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Northstar 491
Echo Sounder
Operations Manual
This manual is for using the 491 sounder with the
Northstar 957, 958, 961 and 962 navigators. For the
Northstar 6000i, information in Section 6 of its manual can
be used instead.
Revision A
Part Number GM494
Northstar
a unit of Brunswick New Technologies Marine Electronics
30 Sudbury Road
Service: 978/897-6600
Sales: 800/628-4487
Acton, Massachusetts 01720
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6
7
Marking fish as waypoints . . . . . . . . . . . . . . 53
Understanding the alarms . . . . . . . . . . . . . . 56
Setting the fish alarm . . . . . . . . . . . . . . . . . . 56
Setting the bottom alarm . . . . . . . . . . . . . . . 58
Setting the temperature alarm . . . . . . . . . . . 60
8
Troubleshooting 491 Operations . . . . . . . . . . . . 63
Troubleshooting the echo sounder . . . . . . . 64
Checking the transducer . . . . . . . . . . . . . . . 65
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1
Using this manual . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
Technical support . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
How echo sounding works . . . . . . . . . . . . . . . . . 1-5
Powering the 491 on and off . . . . . . . . . . . . . . 1-7
Setting up the 491 . . . . . . . . . . . . . . . . . . . . . . . . . 1-7
This chapter introduces the Northstar 491 Operations
Manual, explains how to contact Northstar for technical
support and service, and describes the 491’s basic set-up and
power on/off procedures.
491 Echo Sounder Operations Manual
Page 1
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Welcome to the Northstar 491
Congratulations on your purchase of the Northstar 491 Echo
Sounder. The 491 connects with a Northstar navigator and a
third-party transducer to add echo sounding capability to the
Northstar 957, 958, 961, and 962 navigators. See the Northstar
491 Installation Manual (part number GM495) for
You may be adding the 491 to your existing Northstar
navigator for echo sounding, or you may have purchased your
navigator complete with echo sounding. In either case, the 491
should be installed and configured by a qualified marine
technician.
To get started right away, Section 2, ”Quick Start: Using the
Echo Sounder,” starting on page 2-11.
CAUTION!
Proper installation and configuration of your Northstar
491 is of utmost importance for accurate and effective
performance under a variety of conditions. To get the
best performance from your 491, Northstar strongly rec-
ommends installation and set-up by a qualified marine
technician. For installation procedures, see the Northstar
491 Echo Sounder Installation Manual (Part Number
GM495).
Using this manual
Chapter 1 introduces you to the 491 echo sounder and to this
operations manual.
Organization
Chapter 2 gives you a quick-start introduction to get you
started with echo sounding as soon as the 491 has been
installed and configured.
Chapter 3 tells how to adjust the echo sounder’s display—the
gain, clutter, colors, etc.
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Chapter 4 describes how to adjust the depth settings to choose
what portion of the water under the vessel you’ll display.
Chapter 5 explains other functions—the A-Scope, etc.
Chapter 6 describes Northstar’s exclusive SoundTrac™ feature,
for accessing past echoes and navigating back to their
locations.
Chapter 7 tells how to use the echo sounder’s alarms: the fish
alarm, bottom alarm, and temperature alarm.
At the back of the manual are a glossary and an appendix
outlining the 491’s specifications.
Specific conventions are used to provide a consistent way to
recognize certain information, as follows:
Conventions
•
is the universal symbol used for caution and warning
information that pertains to your personal safety or pre-
vents damage to the 491. The CAUTION and WARNING
boxes contain critical information—please read them!
•
NOTE is the type style used for titles of reader notes. These
notes contain valuable information purposely highlighted
so that you don’t miss it while reading the main text.
•
•
KEY is the type style used to refer to the menu keys on
the display screen.
DISPLAY TEXT is the type style representing text on the
display screens.
•
•
A bulleted list contains a series of related items or topics.
A numbered list contains a series of steps in a procedure.
491 Echo Sounder Operations Manual
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Technical support
After you follow the instructions in this manual, if you need
technical support or if you have any other questions, you can
contact Northstar by email, fax, phone, or U.S. mail as follows:
Table 1: Contacting Northstar
Email:
Service: [email protected]
Sales: [email protected]
Fax:
Service: 978/897-1595
Sales: 978/897-7241
Telephone:
978/897-6600 or 800/628-4487
U.S. mail:
30 Sudbury Road
Acton, MA 01720
Web site:
Northstar directly from this site)
Your feedback is important and helps ensure that this manual
is a valuable resource for all 491 users. Send your questions,
comments, or suggestions about this manual to:
Hearing from you
Service and repair
In case of an operating problem with your Northstar 491, you
may contact your dealer or return the unit to the Northstar
factory for diagnosis and repair. When describing an operating
problem, be as complete and accurate as possible. Be sure to
have the serial number available whenever contacting or
corresponding with either your dealer or the Northstar factory.
The 491’s serial number is located at the top of the unit. If you
need help, feel free to call the Northstar Service Department at
978-897-6600 between 9:00 a.m. and 5:00 p.m. weekdays,
excluding major holidays.
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To prevent delays, it is critical that you first obtain a Return
Materials Authorization (RMA) number before returning your
unit to the factory. If you purchased your 491 through a
dealer, to get an RMA number, call the dealer with the serial
number. The 491’s serial number is located at the top of the
unit.
The 491 should be shipped in a properly designed carton with
packing material. Please reference the RMA number on the
outside of the carton.
Shipments to Northstar should be made to the following
address:
Northstar Technologies
30 Sudbury Road
Acton, MA 01720
If you have overnight or second-day shipping requirements,
please call the Northstar factory for turnaround time and
freight costs before shipping your 491.
How echo sounding works
An echo sounder produces high-voltage electrical pulses that
the transducer converts into sound waves (called “pings”). The
sound waves are sent downward through the water. When a
sound wave hits and reflects off an object, such as fish, debris,
seaweed, or the seabed, the reflected sound wave (an “echo”)
returns back to the transducer along an imaginary vertical line
the water and seabed can be displayed and analyzed on the
echo sounder screen. In essence, this system lets you see a
real-time cross section of what’s happening underneath your
vessel.
Figure 1, ”957/958 echo sounder system components,” below,
and Figure 2, ”961/962 echo sounder system components,”
below, show how the 491 connects to these navigators to
enable echo sounding functions.
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GPS
antenna
33-foot cable
(part of transducer)
491
module
957/958/6000i
Navigator
10-foot cable
Ship's
Power
Transducer
(Northstar-supplied)
10-foot cable
(Northstar-supplied)
Figure 1: 957/958 echo sounder system components
GPS
antenna
Control
Head
33-foot cable
(part of transducer)
491
module
961/962
Processor
10-foot cable
Ship's
Power
Transducer
(Northstar-supplied)
10-foot cable
(Northstar-supplied)
Figure 2: 961/962 echo sounder system components
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Powering the 491 on and off
As part of its power-up sequence, the navigator automatically
activates the 491.
The 491 is automatically shut off by the navigator when you
press and hold PWR until the screen goes dark.
Setting up the 491
Your 491 should be installed by a qualified marine technician.
Your satisfaction with the system’s performance will be greatly
influenced by the practical knowledge and experience of the
installer. Unlike GPS or other marine electronics systems, echo
sounder installation is as much an art as a science.
