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Advantages of Electromagnetic Log (EM Log) | disadvantages of Electromagnetic Log (EM Log)

This page covers advantages and disadvantages of Electromagnetic Log (EM Log). It mentions Electromagnetic Log (EM Log) advantages or benefits and Electromagnetic Log (EM Log) disadvantages or drawbacks.

What is Electromagnetic Log (EM Log)?

Introduction:
• It is used in marine engineering to measure speed of the ship i.e. measures vessel's speed through water.
• It works as per faraday's law and maxwell equations.

Electromagnetic Log, EM Log

• As shown current is fed through the coil of the flow sensor. This induces EM field around itself.
• When water (i.e. conductor) passes through this EM field, voltage is being created. Amount of voltage is directly proportional to speed of water or conductor.
• As a result speed of ship or vessel through the water is measured by EM log.

Benefits or advantages of Electromagnetic Log (EM Log)

Following are the benefits or advantages of Electromagnetic Log (EM Log):
➨It does not have any moving parts.
➨It is less affected due to sea growth compare to pit sword.
➨Modern sensor devices do not project at the bottom of the ship.
➨Modern EM logs are smaller in size.
➨EM logs deliver measurements with higher accuracy for smaller ship speeds.

Drawbacks or disadvantages of Electromagnetic Log (EM Log)

Following are the drawbacks or disadvantages of Electromagnetic Log (EM Log):
➨Water salinity and water temperature affects the calibration of EM log and deliver improper measurement. To avoid this, regular calibration of the EM log is needed.
➨It provides speed of ship relative to the water and not ground.
➨Measurements are influenced by boundary layer. This is due to slowed down of water speed very close to hull as a result of friction.



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