Kestrel Wind & Weather Instruments
Due to overwhelming demand from our military customers. These models have the same features as their more colorful counterparts, but are olive drab with a visible red backlight, which helps sustain the user's natural night vision. Military personnel and pilots flying in darkness are often concerned with preserving their night vision.
It takes 30 to 45 minutes for the average eye to adapt to darkness and maximize night vision. Even a short burst of white, yellow, green or blue light “bleaches out” the rod cell photoreceptors in the eye and causes night blindness until the entire adaptation process can take place again. Light in the red spectrum does not cause this “bleaching out”, preventing night blindness and night vision fatigue. The units' red backlight is also much dimmer than a standard backlight, making it more difficult to detect with the naked eye in night operations.
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Functions: |
| Altimeter,
Altitude, Density Altitude - Vertical distance of an object above some
datum plane, such as mean sea level or a reference point on the earth's
surface. It is usually measured by the reduction in atmospheric pressure
with height, as shown on a barometer or altimeter. |
| Barometric
Pressure, Barometer, Barometric Trend - Measures atmospheric pressure.
Typically, a falling barometer indicates poor weather is approaching, a
rising barometer indicates fair weather approaching. |
| Dew Point
- The temperature to which air must be cooled, at a given pressure and
water-vapor content, for it to reach saturation; the temperature at which
dew begins to form. |
| Heat Index
- A number representing the effect of temperature and humidity on humans by
combining the two variables into an “apparent” temperature, introduced as a
replacement for the temperature-humidity index: a temperature of 90° and
relative humidity of 65 percent combine to produce a heat index of 102. |
| Humidity,
Relative Humidity - The amount of water vapor in the air, expressed as a
percentage of the maximum amount that the air could hold at the given
temperature; the ratio of the actual water vapor pressure to the saturation
vapor pressure. |
| Temperature
- A measure of the warmth or coldness of an object or substance with
reference to some standard value. |
| Time / Date
- The Kestrel 4000 includes clock and calendar functions. |
| Wet Bulb
Temperature - Wet-bulb temperature is measured using a standard
mercury-in-glass thermometer, with the thermometer bulb wrapped in muslin,
which is kept wet. The evaporation of water from the thermometer has a
cooling effect, so the temperature indicated by the wet bulb thermometer is
less than the temperature indicated by a dry-bulb (normal, unmodified)
thermometer. The rate of evaporation from the wet-bulb thermometer depends
on the humidity of the air - evaporation is slower when the air is already
full of water vapour. For this reason, the difference in the temperatures
indicated by the two thermometers gives a measure of atmospheric humidity. |
| Wind Chill
- The wind chill temperature is how cold people and animals feel when
outside. Wind chill is based on the rate of heat loss from exposed skin
caused by wind and cold. As the wind increases, it draws heat from the body,
driving down skin temperature and eventually the internal body temperature.
Therefore, the wind makes it feel much colder. If the temperature is 0
degrees Fahrenheit and the wind is blowing at 15 mph, the wind chill is –19
degrees Fahrenheit. At this wind chill temperature, exposed skin can freeze
in 30 minutes. A revised wind chill table was introduced by the National
Weather Service on Nov. 1, 2001. The old chart was formulated in 1945.
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| Wind Speed,
Max Wind Speed, Average Wind Speed - Wind velocity is measured by means
an impeller in Kestrel units. Max wind speed and average wind speed are
based on these measurements. |
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