In-situ non-linear calibration of grain-yield sensor

In-situ calibration of a mini-yield sensor (mounted on a five-row grain combine) with a non-linear relation to the flow rate was examined. Instead of measuring or controlling the flow rate of grain for calibration purposes, 10 or 12 pairs of grain weights and signal recordings were collected directly in the fields; three such data sets (weights and signals) were obtained. Two parameters of the relation were optimized so as to minimize the standard error. The relative error of validation was 3% to 5% with data sets of a wide range of flow rates, whereas it was up to nearly 10% with a data set of low flow rates. The optimized parameters varied with each data set, but those yielding low errors were common in the response surface of error, regardless of the data sets.