User manual
1
WXT520 Weather Transmitter
1. Introduction
The WXT520 Weather Transmitter, manufactured by Vaisala, measures wind
speed and direction, precipitation, barometric pressure, temperature, and relative
humidity—all in a single device that has no moving parts. The WXT520’s SDI-
12 signal can be measured by any of our SDI-12 equipped dataloggers. The
WXT520 is about the size of our larger Gill radiation shield, making it ideal for
use with our CR200(X)-series dataloggers in applications requiring quick, short-
term deployment. However, the WXT520 is not intended for weather stations that
require research-grade performance.
Before installing the sensor, please study
• Section 2, Cautionary Statements
• Section 3, Initial Inspection
2. Cautionary Statements
• Although the WXT20 is rugged, it should be handled as a precision scientific
instrument.
3. Initial Inspection
• Upon receipt of the WXT20, inspect the packaging and contents for damage.
File damage claims with the shipping company.
4. Overview
4.1 Wind Speed and Direction
The WXT520's wind sensor consists of three equally spaced transducers that
produce ultrasonic signals. Wind speed and direction are determined by
measuring the time it takes for the ultrasonic signal of one transducer to travel to
the other transducers. Wind direction is not calculated when the wind speed drops
below 0.05 m/s. In this case, the last calculated direction output remains until
wind speed increases. The computed wind speeds are independent of altitude,
temperature, and humidity. The WXT520 is preconfigured to provide the
minimum, average, and maximum values for both wind speed and direction.
Default wind speed units are m/s.
4.2 Precipitation
The WXT520 uses the RAINCAP® Sensor to measure accumulated rainfall, rain
intensity, and rain duration. Precipitation is measured one raindrop at a time.
Whenever a raindrop hits the precipitation sensor, an electrical signal is produced
that is proportional to the volume of the drop.
The sensor is also capable of distinguishing hail stones from raindrops. The
measured rain and hail parameters are cumulative amounts of rain or hail, rain or
hail intensity, and the duration of a shower.