, take whatever action you can
to reduce or eliminate the noise.
5.2.2.1 The ROV
Other items of electrical equipment on board the ROV, for example the thrusters, might represent a
powerful source of electrical noise. If these noise components are at a sufficiently high level, they might
mask the relatively weak signals associated with the target tone.
Signal discrimination by the 350 system is extremely good. It removes noise from the calculation
process by examining only a very narrow window of frequencies with the tone at its centre. However,
where noise levels centred on the tone frequency are very high, they might degrade the performance
of the 350 system and affect the accuracy of its survey measurements.
The Scope and Spectrum Analyser Window will show those bands where noise is at a minimum. You
may then adjust the frequency of the target tone to fall within one of these quieter bands.
Summary:
❐
Use DeepView to check all channels of the 350 system with all electrical equipment on the
ROV operating. Select a tone frequency centred on a part of the band that has low noise lev-
els.
❐
Investigate any severe noise sources before you start the survey and reduce or eliminate them
if possible.
❐
Use the display software to perform regular checks on the quality of tone signal.
5.2.2.2 Vibration
Mechanical vibration of the coil triads could create a noise signal at a relatively low level as the coils
move relative to local magnetic fields. This noise would exist across a broad band of frequencies
centred on the frequency of vibration.
Where vibration is fast and severe, the resultant induced signals could interfere with the signal from the
target cable.
Slow movements, such as those of the ROV manoeuvring, will have a negligible effect since the
resulting induced voltages will be at a frequency below the pass-band of the 350 system.
