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6. Glossary of Terms
Term Definition
Absolute Barometric
Pressure
Absolute pressure is the measured atmospheric pressure and is a function
of altitude, and to a lesser extent, changes in weather conditions.
Absolute pressure is not corrected to sea-level conditions. Refer to
Relative Barometric Pressure.
Accuracy Accuracy is defined as the ability of a measurement to match the actual
value of the quantity being measured.
Barometer A barometer is an instrument used to measure atmospheric pressure.
Calibration Calibration is a comparison between measurements – one of known
magnitude or correctness of one device (standard) and another
measurement made in as similar a way as possible with a second device
(instrument).
Dew Point The dew point is the temperature at which a given parcel of humid air must
be cooled, at constant barometric pressure, for water vapor to condense
into water. The condensed water is called dew. The dew point is a
saturation temperature.
The dew point is associated with relative humidity. A high relative humidity
indicates that the dew point is closer to the current air temperature.
Relative humidity of 100% indicates the dew point is equal to the current
temperature and the air is maximally saturated with water. When the dew
point remains constant and temperature increases, relative humidity will
decrease.
HectoPascals (hPa) Pressure units in SI (international system) units of measurement. Same as
millibars (1 hPa = 1 mbar)
Hygrometer A hygrometer is a device that measures relative humidity. Relative
humidity is a term used to describe the amount or percentage of water
vapor that exists in air.
Inches of Mercury (inHg) Pressure in Imperial units of measure.
1 inch of mercury = 33.86 millibars
Rain Gauge A rain gauge is a device that measures liquid precipitation (rain), as
opposed to solid precipitation (snow gauge) over a set period of time.
All digital rain gauges are self emptying or self dumping (also referred to as
tipping rain gauge). The precision of the rain gauge is based on the volume
of rain per emptying cycle.
Range Range is defined as the amount or extent a value can be measured.
Relative Barometric
Pressure
Measured barometric pressure relative to your location or ambient
conditions.
Resolution Resolution is defined as the number of significant digits (decimal places) to
which a value is being reliably measured.
Solar Radiation A solar radiation sensor measures solar energy from the sun.
Solar radiation is radiant energy emitted by the sun from a nuclear fusion
reaction that creates electromagnetic energy. The spectrum of solar
radiation is close to that of a black body with a temperature of about 5800
K. About half of the radiation is in the visible short-wave part of the
electromagnetic spectrum. The other half is mostly in the near-infrared
part, with some in the ultraviolet part of the spectrum.
Thermometer A thermometer is a device that measures temperature. Most digital
thermometers are resistive thermal devices (RTD). RTDs predict change in
temperature as a function of electrical resistance.
Wind Vane A wind vane is a device that measures the direction of the wind. The wind
vane is usually combined with the anemometer. Wind direction is the
direction from which the wind is blowing.
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