Vaisala WS425 - Manual (Page 16)

USER'S GUIDE____________________________________________________________________
16 __________________________________________________________________ M210361EN-E
Measuring the six transmit times allows wind velocity to be calculated
for each of the three ultrasonic paths, which are offset to each other by
120°. The calculated wind speeds are independent of altitude,
temperature, and humidity because they cancel out with the six
measurements even though the velocity of sound affects individual transit
times.
Incorrect readings may occur when a large raindrop or ice pellet hits a
transducer. They are eliminated by a proprietary signal processing
technique. The wind velocity that is most affected by turbulence error is
eliminated so that wind speed and wind direction are calculated from the
best two vectors.
Sensor Operating Modes
There are four modes of operation that give different information:
- Analog
- SDI-12 mode A
- SDI-12 mode B
- Serial mode RS-232/422/485
Only one of these modes can be operated at a time. The sensor must be
ordered according to the desired mode of operation.