DNT WeatherScreen PRO Bedienungsanleitung Seite 86

Notes on the calibration parameters and sources of error
Offset: a djustthe valueusingthe reference. G ain:adjustment b ycomparison or calculation
Parameter
Temperature
Air Humidity
Air Pressure
absolute
Air pressure
relative
Wind direction
Solar
radiation/UV
1 w/m2
Wind
Rain
(l)Common mistake: too close proximity to heat sources, also too close to the floor/subsurface,
near housewalls etc. A shaded area is ideal for a comparison measurementwith a reference
thermometer.Thecomparisontime should beat least 3 hoursbeforereadingthe values.Onlyuse
calibratedthermometersor thosewith mercuryor alcoholfiling as a reference.Temperaturedata
from weather portals etc. are also not suitable for calibration. Firstly,their sourcesare unknown.
Secondly,their update rate may be insufficient.
(2 ) The air humidity is difficult to measurewith electronicsensors,which is why the basic accuracy
is 5 %, depending on the basic accuracy of the sensor used or its production batch, aging, and
contamination.Onlya professionalpsychometershould be used for calibration.
(3 ) In meteorology,a distinction is madebetweenabsoluteair pressureand relative air pressure.The
former is the real air pressureat the respectivelocation.The latter is the air pressurecorrected at
sea level as a worldwide reference air pressure (1013.25 hPa).The absolute air pressuredrops
with the heightof the locationabovesealevel(e.g.Zugspitze:693 hPa).With the correctionfactor
basedon sealevel,the relative air pressureis now comparableto other locationsand canbe used
for the weather forecast for a specific area. It is, however,higher than absolute air pressure.If
the relative air pressure at the location rises above 1013 hPa,one speaksof high pressure. If it
falls below 1013 hPa,one speaksof low pressure.A calibrated reference barometer is required
to calibratethe absoluteair pressure.Tocalibratethe relative air pressure,a timely valuefrom an
official measuringpoint in an immediate environmentis sufficient, e.g. from a weather service.
86
Calibration Basic Setting
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Factory setting
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Factory setting
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Gain I .00
Gain 126,7 lux
Gain I .00
Gain I .00
TypicalCalibrationSource
Comparative t hermometer w ith thermalliquid
(Mercury/Alcohol/Spirit)
Psychometer
(Aspirations/ Spin/ Sling-) (2)
Calibrated reference barometer
Public measuring point, e.g. Weather
service (Internet)or referencedweather
servicefrom the nearestairport (3)
Compass/GPS
Calibrated laboratory solar radiation sensor
Calibrated UV sensor
Conversion factor lux in w/m2 with
considerationof the wavelength (5)
Calibrated wind sensor (6)
Sight glass rain gauge with calibrated
scale and with an opening of at least
10,16 cm (4")