Carbonate based CO2 sensors with high performance

Comparison of three different sodium carbonate based sensor types shows that sensors with solid state references have a nearly drift-free response to CO2 changes (drift <0.5 mV/24 h). Gases as H2O (max. 50% r.h.), CO (max. 30 ppm), CH4 (max. 200 ppm) had no significant influence on the performance of all sensor types. Small amounts of NO2 (100 ppm) led to a (reversible) disturbance of the sensor signal only if the reference electrode is not sealed. It is shown that sensors with encapsulated solid state references resist to SO2 concentrations lower than 500 ppb because the formation of stable sodium sulfate is kinetically hindered.