Simrad NX45 Specifications download pdf (Page 37)

Simrad NX40/45 Installation and Operation Manual 37

9-2 Interpreting the display

The echosounder windows do not show a xed distance

travelled by the boat; rather, they display a history,

showing what has passed below the boat during a certain

period of time.

The history of the echosounder signal shown depends

the depth of the water and the scroll speed setting.

In shallow water, the echoes have a short distance to

travel between the bottom and the boat. In deep water,

the history moves across the window more slowly

because the echoes take longer to travel between the

bottom and the boat. For example, when the scroll speed

is set to

Fast, at depths over 1000 ft (300 m) it takes

about 2 minutes for the data to move across the window,

whereas at 20 ft (6 m) it takes only about 25 seconds.

A School of sh

B Single sh

C Hard bottoms such as rock and coral show as wide

bands

D Soft bottoms such as mud, weed and sand show as

narrow bands

The scroll speed can be set by the user to display either

a longer history with less sh information or a shorter

history with more sh details.

If the boat is anchored, the echoes all come from the

same area of bottom. This produces a at bottom trace

on the window.

The screen shot shows a typical echosounder window

with the Fish symbols turned Off. The echosounder pulse

generated by the unit transducer travels down through

the water, spreading outwards in a cone shape. The cone

width is dependent upon the frequency of the pulse;

at 50 kHz it is approximately 45°, and at 200 kHz it is

approximately 11°.

The differences in the cone width affect what is shown.

Strength of echoes

The colors indicate differences in the strength of the

echo. The strength varies with several factors, such as

the:

Size of the sh, school of sh or other object.•

Depth of the sh or object.•

Location of the sh or object. (The area covered by •

the ultrasonic pulse is a rough cone shape and the

echoes are strongest in the middle.)

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Simrad NX45 Specifications Page 37

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