基于RC网络相频特性的土壤含水率传感器设计

土壤中的水分影响土壤养分的溶解、转移和微生物的活动,是作物赖以生存的基本要素。土壤含水率的快速准确监测对于农业生产具有重要意义。该文设计了一种基于RC网络相频特性的土壤含水率传感器。不同含水率的土壤的介电常数的变化会导致RC电路网络的相频特性的变化。传感器通过感知这种变化进而确定土壤含水率。此外,针对RC网络电路元件参数和工作频率选择的问题,该文采用最优化方法求解从而使传感器在量程范围内具有最佳的灵敏度。其中最优的工作频率为f＊=1.9412×108Hz,最优的串联电阻R＊=13.1Ω。试验表明,该传感器对砖红壤土含水率的预测模型的决定系数R2为0.9889,实际预测误差≤4.58%。...

Full description

Saved in:
Bibliographic Details
Published in农业工程学报 Vol. 29; no. 7; pp. 36 - 43
Main Author 蔡坤 岳学军 洪添胜 徐兴 黄双萍
Format Journal Article
LanguageChinese
Published 华南农业大学南方农业机械与装备关键技术教育部重点试验室,广州 510642%国家柑橘产业技术体系机械研究室,广州 510642%华南农业大学工程学院,广州 510642%南昆士兰大学工程与测绘学院,图文巴 QLD4350 2013
Subjects
RC网络
传感器
土壤含水率
相频特性
设计
设计
sensors
soil moisture
phase-frequency characteristics
design
相频特性
RC network
土壤含水率
RC网络
传感器
Online AccessGet full text
ISSN1002-6819
DOI10.3969/j.issn.1002-6819.2013.07.005

Cover

More Information
Summary:土壤中的水分影响土壤养分的溶解、转移和微生物的活动,是作物赖以生存的基本要素。土壤含水率的快速准确监测对于农业生产具有重要意义。该文设计了一种基于RC网络相频特性的土壤含水率传感器。不同含水率的土壤的介电常数的变化会导致RC电路网络的相频特性的变化。传感器通过感知这种变化进而确定土壤含水率。此外,针对RC网络电路元件参数和工作频率选择的问题,该文采用最优化方法求解从而使传感器在量程范围内具有最佳的灵敏度。其中最优的工作频率为f＊=1.9412×108Hz,最优的串联电阻R＊=13.1Ω。试验表明,该传感器对砖红壤土含水率的预测模型的决定系数R2为0.9889,实际预测误差≤4.58%。
Bibliography:11-2047/S
Dielectric-based methods are widely used due to their non-destruction, efficiency and accuracy. The capacitance of the probe on the sensor is affected by the soil moisture. Therefore the mathematical model can be built between the capacitance of the sensor and the soil moisture. In this paper, a new soil water content sensor based on the phase-frequency characteristic of RC network is proposed. The sensor consists of four parts, that is a VHF oscillator, a phase-detecting circuit, a first-order RC low-pass circuit, and a probe. The VHF oscillator outputs a frequency-specified f＊ signal to drive the RC network, and the capacitor C of the first-order RC low-pass network is replaced by the capacitance of the probe of the sensor. Moreover, the changes of capacitance of the probe brought by the change of the soil moisture will cause a significant change in the phase-frequency response of the RC network. The AD8302 phase-detector is used to measure the change of the phase-frequency response of the RC netwo
ISSN:1002-6819
DOI:10.3969/j.issn.1002-6819.2013.07.005