The standard black globe allows to measure the radiant temperature, necessary parameter to estimate the mean radiant temperature (Tmrt), which is one of the most important parameters that regulate the human energy balance. The Globe Thermometer consists of a copper sphere painted with a special high absorption black paint with a diameter of 150 mm and a thickness of 0,4 mm, containing a thermometer placed in the centre of the sphere. This sensor is described in the ISO7726:2002 standard.
LSI Lastem offers two models of Globothermometer: one for outdoor use and one for indoor applications.
The mean radiant temperature, one of the parameters used for the calculation of numerous microclimatic indices, is calculated thanks to two formulas (based on the air velocity) which take into account the difference between the temperature of the black globe and the air and the air velocity (if greater than 0.1 m/s). LSI Lastem data loggers have on board the formula for calculating this important parameter.
All microclimatic indices that are based on the equation of the thermal balance between the individual and the environment, both for moderate and severe environments, report the thermal power exchanged by radiation (R). The human body absorbs and emits thermal radiation in the form of electromagnetic waves. The transfer of heat by radiation is a function of the surface of the human body, of the emissivity and of the difference between the temperature of the individual’s skin and the average radiant temperature. The following environmental variables are included in the thermal balance between the individual and the environment: temperature, humidity and air speed and average radiant temperature.
Thanks to the EST131 (for indoor) and DMA131 (for outdoor) sensors it is possible to calculate different indices both for indoor microclimatic applications, for example to evaluate comfort and thermal stress at the workplace, and outdoors. The measurement of the radiant temperature in outdoor applications finds its most typical use in monitoring hot thermal stress in public places, such as public parks, stadiums and sports facilities, in order to warn users of situations potentially dangerous for health or for research purposes.
