Main Article Content
Para rubber sheet is one of the primary products of natural rubber, which used in various rubber industries. High quality Para rubber sheet must be clean without air bubble, consistency of beautiful color, and has a moisture content in line with an accepted standard value. Nowadays, Para rubber quality needs to be evaluated by the experts only. Therefore, this research aims to develop a portable device for moisture content determination of Para rubber sheet, leading to more accurate quality evaluation comparing to the traditional method. The research composed of 2 parts, i.e. the development of portable spectrometer in the range of 900-1700 nm worked with smart phone, and the development of prediction model for moisture content determination using partial least squares regression (PLSR) with 3 different spectra pretreatment methods (standard normal variate (SNV), the 1st derivative, and the 2nd derivative). The experiments revealed that the model based on the 1st derivative presented the best prediction results as represented by coefficient of determination (R2) of 0.977, root mean square error for prediction (RMSEP) of 0.227 %db, and residual prediction deviation (RPD) of 6.576, respectively.
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