Low-cost Arduino-based temperature, relative humidity and CO2 sensors - An assessment of their suitability for indoor built environments

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The growing development of digital twins (DT) in AEC industry is an opportunity for deepening the control and management of energy efficiency and indoor environmental quality (IEQ). DT will demand the deployment of many sensors, and low-cost solutions are the only way to achieve that. In this study, low-cost Arduino-compatible sensors were tested considering the indoor environment of Southern European countries. Five different sensors of the following parameters were tested: temperature (T), relative humidity (RH) and carbon dioxide (CO2). The T and RH tests comprise a combination of short-term and long-term exposures over 24 months, ranging between 10 °C and 35 °C, and 50%–95%, respectively. In short-term exposure, CO2 sensors were tested in six different CO2 concentrations from 400 to 2500 ppm. For each CO2 concentration, the values were compared, varying the T (15 °C to 25 °C) and the RH (50%–90%). The results highlighted that some low-cost sensors, open-source and easily connectable to Arduino, showed an excellent behaviour and general compliance with applicable standards. SHT85 T/RH sensor, stood out in the sample, and K30 and T6713-5K CO2 sensors showed good accordance with the reference. The equivalent CO2 sensors, that use algorithms to assess the CO2 value, showed results far from the reference equipment.