Sensors to measure mass-flow-rate through a forage harvester

Four different sensors were used to estimate mass-flow-rate and moisture on a pull-type forage harvester. The sensors measured feedroll displacement, crop impact force against a hinged plate located above the blower, the freq uency drop of a capacitance controlled oscillator near the end of the spout , and the number of light beam interruptions by forage particles in the spo ut. Tests were conducted in a corn field with a commercial forage harvester modified with the first two sensors (feedroll displacement, impact force), and in the laboratory using a forage blower adapted to a forage harvester spout for the last two sensors (capacitance controlled oscillator, light be am interruption). The capacitance controlled oscillator was also characteri zed in a static mode in the laboratory with alfalfa acid timothy particles. When testing in a corn field, good correlations were obtained between esti mated mass-flow-rate and either the feedroll displacement (R-2 = 94%) or th e crop impact force (R-2 = 95%). When testing in the laboratory, the correl ation between mass-flow-rate and the oscillator drop was very good (R-2 = 9 6%) after a correction procedure. The number of light beam interruptions wa s not well correlated with mass flow (R-2 = 43% for LEDs placed after the c apacitor and R-2 = 6% for LEDs placed before the capacitor). During static measures with alfalfa and timothy, the oscillator frequency drop was also r elated to crop moisture but calibration corrections were required to consid er differences between crop species and chop lengths.