Improvements to the Globe Thermometer for Outdoor Use

The rapid changes in radiant conditions outdoors, require a fast response globe thermometer. As part of a research project entitled “Thermal Comfort in Outdoor Urban Spaces”, extensive field studies are being carried out involving environmental monitoring and interviews, thus the development of such an instrument was crucial. This paper describes a series of parametric studies of five 38 mm-diameter globe thermometers, of different thickness and materials, with the objective of reducing the thermometer's response time to approximately 4 min, similar to the duration of the interviews. Contrary to current belief, it is not only the slow heat transfer from the globe to the heat sensor that is responsible for long response times, but the heat capacity of the system as well, and by reducing it, shorter response times were achieved.