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Air temperature:
A PT1000 measuring resistor is used to measure the air temperature. The sensor is mounted on a
flexible printed board and positioned in the lower section of the housing.
Air pressure:
Absolute air pressure is measured with a piezoresistive MEMS sensor.
To make a meaningful comparison between air pressure values simultaneously measured at different
locations, they need to be converted to a common datum (height above sea level). The calculation is
referred to the height above sea level (QNH) according to the international altitude formula (DIN
ISO2533).
P
h
= air pressure at local altitude
P
b
= air pressure at height above sea level
=
-0065K/m
g
n
=
9.80665m/s
2
R
=
287.05287m
2
/K/s
2
T
b
=
288.15K
The station height, required for the calculation, can be entered manually by the
Command SH
, or can
be determined automatically by GPS.
If you want to achieve an accuracy of 0.1hPa, referred to sea level, the local altitude (altitude of the
baro transmitter) must be given up to an accuracy of 0.8m.
Time / date and geostationary data:
The Weather Station has a GPS receiver with a built-in RTC. This allows it to receive the position of
the Weather Station (degree of longitude/latitude, local altitude) time (UTC) and date. The GPS
receiver does not need alignment.
The built-in RTC (Real Time Clock) is buffered with a backup capacitor and retains its data without a
voltage supply for a period of minimum 3 days.
Position of the sun (elevation / azimuth):
On the basis of the GPS data the current sun position is calculated every second.
Humidity measurement:
A built-in hygro-thermosensor is used to measure humidity levels. The sensor has a small air exchange
volume thanks to its compact design and responds to changes in humidity in seconds.
A software module uses the relative humidity and air temperature to calculate absolute humidity and
the dew-point temperature.
R
g
T
b
n
b
h
p
h
p
)
1
(
)
(
