An in-line moisture sensor for grain dryer control
1993
Bruce, D.M. | McFarlane, N.J.B.
An in-line capacitance sensor for grain and oilseed moisture was developed as part of a control system for continuous dryers. The measuring cell comprised two concentric cylinders, the outer of which had a diameter of 150 mm. The inner of the two cylinders was 330 mm long, and the annular gap between them in which the grain was held stationary during measurement was 50 mm wide. A vibrator attached to the cell was used to compact the cell contents prior to measurement, to reduce the effect of variation in bulk density on the readings. A facility to allow the user to recalibrate the device against readings from an off-line moisture meter was incorporated. Brief field trials on both wheat and rapeseed showed that the sensor was robust in use, and that its output was linear and correlated well with moisture contents determined by oven tests over the range 13 to 21% w.b. for wheat and 6 to 15% w.b. for rapeseed. For rapeseed, 97% of the variance was accounted for by a single regression line, while for wheat the value was 96%, using a separate intercept for each sensor. The 95% fiducial intervals for input and output moisture content were, for rapeseed, +/- O.22% moisture in the worst case at the extremes of the calibration line and +/- O.12% at the mean. For wheat the values were +/- O.5% moisture in the worst case and +/- O.15% at the mean.
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