Implementation and Calibration of a Low-Cost Sensor Node for High-Resolution, Continuous and No-Manning Recording of Fruit Growth

This paper describes a low-cost sensor node prototype for in-field, non-invasive fruit growth measurement, with particular emphasis on the calibration procedures required to obtain a significant improvement in stability when environmental conditions change and, thus, optimized performance. Despite the low-cost components used, the prototype allows to continuously monitor the variations in fruit size during night/day and irrigation/chemical cycles with an effective resolution lower than one millimeter. The full-scale implemented achieves 12 cm, overcoming the need of relocating the sensor during the ripening season, as instead typical of high resolution alternative solutions.