Video Sounder Operation; Principle Of Operation - Furuno GP-1610CF Operator's Manual

VIDEO SOUNDER OPERATION

3.1 Principle of Operation

The video sounder of the GP-1610CF deter-
mines 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 ultra-
sonic 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 source. Thus by calculating 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.
Figure 3-1 Underwater conditions and video sounder display
The entire process begins in the display unit.
Transmitter power is sent to transducer as a
short pulse of electrical energy. The electrical
signal produced by the transmitter is converted
into an ultrasonic signal by the transducer and
transmitted into the water. Any returning sig-
nals from intervening objects (such as a fish
school) are received by the transducer and
converted into an electrical signal. The sig-
nals are then amplified in the amplifier sec-
tion, and finally, displayed on screen.
The picture displayed is made up of a series
of vertical scan lines, one for each transmis-
sion. Each line represents a snapshot of what
has occurred beneath the boat. Series of snap-
shots are accumulated side by side across
screen, and the resulting contours of the bot-
tom and fish between the bottom and surface
are displayed.
3-1