The installation procedure includes setting up the following
options:
•
•
•
•
•
the transducer’s depth
the speed and temperature
the calibration for the speed sensor
the calibration for the temperature sensor
the gain calibration for the transducer
You may wish to change the following options from time to
time to match your personal preferences:
•
•
•
•
depth units (feet, meters, or fathoms) on the screen
temperature units (Celsius or Fahrenheit) on the screen
temperature scale (lowest and highest) on the screen
(961/962 only) automatic saving of *FISH##* or
*THERM##* waypoints when the 491 detects the presence
of fish or a certain water temperature that you’ve set
Before starting, you should double-check that the 961/962’s
Port 3 is set to the 490 option:
Using 491 with the
961/962
1. Press STAR until you reach the SERVICE MENU screen.
2. Press PORT SETUP.
3. Press PORT 3.
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4. Check that the FORMAT option is set to “490.” If not, set it
now.
Before starting, you should double-check that the navigator’s
AUX port is set to the Sounder option:
Using the 491 with
the 957/958
1. Press STAR until you reach the OPTIONS/SERVICE INFO
screen.
2. Press the PORT SETUP OPTIONS key.
3. Check that the AUX PORT option is set to “Sounder.” If
not, set it now.
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Figure 3:
STAR key
Auto
Picture
ECHO
SCREEN
Frequency
Zoom
Depth
More
Depth settings
Picture settings
Gain
Shift
Range
Clutter
Noise Limiter
Hue
Signal level
Return
More settings
Alarms
Advance Speed
Snapshot
A-Scope
Data
Bottom box
Return
Return
Alarm settings
Data on-screen
Snapshot
Bottom box
Temp box
Temp graph
Speed
Display
Rename
Fish alarm
Bottom alarm
Temp alarm
Archive
Erase
Return
Return
Return
Figure 4: 961/962 echo sounder menu structure
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STAR key
Auto
Picture
ECHO
SCREEN
Frequency
Zoom
Depth
More
Depth settings
Picture settings
Gain
Shift
Range
Clutter
Noise Limiter
Hue
Signal level
Return
More settings
Alarms
Advance Speed
Video
Bottom box
Return
A-Scope
Data
Return
Alarm settings
Data on-screen
Video setup
Temp box
Temp graph
Bottom box
Speed
Video on
Fish alarm
Bottom alarm
Temp alarm
Return
Return
Return
Figure 5: 957/958 echo sounder menu structure
Page 10
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2
Quick Start: Using the Echo Sounder
Introducing the displayed information . . . . 2-15
Using automatic mode . . . . . . . . . . . . . . . . . . . . 2-16
Changing the frequency of echoes . . . . . . . . 2-17
Zooming in and out . . . . . . . . . . . . . . . . . . . . . . . 2-19
Setup functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-22
This chapter shows you how to start using the echo sounder,
and explains several of the echo sounder’s important features.
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Displaying the echo sounder’s picture
Once the navigator has been configured to operate with the
491, you’re ready to start viewing echo sounding data.
To see the echo sounding screen at any time, press STAR from
any screen. You’ll see live echoes moving across the screen.
Depth
marker
and
Echo data
Depth Scale
indicator
Water
temperature
box
Color
bar
Water
temperature
scale
Frequency
selection and
indicator
Depth
box
Navigation
information
Lat/lon of
vessel
Dist/brg
to waypoint
Steering indicator
Speed, course, and speed
through the water
Figure 6: Illustrated ECHO screen
You can also review old echoes using Northstar’s SoundTrac™
feature. To activate SoundTrac, press the CURSOR PAD left or
right on the ECHO screen. The position marker appears
(controlled by the CURSOR PAD), and movement of echoes to
the left stops. The data boxes at the bottom of the screen turn
white and refer to the position marker rather than to your
current position. Press the green LIVE DATA key to return to
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real-time echoes. For details, see “Reviewing past echoes using
SoundTrac” starting on page 51.
Depth
marker
and
Echo data
Depth Scale
indicator
Water
temperature
box
Color
bar
Position
marker
and
Water
temperature
scale
indicator
Depth
box
Lat/lon of
position
marker
Dist/brg to
position
marker
Steering indicator
Speed, course, and speed
through the water
Figure 7: Illustrated SOUNDTRAC screen
NOTES:
All of the alarm messages always appear on all of the echo
sounder’s screens. You won’t miss any alarms while displaying
echo sounding data, and you never have to press any keys to view
the current alarms (although you must press STAR to clear alarms
that don’t automatically clear).
The SAVE and MOB functions always work normally. Moreover,
on the 961/962, whenever you press either of these keys, the corre-
sponding *SAVE##* or *MOB##* waypoints will be displayed
automatically on the echo sounder’s picture, as well as on the
CHART screen (after you press CHART).
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Using demo mode
The echo sounder can be operated in “demo mode” for
training and familiarization. Simulated echo data generated by
the 491 will be displayed.
To enter demo mode:
1. Press STAR several times to display the ECHO SOUNDER
SETUP screen.
2. Press the CURSOR PAD down to select demo mode, then
press EDIT.
3. Press the CURSOR PAD left or right to highlight “ON,”
then press ACCEPT.
While in demo mode, the word “Demo” appears in the
upper right corner of the ECHO screen.
To leave demo mode, repeat this procedure, selecting “OFF”
instead of “ON.”
You can overlay a smaller version of the echo screen onto the
CHART screen.
Displaying echo
sounder data on the
CHART screen
To overlay the echo screen:
For the 961/962
1. Press CHART to display the CHART screen, then press
OVERLAY.
2. At the CHART OVERLAY SELECTION window, press
SHOW 490.
Both chart views A and B will display live echo sounder
data on the right-hand side of the screen.
3. To remove echo sounder data, press HIDE 490 on the
CHART OVERLAY screen.
To overlay the echo screen:
For the 957/958
1. Press CHART to display the CHART screen, then press
SOUNDER. The CHART screen will display live echo
sounder data on the right-hand side of the screen.
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Introducing the displayed information
The following information can be displayed on the ECHO
screen.
•
•
•
•
•
•
•
echo sounder data
Echo sounding
echo sounder frequency in use (50 or 200 kHz or both)
A-scope
automatic mode indicators (fishing or cruising)
manual operation indicator
echo colors in use (the “color bar” at the far left)
SoundTrac’s position marker for scrolling to old echoes
•
•
•
water-depth digital display (on the left side of the screen)
depth scale (on the right side)
Depth and
temperature
depth marker (press the CURSOR PAD to scroll the
marker down)
•
•
water-temperature digital display (if temperature sensor is
connected; can be turned off)
water temperature graph (if temperature sensor is con-
nected; can be turned off)
•
vessel’s current lat/lon (on the SOUNDTRAC screen, this
lat/lon indicates the position marker’s location)
Navigation
Status tabs
•
•
•
vessel’s SOG and COG
active waypoint, if any, and graphic steering indicator
vessel’s Speed Through the Water (if speed sensor is con-
nected; can be turned off)
To help you use the echo sounder’s functions, many of the
key’s labels on the right edge of the screen show the status of
that key’s function in a tab directly under the label.
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Using automatic mode
To operate the echo sounder automatically, just press AUTO.
All of the 491’s adjustments will be set to produce a useful
picture under most conditions. When you’re too busy to
optimize the settings manually, the echo sounder can
automatically set the optimal gain, clutter, and range settings,
to show an excellent picture, from the surface to the bottom.
When you select auto, the range setting may change from time to
time to keep the seabed in view as the water depth changes.
It is recommended that the 491 be operated automatically
whenever possible. The 491 can reliably detect the seabed
depth only when it controls the gain and clutter settings.
You can always press AUTO on the ECHO screen to remove
any manual settings you’ve made and return to the standard
automatic configuration.
Automatic mode has two variations: autocruising and
autofishing.
