Vaisala WMT700 - Manual (Page 39)

Chapter 3 _______________________________________________________ Functional Description
The microcontroller calculates WS from the measured transit
times using the following formula:
) t / 1 (1/t L 5 . 0 V
r f W
− ⋅ ⋅ =
where
V
w
= Wind velocity
L = Distance between two transducers
t
f
= Transit time in the forward direction
t
r
= Transit time in the reverse direction
Measuring the six transit times allows V
w
to be computed for each
of the three ultrasonic paths. Using V
w
values of two array paths
is enough to compute WS and WD.
Figure 12 below shows the different paths of WMT700 and the
vectors provided by the wind sensor:
1104-066
Figure 12 Measurement Paths of WMT700
where
1–6 = Measurement paths 1 to 6 of WMT700
L
a
, L
b
, L
c
= Distance between two transducers
VAISALA ________________________________________________________________________ 37