Good performance of low-cost carbon dioxide sensor based on intercomparisons with the standard eddy-covariance system

Abstract. Flux measurements have started to play an important role outside academia in assessing carbon sinks of different ecosystems and land-use types. If natural carbon solutions are to be deployed and monetized in carbon markets, more low-powered and low-cost flux systems should be deployed. There is a growing need for low-cost sensors that still fulfil the requirements for scientific applications. We present a case study where Vaisala company and the University of Helsinki joined their industrial and academic competencies to create an inexpensive yet precise fast-response carbon dioxide (CO2) and water vapour (H2O) sensor. A working prototype was developed and field-tested against a scientific reference eddy covariance (EC) setup. Special attention was paid to response time, lowered sampling frequency, and auto-calibration related to the temperature. The results at the end of the project were very promising. The enclosed-path EC prototype had a CO2 response time of 0.18 sec and a noise level of 1 ppm at a 5 Hz sampling rate. The internal auto-calibration procedure was continuously improved such that CO2 signal drifting was avoided and the instrument was capable of measuring CO2 fluxes with high correlation relative to the reference EC setup (R2 = 0.98).