What is an Echo Sounder, its principle, errors and corrective action?

 

echo sounder

 Working  of  Echo Sounder
  • The recorder sends a signal to the pulse generator which triggers a pulse and simultaneously starts the recorder trace.
  • The rate may be between 5-600 pulses a minute depending upon the depth to be measured.
  • Lesser the depth scale, faster the Pulse Repetition Frequency.
  • The pulse from the Pulse Generator activated the transmitter which sends a powerful electric pulse to the Transducer.
  • The transducer converts the electric energy into sound energy producing a pulse.
  • The sound energy travels to the bottom, hits the bottom and gets reflected back to the transducer.
  • The transducer converts the received sound energy of the echo into an electric pulse and sends it to the receiver.
  • In the receiver the received pulse is processed and then amplified and sent to the Recorder.
  • At the recorder, the stylus which has been at a speed proportional to the speed of sound, creates a physical mark on a paper or a visual blip or a digital signal for the recorder.
What is Transducer of Echo-Sounder?
  • Magneto-Striction is an effect which occurs in all ferromagnetic material, but particularly pronounced in iron, nickel and cobalt.
  • These items when placed in a magnetic field change their length.
  • Conversely, when subjected to physical stress they generate an emf.
  • When alternating current is used to create a magnetic flux, the transducer will vibrate producing a sound pulse.
  • Sighting of the Transducer
    • Away from noise sources and areas of turbulence like the propeller and discharges.
    • Away from aeration which is caused due to bubbles generated by the bow wave or irregularities on the hull, log tubes and discharge orifices.

echo sounder transducer

What is Recorder of Echo-Sounder?
  • This is the component of the ES a mariner would be using on the bridge.
  • Earlier, the echo of the bottom used to be recorded as a mark on paper.
  • Currently the old style paper recorder have been replaced by electronic displays showing the bottom echo as blip.
  • However, IMO regulations require that a ship must have hard copies of past depth soundings which can only be done on paper. 
  • A paper recorder consists of a stylus which is made to move across electro-sensitive paper.
  • When the transmitter fires its pulse, the stylus marks the paper at the zero of a graduated scale.
  • While the pulse travels to the bottom the stylus moves in tandem across the paper but at a speed proportional to half the speed of sound.
  • Why half? Because the stylus has to represent the to and fro journey of the transmitted pulse.
  • On detection of an echo, the stylus again marks the paper which shows depth of water.
  • Even after marking the depth, the stylus will continue traveling towards the end of the paper.
  • On reaching the end, the stylus flies back to the zero signifying next transmission and the paper moves down providing a fresh surface for the next echo.
  • The process above will be repeated.
  • A trace can be seen to be developing on the paper with time on one axis and the echoes on the other building a profile of the sea bottom on paper.
  • The speed of the stylus will move depending upon the chosen range scale.

echo sounder digital recorderecho sounder paper recorder

About the author

Amit Sharma

Graduated from M.E.R.I. Mumbai (Mumbai University), After a brief sailing founded this website with the idea to bring the maritime education online which must be free and available for all at all times and to find basic solutions that are of extreme importance to a seafarer by our innovative ideas.

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