RESUMO
Objetivou-se, com este trabalho, obter um modelo para o cálculo do teor de umidade do trigo, independentemente de sua massa específica aparente, ρ, a partir da medição simultânea da permissividade elétrica relativa, ε', do produto, em duas freqüências, utilizando-se um medidor do fator de qualidade Q. Avaliaram-se as possíveis fontes de erro durante a medição, em função das diferenças entre os valores experimental e calculado da capacitância do sensor. Verificou-se, também, o efeito causado pela utilização de grânulos de poliestireno expandido para redução artificial do valor da massa específica aparente dos grãos de trigo. O modelo obtido permitiu estimar-se o teor de umidade do trigo, variedade Estica, no intervalo entre 12 e 18% b.u., com desvio-padrão e erro máximo de 0,8 e 1,1 pontos percentuais de umidade, respectivamente. Concluiu-se que a metodologia proposta não permite, para as condições estudadas, a obtenção de um modelo para a estimativa do teor de umidade do trigo e que seja independente de ρ.
Palavras-chave:
instrumentação; teor de umidade; trigo
ABSTRACT
The object of this research work was to develop a density-independent equation to estimate the moisture content of wheat by simultaneously measuring the relative permittivity, ε', of the product at two different frequencies using a Q-Meter. Owing to the difference observed between the measured and theoretical capacitance of the empty sample container, an analysis of errors that arise during the measurement procedure was carried out. The effect due to the presence of polystyrene beads on the dielectric properties of wheat, which were used to artificially reduce the bulk density of the seeds, was also investigated. The resulting equation was capable of estimating wheat moisture content, variety Estica, in the range from 12 to 18% w.b. with a standard deviation and a maximum error of 0.8 and 1.1 percentage points moisture, respectively. It was concluded that the proposed method does not allow the derivation of a bulk density-independent model to estimate wheat moisture content for the conditions studied.
Key words:
instrumentation; moisture content; wheat
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Apoio financeiro da International Foundation for Science (IFS) da Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) e da Fundação Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Datas de Publicação
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Publicação nesta coleção
May-Aug 1999
