Theory Of Echo Sounder - Hondex HDX-121 Operation Manual

THEORY OF ECHO SOUNDER

1 Theory of Echo Sounder

Theory of echo sounder is same as echo among hills.
Ultrasonic wave transmitted from the transducer directly beneath the vessel is
reflected at the sea bottom and received by transducer.
Echo sounder indicates the depth by calculating the round-trip time to distance.
Also, the unit shows the color image of fish school size/density or sea floor
condition according to the strength of reflected wave.
Ultrasonic wave runs at 1500m/sec inside the water. Therefore, the depth to fish
school and sea bottom can be captured by calculating the round-trip time.
Display Method
Current image is shown at 1st line of right edge after processing the reflected
wave of transmitted ultrasonic. The line image previously located at the right
edge moves to one line to the left.
Keep executing this operation to create the cross section view.
Therefore, the latest image beneath the vessel is located at the right edge. More
left side the image moves, more past image the screen shows.
You can assume that echo sounder screen shows the image from the side view.
The sea floor shape can be only captured when sailing the vessel. No matter
how the bottom is shaped, the image shows the flat bottom if the vessel is
stopped.
Caution : There is no relationship between vessel speed and image line speed.
e.g.) 1sec is round-trip time from sea bottom.
Round-trip distance = 1500m/sec x 1sec
The depth is half the size, so
Depth = 1500m÷2
0.5sec is round-trip time from fish school
Round-trip distance = 1500m/sec x 0.5sec
The depth is half the size, so
Depth = 750m÷2
122
= 1500m
= 750m
= 750m
= 375m