Construction, calibration and performance evaluation of a lysimeter, with a double weighing system: Hydraulic and mechanical

Abstract

According to the literature, hydraulic and mechanical weighing lysimeters, which use electronic load cells, are considered the most accurate equipment to directly determine reference evapotranspiration (ETo) and crop evapotranspiration (ETc). However, the lack of comparative performance studies between these systems makes it impossible to make accurate statements about which is the most stable system and has the highest accuracy measurement. To evaluate the performance, it is important to consider parameters such as calibration, error analysis, accuracy test, hysteresis, and also the susceptibility to interference from external factors. Therefore, this study aimed to compare hydraulic and mechanical weighing systems through the construction, calibration and performance evaluation of a lysimeter with a dual weighing system operating simultaneously under the same environmental conditions. This study aimed to fill in the gaps found in the literature and help to solve questions related to the performance of these systems. Both systems have a high degree of linearity, with R² above 0.999, responding proportionally to mass variations in the lysimeter. However, the mechanical weighing system performed better with lower hysteresis, higher accuracy measurement, and more stable behavior, being less susceptible to environmental interference than the hydraulic weighing system. Both systems are suitable for instantaneous measurements of mass and determination of ETo and ETc, but for purposes that require greater accuracy measurement, it is recommended to opt for the mechanical weighing system.