SYSTEMS TO ASSESS, MONITOR, AND PRESERVE PEANUT QUALITY AND SAFETY
Location: Peanut Research
Title: Nondestructive measurement of moisture content of different types of wheat using a single calibration with a parallel-plate capacitance sensor
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2012
Publication Date: June 1, 2012
Citation: Kandala, C., Settaluri, V., Sundaram, J. 2012. Nondestructive measurement of moisture content of different types of wheat using a single calibration with a parallel-plate capacitance sensor. Transactions of the ASABE. 55(4).
Interpretive Summary: Moisture content is an important factor to be measured and controlled for a variety of grain such as corn and wheat, and nuts such as peanuts and pecans. Wheat is an important crop produced world wide and is are popular crops produced in North America and cultivated inconsiderably large areas. Moisture content* in cereal grains is an important factor determining suitability for storage, transport, milling, and other processes. Knowledge of grain-lot moisture contents is also very important whenever grain is traded, not only for the reasons stated, but also because the moisture level influences the trading price. Moisture content affects the economic value of grain lots because of drying costs, if moisture content is above safe storage levels, and because of the "shrinkage" that takes place when the moisture content is reduced. Loss in weight because of moisture driven off when grain is dried must be taken into account in determining the fair market value.
In this work it is established that from impedance measurements made with a low-cost moisture meter developed at the National Peanut Laboratory the moisture content of wheat samples, in the moisture ranges of 9% to 25%, could be determined within an accuracy of 1%. The same calibration equation worked well for six different types of wheat and this method being nondestructive and rapid would be suitable for moisture content measurements of wheat and similar crops.
A simple, low cost instrument that measures impedance and phase angle was used along with a parallel-plate capacitance system to estimate the moisture content (MC) of six types of wheat. Moisture content of grain is important and is measured at various stages of their processing and storage. A sample of about 150 g of wheat was placed separately between a set of parallel plate electrodes and the impedance and phase angle of the system were measured at frequencies 1 and 5 MHz. A semi- empirical equation was developed using the measured impedance and phase angle values, and the computed capacitance and the MC values obtained by standard air-oven method. Multi Linear Regression (MLR) method was used for the empirical equation development using statistical methods. In the present work, a low-cost impedance analyzer designed and assembled in our laboratory was used to measure the impedance and phase angles. MC values of wheat samples in the moisture range of 9% to 25%, not used in the calibration, were predicted by the equations and compared with their standard air-oven values. For over 93% of the samples tested from the six varieties of wheat, the predicted MC values were within 1% of the air-oven values. This method, being nondestructive and rapid, will have considerable application in the drying and storage processes of wheat and similar field crops.