Smart monitoring system for air quality control with capacitive sensors

A low power, network-ready demonstrator for sensing carbon dioxide, humidity and temperature simultaneously is designed. Contrary to conventional NDIR systems, the sensor's detection principle is based on a capacitive readout of an interdigitated transducer coated with polymeric sensing materials sensitive to CO2 and humidity, respectively. A microcontroller is used to control the optimum working temperature of the sensor. The capacitance is measured based on the charge transfer capacitance measuring circuit. A restricted number of components is employed to meet low-cost and low power requirements. The system is tested in an office environment and compared to commercially available systems. It exhibits excellent results and is suited for an integration in automated HVAC systems.