ON-LINE MEASUREMENT OF GRAIN QUALITY WITH NIR TECHNOLOGY

Abstract

During the summer season of 2000, a feasibility study is carried out to measure grain quality(moisture and protein content) with Near Infrared Reflection (NIR) technology on a conventionalTX64 New Holland combine harvester. A Zeiss Corona 45 NIR 1.7 sensor was installed on abypass of the clean grain elevator. Parallel with the NIR measurement, grain samples were taken atthe end of the bubble-up auger that transports the grain from the clean grain elevator to the grainbin. Measured signals at the diode array of the spectrophotometer are highly variable in time and sincedata is acquired at a sampling rate of 23 Hz, an appropriate low pass filter is designed to obtainevery second a relevant spectrum. In addition, an optimal time shift is calculated between thelocation of the NIR measurement and the sampling spot, in order to make the comparison betweenthe estimated spectra and grain samples as accurate as possible. The spectra are first spectrally converted to either absorbance or Kubelka-Munk values. Therequired spectra of a white and black standard are time-interpolated between the standardmeasurements executed closest before and after the selected on-line spectrum. Preprocessing,calibration and validation are executed using the PLSplus/IQ module included in the GRAMS/32software package. After application of Mean Centering, the Multiple Scatter Correction, StandardNormal Variate and detrending algorithm are applied. The calibration models are developed usingthe PLS algorithm and validated through cross-validation.