Assessment of black globe thermometers employing various sensors and alternative materials

Abstract

The black globe temperature (Tg) is employed in thermal comfort studies. It is mainly used to compute the Mean Radiant Temperature (MRT) required in bioclimatic analysis. A set of low cost Black Globe Thermometers (BGT) was developed to establish a suitable combination of temperature transducers, materials and globe diameters. The dynamic and static responses of the BGT were studied. A total of 18 BGT was deployed along with a data acquisition system based in the Arduino open-source platform. It was analyzed the influence of the globe material (metallic and polyethylene), globe diameter (100 mm and 67 mm for the metallic and 78 mm for polyethylene) and six types of temperature transducers (K type thermocouple, infrared temperature sensor, thermistor, RTD and two semiconductor-based transducers). It was observed that Tg estimation and response time were transducer and stimuli dependent. The BGT presents good responses for indoor measurements and it was established that the most accurate combination was achieved by the DS18B20 digital temperature sensor with a metallic globe of 67 mm of diameter.