Teledyne 440, System Manual, Page: 122 / 256

6 – Operating Procedure
6-18 © Teledyne TSS DPN 402196 Issue 4.1
Signal saturation may occur if the target is too close to the coil array. Whenever this happens, an
automatic gain facility immediately reduces the voltage gain of the System by a factor of 10.
If the target is very close to the search-coils, it is likely that saturation will continue even if the surveyor
reduces the System voltage gain. Under these circumstances saturation will persist until the target
moves farther from the search-coil array, and the target track shown on the Run Display screen will
appear as a solid red line.
Left/Right Tracking occurs when the 440 system is able to calculate a valid lateral offset but unable to
calculate a valid vertical offset. This condition will set the Quality Code to ‘99’ and the Quality Flag will
be SET.
The top region of the Run Display screen represents a cross-sectional rear view of the coil array, the
target and the seabed. The coil array appears at the top edge of the screen and a vertical broken white
line extends down from its centre.
A hollow white circle represents the target. This circle moves to the left and right, and up and down as
the position of the target moves relative to the coil array. Note that the
diameter of this circle does not
change with different target sizes.
Whenever the System cannot measure the vertical range to target, for example during signal
saturation or when the target falls within the range of one coil only, the circle that represents the target
will disappear from the screen.
The seabed appears on the Run Display screen as a horizontal white line. This line moves up and
down in response to measurements made by the altimeter if you have one connected to the System.
If your System has no altimeter, the position of the seabed line will show the fixed coil height. You
should configure the SDC with a fixed coil height if your System does not use an altimeter.
The seabed line will disappear from the screen whenever the altitude exceeds 5m.
Near the right-hand edge of the top region, there is a scale of vertical range. You may estimate the
vertical range to the target and the coil altitude against this scale. Press [CTRL]+[H] or use the ‘Toggle
Height Scale’ from the ‘View’ to toggle between the 5 metre and the 2 metre scale range.
There are other data fields presented on the screen. These provide a digital indication of:
❐ Altitude of the search-coils above the seabed (ALT).
❐ Vertical range to the target (VRT).
❐ Depth of target cover (COV).
❐ Lateral offset between the target and the centre-line of the coil array (LAT). A positive value
indicates that the target is to starboard of the centre-line.
❐ Quality Code (QC).
There is also a scale of lateral offset distance displayed between the top and the bottom regions of the
Run Display screen, with gradations at zero, ±1.0 and ±2.0 metres. You cannot change the range of
this scale.
The Quality Code is also displayed in the right side of the Snail Trail Window displaying system status
relative to coils in use/ signal stengths obtained.
All measurements of distance are in units of metres to two decimal places.