23
22
58.5
WET BULB
F
Globe Temperature
The Black Globe on the Kestrel Heat Stress Trackers is representative of the amount of heat-absorption
via the color black. Typically, Globe Temperature is taken using a 6” diameter copper globe painted black
with an internal thermometer. However, the Kestrel 4400 and 4600 use a 1” copper globe painted black
for calculations.
Globe Temperature is representative of the temperature of the Black Globe itself without accounting for
air temperature.
Naturally Aspirated Wet Bulb Temperature
The Kestrel Heat Stress Trackers' Naturally Aspirated Wet Bulb Temperature function accounts for the
effects of humidity on the human body. By combining relative humidity and wind speed, the temperature
displayed is indicative of the evaporative cooling happening to the Kestrel 4400 or 4600.
Wet Bulb Globe Temperature (WBGT)
The WBGT is a composite measurement of Naturally Aspirated Wet Bulb, Globe Temperature & Dry Bulb
Temperature. This environment data combines temperature, humidity, wind speed and thermal radiation
to access heat stress.
Outdoor WBGT
Indoor WBGT
GLOBE TEMP
F
75.2
GLOSSARY
DATA LOGGING AND MIN/MAX/AVERAGE
When Autostore is on and the unit is off, the heat stress measurements will not be stored because they use
calculations that cannot be performed without power. When reviewing data in the graphical display, the
symbol “–“ will appear at the top of the display for any points not logged due to the above condition.
In wind-related measurements, a timer will appear at the bottom of the screen after starting the MMA
feature – this timer displays the elapsed time. Additionally, for each minute this feature is running a data
set will be stored in memory reflecting the instantaneous conditions at that time. This will happen regard-
less of memory settings.
For additional information on memory options and logging data, please refer to the main
Kestrel 4000 series manual.
= 0.7 T + 0.2 T + 0.1 T
NWB
G
D
T = Naturally Aspirated Wet Bulb Temperature
NWB
Where =
T = Globe Temperature
G
T = Dry Bulb Temperature
D
Thermal Work Limit (TWL)
Like WBGT, TWL uses environmental measurements, including thermal radiation, to predict work
limits for people exposed to heat stress. Different attributes of clothing (such as its ability to insulate
and allow water vapor to pass through it) are also used to calculate TWL.
Acclimatization (Acclimatize)
Defined as the process of gradually adjusting to a change in environment (such as
a change in temperature, humidity, etc). During TWL mode “Acclim” will flash when
the value being displayed falls within the acclimitization zone. For example, people
who have not worked in such conditions should not be left alone until they have
acclimatized, a process requiring several days of gradually increased exposure to heat
stress conditions.
Black Globe
Typically a 6” copper sphere colored matte black with a thermometer in the center. This
thermometer reads the surface temperature of the Black Globe, which indicates the ra-
diant heat exposure of one in sunlight. The Kestrel 4400 and 4600 Heat Stress Trackers
use a 1” Black Globe that is calibrated to achieve the same measurements as a 6” globe.
