Vaisala Hydromet Data Collection Platform - Manual (Page 157)

Appendix A ________________________________________________________________ Glossary
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Modem A device that allows a terminal or computer at one location to
communicate with a terminal or computer at a distant location via
wire or telephone lines.
Precipitation Term that refers to all forms of water particles that fall upon the earth.
This includes rain, snow, and hail. It is the universal practice to
distinguish between rain, snow, and total precipitation. Snow is
sometimes measured as such and sometimes it is melted and
measured as water.
Pslevel The pressure sensor level in meters from the station altitude.
Pyranometer An instrument that measures solar energy received from the entire
hemisphere (180 degrees field of view). The output is expressed in
Watts per square meter (W/m
2
).
QFE The actual atmospheric pressure at the level of station altitude or at
the height of the runway threshold. The difference of the pressure
sensor level and the station altitude (or runway threshold) is indicated
by the pressure sensor (pslevel) setting in the QML logger. QFE is
normally used for aviation purposes.
QFF The sea level pressure as QNH, but the value is corrected by the
actual air temperature (or in some cases by virtual temperature, that
is, temperature 12 hours ago). QFF is used in synoptical observations.
QNH (altimeter
setting) The atmospheric pressure at sea level in the standard atmosphere. The
station altitude is indicated by the station altitude setting in the QML
logger (difference of mean sea level and station altitude). QNH is
used for aviation purposes.
Rain gauge Measures precipitation based on depth, that is, the depth to which a
flat surface would be covered if no water were lost by run-off or
evaporation.
RS-232 Standard serial transmission protocol. A standard interface between a
computer input/output port and a peripheral device.
RS-485 Standard serial transmission protocol. This protocol permits multi-
drop networks (up to 32 nodes) using a single twisted pair cable.
Solar radiation The solar energy received from the entire hemisphere. It is measured
with a pyranometer.
Synchronizing time Ties the operation to the clock for software operations. For instance,
if an operation is always to be performed twenty minutes to the hour,
the synchronizing time should be set to 00:40:00.
WMO The World Meteorological Organization.