Humidity - DAVIS Weather Monitor II Owner's Manual

The Barometric Trend Function
The barometric trend arrow, which appears on
the bottom right hand corner of the display,
gives you an indication of which way baro-
metric pressure is moving. If barometric pres-
sure changed by less than 0.02 inches of Hg
(1 millibar 0.75 millimeters of Hg) over
approximately the past hour, the arrow will be horizontal—steady barometric
pressure. If barometric pressure rose by 0.02 inches of Hg or more, the arrow
will have an upward slope—rising barometric pressure. If barometric pressure
fell by 0.02 inches of Hg or more, the arrow will have a downward slope—fall-
ing barometric pressure.
The barometric trend arrow is updated approximately every 15 minutes.
To Use the Barometric Trend Alarm
For instructions on how to use the barometric trend alarm, see "Alarms" on
page 30.
H
UMIDITY
Much of the air surrounding us consists of water vapor. Consequently, water
vapor plays an important role in determining weather conditions. When it con-
denses, the result is dew, fog, rain, snow, frost, and other forms of precipitation.
The amount of water vapor in the air also influences how we perceive temper-
ature. Humid days feel hotter because water vapor slows down the natural
cooling processes of the human body.
A measurement of the amount of water vapor in the surrounding air is depen-
dent upon temperature since warmer air is capable of holding much more
water than cooler air. Thus, relative humidity (usually simply called humidity)
is defined as the amount of water vapor presently in the air, divided by the
maximum amount of water vapor that the air could hold, given the current
temperature. The result is expressed as a percentage.
The Weather Monitor II can measure and display two sets of humidity read-
ings. One reading comes from the sensor located inside the console. The other
reading comes from the optional External Temperature/Humidity Sensor. If
you do not have this sensor, the Weather Monitor II will not measure outside
humidity and all outside humidity display readings will appear as a series of
dashes.
The Weather Monitor II also records high and low humidities for each set of
humidity readings.
To Display Current Humidity
1. To display inside humidity, press HUM.
The inside humidity reading and the word INSIDE appear on the display.
Weather Monitor II
BAROMETRIC
TREND
B T
AROMETRIC REND

Humidity

A
RROW
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