Teledyne 440, System Manual, Page: 38 / 256

3 – Physical Installation
3-6 © Teledyne TSS DPN 402196 Issue 4.1
3.1.3.1 Search-coil Configuration
The standard 440 System uses three search-coils of dimension 1.0m × 0.94m × 0.03m. They must be
mounted so that the sides without mounting holes point in a fore-aft direction.
NOTE
Versions of the 340 System used search-coils of different dimension. Do not use
type 41 or other old coil types with the 440 System.
To protect the coils, mount them on the ROV with their potting compound uppermost.
Where necessary, after you have installed the coils you may restore a neutral ROV trim by firmly
attaching a small non-conductive buoyancy aid to the front of the coil array.
3.1.3.2 Positioning the Search-coils
NOTE
The Search-coils must be firmly secured, so that there is no movement during the
survey. A poor Search-coil mounting arrangement will reduce the performance of
the system.
Consider these factors carefully when you choose a position to mount the coil array, and then read the
following paragraphs for an explanation of these factors.
1. Coil separation distance .
This is the distance between the coils and the body of the ROV after installation.
2. Mounting position .
Consider whether you will mount the coils on the front or the rear of the ROV.
3. Height of coils .
This is the vertical distance between the coils and the lowest point on the ROV. Mount the coils
so they are parallel with the horizontal axis of the ROV.
1. Coil separation distance
This is the shortest distance between the edge of the search-coils and the region of the ROV where
significant conductive material begins (see
Figure 3-4 ). It is the most important consideration you must
make when you plan your installation. There are conflicting requirements when you make this decision,
and so you may have to make a compromise:
❐
Mounting far away from the ROV :
A large coil separation distance will reduce the size of the background signal caused by the
ROV body. This will reduce any tendency for the coils to saturate when they are over an
exposed section of the target.
❐
Mounting close to the ROV :
A small coil separation distance will allow you to deploy, manoeuvre and recover the ROV
more easily.