Furuno GP-1640F, Руководство оператора, Страница: 17 / 108

2-1
2. VIDEO SOUNDER OPERATION
2.1 Principle of Operation
The video sounder determines the distance
between its transducer and underwater objects
such as fish, lake bottom or seabed and
displays the results on screen. It does this by
utilizing the fact that an ultrasonic wave
transmitted through water travels at a nearly
constant speed of 4800 feet (1500 meters) per
second. When a sound wave strikes an
underwater object such as fish or sea bottom,
part of the sound wave is reflected back toward
the source (transducer). Thus by calculating
the time difference between the transmission
of a sound wave and the reception of the
reflected sound wave, the depth to the object
can be determined. The entire process begins
in the display unit. Transmitter power is sent to
the transducer as a short pulse of electrical
energy. The electrical signal produced by the
transmitter is converted into the water. Any
returning signals from intervening objects
(such as a fish school) are received by the
transducer and converted into an electrical
signal. The signals are then amplified in the
amplifier section, and finally, displayed on
screen.
The picture displayed is made up of a series of
vertical scan lines, one for each transmission.
Each line represents a snapshot of what has
occurred beneath the boat. A series of
snapshots are accumulated side by side
across the screen, and the resulting contours
of the bottom and fish between the bottom and
surface are displayed.
Underwater conditions and video sounder display