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The display will briefly show CON to confirm the operation and
then return to the SET ENG display. If no further settings are
to be made then pressing the ILLUM key will exit the
configuration mode and return to normal operation
SETTING THE KEEL OFFSET
The Echo Sounder measures the depth from the transducer to
the seabed. If the craft has a keel it is more often convenient to
show the depth from the keel to the seabed. To operate in this
way the depth of the keel (keel offset) must be entered into the
instrument as follows:
Put the instrument into the configuration mode. The display will
now show SET ENG. Press SPEED, the upper half of the
display will show USET and the lower half the current keel
offset value. Use TRIP to decrement and TOTAL to increment
this value. Pressing SPEED will enter this new value. The
display will briefly show CON to confirm the operation and then
return to the SET ENG display. If no further settings are to be
made then pressing the ILLUM key will exit the configuration
mode and return to normal operation.
CHANGING THE GAIN THRESHOLD
The Echo Sounder emits a high frequency pulse which
bounces off the seabed back to the transducer. Echoes from
nearby objects are much stronger than those from distant
objects so an automatic gain control compensates for these
different strength signals. However, reflections from nearby
turbulence or bubbles can sometimes be confused with those
from the bottom. To prevent nearby reflections from causing a
problem, the sensitivity to nearby objects can be reduced.
