Drift reduction of gas sensors by temperature modulation and signal-proccessing

Drift effects and cross sensitivities hinder the application of chemical sensor, especially with coatings based on organic or organically modified substances. A temperature modulated mode of sensor operation (AT-mode) is investigated to reduce drift and humidity influence on organic gas-sensitive coatings. The transducers are interdigital capacitance structures with ring heater (IDC). As sensitive material a CO2 sensitive organically modified heteropolysiloxane is used. Heteropolysiloxanes are well known materials for gas-sensing. They also have common weaknesses of organic sensor coatings. Different kinds and patterns of temperature modulation together with adapted signal-processing were used to reduce long time drift effects and diminsh cross-sensitivities. A typical application for CO2 sensors is the field of home automation. The hardware and software realization of the system will be discussed for two systems: First as a subpart of a complex, flexible, intelligent multi-gas sensor system based on the CAN field bus and secondly as stand-alone low cost solution for a CO2 alarm device.