Vaisala WS425 - Manual (Page 47)

Chapter 4 ________________________________________________________________ Operation
VAISALA _______________________________________________________________________ 47
Wind Speed Units
There are four wind speed units available:
a. Miles/hours
b. Knots
c. Kilometers/hours
d. Meters/seconds
NOTE When the operation mode is WAT11 (selected from the configuration
parameter 1), the only option for the wind speed unit is meters/second as
the WAT11 message does not contain wind speed unit information.
Average Interval
The averaging interval can be selected as full seconds between 1 and 9
seconds. For the WS425 sensor, the time between each consecutive wind
direction measurement is one second. Each wind direction measurement
taken over the preceding averaging interval is summed and the sum is
divided by the number of measurements.
The same averaging interval is used for both the average wind speed and
average wind direction.
The sensor computes a true running average. If the data acquisition
system requests data before the initial averaging interval completes, the
sensor returns the best possible running average.
Averaging Method
These settings affect the calculation of wind speed and direction. The
available options are as follows:
a. Scalar averaging
b. Vector averaging
Scalar Averaging
When the scalar averaging is selected, the wind direction is a circular
function with a discontinuity at due north, where 360° is equal to 0°. For
example, 359° + 5° = + 4° and
0° - 5° = 355°.