WAVELENGTH SELECTION FOR NEAR-INFRARED REFLECTANCE MOISTURE METERS

There can be significant errors in estimating moisture content from the near-infrared reflectance of samples in which there is a moisture content gradient. This paper shows that a moisture meter based on the reflectance at the weak, 970 nm, water absorption band is less sensitive to variability in the moisture gradient across unmilled grain, than one using the strongly absorbed 1450 nm band. This is because of the greater penetration of the 970 nm radiation into the sample. A further experiment on spruce sawdust samples shows the importance of selecting a suitable reference wavelength in a two wavelength device. © 1991 The British Society for Research in Agricultural Engineering.