User`s guide

Chapter 3 ______________________________________________________ Functional Description
VAISALA _______________________________________________________________________ 27
The microprocessor of the microcontroller calculates WS from the
measured transit times using the following formula:
)t/1(1/tL5.0V
rfW



where
V
w
= Wind velocity
L = The distance between two transducers
t
f
= The transit time in the forward direction
t
r
= The transit time in the reverse direction
Measuring the six transit times allows Vw to be computed for each of the
three ultrasonic paths. Using Vw values of two array paths is enough to
compute WS and WD.
Figure 7 below shows the different paths of WMT700 and the vectors
provided by the wind sensor:
1104-066
Figure 7 Measurement Paths of WMT700
where:
1-6 = Measurement paths 1 to 6 of WMT700.
L
a,
L
b,
L
c
= The distance between two transducers.