Radar Sensor System for Unobtrusive Level Monitoring of Granular Solids Stored in Silos

This work explores the possibility of measuring from the outside of a fiberglass silo the level of stored granular solids, such as grains, flour, sand, or feed, by employing an unobtrusive millimeter-wave radar sensor system without the need for a specific hatch. A prototype embedding a frequency-modulated continuous-wave (FMCW)radar sensor system operating at 76-81 GHz, combined with a dedicated electronic board has been developed to acquire and manage data through Wi-Fi connection. The prototype has been installed on the outside of a fiberglass silo containing granular and dusty material with a density of about 800 kg/m3 while employing four load cells as referencemeasurement system. The proposed prototype has been tested over repeated cycles of load and unload of the silo, during which the level of the stored granular solid has varied between 0.5 and 5.2 m. The measurement repeatability, which defines the equivalent resolution of the sensor system, has been estimated at one standard deviation resulting in 0.037 m. The obtained experimental results showthe effectiveness of the proposed radar sensor system in estimating the level of the material stored into the silo, without the need for an opening in the silo.