Cruising or fishing
•
autocruising optimizes the gain and clutter for tracking
the bottom, with less emphasis on any fish in the water
•
autofishing optimizes the gain and clutter for searching
for fish
Press AUTO to switch between autocruising and autofishing.
The colored tab below the menu key indicates whether the
unit is optimized for cruising or fishing.
Colored status tabs just below the AUTO and PICTURE keys
are green when the echo sounder is operating fully
automatically. They turn yellow when any of the settings has
been set manually. (In some cases, the picture tab may be
yellow while the auto tab is still green, if the Noise Limiter is
turned on, for example.)
The status tabs
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You can always manually change any of the echo sounder’s
settings: the gain, clutter, noise limiter, shift, and range.
Manually
overriding
automatic mode
Changing the appearance of the picture (colors, gain, clutter,
and the noise limiter) is described in Chapter 3.
Setting the range and shift is described in Chapter 6.
Changing the frequency of echoes
The 491 uses two transducer frequencies: 50 kHz and 200
kHz. The advantages and disadvantages of each frequency are
shown below.
Table 2: 50 kHz vs. 200 kHz
50 kHz
200 kHz
Longer wavelength goes deeper,
but with somewhat lower resolu-
tion.
Shorter wavelength provides a
sharper picture, but can’t go as
deep.
Less resolution is better at finding
big fish, but may miss the bait
fish.
Finer resolution is better at find-
ing small fish (baitfish) and subtle
bottom details.
Wider beam is good for seeing
Narrower beam is very focused.
fish not directly beneath the boat. Reduces the influence of a rough
sea.
You can choose from four settings for the transducer
frequency:
•
•
•
•
50 kHz displayed on a full screen
200 kHz displayed on a full screen
50 kHz on the left half of the screen, and 200 on the right
200 kHz on the left half of the screen, and 50 on the right
There are two reasons why you might want to operate with
your preferred frequency on the right side of the screen:
•
the zoom function magnifies the frequency on the right
side
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•
when adjusting the picture, you can see the effect of
changes on the right side
50 kHz echoes
200 kHz echoes
Adjusts the frequency
of the data displayed
(currently showing dual
frequency on a split
screen, with 50 kHz to
the left and 200 kHz to
the right)
Figure 8: ECHO screen with both frequencies displayed
To change the display frequency:
1. On the ECHO screen, press FREQUENCY until you
display the desired frequency or frequencies.
The frequencies in use are shown pictorially on the tab
just below the FREQUENCY key.
When you change the frequency, echoes already on the screen
don’t change, they just move off the screen as they are
replaced by echoes at the new frequency.
A dual-frequency screen is split into two halves separated by a
gray vertical line in the center.
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When using the zoom feature (which also splits the screen
into halves), both sides of the screen always display the same
frequency.
Zooming in and out
On the ECHO screen, the echo sounder’s zoom feature
expands a portion of the echoes. You can examine closely any
part of the water column, to determine the composition of the
bottom or look at the echoes of fish, rocks, or wrecks. When
fishing, the zoom function is useful for showing a detailed
view of any echoes below the vessel.
Press IN to zoom in and increase the magnification of the
echoes you see below the top edge of the marker. Press OUT to
zoom out and increase the amount of water seen.
Choosing the zoom
scale
You can choose from any of six depth scales for the magnified
echoes. These scales cover the same depths regardless of the
scale of the original echoes.
The available scales are: 15’, 30’, 60’, 120’, 240’ and 480’ when
using units of “feet.” Similar scales are available for the other
depth units.
NOTE:
When zoom is in use, only a single frequency is displayed.
Unzoomed echoes are on the right, and the same frequency is
shown magnified on the left. Whatever frequency was previously
shown on the left is replaced by a magnified view of the right side.
NOTE:
You cannot zoom out to a scale that shows more water than the
original picture. For example, if the original picture is set to a scale
of 50’, the only zoom scales available will be 15’ and 30’.
Press ZOOM on the ECHO screen to cycle through the four
zoom modes (and choose the one you want):
Choosing a zoom
mode
•
•
•
bottom zoom
bottom lock
bottom lock/center
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•
marker zoom
The original unzoomed echoes are on the right side, and the
magnified area is shown on the left side of the screen.
A tab below the ZOOM key shows which zoom mode is in use.
When you select bottom zoom, the contour of the bottom is
magnified, clearly displaying canyon edges and echoes near
the seabed. The 491 automatically locates the seabed and
displays it on the lower left side of the screen (normal echoes
are displayed on the right side).
Using bottom zoom
If the seabed moves out of the lower half of the screen (for
example, if you travel into deeper water), the 491
automatically repositions the bottom back into the lower half.
You’ll see the zoomed image jump up or down from time to
time, as the 491 keeps the seabed displayed on the screen.
When you select bottom lock zoom, the magnified sea bottom
is flattened out and displayed on the left side of the screen at
the lower edge. You can see any fish that are swimming near
the bottom.
Using bottom lock
zoom
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When you select bottom lock/center zoom, the sea bottom is
flattened out and displayed in the center of the screen. You
can see any fish near the bottom, as with the bottom lock
zoom, and also examine the seabed’s composition.
Using bottom lock/
center zoom
When you select marker zoom, you can choose the part of the
water column to magnify. The top edge of the magnified area
is determined by the location of the depth marker. To move
Using marker zoom
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the magnified area up or down, press the CURSOR PAD to
move the depth marker.
You can return to the normal unzoomed display just by
pressing and holding ZOOM for more than one second, or by
pressing ZOOM repeatedly until you have cycled through all
the zoom modes.
Leaving zoom mode
Setup functions
Several setup functions are available to configure the echo
sounder to your preferences.
CAUTION:
Be careful not to change any of the functions that are not described
here unless you first read about them and understand their functions
in the Northstar 491 Installation Manual.
To access the ECHO SOUNDER SETUP screen, press STAR
several times until “Echo Sounder” is highlighted at the top of
the screen.
Accessing the setup
screen
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961/962 echo sounder setup screen
957/958 echo sounder setup screen
When changing the numerical value of the echo sounder’s
settings, you can either press the CURSOR PAD to increase or
decrease the value, or use the KEYPAD to manually type in
the desired value.
Entering numerical
values
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This option specifies how far below the surface of the water
the transducer is mounted. The number is added to all depths
measured by the 491 so they will refer to depth from the
surface, not from the transducer. This value should have been
set correctly during installation and should not be changed.
Transducer depth
You can change the depth units to feet, meters, or fathoms:
Changing the depth
units
1. Press the CURSOR PAD up or down to highlight the
DEPTH UNITS option.
2. Press EDIT.
3. Press the CURSOR PAD left or right to highlight the
desired units. Press ACCEPT.
You can change the highest and lowest water temperatures
that will be displayed on the temperature graph:
Changing the
temperature
graph’s units and
scale
1. Press the CURSOR PAD up or down to highlight the line
containing the temperature scale.
2. Press EDIT.
This option only
3. Press the CURSOR PAD left or right to highlight °C or °F,
appears on the screen
if a temperature sensor
is connected.
as desired, then press ACCEPT.
4. To change the endpoints of the scale, press EDIT DATA.
5. Enter the lower temperature limit using the KEYPAD.
6. Press the CURSOR PAD to the right to highlight the
upper limit and enter its value on the KEYPAD.
7. Press ACCEPT.
In the 961/962, the echo sounder can be set to store waypoints
automatically at the following location:
Number of special
waypoints
•
•
•
where fish are detected by the fish alarm
where the water temperature passes preset limits
where fish or other echoes are marked by the user
These waypoints are automatically given names such as
*FISH##*, where ## is a waypoint sequence number that
increases to a preset limit. When this limit is reached, the
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sequence number restarts at 00, and the oldest waypoints with
this same name will be overwritten (unless they have been
renamed).
