WatchDog WatchDog 3349SS, Руководство по эксплуатации продукта

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About the Ultrasonic Wind Sensor
The ultrasonic wind sensor (an ultrasonic anemometer) measures ap-
parent wind speed and direction. The Sprayer Station contains four
ultrasonic transducers, visible through the four holes in the top of the
sensor’s wind channel. These transducers operate in pairs—one trans-
ducer injects a pulse into the air, and the other (directly opposite to it)
listens for the arrival of that pulse. Each pulse bounces off the metal
plate at the bottom of the wind channel and is carried by the wind to
arrive at the opposing transducer a short time later.
When there is no wind, the pulse travels at the speed of sound from
the sender to the receiver. Whenever the wind is blowing in that direc-
tion, the pulse will arrive sooner than if the air is still. Similarly,
whenever the wind is blowing in the opposite direction, the pulse will
arrive later than if the air is still. The four transducers take turns in
sending and receiving pulses to cover all possible wind directions.
A microprocessor within the Sprayer Station then combines the meas-
urements from all four transducers to calculate the resultant wind
speed and direction. Throughout this process, the sensor monitors the
air temperature, to compensate for the fact that the speed of sound in
air changes with temperature.
Understanding True and Apparent Wind
The Sprayer Station has the unique ability to display both true and
apparent wind. True wind is the actual motion of the air relative to the
earth. Apparent wind is the wind which an observer experiences while
moving. It is the result of two motions—the actual motion of the air
(the true wind) and the motion of the vehicle. If the vehicle is not
moving, then the true and apparent wind will be the same.
There are two components to any wind measurement: speed and di-
rection. By convention, the wind direction is an angle representing the
direction from which the wind is blowing.
How the Sprayer
Station Works