DAVIS Weather Monitor II (7440, 7440CS) - Manual (Page 28)

Using the Weather Functions
Page 24 Weather Monitor II
To Clear the Low Wind Chill
1. Press WIND CHILL.
2. Press RECL.
3. Press CLEAR and hold it down.
The display will flash several times, and then the low wind chill will be replaced
by the current wind chill. As the wind chill falls, the low will be updated.
4. Press any key to exit.
To Use the Low Wind Chill Alarm
For instructions on how to use the low wind chill alarm, see “Alarms” on
page 30.
R
AINFALL
Before you can use the rainfall function on your Weather Monitor II, you must
first set up and install the optional Rain Collector. See the booklet included
with the Rain Collector for instructions on its use.
B
AROMETRIC
P
RESSURE
The Weather Monitor II uses a solid state transducer to measure atmospheric
pressure. Since atmospheric pressure varies with altitude, the console adjusts
this measurement to give the equivalent sea level pressure, referred to as "baro-
metric pressure." The Weather Monitor II can display barometric pressure in
inches of mercury (IN), millimeters of mercury (MM), or millibars (MB).
Atmospheric pressure (and barometric pressure) also varies with local weather
conditions. Falling pressure is associated with deteriorating weather, while ris-
ing pressure is associated with improving weather. Standard or normal baro-
metric pressure is 29.92 inches or 760.0 mm of mercury (Hg) or 1013.2 millibars.
Since atmospheric pressure varies with both altitude and local weather condi-
tions, you must enter the current barometric pressure for your location when
you turn on your Weather Monitor II. Once the barometric pressure is set, the
Weather Monitor II calculates and display the correct barometric pressure until
the unit is moved to a different altitude.
The Weather Monitor II can also store a barometric pressure reading for com-
parison. With stored barometric pressure you can determine exactly how much
the barometric pressure has risen or fallen over a given period of time. Like the
highs and lows for other functions, the stored barometric pressure is accompa-
nied by the time and date it was recorded.
The Weather Monitor II also displays the barometric trend over approximately
the past hour. This trend is shown as an arrow in the bottom right hand corner
of the display.