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7 – Operational Considerations
DPN 402196 Issue 4.1 © Teledyne TSS 7- 1
7 Operational Considerations
There are some operating circumstances when the performance and accuracy of the 440 System may
degrade. This section of the Manual describes some of the major causes of performance degradation
so that you may avoid them or compensate for their effects.
7.1 Operating Performance
Together with the skilful operation of the 440 System, two major factors influence the response and the
performance of the System during survey operations:
1. Target size and conductivity
The System detects any conductive target close to the coil array. Targets that have a larger conductive
mass will return a stronger signal than smaller targets. It follows therefore that the System can detect
large targets at a considerably greater range than small ones.
2. Coil arrangement on the ROV
The performance of the 440 System depends heavily on the mounting arrangements of the coil array.
The standard System is optimised for use with three search-coils having dimensions 1.0m × 0.94m ×
0.03m. Considerable field experience confirms the ability of this coil arrangement to provide the best
combination of accuracy, detection range and ease of deployment.
See section 6.4.1.1 "External Logging Format" on page 6-23 for a full description of the external
logging format to a data logger. The SDC includes a indication of the quality of the measurement.
NOTE
The Quality Control feature eases quality control review during subsequent post-
processing and data analysis.
The minimum operating range of the System depends on the tendency for the search-coils to saturate
when they are too close to a conductive mass. Since the strength of signals relates to the size of the
target, saturation occurs more readily for large targets and their minimum detection range is therefore
greater than for small targets.
Summary :
The logged data packets include a Quality Control flag to identify data that might show degraded
accuracy.
You may use all the information and facilities available from the 440 System to identify any drop in
System performance so that you may take effective and appropriate corrective action.
7.2 Sources of Error
There are other error sources that might degrade System performance. You should make yourself
aware of these so that you may take action to avoid them or to reduce their effect on survey results.
These error sources fall within two categories:
❐ ROV handling