Determining lag time for mass flow in a combine harvester

Lag time through a combine harvester was investigated using a stationary combine in the laboratory. Grain flow into the machine was modulated using electronically controlled gate valves. Base grain flows ranged from 0.91 to 6.36 kg s^-1 in 0.91 kg s^-1 steps. Flow perturbations of 0.91, 1.82, and 2.73 kg s^-1 were introduced into the combine through a separate conduit. The results showed that lag time varied with the mass flow through the harvester. Grain flow was measured using both an experimental torque-based sensor and an impact plate-type sensor. Lag time was determined using an author-written software program, LagFinder. LagFinder was used to determine lag times for both the grain flow plate and torque-based sensors. Lag time increased with increasing flow rates. Applying varying lag times using a quadratic delay model to yield monitor output could be a simple way to improve the accuracy of yield maps over using constant lag times.