Kestrel 4000 Instruction Manual page 23

23
Reference Pressure
The local barometric pressure. Input to the altitude screen to provide correct altitude readings. Also known
as the altimeter setting.
Relative Humidity
The amount of water vapor actually in the air divided by the maximum amount of water vapor the air could
hold at that temperature, expressed as a percentage.
Station Pressure
The air pressure of your location, NOT reduced to the sea level equivalent.
Temperature
The ambient air temperature.
Wet Bulb Temperature
The lowest temperature to which a thermometer can be cooled by evaporating water into the air at constant
pressure. This measurement is a holdover from the use of an instrument called a sling psychrometer. To
measure wet bulb temperature with a sling psychrometer, a thermometer with a wet cloth covering over
the bulb is spun rapidly through the air. If the relative humidity is high, there will be little evaporative
cooling and the wet bulb temperature will be quite close to the ambient temperature. Some exercise
physiology guides use wet bulb temperature, rather than heat index, as a measure of the safety of exercise in
hot and humid conditions.
Wind Chill
The cooling effect of combining wind and temperature. The wind chill gives a more accurate reading of
how cold it really feels to the human body. The Kestrel Meter's wind chill is based on the National Weather
Service standards as of November 1, 2001.