Thies CLIMA Compact WSC10 - Structure and Mode of Operation; Wind Speed and Direction; Brightness Measurement; Twilight Measurement

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3 Structure / Mode of operation

Wind speed / wind direction:

Wind measurement is based on the hot wire principle. The underside of the housing is

equipped with a heated cylindrical sensor. A PID controller adjusts the temperature of the

cylinder to a temperature that is constantly increased in relation to the environment. The

supplied heat energy is a measure of wind speed.

The metal cylinder contains four temperature-measuring resistors. These resistors are

thermally coupled with the cylinder and positioned according to the 4 points of the compass.

When an incident flow affects the cylinder as a function of the wind direction, this is

accompanied by a temperature gradient which is registered by the measuring resistors. The

relationships between the 4 temperature values are used to calculate the wind direction.

In case the wind direction cannot be determined because the wind velocity is 0m/s, the value

is set to 0. Wind from the north is displayed with 360°.

Brightness:

The brightness measurement is carried out via 4 Silicium photo sensors, which are aligned to

the 4 cardinal directions in the mean elevation angle (40°).

Twilight:

Twilight means the light diffusion in the atmosphere, which arises with the smooth transition

between day and night before the beginning or after the end of day.

i.e., the solar disc is not visible.

The twilight is direction-independent.

It is calculated from the sum of the 4 measuring values of the direction-independent

brightness sensors. A change to the mean value from the 4 brightness values is possible by

command.

Global irradiance:

A silicon PIN photodiode is used to measure global irradiance. The sensor is positioned

horizontally and registers the diurnal values of the solar irradiation intensity.

Precipitation:

The detection of precipitation is based on capacitance measurement, i.e. the capacity of the

sensor surface varies when wet. The sensor is installed in the housing cover. An integrated

heating system adjusts the sensor area to an overtemperature in relation to the ambient

temperature. This overtemperature (approx. 2K) prevents bedewing of the sensor surface.

The thermal output is increased with precipitation. This accelerates drying of the sensor,

allowing the time at which precipitation ended to be identified more accurately.