Echo Sounder

Even in the clearest water, it is difficult to judge the depth of objects using only your eyes. The water bends the light in a way that makes the objects appear closer to the surface than they really are. The only way to get an accurate measurement of their depth is to use an echo sounder. It is mainly used for monitoring the water depth under the keel of a boat but it can also be made to work as a fish finder. There are plenty of models that are suitable for a small yacht or cruiser, and even a few portable models that can be used on a small tender.

An echo sounder uses active sonar to detect objects under the surface of the water. The two main components of an echo sounder are its transducer and display unit. The transducer creates sound waves that travel through the water at the speed of sound. When one of these waves strikes a solid object, an echo of the wave travels back towards the boat. Before sending out another wave, the display unit pauses and waits for the echo to strike the transducer. If the echo is detected, the distance to the object is calculated using the time it took for the wave to travel out and back. The distance is shown on the display unit, which also sounds an alarm if the distance goes below a certain value.

As a boat moves along the surface of the water, the distance between the keel and the sea bed can change very quickly, especially when the boat is moving quickly towards the shoreline. The skipper must keep a constant eye on the water depth to avoid running around and potentially damaging the boat. Another common application for an echo sounder is finding large schools of fish. When fish travel close together in a school, they create an echo when a sound wave hits them, similar to the echo created by the sea bed. It is even possible to determine the species of fish from the size of the echo they create.

A basic echo sounder shows the water depth as a number but does not usually show a profile of the sea bed. Most of the basic models can be used as a fish finder but will only give a rough indication of the position of large schools. Their display is often just a small monochrome LCD which is hard to read. For a bit more money, you can get an echo sounder that has a good color display, and maybe even an integrated GPS unit that shows your position on the Earth’s surface. When choosing a basic model, make sure that the maximum depth is enough for the places you want to use it. If the echo sounder is to be used at night, make sure it has a good backlight and illuminated buttons.

To get a better view of the sea bed, you need to upgrade to an advanced echo sounder. Obviously, it costs more than a basic model but its extra features are definitely worth it. With a dual frequency transducer and a high-resolution color screen, it can show greater detail than a basic model. It has a digital signal processor that removes signal noise and makes the picture sharper. An adjustable depth range is essential for looking at rockshelfs in more detail. Screen images can be saved to the onboard memory and they can also be sent to a printer. The fish finder mode is more advanced and can even identify the species of fish in most cases.

A typical echo sounder is permanently fixed to the structure of a boat. There are some exceptions though, like the portable fish finders which have a transducer that floats on the surface of the water. However, the vast majority of transducers are installed through a hole in the hull and bolted in place. A long length of cable connects the transducer to the display unit, which is usually mounted inside the cabin, or the flybridge if the boat has one. A smaller display unit that shows the water depth can be placed next to the steering wheel for quick reference. It may also be capable of showing the GPS position, compass bearing, boat speed, wind speed, and engine performance.

This Echo Sounder Review is Written/Updated on Oct 15th, 2010 and filed under Consumer Electronics. Both comments and pings are currently closed.

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