The wet bulb globe temperature can be used to measure general heat-stress index
The Wet Bulb Globe Temperature (WBGT) can be measured by
- the black globe temperature
- the natural wet-bulb temperature
- the shade air temperature
Outdoor with Solar Radiation
The Wet Bulb Globe Temperature (WBGT) for outdoor conditions:
WBGT = 0.7 Tnwb + 0.2 Tg + 0.1 Ta (1)
WBGT = the Wet Bulb Globe Temperature (oC)
Tnwb = the natural wet-bulb temperature (oC)
Tg = the black globe temperature (oC)
Ta = the (shade) air temperature (oC)
The black globe thermometer (Tg)
A 150 mm (6 inch) black globe with a thermometer located at the centre.
Represents the integrated effects of radiation and wind.
The natural wet-bulb temperature (Tnwb)
A thermometer with its bulb covered with a wettened cotton wick supplied with water. Evaporation cools the thermometer. Not shielded from wind or radiation.
Represents the integrated effect of humidity, wind and radiation.
The (shade) air temperature (Ta)
Measured by a thermometer shielded from radiation.
Indoor - with negligible Solar Radiation
The Wet Bulb Globe Temperature (WBGT) can be calculated for indoor conditions as
WBGT = 0.7 Tnwb + 0.3 Tg (2)