To turn this feature on or off, or to change the maximum
number of each of these waypoints:
1. Press the CURSOR PAD up or down to highlight the
waypoint type you want to change:
The line “*Fish##*:” controls fish waypoints
The line “*Therm##*:” controls temperature waypoints
The line “Mark Wpts:” controls waypoints marked by the user
2. Press EDIT.
3. Press the CURSOR PAD left or right to highlight the
desired number of waypoints to be saved.
4. Press ACCEPT.
These functions are set during installation. The calibrations
should not be changed unless they are known to need
adjustment.
Speed and
temperature sensor
setup
From the ECHO SOUNDER SETUP screen, press SPEED/TEMP
to access the SENSOR SETUP screen.
961/962 sensor setup screen
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957958/ sensor setup screen
To simplify operation, the “sensor installed” options can be set
to “No” to remove all references to temperature and speed
from all the screens.
Highlight the appropriate line and press EDIT to change an
option.
Speed calibration is entered as a percentage from –99% to
+99% to make the speed read lower or higher than the
uncalibrated value.
NOTE:
You must enable the speed setting under the Data menu on the
ECHO SOUNDER screen; see ”Setting the ECHO screen data”
starting on page 5-44..
Temperature is calibrated by entering the temperature error as
a number of degrees from –99 to +99. This offset is added to
the uncalibrated temperatures before they are displayed or
graphed.
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3
Adjusting the gain (strong echoes) . . . . . . . . 3-28
Adjusting the clutter (weak echoes) . . . . . . . 3-29
Adjusting the signal level (weak echoes) . . 3-30
Suppressing interference (the noise limiter) 3-31
Selecting the color bar (hue) and white level 3-32
This chapter explains the different ways you can adjust the
echo sounder’s picture, including gain, clutter, the noise
limiter, white level, and signal level.
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The picture menu
You can adjust the appearance of echoes in five different ways:
•
•
•
•
•
gain (for high intensity echoes)
clutter (for low intensity echoes)
noise limiter (for interference)
hue (to choose colors and white level)
signal level (to remove weak echoes)
Gain and clutter changes are applied only to new echoes as
they appear on the right side of the screen—earlier echoes are
not affected.
NOTE:
When you override the gain’s automatic settings, the tabs on the
PICTURE key and AUTO key change from green to yellow, indi-
cating the system is no longer in automatic mode. When you turn
the noise limiter on, only the PICTURE key tab changes from green
to yellow. Changing the hue or adjusting the signal level has no
effect on the operating mode (the tabs stay green).
Adjusting the gain (strong echoes)
The gain setting selects the echo strengths that will be
displayed using the top color in the color bar (the strongest
echoes). Any echoes stronger than this selection will use the
same color and no detail can be distinguished. The gain is
usually set so that seabed echoes are displayed in brown, the
strongest level.
The gain can be also be set automatically by pressing the
AUTO key. This will provide an excellent picture under most
conditions, and will allow the 491 to reliably detect the seabed
depth.
Gain is normally adjusted in conjunction with clutter, as
described on the next page, to maximize its effectiveness.
To adjust the gain:
1. On the ECHO screen, press PICTURE.
2. On the PICTURE screen, press GAIN.
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3. At the GAIN window, press the CURSOR PAD left or right
to adjust the gain, or use the KEYPAD to manually enter
the desired gain value. The available settings range from
zero (minimum) to 75 (maximum).
Gain window
The window shows the effect of adjusting the gain. The
fish symbols near the bottom of the window represent
various echo strengths, and the expanding and
contracting color bar above shows the colors that will be
used to display these echoes. As you adjust the gain to
obtain the best looking picture, also watch the real echoes
on the right side of the screen .
4. Press RETURN to go back to the ECHO screen.
When you adjust the gain, the color of the AUTO and
PICTURE key tabs changes from green to yellow, since
the echo sounder is no longer in automatic mode. Also, a
yellow tab appears under the DEPTH key, indicating that
the range setting is no longer automatically controlled and
that the 491 may not always identify the bottom reliably.
Adjusting the clutter (weak echoes)
The clutter setting selects the echo strength that will be
displayed using the bottom colors of the color bar (the weaker
echoes). Any echoes weaker than this selection will not be
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displayed. If you select 5, for example, all weak and moderate
echoes will be displayed using the background color (just as if
they weren’t there). You might choose this setting to eliminate
high levels of background noise and echoes from turbulence
or plankton. A setting of 0 allows all echoes to be displayed.
To adjust the clutter:
1. At the ECHO screen, press PICTURE.
2. At the PICTURE screen, press CLUTTER.
3. Press the CURSOR PAD left or right to adjust the clutter,
or use the KEYPAD to manually enter the desired clutter
value. The available settings range from zero (minimum)
to nine (maximum).
Clutter window
4. Press RETURN to go back to the ECHO screen.
When you adjust the clutter, the color of the AUTO and
PICTURE key tabs changes from green to yellow, since
the echo sounder is no longer in fully automatic mode.
Adjusting the signal level (weak echoes)
As with the CLUTTER key, the SIGNAL LEVEL key controls
the appearance of low level noise in the picture. Whereas
clutter compresses or expands the available colors to fit the
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desired signal range, Signal Level completely removes the
weaker colors and their echoes.
To adjust the signal level:
1. On the ECHO screen, press PICTURE.
2. On the PICTURE screen, press SIGNAL LEVEL.
3. At the SIGNAL LEVEL window, press the CURSOR PAD
up or down to remove the weaker color levels from the
picture, or use the KEYPAD to manually enter the desired
signal level.
The available settings range from 1 (minimum) to 5 (max-
imum). For example, if you select a signal level of 3, echo
strengths of 0 through 3 are all displayed using the same
color.
4. Press RETURN to go back to the ECHO screen.
Suppressing interference (the noise limiter)
The noise limiter reduces the adverse effects of interference
from other nearby echo sounders or electronic devices.
however, the noise limiter may cause some very weak echoes
to be made smaller or entirely eliminated, since it removes any
echoes that aren’t sustained for at least two pings.
To turn on the noise limiter:
1. At the ECHO screen, press PICTURE.
2. At the PICTURE screen, press NOISE LIMITER.
3. At the NOISE LIMITER window, press the CURSOR PAD
up to turn the noise limiter on (or press NOISE LIMITER
again).
4. Press the RETURN key to go back to the ECHO screen.
Turning the noise limiter on changes a portion of the
PICTURE key tab from green to yellow, as a reminder.
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Selecting the color bar (hue) and white level
The color bar displayed at the extreme left of the ECHO screen
Understanding the
color bar
shows the range of colors used to display different echo
strengths. Weaker echoes are displayed with colors near the
bottom of the scale, and stronger echoes are displayed with
colors near the top.
You can choose any one of nine palettes of colors to represent
the echo strengths from weakest to strongest.
•
•
Color bar #1 is the one most often used.
Color bar #2 is similar but with fewer colors, to aid visibil-
ity under some conditions.
•
•
Color bars # 3-8 are additional variations with different
background colors.
Color bar #9 uses only a single color, ranging from very
dark to very bright.
To select the color bar:
Selecting the color
bar (hue)
1. On the ECHO screen, press PICTURE.
2. Press HUE.
3. At the HUE AND WHITE LEVEL window, press the
CURSOR PAD left or right to select the color bar desired,
or use the KEYPAD to manually enter the number of the
color bar.
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Hue and white level window
4. Press RETURN to go back to the ECHO screen.
You can replace any single color in the color bar with white.
