Working of Doppler Log
The Doppler log is a type of sonar system that uses the Doppler shift principle to measure the speed of a vessel through water.
The system works by using a transducer that is mounted on the ship’s hull or keel to transmit a beam of acoustic waves down into the water.
As the beam of sound waves travels through the water, it encounters the seabed or a layer of water and is reflected towards the transducer. The transducer then receives the reflected signal, which is processed to determine the speed of the vessel.
The Doppler effect causes a change in the frequency of the sound wave as it travels towards the seabed and back. If the transducer is moving towards the seabed, the frequency of the reflected signal is higher than the transmitted frequency.
If the transducer is moving away from the seabed, the frequency of the reflected signal is lower than the transmitted frequency.
By measuring the difference in frequency between the transmitted and received signals, the Doppler log can determine the speed of the vessel relative to the seabed or layer of water.
The speed of the vessel can then be displayed on a digital or analog gauge on the ship’s bridge.
In addition to measuring the speed of the vessel, Doppler logs can also provide information on the depth of the water and the distance to the seabed.
Some Doppler logs are also equipped with additional features, such as alarms to alert the crew if the vessel is approaching shallow water or if the speed exceeds a certain limit.