Abstract
It is well recognized in the literature that thermal sensation and comfort are dependent on both core and skin temperatures. In particular, some regions of the human skin, such as the forehead, have a higher density of thermal receptors, giving a higher sensitivity to the skin temperature. Some studies suggest that the forehead skin temperature and its rate of change alone could potentially be a good indicator of one’s overall thermal comfort. To validate this claim, an idea for a smart sensor which would be able to read the occupants’ forehead temperature and other environmental parameters in a proximal way is here considered. Moreover, with the aim of exploiting the system not only in lab or test facility environments but, considering the 4.0 revolution, also in the building automation context, a non-invasive solution has been searched so as the occupants are not disturbed while the measurement is performed. Therefore, in this study, a new cheap and smart mechatronic sensor device for a non-invasive measurement of the occupants’ thermal comfort is proposed. The main components consist of a central unit, i.e. microprocessor, a small infrared sensor for thermal imaging, i.e a Lepton infrared camera by FLIR, as well as other sensors for measuring distance, humidity and temperature. The setup was imagined as the sensor being placed on the top of each desk, so it is not easily obstructed by a laptop or a similar object that can be found on top of the working surface. After the conceptual hardware definition and software development, an accurate experimental calibration has been performed exploiting an ad-hoc developed set-up based on a hot plate with an emissivity factor similar to the one of the human skin and with adjustable temperature. Finally, a first design for embedding the whole smart mechatronic system in a unique box has been developed and built.