On the HUE AND WHITE LEVEL window, press the CURSOR
PAD up or down to select that color.
Setting the white
level
To remove the white level and return to using all the colors on
the color bar, press the CURSOR PAD down until the white
level moves off the color bar.
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4
Understanding Depth Settings
Viewing the seabed depth . . . . . . . . . . . . . . . . 4-36
Viewing the depth marker . . . . . . . . . . . . . . . . 4-36
Changing the depth settings . . . . . . . . . . . . . . 4-36
Setting the picture’s shift (starting depth) . . 4-37
Setting the picture’s range . . . . . . . . . . . . . . . . 4-38
This chapter explains how to override the system’s auto-
matic depth settings and manually control the depth range
shown on the screen, and how to use the depth marker.
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Viewing the seabed depth
The seabed depth (the “bottom”) is displayed in a black box at
the left edge of the ECHO screen.
You can change the size and location of the depth box on the
ECHO screen. Its size on the SOUNDTRAC screen is always
small.
There are four available sizes:
•
•
•
•
small
medium
large
huge
To resize the depth box or move it up or down:
1. At the ECHO screen, press DEPTH.
2. To cycle through the size choices, repeatedly press
BOTTOM BOX. To move the box up and down, press the
CURSOR PAD.
3. Press RETURN to go back to the ECHO screen.
The depth box can also be adjusted by pressing MORE, then
pressing DATA.
Viewing the depth marker
You can use the depth marker to accurately measure the depth
of an echo. To display the depth marker—a dashed horizontal
line—and move this marker up or down, press the CURSOR
PAD down. Attached to the depth marker line is a small black
box, which displays the marker’s exact depth.
The depth marker also affects the display in Marker Zoom
mode.
Changing the depth settings
You can adjust the shallowest and deepest echoes to be shown
on the ECHO screen. In automatic mode, the echo sounder
sets these values based on its current environment. However,
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you can manually override these auto values for your specific
needs at any time. There are two depth settings:
•
shift (how far below the surface the echo sounder picture
starts)
•
range (the depth covered by the echo sounder picture
from the top of the screen to the bottom of the screen)
Setting the picture’s shift (starting depth)
The shift setting adjusts the depth of the top edge of echoes
pictured on the ECHO screen. You can “shift” the entire pic-
ture up and down to start at the surface of the water, or any
other depth you choose.
To shift the picture:
1. At the ECHO screen, press DEPTH.
2. Press SHIFT.
Shift window
The SET SHIFT window shows a picture of the current
shift settings (and range). The large white number in the
black box shows the current shift value. A sliding vertical
bar shows the portion of the water that the echo sounder
displays on the screen, based on the shift and range set-
tings.
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In the large rectangle on the right, the blue area at the top
(with waves) represents the surface of the water, and the
brown area below represents the seabed.
The number at the bottom is the depth of the picture, and
the seabed depth is also labelled.
The smaller rectangle inside the larger one represents the
echo sounder’s picture. As you move the shift (and range)
settings, this rectangle adjusts to show what you will see
on the echo screen.
A horizontal black arrow points to the value that this win-
dow adjusts: the depth at which the echo sounder picture
starts, relative to the surface of the water.
3. Press the CURSOR PAD up or down to shift the picture,
or use the KEYPAD to enter the digits of the desired
depth. If you type the number on the keypad, wait a
moment for the system to enter the number.
4. Press RETURN to go back to the ECHO screen.
Adjusting shift changes the AUTO and DEPTH key tabs
from green to yellow, since the echo sounder is no longer
in automatic mode.
Setting the picture’s range
The range setting adjusts the overall depth covered by the
echo sounder picture, from the top of its display to the bottom.
The range can be set automatically (by pressing AUTO), or
manually on the SET RANGE window.
To set the range:
1. At the ECHO screen, press DEPTH.
2. Press RANGE.
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Range window
The vertical black arrow in the SET RANGE window ind-
cates the values that this window adjusts: the range of the
echo sounder picture, relative to the depth of the water.
The white number in the black box indicates the current
range setting.
3. Press the CURSOR PAD up or down to adjust the range,
or use the KEYPAD to manually enter the desired depth.
4. Press RETURN to go back to the ECHO screen.
Adjusting the range changes the AUTO and DEPTH sta-
tus tab from green to yellow, since the echo sounder is no
longer in fully automatic mode.
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5
Changing the advance speed . . . . . . . . . . . . . 5-42
Displaying the A-scope . . . . . . . . . . . . . . . . . . . 5-43
Setting the ECHO screen data . . . . . . . . . . . . . 5-44
Introducing snapshots . . . . . . . . . . . . . . . . . . . . 5-46
Setting up the video image overlay . . . . . . . 5-49
This chapter describes all of the functions of the MORE key,
except for the alarms, which are covered in Chapter 7.
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Using the MORE key
Pressing the MORE key accesses the following functions:
•
•
•
•
alarms (described in Chapter 7)
advance speed
A-scope
data (numeric and graphic information on the ECHO
screen)
•
•
snapshots (961/962 only)
video overlay setup (957/958 only)
When the menu function is in use in the 961/962, the ECHO
screen moves every half second, giving the picture a less than
smooth appearance. Press RETURN to go back to the main
screen for a normal smooth appearance.
Changing the advance speed
Advance speed refers to the speed at which the vertical scan
lines move from right to left across the ECHO screen. There
are five advance speeds (plus the STOP setting, which freezes
the advance of all data):
•
2/1 - two identical lines of data are displayed for every
ping
•
•
•
•
1/1 - one line of data is displayed for every ping
1/2 - one line of data is displayed for every two pings
1/4 - one line of data is displayed for every four pings
1/8 - one line of data is displayed for every eight pings
For speeds 1/2, 1/4, and 1/8, each displayed line of data is
averaged over 2, 4, or 8 pings.
To set the advance speed:
1. At the ECHO screen, press MORE, then press ADVANCE
SPD.
2. At the SET ADVANCE SPEED window, keep pressing the
ADVANCE SPD key to select the desired advance speed.
3. Press RETURN to go back to the ECHO screen.
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The A-Scope shows every ping received, even when the
advance speed setting causes pings to be averaged before
display
Displaying the A-scope
The echo sounder’s A-scope lets you look closely at present or
past echoes by horizontally magnifying the echo from each
ping.
To display the A-scope:
1. Press MORE.
2. Press A-SCOPE to turn the A-Scope on or off.
A-scope on single-frequency echo screen
The A-scope appears on the far right-hand side of the
screen, magnifying the water column designated by the
position marker.
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If you’re displaying both 50 and 200 kHz echoes, the A-scope
magnifies echoes from the frequency shown on the right side
of the screen.
Using the A-scope
with dual
frequencies
A-scope on dual-frequency echo screen
If you’re in zoom mode, the A-scope magnifies the unzoomed
echoes on the right side of the screen.
Using the A-scope
with zoom mode
Setting the ECHO screen data
Screen data refers to numeric and graphic information
displayed on top of the echoes, including bottom depth, water
temperature, and speed through the water (STW).
To access these functions, press MORE, and then DATA.
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Echo screen data selections
Press BOTTOM BOX to set the size and location of the box
displaying the bottom depth (white numbers on a black
background).
Bottom depth box
Temperature box
Press this key again to cycle through the available sizes: small,
medium, large, and huge.
Press the CURSOR PAD up and down to set the position of the
box at the left edge of the screen.
Press TEMP BOX key to set the size and location of the box
displaying the water temperature (white numbers on a black
background).
This key won’t appear
unless a temperature
sensor is installed and
configured.
Press this key again to cycle through the available sizes: off,
small, medium, large, and huge.
