Wheat Moisture Measurement with a Fringing Field Capacitive Sensor

Grain storage managers could improve the quality of stored grain if they could directly monitor stored grain moisture content, which is a key indicator of stored grain quality and an early indicator of deterioration. However, currently available sensors are too expensive and lack the necessary reliability in that harsh environment. A new fringing field capacitive (FFC) sensor was tested to determine its suitability and accuracy for moisture content measurements in grain. Sensors were calibrated using six samples of hard red winter (HRW) wheat from three locations and two crop years over a temperature range of 10° to 30°C. The linear calibration models had standard error of prediction (SEP) values that averaged 0.68% wet basis (w.b.) moisture content for data not corrected for bulk density. The average SEP improved to 0.50% w.b. when the readings were corrected based on sample bulk density, yielding a 95% confidence interval of ±0.99% w.b. for these data. The measured sensor accuracy, close to that of laboratory instruments, is appropriate for an in situ instrument for monitoring stored grain and for rapid determination of grain moisture content in bulk containers.