• Steep slopes
• Heat sources
• Swamps
• High vegetation
• Places that may hold water after rain
To ensure correct measurements, align wind sensors as instructed. The wind direction can
refer either to true North, which uses the earth's geographic meridians, or to the magnetic
North, which is read with a magnetic compass. Magnetic declination is the
dierence in
degrees between the true North and the magnetic North. The source for the magnetic
declination needs to be current, because the declination changes over time.
The same guidelines apply to the weather transmitter.
3.3.3.1 Placing Meteorological Sensors
To make sure that precipitation sensor observations are correct:
• Make sure that the opening of the precipitation sensor is horizontal, open to the sky,
and above the level of in-splashing and snow accumulation.
• In general, objects must not be closer to the precipitation sensor than a distance twice
their height above the precipitation sensor surface.
• To avoid water dripping, install the precipitation sensor so that the guy wires of the
mast are not positioned above the sensor.
• The standard cable length is 10 m (32 ft 10 in), and the precipitation sensor must not be
mounted at a distance more than 6 m (19 ft 8 in) from the mast. The precipitation
sensor is light, so it must be mounted securely.
• For the OTT Pluvio
2
L Precipitation Gauge installation, choose a setup location that is
free of vibration. For example, vibration from nearby
trac can influence the
measurement results.
Make sure that no building or object shadows the solar radiation sensor during the day. In
the Northern Hemisphere, install the solar radiation sensor on the southern side of the mast.
In the Southern Hemisphere, install the sensor on the northern side of the mast.
To make sure that present weather detector observations are correct:
• Avoid heat sources, obstructions, and reflective surfaces in the proximity of the sensors.
• Point the optics away from powerful light sources.
• Point the optics away from any obvious source of contamination, such as spray from
passing vehicles.
To ensure correct ceilometer measurements, position the ceilometer so that it has a clear
view of the sky.
More Information
‣
Placing PWD (page 131)
3.3.3.2 Placing Subsurface Sensors
For the soil temperature sensor, the measurement site must be 1 m
2
(10.76 sq ft) and typical
of the surface of interest. The ground surface must be level with respect to the immediate
(10 m / 32 ft 10 in radius) area.
Chapter 3 – Installation Preparation
23
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