Eagle Electronics FISHMARK 640C - Manual (Page 84)

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4. Press
→ to the second number, them press ↑ to change the num-
ber to 5, then press EXIT . The depth indicators now accurately show
the water depth from surface to bottom.
Sensitivity & Auto Sensitivity
The sensitivity controls the ability of the unit to pick up echoes. Sensi-
tivity can be adjusted because water conditions vary greatly. A low sen-
sitivity level (from zero to 50 percent) excludes much of the bottom in-
formation, fish signals and other target information.
High sensitivity levels let you see this detail, but it can also clutter the
screen with many undesired signals. Typically, the best sensitivity level
shows a good solid bottom signal with Grayline

and some surface clut-
ter.
Automatic Sensitivity
The default sensitivity mode is automatic. The unit bases the sensitiv-
ity level on water depth and conditions. When the unit is in the auto-
matic mode, sensitivity is automatically adjusted to keep a solid bottom
signal displayed, plus a little more power. This gives it the capability to
show fish and other detail.
Situations will occur when you will want to increase or decrease the
sensitivity. If you want to see more detail an increase in sensitivity will
be necessary. Wave action and boat wakes can create enough tiny air
bubbles to clutter much of the water column. In this case, a decrease in
sensitivity is indicated to reduce some of the clutter.
The control bar used to adjust sensitivity up or down is the same
whether the unit is in the automatic or manual mode. In automatic
mode you can adjust sensitivity up to 100 percent but the unit will limit
your minimum setting. In auto mode the unit will continue to make
small adjustments allowing for the setting you selected.
In manual mode you have complete control over sensitivity with the
ability to set it anywhere from zero to 100 percent. Once you select a