Publicação: Autonomous Soil Water Content Sensors Based on Bipolar Transistors Encapsulated in Porous Ceramic Blocks
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Data
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Coorientador
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Editor
Mdpi
Tipo
Artigo
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Resumo
We present an autonomous sensor to measure soil water content that uses a single heat pulse probe based on a transistor encapsulated in a porous block. The sensor uses a bipolar junction transistor, which performs as both a heating and temperature-sensing element. Since the sensor depends on a porous block to measure the matric potential of the soil, it does not suffer from accuracy problems if the contact between the probe and the soil is not perfect. A prototype of the sensor showed a temperature variation of Delta T=2.9 degrees C when the porous ceramic was saturated with water. The sensor presented an almost linear behavior for small changes in the matric potential of a red latosol when tested in the 1-kPa and 35-kPa pressure range, showing a sensitivity of S=0.015 degrees C/kPa. The ultra-low power signal conditioning circuit can read the sensor's temperature with a resolution of approximately 0.02 degrees C, so the matric potential can be read in increments of at least 1.33 kPa. When powered only by a 2-F supercapacitor from the energy-harvesting system, the interrogation circuit is able to take one soil water content measurement per day, for eleven days.
Descrição
Palavras-chave
soil water content, porous ceramic, bipolar transistor, embedded circuits, heat dissipation soil moisture sensors, low-power circuits
Idioma
Inglês
Como citar
Applied Sciences-basel. Basel: Mdpi, v. 9, n. 6, 13 p., 2019.
