Inductive Sensor for Real-Time, Autonomous and Non-Destructive Fruit Size and Growth Monitoring

This work presents preliminary studies of an innovative and low-cost sensing solution for real-time fruit growth measurement directly on the tree, overcoming traditional mechanical and electrical issues. Implementability of high resolution inductive angular sensing technique on a fruit caliper is evaluated while suitability of the same FR4 substrate as both PCB and structural material for the pliers is analysed. A 71 μm resolution over a 120 mm is achieved and a maximum diameter absolute error estimation lower than 247 μm is obtained exploiting a calibration procedure. Finally, a thermal compensation procedure which takes into account material expansion is proposed.