Small Non-Dispersive Infrared (NDIR) sensors that can be deployed in-situ offer great opportunities for monitoring and understanding the biological, chemical and physical processes that drive gas production and consumption in natural environments. Often in these in-situ studies, researchers observe gas concentrations that span several orders of magnitude spatially and temporally. However, many sensors are calibrated to measure a single range of gas concentration (e.g. 0-50,000 ppm CO2). In general, NDIR sensors that are calibrated to low concentration ranges tend to be quite accurate, but suffer from data loss once the observed concentration exceeds their maximum threshold. Conversely, sensors that have a high calibration range are well suited for measuring large changes in gas concentrations that occur seasonally, but suffer from reduced accuracy when concentrations are low. In this application note we will demonstrate the “dual-range” calibration method that allows the eosGP sensor to make accurate measurements at low concentration while maintaining the ability to measure CO2 concentrations over several orders of magnitude.
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