නැවේ වැඩ #2 | changing the speed log sensor on a floating vessel.

Speed logs, also known as ship logs, measure the speed of a vessel. The speed is determined with reference to water flowing by the hull (water reference speed) or to the seabed (ground reference speed)
There are several types of speed logs fitted in vessels and in here it is Electromagnetic type sensor..
Electromagnetic log, also called EM logs, rely on a coil in an electromagnetic sensor. When the AC current energizes the coil, it creates a magnetic field surrounding the sensor. As a vessel moves through water, an electrical field running perpendicular to the magnetic field is produced. The sensor electrodes detect and deliver the resulting signal representing the ship's speed to a preamplifier, which then converts it to a digital format for viewing. This process is inexpensive and has the advantage of not requiring any moving parts. However, water salinity and temperature can affect calibration. The water flow slows down closer to the hull due to friction, affecting measurements.
source: www.globalspec....