Press the CURSOR PAD up and down to set the position of the
box at the left edge of the screen.
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Press TEMP GRAPH to turn the temperature graph on or off.
Temperature graph
The temperature graph displays an orange temperature scale
at the left of the screen, and an orange line tracing out the
varying water temperature measurements, superimposed on
the echoes.
This key won’t appear
unless a temperature
sensor is installed and
configured.
Press SPEED to turn the Speed Through the Water display on
or off. STW is displayed on the bottom right corner of the
screen.
Speed through the
water
This key won’t appear
unless a speed sensor
is installed and
configured.
Introducing snapshots
A snapshot is a picture of the 961/962’s echo sounder screen.
You can store up to 10 different snapshots of echo sounder
screens for later review. These can be stored on floppy disk
(one snapshot per floppy) or zip disk for permanent archiving.
The snapshot feature is not available in the 957/958 or 6000i.
To take a snapshot, press MORE and then SNAPSHOT. The
echo sounder screen will be recorded at that instant.
Taking and storing
a snapshot
To store the snapshot, you must save the snapshot in one of
the ten available storage slots. Choose a slot by pressing the
CURSOR PAD up or down to highlight the desired slot, then
press SAVE to store the snapshot.
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Snapshot screen (961/962 only)
To rename a stored snapshot, from the SNAPSHOT screen,
press the CURSOR PAD to highlight the desired slot, and press
RENAME. Use the KEYPAD to enter a new name and press
ACCEPT.
To display a stored snapshot, from the SNAPSHOT screen,
press the CURSOR PAD to highlight the desired slot, and press
DISPLAY. When finished, press RETURN.
To erase a snapshot from a slot, from the SNAPSHOT screen,
press the CURSOR PAD to highlight the desired slot, and press
ERASE. You’ll be asked to confirm erasure by pressing YES.
The slot will be erased to make room for a new snapshot.
If your 961/962 has a floppy disk drive installed, you can save
one snapshot on each disk.
Archiving and
restoring a
snapshot with a
floppy disk
To save a stored snapshot onto a floppy disk, from the
SNAPSHOT screen, press the CURSOR PAD to highlight the
desired slot, and press ARCHIVE. Insert a floppy disk and press
OK. Any old data on the disk will be erased!
To restore a snapshot from a floppy disk to any empty slot,
from the SNAPSHOT screen, press the CURSOR PAD to
highlight the desired empty slot, and press RESTORE. Insert
the floppy disk and press OK.
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If your 961/962 has a zip drive installed, you can save up to 10
snapshots on each disk.
Archiving and
restoring snapshots
with a Zip disk
To save a stored snapshot onto a zip disk, from the SNAPSHOT
screen, press the CURSOR PAD to highlight the desired slot,
and press ARCHIVE. A new screen appears displaying the 10
slots available on the zip disk.
Archiving snapshots screen (961/962 only)
Press the CURSOR PAD to select an empty slot on the disk,
and press OK. The snapshot will be written to that slot on the
zip disk.
To restore a snapshot from a zip disk to any empty slot, from
the SNAPSHOT screen, press the CURSOR PAD to highlight
the desired empty slot, and press RESTORE. A new screen
appears displaying the 10 slots on the zip disk. Use the
CURSOR PAD to select the slot containing the snapshot you
want to restore, and press OK.
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Setting up the video image overlay
If you’ve connected the 957/958 to an NTSC-compatible
device, you can display the image on the echo sounder screen.
To display the video image on the ECHO SOUNDER screen,
first press MORE, then press VIDEO.
To change the transparency of the image while you’re
displaying the ECHO SOUNDER screen, go to a different
screen, press the navigator’s IN or OUT keys, then return to the
ECHO SOUNDER screen.
To change the size and placement of the image on the ECHO
SOUNDER screen, press the STAR key to display the
navigator’s VIDEO SETUP screen, then follow the instructions
on the screen.
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6
Viewing past echoes using SoundTrac . . . . 6-52
Marking fish as waypoints . . . . . . . . . . . . . . . . 6-53
Navigating to a past echo position . . . . . . . . 6-53
This chapter describes how to use SoundTrac to view past
echoes, and how to navigate to any past echo positions.
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Viewing past echoes using SoundTrac
On the SOUNDTRAC screen, you can use Northstar’s exclusive
SoundTrac feature to look back and examine past echo data.
To enable SoundTrac, at the ECHO screen, press the CURSOR
PAD to the left. A dashed vertical line—called the position
marker—is now displayed.
Echoes from at least
the past three minutes
are available,
depending on the
depth of the water and
the advance speed
you’ve set.
To move back to echoes that were displayed within the past
few minutes, continue pressing and holding the CURSOR PAD
to the left.
As you move the position marker with the CURSOR PAD, the
marker speed accelerates to quickly scroll to the desired location.
SoundTrac screen
The lat/lon of the position marker is displayed at the bottom of
the picture, along with the time elapsed since the ping, and the
distance and bearing from your present position to the marker
(assuming the navigator is providing position data.) As you
move the position marker left and right, these coordinates
change accordingly.
NOTE:
When you use the position marker on a split screen (showing either
two frequencies, or zoom mode), each half of the screen has a posi-
tion marker. Both markers designate the same physical location.
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Echoes from the last 3000 pings are stored.
The number of minutes of past echo data available depends on
two factors:
•
•
the depth of the water
the advance speed
In deeper water, the 491 pings at a slower rate, so the echo
sounder saves data over a longer period of time. A slower
advance speed will have the same effect.
Marking fish as waypoints
The 961/962’s fish marking function lets you use SoundTrac
to mark fish, wrecks, or any other objects that you see at any
past echo displayed on the screen.
To mark echoes as waypoints:
1. At the ECHO screen, press the CURSOR PAD to the left to
move the position marker—a dashed vertical line—to the
position of the echo.
2. Press MARK.
A *MARK##* waypoint immediately appears on the
SOUNDTRAC screen and on the CHART screen. Each
marked echo becomes a waypoint (named *MARK##*)
stored in the waypoint database. You can perform all of
the usual waypoint functions, including going directly to
this waypoint, adding it to the end of your trip, changing its
name, etc.
Navigating to a past echo position
On the SOUNDTRAC screen, the GO TO function can be used
for any of the following functions:
•
•
•
to go directly to a past echo position
to add a past echo position to the end of your trip
to store a past echo position as a waypoint or avoidance
point
•
to make a new route with a past echo position as its first
waypoint
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•
to add a past echo position to the end of an already dis-
played route
Going to a past echo position is described below. The other
options are described in the Operator’s manuals for your
Northstar navigator.
To go directly to a past echo position (as long as the GPS is
providing position data):
Going directly to a
past echo position
1. On the SOUNDTRAC screen, press the CURSOR PAD left
or right to move the position marker to the desired posi-
tion, then press GO TO.
The SELECTED CURSOR POSITION window appears.
2. Press GO NOW.
The navigator creates a new temporary waypoint called
COORD and returns to the SOUNDTRAC screen. The
COORD waypoint isn’t stored in the waypoint database;
instead, it’s placed in the trip, where it replaces any future
trip points. To see this current waypoint on the CHART
screen, press CHART at any time. Your present vessel
position and time have now become a past trip point.
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7
Understanding the alarms . . . . . . . . . . . . . . . . 7-56
Setting the fish alarm . . . . . . . . . . . . . . . . . . . . . 7-56
Setting the bottom alarm . . . . . . . . . . . . . . . . . 7-58
Setting the temperature alarm . . . . . . . . . . . . 7-60
This chapter describes the echo sounder’s three alarm
functions (for fish, bottom, and temperature conditions): the
settings for each alarm, and how to turn them on and off.
