3-3
IM80B80T10E 21th Edition : Jul.1,2007-00
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3.3 Components and Their Functions
3.3.1 Sensor Unit
A variety of sensor units are available depending on the installation conditions, but all of them con-
sist of the following components:
(1) Sensor(withbuilt-inamplier)
Detects the ship’s speed in the water, and transmits the data to the master unit. If an emf is induced
by the relative motion between the water ow (the ship’s speed in the water) and the magnetic eld
established by the coil, a voltage proportional to the ship’s speed is detected at the electrodes lo-
cated at the tip of the sensor. This voltage is then fed to the built-in amplier, converted into a current
signal (0 mA to 20 mA) proportional to the speed, and nally output.
(2) seawater valve
Holds the sensor and prevents seawater from spurting out when the sensor is removed.
(3) Mounting plate: LV902 and LV910 (for sensors 48 mm in dia.)
This is welded onto the bottom of the ship’s hull to allow the seawater valve to be installed. The
mounting plate is ordered from the shipbuilder as standard. For sensors installed through the dou-
ble-bottom hull of a ship, the mounting plate for the seawater valve ange is also included.
(4) Protection tube : LV905
This is watertight tubing for sensors which are installed through the double-bottom hull of a ship.
the tubing is made of brass (BS) or stainless steel (SUS304) depending on the class of the ship.
Brass (BS) ..... NK, LR, DNV
Stainless steel (SUS304) .....ABS
(5) Seawatervalveange:LV904
This is used for supporting the bottom of the protection tube for sensors which are installed through
the double bottom hull of a ship. The ange has a structure which allows the protection tube to slide
in consideration of variations in the distance between the two bottom plates. The seawater valve
ange is made of bronze casting (BC3).
(6) Zinc plate: LV901
Protects the sensor unit from corrosion. The zinc plate is ordered from the shipbuilder as stand-
ard.
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