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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
, 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.
R
g
T
b
n
b
h
p
h
p
)
1
(
)
(
