Teledyne 440, System Manual, Page: 119 / 256

6 – Operating Procedure
DPN 402196 Issue 4.1 © Teledyne TSS 6- 15
Wait approximately one minute until the System has completed at least five measurement cycles. The
results will appear on the SDC screen. Check that all the measurements appear in black – red figures
on any channel indicate signal saturation.
As the System completes each measurement cycle, the background compensation measurements
appear on the screen and on a printer if one is connected.
Press any key to stop the background compensation process. There will be a delay of about ten
seconds while the System completes its final set of measurements. The background compensation
results used by the 440 System are those included in the last line on the display.
Examine the columns of figures that appear under each of the three channels. Within each of the used
channels, the column of figures should all be the same within ±5µV. If they are not, then there may be
a fault on the System. See
section 9.3.1 "Fault on Single Channel Only" on page 9-11 for fault
identification procedures.
It does not matter if the figures in one channel are different from those in another.
Ideally, the figures for channels 1–3 should all be below 1000µV for standard coil values and below
7500uV for early coil values. If any channel shows a background compensation figure significantly
above this level, do the following:
1. Move the ROV to another area of clear ground and repeat the background compensation pro-
cess. If the values fall to below 0µV this means that the original site had some hidden conduc-
tive debris near the coils.
2. See section 3.1.3.2 "Positioning the Search-coils" on page 3-6 and reposition the search-coils
farther from the ROV body.
Upon successful completion of the background compensation procedure, include a written or printed
copy of the compensation values with the survey log and return to the Run Display screen. Examine
the coil voltage displayed for each channel and note that they should all show values close to zero. The
display should also show a large red ‘Target Out of Range’ banner to indicate that there is no target
within the detection range of the search-coils.
Move the ROV by two metres and confirm that the displayed signal strength values do not go negative .
If they do, this indicates that you conducted the background compensation procedure in the presence
of conductive debris on the seabed. In this event, move the ROV to another clear area and repeat the
background compensation procedure.
Background Compensation Check
NOTE
The background compensation check is a different procedure from the full back-
ground compensation. You must perform the check at regular intervals (at least
once every hour), and after every deployment of the manipulator arms. You may
configure the SDC to show a message banner that reminds you to perform this
operation at pre-set intervals.
At regular intervals, move the ROV approximately 10 metres away from the target. Confirm that the
signals on each channel fall to within ±5µV of zero. You may resume the survey if the signals fall to an
acceptable value. The Background Noise Profile facility allows for these signals to be monitored and
logged fro post-survey analysis.