How The Echosounder Works - Simrad EQ33-2 Instruction Manual

Chapter 9-2

9.2 How the echosounder works

Fig. 1 Transmitted 'ping'
from the transmitter/receiver.
Fig. 2 The up arrow indicates:
Echo returning to the receiver.
The down arrow indicates:
Transmitted pulse.
When the EQ33-2 is turned on, the processor begins
to send electrical pulses to the transducer. The
ceramic resonator in the transducer has a special
property which enables it to change dimensions
slightly when a varying voltage is applied.
The voltage is thus converted to mechanical vibra-
tions (sound waves) which are then transmitted down
through the water.
See Fig. 1.
The sound waves move through the water until they
encounter a change in density, such as a fish or the
bottom. This causes the sound waves to 'echo' back
up through the water. When the reflected sound
waves (echoes) hit the transducer, the ceramic disk
vibrates at the same frequency. This generates a
varying voltage which goes back up through the
cable to the receiver.
The EQ33-2 processes the signals and presents them
on the display screen.
See Fig. 2.
EQ33-2 Principles of operation