A calibration procedure for load cells to improve accuracy of mini-lysimeters in monitoring evapotranspiration

SummaryWe used twelve load cells (20 kg capacity) in a mini-lysimeter system to measure evapotranspiration simultaneously from twelve plants growing in separate pots in a glasshouse. A data logger combined with a multiplexer was used to connect all load cells with the full-bridge excitation mode to acquire load-cell signal. Each load cell was calibrated using fixed load within the range of 0–0.8 times the full load capacity of load cells. Performance of all load cells was assessed on the basis of signal settling time, excitation compensation, hysteresis and temperature. Final calibration of load cells included statistical consideration of these effects to allow prediction of lysimeter weights and evapotranspiration over short-time intervals for improved accuracy and sustained performance. Analysis of the costs for the mini-lysimeter system indicates that evapotranspiration can be measured economically at a reasonable accuracy and sufficient resolution with robust method of load-cell calibration.

► Evapotranspiration (ET) is an important aspect of hydrologic cycle on all terrestrial landscapes.
► Lysimeters are used to measure ET as losses of water from a container of growing plant(s).
► Calibrated load cells are important components of modern lysimeter to improve accuracy of ET.
► Design and performance of lysimeters is dependent on statistical treatment of calibration data.