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These different procedures can be selected for averaging wind velocity as well as wind direction
depending on the actual application.
Vectorial averaging involves the wind direction for averaging of the wind velocity, and wind velocity
for averaging of the wind direction.
Both averaged variables, wind velocity and wind direction, thus each undergo evaluation with the
other measured variable.
This averaging procedure is very suitable e.g. for measuring and evaluating the propagation of
pollutants.
Scalar averaging averages both variables, wind velocity and wind direction, independently of each
other.
This averaging procedure leads to comparable results with mechanical wind velocity and wind
direction pickups.
The scalar averaging procedure is suitable e.g. for location analysis for wind turbines where only
the wind vector variable relevant for the generation of energy is of interest and not its direction.
The vectorial and scalar procedure can be used within one output telegram independently of the
wind velocity and wind direction.
For this purpose one of the four possible combinations is selected using the Command AM as for
Average Method.
Command for selection of averaging procedure:
AM0 (Average Method) Vectorial averaging of velocity and direction
AM1 Scalar averaging of velocity and direction
AM2 Scalar averaging of velocity and vectorial averaging of direction
AM3 Vectorial averaging of velocity and scalar averaging of direction
7.3.3 Standard deviation
Calculation of the standard deviation is another feature offered by the ULTRASONIC. The standard
deviation values are determined for the wind velocity, wind direction and virtual temperatures with
an averaging time > 1sec. Values are calculated according to the following formula:
(
)
∑
<
=
−
=
n
i
i
Xi
M
n
Y
0
2
1
where
∑
<
=
=
n
i
i
Xi
n
M
0
1
Standard deviation is switched on with the command "DE1". When using standard deviation the
averaging memory used is limited to 2000 measured values. Otherwise there are no restrictions
when using standard deviation. Which calculated values are available when using standard
deviation can be found under Available measured values and Data formats in the section User-
specific telegram.
In the presetting calculation of the values for standard deviation is switched off. It must be switched
on explicitly with the command 00DE1.