Abstract
Non-dispersive infrared (NDIR) sensors are a low-cost way to observe carbon dioxide concentrations in air, but their specified accuracy and precision are not sufficient for some scientific applications. An initial evaluation of six SenseAir K30 carbon dioxide NDIR sensors in a lab setting showed that without any calibration or correction, the sensors have an individual root mean square error (RMSE) between ~5 and 21 parts per million (ppm) compared to a research-grade greenhouse gas analyzer using cavity enhanced laser absorption spectroscopy. Through further evaluation, after correcting for environmental variables with coefficients determined through a multivariate linear regression analysis, the calculated difference between the each of six individual K30 NDIR sensors and the higher-precision instrument had an RMSE of between 1.7 and 4.3 ppm for 1 min data. The median RMSE improved from 9.6 for off-the-shelf sensors to 1.9 ppm after correction and calibration, demonstrating the potential to provide useful information for ambient air monitoring.
Highlights
Carbon dioxide (CO2) is a major greenhouse gas, with fundamental importance to Earth’s climate
The cavity-enhanced absorption spectrometry (CEAS) instrument determines the concentration of a gas by how long it takes for the signal to degrade inside the cavity, whereas an Non-dispersive infrared (NDIR) sensor merely measures the intensity of the signal received relative to the total intensity emitted
The K30 is a small, low-cost NDIR CO2 sensor designed for industrial OEM applications
Summary
Carbon dioxide (CO2) is a major greenhouse gas, with fundamental importance to Earth’s climate. Since measurements started at the Mauna Loa Observatory in the 1950s (Keeling et al, 2005), the global mean concentration of CO2 has steadily risen from the preindustrial mole fraction of approximately 280 μmol mol−1 of dry air (parts per million, or ppm) to today’s level exceeding 400 ppm. These observations, both from flask samples and state-of-the-art continuous measurement instruments, have a typical compatibility goal of ∼ 0.1 ppm, recommended for observations at background global network sites (World Meteorological Organization, 2013). High-accuracy CO2 observations are relatively sparse compared to other climatological variables such as temperature and precipitation
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