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Understanding the alarms
The echo sounder’s alarms work just like the other alarms.
Their status is updated every second, and their messages are
displayed in the following ways:
•
at the bottom of the ECHO screen, and also on various
windows that may be overlaid onto these screens
•
on the ALARMS screen
On this screen, you can manually “clear,” or stop, new alarms,
although some are auto-clearing, and you can view old alarms,
which are alarms that already have cleared.
To alert you automatically in situations related to echo
sounding, you can set three alarms:
•
•
•
fish alarm
temperature alarm
NOTE:
You also can set the echo sounder to automatically save *FISH##*
or *THERM##* waypoints, when fish or a certain temperature are
detected, if the fish or temperature alarms are on. To automatically
save these waypoints, see ”Number of special waypoints” starting
on page 2-14.
Setting the fish alarm
When the fish alarm is on, an alarm sounds if an echo returns
from either inside or outside specific upper and lower limits
you’ve set.
To set the fish alarm:
1. At the ECHO screen, press MORE.
2. Press ALARM.
3. At the ALARM screen, press FISH ALARM.
The options on the FISH ALARM window are on/off, echo
strength level, upper and lower marker depths, and inside
or outside markers.
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4. Follow the instructions below for each of these five
settings.
Fish alarm window
To set the fish alarm’s minimum echo-strength level:
Setting the alarm’s
echo strength level
1. At the FISH ALARM window, press SET ALARM LEVEL.
2. Press the CURSOR PAD up and down to set the echo
strength level from 1 to 15, as represented on the vertical
color bar.
Echoes received that are strong enough to be within the
crosshatched area on the vertical bar will cause an alarm
(weaker echoes will be ignored).
The fish alarm will sound only when there are echoes inside
(or optionally, outside) the upper and lower markers. These
markers are displayed on the ECHO screens.
Setting the upper
and lower marker
depths
To set the depth of the upper marker:
1. At the FISH ALARM window, press SET UPPER MKR.
The upper marker window is highlighted in black.
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2. Press the CURSOR PAD up or down to set the depth, or
use the KEYPAD to manually enter the desired depth.
The depth is displayed in the tab below the SET UPPER
MKR key.
To set the depth of the lower marker:
1. At the FISH ALARM window, press SET LOWER MKR.
The lower marker window is highlighted in black.
2. Press the CURSOR PAD up or down to set the depth, or
use the KEYPAD to manually enter the desired depth.
The depth is displayed in the tab below the SET LOWER
MKR key.
If you designate the markers as inside markers, the fish alarm
sounds when fish are detected within these markers. If you set
these markers as outside markers, the fish alarm sounds when
fish are detected outside of these markers.
Setting inside or
outside fish
markers
To set the markers to inside or outside, at the FISH ALARM
window, press INSIDE/OUTSIDE MKRS to toggle between the
inside and outside settings. The setting is displayed in the tab
below the INSIDE/OUTSIDE MKRS key.
To turn the alarm on, at the FISH ALARM window, press TURN
ALARM ON. Generally, you’ll want to turn the alarm on after
making all the other settings.
Turning the fish
alarm on and off
To turn the alarm off, press TURN ALARM OFF.
When fish are detected, the alert tone sounds and the message
“FISH!” is displayed. This message clears automatically after 20
seconds and the alarm is rearmed.
The alarm
Setting the bottom alarm
When the bottom alarm is set, an alarm sounds if the echo
sounder detects that the bottom is shallower than the limit
you’ve set.
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To set the bottom alarm:
1. At the ECHO screen, press MORE.
2. Press ALARM.
3. At the ALARM screen, press BOTTOM ALARM.
The options on the BOTTOM ALARM window are on/off
and the depth setting.
Bottom alarm window
You can set the depth level for the seabed, so that as soon as
the bottom is shallower than this depth, the bottom alarm will
sound.
Setting the bottom
level
To set the bottom level, at the BOTTOM ALARM window, press
the CURSOR PAD up or down to set the depth, or use the
KEYPAD to manually enter the desired depth.
NOTE:
The 491’s depth indicator reflects the depth below your vessel’s
transducer, not below the keel. Ask your installer for the exact dis-
tance between your transducer and your keel. This value must then
always be manually added to the 491’s depth indicator, or else
entered into the transducer’s depth setting on the ECHO
SOUNDER SETUP screen for an automatically correct reading.
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To turn the alarm on, at the BOTTOM ALARM window, press
TURN ALARM ON. To turn the alarm off, press TURN ALARM
OFF.
Turning the bottom
alarm on and off
When the bottom is detected, the alert tone sounds and the
message “Bottom Collision!” is displayed. This message clears
automatically after 20 seconds, and the alarm is reset.
The alarm
Setting the temperature alarm
When the temperature alarm is set, an alarm sounds if the
echo sounder detects that the water temperature has either
risen above or dropped below the limit you’ve set.
This alarm isn’t present
unless a temperature
sensor is installed and
configured.
To set the temperature alarm:
1. At the ECHO screen, press MORE.
2. Press ALARM.
3. At the ALARM screen, press TEMP ALARM.
The options on the TEMPERATURE ALARM window are
on/off, upper and lower limits, and inside or outside limits.
Temperature alarm window
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You can set the upper and lower temperature limits. When the
water temperature is either inside or outside these limits, the
temperature alarm will sound.
Setting the upper
and lower
temperature limits
To set the upper temperature limit:
1. At the TEMPERATURE ALARM window, press SET UPPER
LIMIT.
The upper limit window is highlighted in black.
2. Press the CURSOR PAD up or down to set the
temperature, or use the KEYPAD to manually enter the
desired temperature.
The temperature is displayed in the tab just below the
SET UPPER LIMIT key.
To set the lower temperature limit:
1. At the TEMPERATURE ALARM window, press SET
LOWER LIMIT.
The lower limit window is highlighted in black.
2. Press the CURSOR PAD up or down to set the
temperature, or use the KEYPAD to enter the desired
temperature.
The temperature is displayed in the tab just below the
SET LOWER LIMIT key.
If you set the upper and lower temperature limits as inside
limits, the temperature alarm sounds when the temperature is
detected within these limits. If you set these limits as outside
limits, the temperature alarm sounds when the temperature is
detected outside of these limits.
Setting inside or
outside
temperature limits
Press INSIDE/OUTSIDE LIMITS on the TEMPERATURE ALARM
window to switch between the inside and outside settings. The
current setting is displayed in the tab just below the INSIDE/
OUTSIDE LIMITS key.
To turn the alarm on, at the TEMPERATURE ALARM window,
press TURN ALARM ON. To turn the alarm off, press TURN
ALARM OFF.
Turning the
temperature alarm
on and off
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When the temperature alarm sounds, an alert message is
displayed. This message clears automatically after 20 seconds
and the alarm is reset.
The alarm
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8
Troubleshooting 491 Operations
Troubleshooting the echo sounder . . . . . . . 8-64
Checking the transducer . . . . . . . . . . . . . . . . . . 8-65
This chapter explains how to troubleshoot the echo sounder
system before returning the equipment for factory service.
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Troubleshooting the echo sounder
No echoes displayed when STAR key is pressed.
Is the
Advance
Speed set to
zero?
Change the Advance Speed
setting.
YES
NO
Is the
961/962
Contact Northstar Service to
upgrade to the latest version
of 961/962 software.
NO
NO
software
Version 3.0 or
greater?
YES
Has
Configure NMEA Port 3 for
the 491. See Section 1 of
this manual for instructions.
NMEA Port 3
been configured
for the 491?
