From sensor voltage to methane fluxes

Last week, we began a crucial step in calculating our CH₄ fluxes: calibrating our methane sensors!

In the field, our sensors record voltage rather than CH₄ concentration directly. Sensor response is influenced not only by methane concentration, but also by temperature and relative humidity (RH)—particularly important during hot and humid summer conditions. 🌡️💧

To account for these effects, we built a calibration chamber in which we could systematically vary temperature, humidity, and CH₄ concentrations, from ambient levels (~2 ppm) up to 45 ppm. At the same time, actual CH₄ concentrations were measured using a LI-COR LI-7810.

Using these data, we developed calibration relationships that account for the effects of temperature and RH on sensor response. These relationships allow us to convert the voltage recorded in the field into reliable CH₄ concentrations and, ultimately, methane fluxes.

A lot happens behind the scenes before field measurements become greenhouse gas flux data!