Metrological Validation of a Low-Cost Microcontroller-Based Reference Device for Neonatal Incubator Calibration

Closed neonatal incubators are critical medical devices for preterm infant survival. Their efficacy relies on providing a controlled microenvironment, requiring the regulation of temperature and humidity. Inaccurate measurement of these variables compromises the equipment's regulation, potentially leading to hypothermia or dehydration. Despite their criticality, regular calibration is often hindered in developing countries by the prohibitive costs of commercial reference analyzers. This study presents the design, implementation, and metrological validation of an affordable, microcontroller-based reference device utilizing a digital temperature and humidity sensor (DHT11). To determine the metrological reliability of the prototype, an experimental validation was conducted inside a controlled climate chamber. A dataset comprising 30,478 measurements was collected across different clinical setpoints. Statistical analysis demonstrated stability and a predictable systematic error. For temperature, the sensor exhibited a mean absolute error ranging from +0.23 °C to +0.46 °C, with a precision (standard deviation) between ±0.11 °C and ±0.16 °C. For relative humidity, the mean absolute error ranged from +3.68% to +4.12%, with a precision between ±1.25% and ±1.54%. The linear correlation observed confirms that the systematic error can be modeled and compensated via software. Additionally, a standardized technical protocol, based on the IEC 60601-2-19 standard, was structured for clinical application. This work demonstrates that the limitations of low-cost hardware can be mitigated through metrological characterization, providing a functional solution to strengthen biomedical metrology and guarantee neonatal care in resource-constrained healthcare systems.