Endres, H.-E.H.-E.EndresHartinger, R.R.HartingerSchwaiger, M.M.SchwaigerGmelch, G.G.GmelchRoth, M.M.Roth2022-03-032022-03-031999https://publica.fraunhofer.de/handle/publica/19447510.1016/S0925-4005(99)00060-XThis paper presents a capacitive CO2 sensor system with an effective numerical suppression of the humidity interference. The system consists of an heatable interdigital capacitor (IDC) with a CO2 indicator coating (heteropolysiloxane), a ca-pacitive humidity sensor and (op-tional) a temperature sensor. The CO2 measurement range has a high resolution between 100 and 3000 ppm CO2 and covers with a lower resolution 100 - 10000 ppm CO2 (twice TLV). These specifications follow the needs of indoor air quality monitoring (e.g. for mechanical ventilation). The software algo-rithm for the humidity interference rejection can be scaled down to a microcontroller (i.e. 8051 family). A long term study results in a lifetime of the CO2 sensors of more than eight months.enchemical sensorCO2 sensorhumidity compensationIDCindoor air quality monitoringsignal evaluation541journal article