A lot of research is done to monitor yield during harvesting. Combined with a positioning system, this information can be used to produce yield maps. Based on the yields of successive years, site-specific field management can be done, aiming for higher local economic and ecological yield efficiencies. In this research, a curved plate mass flow sensor for sugar beet is designed with the aid of a mathematical model. The principle is based on measuring the impulse flow colliding with the plate. For granular materials, an accuracy of 2% is achieved.