YES
491 is communicating with
the navigator
1. Check fuses and circuit
breakers
1. Check transducer
connector for the
STEADY
GREEN
2. Check power to 491 with
a voltmeter.
Check
the 491's STAT
indicator
OFF
proper wiring.
3. Verify that the data cable
between the 961/962 and
the 491 is properly wired
and connected.
2. If wiring is correct,check
transducer impedance
with an ohmmeter.
3. If the transducer is open
or shorted, replace it
FLASHING
GREEN
RED
The 491 and the 961/962
aren't communicating properly.
Check the wiring of the data
cable between the 961/962
and the 491.
There's a hardware problem
with the 491.
Figure 9: Troubleshooting the echo sounder (961/962)
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No echoes displayed on sounder screen.
Is the
Advance
Speed set to
zero?
YES
Change the Advance Speed
setting.
NO
Has the
navigatorʼs
Aux Port been
configured
for the
Configure the navigatorʼs
Aux Port for the 491. See
Section 1 of this manual
for instructions.
NO
491?
YES
491 is communicating with
the navigator.
1. Check fuses and circuit
breakers.
1. Check transducer
connector for the
STEADY
GREEN
2. Check power to 491 with
a voltmeter.
Check
the 491's STAT
indicator
OFF
proper wiring.
3. Verify that the data cable
between the navigator and
the 491 is properly wired
and connected.
2. If wiring is correct,check
transducer impedance
with an ohmmeter.
3. If the transducer is open
or shorted, replace it
FLASHING
GREEN
RED
The 491 and the navigator
aren't communicating properly.
Check the wiring of the data
cable between the navigator
and the 491.
There's a hardware problem
with the 491.
Figure 10: Troubleshooting the echo sounder (957/958)
Checking the transducer
To provide the best possible performance with the 491 echo
sounder, Northstar recommends the use of an Airmar
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transducer. The models below can be purchased from
Northstar.
Table 3: Northstar-recommended transducers
Manufacturer Model
Power
1 kW
Northstar P/N
TD1004
Airmar
Airmar
B260
B744V
600 W
TD1005
(w/3-wire speed)
Airmar
P66
600 W
TD1006
Airmar Technology Corporation may be reached at 35
Meadowbrook Drive, Milford, New Hampshire 03055-4613;
phone 603/673-9570; fax 603/673-4624.
NOTE:
Detailed information on maintaining and troubleshooting a trans-
ducer is outside the scope of this manual. Refer to the transducer
manufacturer’s documentation. Do not return a transducer to North-
star. If you need to return a transducer for service, contact the man-
ufacturer directly for instructions.
Do not expose a transducer to gasoline or clean it with strong
solvents. These can penetrate and degrade the housing. If a
transducer will be exposed to saltwater, coat it with
anti-fouling paint to prevent sea growth. To clean a transducer
of sand, debris, or sea growth, use a stiff brush or putty knife.
Use sanding sparingly, as repeated sanding may affect a
transducer’s performance at high speeds. If necessary, wet
sand with finer grade wet or dry paper. Check the transducer
periodically.
Maintaining a
transducer
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A
491 Features and Specifications
Table 4: 491 echo sounder features
Performance characteristics
Output
Single/Dual Channel, 50/200kHz, 600W
Fish, seabed, temperature
Alarms
Update rate
Auto modes
10 Hz maximum (depends on water depth)
Fishing and cruising
Zoom modes Marker, bottom, bottom lock, bottom lock/center
Features
Mark present or past echo as waypoint (961/962)
Go directly to any past echo
A-scope analyzes present or past echoes
Navigation data shown at bottom of screen
Demo mode for training
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Table 4: 491 echo sounder features (Continued)
Screen notations
Echo data
Seabed depth (various size digits)
Frequency of each window
Speed through water (if connected)
Water temperature (if connected)
Depth scale for each window
Depth of depth marker
Latitude/longitude of position marker and vessel
Alarm status and auto/manual status
Zoom mode
Name of waypoint, and distance and bearing to
waypoint
Steering indicator
Interfacing
Connects
Northstar 961/962 GPS Chart Navigator
Northstar 957/958/6000i GPS Chart Navigator
Northstar-recommended or compatible transducer
Other
Transducer outputs protected against open circuit/
short circuit
LED monitors input power and system status
Physical characteristics
Dimensions
Weight
8.78 x 7.22 x 2.35 inches
2 pounds
Environmental characteristics
Temperature
Protection
Standards
-25ºC to +60ºC operating temperature
-55ºC to +90ºC storage temperature
8 to 36 VDC, 8 Watts, reverse polarity and over-
voltage protection
Waterproof design meets the following: IEC60529
IP6; IEC60945 emissions; CE mark
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Table 4: 491 echo sounder features (Continued)
Manual controls
Gain
0 to 75 db
0 to 9
Clutter
Signal level
Noise limiter
White level
Other
0 to 5
ON/OFF
Any single color
Screen color palette
Depth marker
Position marker
Zoom in/out
Shift
Ranges
15, 30, 60, 120, 200, 400, 800, 1000, 2400 feet
5, 10, 20, 40, 80, 150, 300, 500, 800 meters
Advance
speed
1/8 to 2/1
Depth units
Feet, meters, fathoms
Installation
calibrations
Include speed, temperature, gain, and transducer
type
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G
Glossary
A-scope
COG
A horizontally magnified view of each echo, where the
strength is shown by the width as well as the color of the line.
Course-Over-Ground. The actual path of your vessel relative
to the surface of the earth.
clutter
current
default
echo
Distracting echoes caused by turbulence, plankton, etc. Can be
reduced by the clutter control.
The horizontal movement of water caused by tidal or other
forces.
A choice made automatically by the echo sounder; some
defaults can be overridden in partial automatic mode.
The sound returned by either an object below the water’s sur-
face or by the seabed, when this object or seabed is detected
by a sound wave.
echo sounder
An instrument that uses sound waves to measure the depth of
a body of water or an object (such as a school of fish) below
the water’s surface.
fathom
gain
A depth measurement that equals six feet or 1.83 meters of
water.
The amount of amplification given to the received echo before
it is displayed.
GPS
hue
Global Positioning System.
The gradations of a color.
interference
The electromagnetic interruption of a radio signal that causes
a poor signal reception. Interference may originate from exter-
nal sources, such as another nearby echo sounder, or from the
vessel itself, such as alternator noise.
latitude
Imaginary lines on the earth's surface running East/West and
expressed in degrees (0-90) north or south of the Equator.
Used in conjunction with the North/South lines of longitude to
determine position.
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longitude
Imaginary lines on the Earth's surface running North/South
and expressed in degrees (0-180) east or west of the Prime
Meridian (a line running from the North to South Pole, passing
through Greenwich, England).
meter
A unit of measurement (length) equal to 39.37 inches, slightly
more than a standard yard.
nautical mile (nm)
An international unit equal to 6,076.115 feet (1,852 meters)
used officially in the U.S. since 1959. A nautical mile is about
800 feet more than a statute mile. One nm is equal to 1
minute of latitude.
ping
SOG
A pulse transmitted from the 491 echo sounder. Also, the act
of transmitting a pulse from the echo sounder ("pinging").
Speed Over Ground. The actual speed of your vessel relative to
the earth, not the water.
tide
The vertical rise and fall of water caused by the gravitational
pull of the moon and sun.
transducer
The device mounted through the hull to send and receive
ultrasonic beams that determine seabed conditions and locate
fish.
waypoint
A particular location, saved by marking fish on the echo
sounder’s LIVE-DATA screen, which is used as an intermediate
or final destination.
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