Simrad SH90
How to check for electrical noise
This procedure provides a simple method to check the electrical
noise.
1
Switch off all electric equipment that can cause electrical
noise.
This includes motor, propellers, thrusters, winches, cooling-
and air conditioning systems, pumps, cranes, hydraulic
systems etc.
2
Switch the equipment on again one at the time, and check
the sonar every time.
With luck, you will spot which of your electrical systems
that create the noise. To deal with the problem, consult your
dealer and/or a certified ships electrician.
Layers and deflections
Your sonar operations may also be disturbed by environmental
situations that you are unable to control. Two typical conditions
are temperature and salinity layers, and deflections caused by
increasing or decreasing water temperature.
Temperature and salinity layers
You may experience that temperature and/or salinity layers exist
in the water column. Since the speed of sound in water depends
on its temperature and salinity, such layers will cause the sound
beam to be reflected.
Figure 18
Temperature and salinity layers
B
(CD015005F)
A
If you transmit a sonar beam down towards a temperature
or salinity layer (A), it may be reflected as indicated in the
illustration. The school of fish (B) you thought you would see
will not be visible at all.
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Summary of Contents for SH90 - REV A
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