Waldbeck Huygens Mode D'emploi page 95

Viewing absolute vs. relative pressure:
• To switch between absolute and relative pressure, press and hold the
[PRESSURE -] button for two seconds.
• 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.
• Relative pressure is corrected to sea-level conditions.
Rate of change of pressure graph:
The rate of change of pressure graphic is shown to the left of the
barometric pressure and signifies the difference between the daily
average pressure and the 30 day average (in hPa).
Viewing pressure history:
Press the [PRESSURE -] button to view the 12 hour, 24 hour, 48 hour
and 72 hour pressure average.
Relative pressure calibration discussion:
• To compare pressure conditions from one location to another,
meteorologists correct pressure to sea-level conditions. Because the air
pressure decreases as you rise in altitude, the sea-level corrected pressure
(the pressure your location would be at if located at sea-level) is generally
higher than your measured pressure. Thus, your absolute pressure may
read 28.62 inHg (969 mb) at an altitude of 1000 feet (305 m), but the
relative pressure is 30.00 inHg (1016 mb).
• The standard sea-level pressure is 29.92 inHg (1013 mb). This is
the average sea-level pressure around the world. Relative pressure
measurements greater than 29.92 inHg (1013 mb) are considered high
pressure and relative pressure measurements less than 29.92 inHg are
considered low pressure.
• To determine the relative pressure for your location, locate an official
reporting station near you (the internet is the best source for real time
barometer conditions, such as Weather.com or Wunderground.com), and
set your weather station to match the official reporting station.
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