Low-cost infrared sensor array and open-source hardware for monitoring mean radiant temperature

In developing an innovative wearable monitoring system for research purposes, we focused on using low-cost sensors and open-source hardware to ensure affordability and accessibility. The main objective of this research was to evaluate the measurement performance of a conceptual system specifically designed to measure mean radiant temperature, a key parameter when evaluating thermal comfort in different environments. Although the Vernon and Humphreys globe thermometers, with diameters of 150 mm and 40 mm respectively, are standard tools—typically used alongside thermohygrometers and anemometers—for measuring mean radiant temperature, their slow response times and sensitivity to fluctuating outdoor conditions limit their suitability for wearable applications. This study therefore investigates more adaptable, low-cost alternatives that can be seamlessly integrated into wearable devices, addressing the limitations of conventional methods. The proposed system is based on a low-cost infrared sensor array composed of several Melexis MLX90640-ESF-BAA infrared modules connected to a Raspberry Pi 3A+. This low-cost system was directly compared with a calibrated, standardized reference system in a controlled test conducted at the ZEB lab at ITC-CNR. The results suggest that, despite its low cost, this new system can effectively estimate the mean radiant temperature in built environments.