Anemometer

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Anemometer and Anemoscope

How does Windmeter Windmeter work? Windmeter is a composite term for anemometer and anemoscope. While anemometer measures wind speed, anemoscope anemoscope provides wind wi nd direction. Wind-mill type is the most commonly used on ships and consists of both transmitter and receiver. The transmitter transmits the wind direction and speed signals to the receiver. The receiver converts these signals into wind direction and wind speed values, which are displayed on indicators. The indicators are mounted, usually, on front bulkhead of ship’s bridge above the windscreen. The indicators are also provided with dimmer control for adjusting the li ghting for day/night conditions.

Anemometer

Anemoscope

Windmeter Indicator

The indicators provide relative wind speed and direction. True wind and direction need to be calculated mathematically or graphically by using true wind triangle OAT. OAT consists of three vectors namely: OA (apparent wind and direction), OT (true wind and direction) and AT (own ship course and speed). Caution needs to be exercised to see that ship’s speed and wind speed are in same units. An example of wind-mill type of transmitter is shown in photograph. It is mounted high hi gh on aft mast, free of obstructions. Propeller is attached to the leading edge of the magneto generator. The rear end consists of tail wing (wind vane). The entire assembly is carefully balanced and pivoted to rotate freely about vertical axis. The weight is evenly distributed on each side of the

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surface of tail wing. However, the surface area is unequally divided so that the side with the larger surface area is blown away from the wind direction and the smaller side, where the propeller is fitted, pivoted to face the wind direction. direction.

Tail Wing (Wind Vane)

Propeller

Generator in casing

Wind-mill Transmitter

Operation and Principle:


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EMF generated, calibr ated to wind speed in knots and m/s Anemometer (wind speed measurement) works on principle of generator and anemoscope (measurement of wind direction) employs the system of synchro motors. The propeller of the transmitter rotates under the action of wind blowing past, which in turn causes a small internal AC magneto generator to spin. The generated electromotive force is proportional the revolutions of the generator, which means proportional to wind speed. The indicator is calibrated to show the wind speed in knots and meters/second. Wind direction measurement makes use of the property of the synchronization that can convert mechanical changes in angles into corresponding electric signals. The anemoscope is calibrated to show the angle which the relative wind makes with respect to ship’s port bow or starboard bow. The synchro system works by aligning the shaft at the receiver side with the shaft at the transmitter side. On alignment, the flow of current is nil, but when transmitter shaft changes direction, voltage is induced and torque is produced which brings the receiver shaft in line with that of the transmitter. This angular displacement is displayed as angle between relative wind and ship’s bow on the indicator.


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Transmitter

Receiver

Synchro Moto r system for direction direction


Anemometer

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