High-precision PTAT current source based on the Meijer cell

Carvalhaes-Dias, Pedro; Guimarães, Hélio; Dias, José Antonio Siqueira

doi:10.1080/00207217.2017.1335796

Cited by 1 publication

(1 citation statement)

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“…The variation of V BE with temperature is well known [15]. For a transistor biased with a constant collector current I C0 , it can be conveniently expressed as the sum of a constant term, a linear term (which decreases with temperature), and a term that is non-linear with temperature [16]:…”

Section: Principle Of Operation Of the Single Transistor Soil Water Cmentioning

confidence: 99%

Autonomous Soil Water Content Sensors Based on Bipolar Transistors Encapsulated in Porous Ceramic Blocks

et al. 2019

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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 Δ T = 2.9 ∘ 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 ∘ C/kPa. The ultra-low power signal conditioning circuit can read the sensor’s temperature with a resolution of approximately 0.02 ∘ 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.

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Section: Principle Of Operation Of the Single Transistor Soil Water Cmentioning

confidence: 99%