Comparison of impact plate and torque-based grain mass flow sensors

The performance of two grain flow sensors was compared on a stationary combine in the laboratory. The separator mechanism was intact, and the threshing cylinder was immobilized. Grain flow to the machine was controlled by electronically modulating gate valves on two grain conduits. Base grain flows ranged from 0.91 to 6.36 kg/s in 0.91 kg/s steps. Perturbations of 0.91, 1.82, and 2.73 kg/s could be introduced into the machine through a separate conduit. The results showed that the torque sensor was ten times more sensitive to changes in flow rate when compared to the impact plate sensor. Standard errors for both sensors increased at flow rates below 3 kg/s. For flows less than 1 kg/s, the standard error for the impact plate sensor was ±60%, and the standard error for the torque sensor was ±18%. At flow rates greater than 3 kg/s, the error for the impact plate sensor was ±15%, whereas the error for the torque sensor was ±5%. Measuring the torque required to lift the grain in the clean grain elevator is an alternative and more precise method of quantifying grain flow when compared to the impact plate sensor.