30 Raymarine DSM400 Digital Sounder Module
Achieving Accurate Sonar Readings
If you are using the DSM400 at depths of
less
than 100 feet,
thermoclines are always penetrated correctly by the sonar,
providing accurate depth readings. If you are using the DSM400
at depths
greater
than 100 feet, and displaying
low
frequencies
only:
1. Press the
RANGE IN
or
RANGE OUT
button to open the
Range Adjust toolbar.
2. Toggle the
RANGE
softkey to the
MAN
option.
3. Press
OK
.
4. In the main fishfinder view, press the
RANGE SHIFT
softkey.
5. Using the rotary control, adjust the range so that the true sea
bottom and the thermocline return are displayed. Continue to
adjust the range until the thermocline is shifted off the top of
the screen, while the true bottom remains on the screen. The
correct depth is then displayed, as shown in the following
diagram:
If you are using the DSM400 at depths
greater
than 100 feet,
and displaying
high
frequencies only, the Range Shift function
has no impact, as the high frequencies mean that it is less likely
that a thermocline will be detected as a bottom
in any range
.
However, in the event that a thermocline
is
mis-interpreted as
the bottom, you must adjust the fishfinder display to show low
frequencies only, and then use the Range Shift function to
penetrate the thermocline. This procedure is described in the
steps above.
If you are using a combination of the low and high frequencies
(for example, using the split display function and/or one of the
dual-frequency preset modes), you may be able to see the
bottom correctly by range-shifting the low frequency part of the
display. If the correct bottom depth is not returned, you may
need to switch to low frequencies only, and then use the Range
Shift function to penetrate the thermocline, as described above.
3.6 Warnings and errors
The status Light Emitting Diode (LED) on the top casing of the
sounder module provides information on the status of the
sounder module and notifies you of any problems within the unit.
The LED blinks the following colors:
•
Green
- shows the unit is operating normally.
•
Amber
- warns of a problem in the unit.
•
Red
- shows that there is an error in the unit.
The number of times the LED ‘blinks’ is a code which represents
the errors or warnings shown in the table below. If there are
multiple warnings or errors, the codes are given in a sequence
with a 1.5 second pause between sequence strings.
D11151_1
Here, the bottom of the
thermocline can still be
seen, as it was range-shifted
to the top of the display.
Thermocline
This is the actual bottom
depth (2289 ft).
Actual Bottom
The DSM400 sonar has
penetrated the thermocline,
and is now displaying the
correct depth reading.
True Depth Reading
The scale for this part of the
display is not relevant in
this particular example.
Zoomed Area
DSM400 Installation Guide.book Page 30 Tuesday, November 4, 2008 4:53 PM
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