Instructions

HD32.2 - 6 - V1.4
2. WORKING PRINCIPLE
Microclimate term means the environmental parameters that influence the thermal exchanges be-
tween the being and the environments inside limited places and that determinate the so-called
“thermal well-being”.
The micro-environmental weather factors together with your own job influence a series of your bio-
logic responses connected to well-being situations (Comfort) or thermal uneasiness (Discomfort).
In fact, the human body tries to keep the thermal balance in equilibrium conditions in order to keep
the body temperature on optimal values.
HD32.2 detects the following sizes:
• t
nw
: wet bulb with natural ventilation temperature probe
• t
g
: globe thermometer temperature
• t
a
: ambient temperature
It realizes direct measurements with the probes connected to the instrument and it also calculates
and directly visualizes WBGT index.
WBGT (Wet Bulb Globe Temperature) - wet bulb and globe thermometer temperature - is one of
the indexes used for determining the thermal stress to which is submitted a being in a warm envi-
ronment. It represents the value, with reference to the metabolic waste connected to a special job,
over which the being is in a thermal stress condition. WBGT index combines the temperature meas-
urement of natural ventilation wet bulb t
nw
with the Glob thermometer t
g
and, in some situations,
with the air temperature t
a
. The formula for the calculation is the following one:
• inside and outside the buildings in absence of solar irradiation:
WBGT
close environments
= 0,7 t
nw
+ 0,3 t
g
• outside the building in presence of solar irradiation:
WBGT
external environments
= 0,7 t
nw
+ 0,2 t
g
+ 0,1 t
a
where:
t
nw
= natural ventilation wet bulb temperature
t
g
= globe thermometer temperature;
t
a
= air temperature.
The detected data must be compared with the limit values established by the regulation; if they are
over passed, it’s necessary to:
• directly decrease the thermal stress in the considered working place;
• go on with a detailed analysis of the thermal stress.