Development of simplified grain-yield sensors for general-purpose combine harvesters

Measurement of yield variability in crop fields is important for implementation of Precision Agriculture. Yet, the sensors for such purpose are expensive and difficult in the maintenance especially in East Asian countries. We therefore developed and installed two simplified yield sensors: a force strain gauge sensor and an acoustic microphone sensor to estimate wheat grain weight. Impact waves from each sensor were extracted and calibrated with linear and non-linear models to actual grain weights. The output of the acoustic sensor was large enough without amplification and was not as affected by the vibration of the combine as that of the force sensor. Contrary to such advantageous expectation, however, the calibration of the force sensor showed the standard error of 27.9kg, and the relative error of 5.8%, whereas for the acoustic sensor, the standard error was 49.6kg and the relative error was 11.4%.