GMI Magnetoelastic Sensor for Measuring Trunk Diameter Variations in Plants

Sensors based on giant magnetoimpedance effect are widely used in different technological applications. In this paper, a magnetoelastic sensor based on the changes of the high-frequency electrical impedance (Z) of a soft magnetic sample under applied mechanical stress has been optimized to measure the cyclical diameter variations in plants (grapevines in particular) in order to characterize their water status. Micrometric trunk shrinkage and growth take place during daylight and night, respectively, due to the changes in transpiration process and in within-plant water balance in a daily basis. The characterization of these variations (usually performed through linear variable differential transducers) represents a powerful tool in the agronomic sector regarding irrigation plant schedule.