NorthStar Navigation EXPLORER 435 - Manual (Page 7)

Northstar Explorer 435/438 Installation and Operation Manual 7
1-2 How the Explorer 435 and Explorer 438 work
The Explorer 435 and Explorer 438 have two parts:
- the transducer attached to the hull
- the display unit.
The transducer generates an ultrasonic pulse
(sound that is above the hearing range of
the human ear), which travels down towards
the bottom at a speed of about 4800 ft/sec
(1500 m/sec), spreading out into a cone shape.
When the pulse meets an object, such as a fish or
the bottom, it is partly reflected back up towards
the boat as an echo. The depth of the object
or bottom is calculated by the Explorer 435
and Explorer 438 by measuring the time taken
between sending a pulse and receiving the echo.
When an echo has been returned, the next pulse
is sent.
The Explorer 435 and Explorer 438 convert each
echo into an electronic signal, displayed as a
vertical line of pixels. The most recent echo
appears on the extreme right of the display, with
the older echoes being scrolled towards the left,
eventually disappearing off the display.
The scroll speed depends upon the water depth
and scroll speed setting. See section 3-2 Setup >
Sonar and section 4-1 Interpreting the display, for
more information.
The appearance of echoes displayed are affected
by:
• the fishfinder settings (range and gain
settings)
• echoes (different fish types, different bottom
types, wrecks and seaweed)
• noise (water clarity and bubbles).
See section 4-1 Interpreting the display, for more
information.