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Title: Wheat moisture measurement with a fringing field capacitive sensor

item Casada, Mark
item Armstrong, Paul

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2009
Publication Date: 9/1/2009
Publication URL:
Citation: Casada, M., Armstrong, P.R. 2009. Wheat moisture measurement with a fringing field capacitive sensor. Transactions of the ASABE. 52(5):1785-1791

Interpretive Summary: A new low-cost moisture sensor has been developed for measuring the moisture content (MC) and temperature of agricultural commodities. The sensor, which can be supported on cables in grain storage bins, was tested in the laboratory to determine the accuracy using HRW wheat samples from three states (Kansas, Oklahoma, and South Dakota) over two crop years. The accuracy was ±1% MC compared to the air-oven in these test. This accuracy was slightly lower than the best laboratory instruments, but this accuracy is appropriate for a low-cost in-bin grain moisture monitoring sensor.

Technical Abstract: 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.