Soil water content measurement by capacitance technique: sensor design and performance
Palavras-chave:
Manejo da irrigação, Umidade do solo, Permissividade do soloResumo
O conteúdo de água do solo é uma importante variável no manejo da irrigação e pode ser determinado por sensores eletrônicos. Este estudo teve como objetivo desenvolver um sensor capacitivo e avaliar seu desempenho em materiais de solo/substrato. Foram desenvolvidos protótipos de sensores com placas paralelas e coplanares, utilizando diferentes placas de circuito impresso e materiais isolantes. Na avaliação inicial, o sensor coplanar (SCP) construído em placa de fibra de vidro e isolado com verniz apresentou maior sensibilidade na estimativa da umidade do solo e maior facilidade de construção. O desempenho do SCP foi comparado ao sensor comercial 5TE da Decagon Devices (SC), após calibração em diferentes materiais de solo/substrato condicionados em colunas de PVC. Nesta etapa, as medidas do conteúdo de água (θ) obtidas pelo monitoramento das massas dos vasos em balanças de precisão foram comparadas às leituras dos sensores, gerando modelos de regressão relacionando θ com período (SCP) e permissividade (SC). Os valores estimados de θ foram comparados aos valores medidos e avaliados por índices de desempenho. A sensibilidade do SCP à salinidade e à temperatura foi avaliada posteriormente em água, para a faixa de 0,5 a 3,0 dS m-1 e 15 a 40 °C, respectivamente. O sensor desenvolvido apresentou baixo custo de fabricação (US$ 4.13) e desempenho satisfatório, com erro médio absoluto máximo de 0,0178 cm3 cm-3 e menor sensibilidade (9,9%) que o SC (34,2%) em relação à salinidade. Ambos os sensores apresentaram variação de, aproximadamente, 15% para temperatura variando de 15 a 40 °C.
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Copyright (c) 2026 Gabriela Rodrigues da Costa, Marinaldo Ferreira Pinto, Jaídson Gonçalves da Rocha, Celita Nathalia Vasconcelos Perdigão, Daniel Fonseca de Carvalho
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