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

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 that aimed to develop an inexpensive yet precise fast-response carbon dioxide (CO 2 ) and water vapour (H 2 O) sensor. A working prototype was 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 enclosed-path EC prototype achieved a CO 2 response time of 0.18 s and a noise level of 1 ppm at a 5 Hz sampling rate. The internal auto-calibration procedure was improved throughout the project such that CO 2 signal drifting was avoided and the instrument was capable of measuring CO 2 fluxes with high correlation relative to the reference EC setup ( R 2 =0.96 during high-flux season).