Thies CLIMA Ultrasonic Anemometer 2D Operating Instructions Manual page 7

7. Averaging Procedure:
The Ultrasonic 2D forms the gliding mean value through a FIFO-memory the capacity of which comprises up
to 600 values.
In the free running measurement mode the measurement data rate is exactly 10 Hz or 100msec, and forms,
at the same time, the updating rate for the averaging memory (FIFO-memory).
If averaging is requested the measured data are recorded in the FIFO-memory stated above, the capacity of
which is built-up depending on the selected averaging period.
If the averaging period is, for example, 10 seconds, 100 memory cells are used, and in case of an averaging
period of 1 minute 600 cells.
From a selected averaging period > 1 minute up the data flow will be pre-averaged; because the memory
capacity of 600 values cannot be exceeded.
The Ultrasonic 2 D combines two different and useful procedures of mean value forming:
•
The forming of vectorial mean values
•
The forming of scalar mean values
These different procedures can be selected for the averaging of both the wind speed and wind direction,
depending on the application.
The procedure of forming the vectorial mean value takes the wind direction into account when averaging the
wind speed and vice versa.
Thus, the averaged dimensions of wind speed and wind direction are valued each one with the other.
This procedure of forming the mean value is well suited, for example, for measurements and analysis of
pollutant-propagation.
The procedure of forming the scalar mean value averages both dimensions of wind speed and wind direction
independently from each other.
These averaging procedures lead to results comparable with mechanical wind speed- and wind direction
transmitters.
The scalar averaging procedure is suited, for example, for location-analysis for wind power plants, where only
the dimension of the wind vector – important for power generation – is interesting but not its direction.
The vectorial and scalar procedure can be used independently with wind speed and wind direction within an
output telegram.
For this, you have to select one of the four possible combinations through the command AM (Average
Method).
Command for selecting the averaging procedure:
AM00000 (Average Method) vectorial averaging of speed and direction
AM00001 scalar averaging of speed and direction
AM00002 scalar averaging of speed and vectorial averaging of direction
AM00003 vectorial averaging of speed and scalar averaging of direction
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