Vaisala vLog 4.5 - Manual (Page 116)

Glossary
110 © 2011 Vaisala Canada Inc
Channel
The path through which an instrument receives the input
signals it measures
Dewpoint
Dewpoint is defined as the temperature at which the amount
of moisture present in the air is the MAXIMUM amount the air
can hold (at a constant pressure and water vapor content).
This means that when the temperature falls to the dew point,
the relative humidity is 100% and the air is considered
saturated.
Dewpoint does not vary with temperature, as does relative
humidity (RH). Rather, dewpoint is a DIRECT measure of the
actual moisture content in the air and thus is preferred as the
unit of measurement in many scientific and industrial
applications—particularly in tightly controlled environments
where precise indications of water content in the air are
required.
The dewpoint is never greater than the air temperature. Once
the dewpoint is reached and the air temperature continues to
drop, water vapor is forced to leave the air through
condensation. This condensation may take the form of water
droplets, dew, or may remain suspended in the air as clouds
or fog.
To better understand how dewpoint and relative humidity are
related to each other, try inserting a logger file with relative
humidity (RH) channel values into a graph twice—once,
displaying RH using dewpoint and once displaying RH using
relative humidity.
in vLog, dewpoint readings below 0 degrees C are recorded
as frostpoint.
F–K
FDA
An acronym for the US Food and Drug Administration; this is
a government agency responsible for enforcing the Federal
Food, Drug and Cosmetic Act