A modern sea or river vessel cannot do without navigational instruments, one of which is a sonar.
With the help of this equipment, sailors evaluate the bottom topography, and fishers look for places rich in fish.
How and when was the sonar invented?
In 1912, the world was rocked by a terrible tragedy: the sinking of the Titanic, which took 1,500 lives. It was urgent to find a solution to the safety of ships, so that accidental collisions could be avoided.
It took only a year for the German experimenter Alexander Böhm to develop and patent a new device for detecting solid objects in low visibility conditions. It took another eight years to perfect the device and bring it into series production.
The first sounders were quite cumbersome because they used bulb equipment. They were installed only one large enough civilian and military ships. The first echo sounders could determine the distance to the seabed or detect large underwater masses – submarines, large schools of fish, etc.
In the late 50s C. Lowrance set his sights on making a sounder that could be used on any boat and even a motorboat. To develop the device, he used new radio elements on semiconductors, which were much smaller than radio tubes.
In the mid-1970s, the new echo sounders went on sale. Modern devices with high accuracy can determine the structure of the bottom topography and detect individual fish swimming under the bottom of the boat. They are gladly used not only by professional sailors but also by amateur anglers, yachtsmen and others.
Operating principle of an echo sounder
In its work, the echo sounder uses the reflected ultrasonic signal. The principle of operation is quite simple: a special transmitter generates an electromagnetic signal, which is converted into an ultrasonic wave of a certain frequency.
The wave reaches the bottom or any solid obstacle is reflected from it and returns. According to the speed of the reflected ultrasound returning, the device makes a picture on the screen of what is happening under the bottom of the ship or boat. The speed of sound propagation in the water is a constant and does not affect the passage of ultrasonic waves, even if the sea is stormy.
The device emits ultrasonic waves with a frequency of not less than 50 KHz, the most common are the operating frequencies of 190-200 KHz. The frequency of the sent signals is not perceived by human ear, fish or other sea inhabitants, so the sonar is a very useful device for fishers.
Modern echo sounder
Structurally, a modern sonar comprises the following units:
– a powerful transmitter that generates electromagnetic waves;
– Transducer of electromagnetic radiation in ultrasound and vice versa;
– receiver of ultrasonic signals with high sensitivity;
– contrast screen with good resolution.
The results of the echo sounder are displayed on the screen in a simple form. In order to recognize objects at the bottom of the reservoir or in the water under the boat, a little practice is enough. Usually the screen is divided into two parts: in the right one the so-called vertical scan is displayed, in the left one – horizontal.
The vertical sweep is the picture displayed at the current moment – what is currently under the bottom of the boat. Reflected signals are shown as dark dots or stripes lying at different distances from the surface line.
Horizontal sweep shows the changing picture in depth and time coordinates. The picture shifts from right to left at a preset speed, which is manually or automatically synchronized with the speed of the ship for maximum accuracy. The picture of the horizontal sweep changes when the depth changes, appearance and disappearance of floating objects.
The echo sounders, with several transmitters and receivers spaced along the length and width of the hull, are the most accurate. Based on the difference between received signals, the device calculates and displays the most accurate picture of the bottom and everything in the water under the ship.