Simrad SL 30, Руководство пользователя

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SL 30/35 Hull Sonar Operators Manual 974-25007001/2.0
System Description Page 2.3
Kongsberg Simrad Mesotech Ltd.
Port Coquitlam, BC - Canada
2.
SYSTEM DESCRIPTION
2.1 INTRODUCTION
This section explains the theory of operation of the SL 30/35 Mechanical Scanning
Sonar System.
2.1.1 Basic Principles
•
Sound waves travel very efficiently through water.
•
A sound pulse can be projected through water in a controlled direction with the
sonar transducer.
•
An object in the path of the projected sound pulse will reflect some sound pulse
back toward the sonar transducer.
•
The speed of the sound pulse projected through the water can be predicted for
given conditions.
2.1.2 Determining Target Position
The SL 30/35 scanning sonar processor measures the time from the start of the
sound pulse projected through water, to the reception of the sound pulse reflected
back to the sonar transducer. The measured time is then converted to distance by
using the speed of sound through water.
Since the sound pulse is projected in a known direction, the bearing of the reflected
object is also known. This makes it possible to locate the object with respect to the
sonar transducer; the information will be used to plot the position of the reflected
target on a video graphic display monitor.
2.1.3 Forming an Image
The sound pulse projected will be attenuated as it travels through the water from the
transducer to the target and back. Much of this attenuation is a predictable function
of the total time or the distance the sound pulse traveled through water. Increasing
the receiving gain with time can compensate for this decrease in the signal level.
This is done automatically in the sonar with a
Time Varying Gain circuit.