基于CC2530的无线土壤水分传感器节点设计

土壤含水量的准确测定是实现节水灌溉和精准农业的基础。为实现土壤水分的自动测量和无线传输,基于FDR和CC2530芯片设计了无线土壤水分传感器节点。FDR实现了快速、精确的土壤含水量测量,CC2530完成模数转换、数字信号处理和射频信号的发送等工作。讨论了节点的低功耗问题,最后对节点进行了丢包率测试。试验结果表明:所设计开发的基于CC2530的传感器节点具有丢包率低、运行稳定可靠的特点,能够满足土壤水分的无线数据采集的要求。     

基于ARM嵌入式节水灌溉系统的研究

论文设计了一种基于ARM9控制的节水灌溉系统,用于实时监控土壤湿度状况,自动实现对土壤的节水灌溉。系统以S3C2440为核心,采用AQUA-TEL-TDR传感器的TDR原理,将输出的电信号通过MAX1246转化为数字信号;通过串口与PC机相连,PC机将计算出所需的灌溉量和时间并反馈给S3C2440,启动报警装置和开始灌溉。     

基于ARM嵌入式节水灌溉系统的研究

论文设计了一种基于ARM9控制的节水灌溉系统,用于实时监控土壤湿度状况,自动实现对土壤的节水灌溉。系统以S3C2440为核心,采用AQUA-TEL-TDR传感器的TDR原理,将输出的电信号通过MAX1246转化为数字信号;通过串口与PC机相连,PC机将计算出所需的灌溉量和时间并反馈给S3C2440,启动报警装置和开始灌溉。     

FDR和TDR测定几种典型土壤含水量的对比分析

针对基于时域反射(TDR)和频域反射(FDR)原理的土壤水分传感器,以潮土、红壤和黑土3种典型土样为实验对象进行室内标定,用不同标定方式对传感器与烘干法的测量值进行拟合及回归分析。结果表明:1)对于TDR和FDR,二次多项式拟合效果均优于线性及指数形式;2)在潮土中,TDR的测量精度高于FDR,而在红壤和黑土中,FDR的测量精度高于TDR;3)在3种测试土壤内,TDR相对于FDR普适性强。选择的3种土壤是中国北部、中部及南部地区的典型土壤,具有一定代表性,可为全国大部分地区土壤类型普适性研究提供实验基础。     

基于STM32的连栋温室精准灌溉控制系统

以STM32F103芯片为控制核心,选用FDR型土壤水分传感器测定作物当前生长期的土壤水分含量,结合当前作物所需要的土壤含水量,实时计算出差值,给出当前作物所需要的灌溉量,通过PC机给出灌溉命令,控制恒压变频柜的运行和灌溉电磁阀的开关。同时控制器能将变频器和各个电磁阀的运行状态、当前灌溉量和实时的土壤含水量传输给PC机。该系统不仅能精确的自动控制灌溉,而且可以根据种植者的要求提供灌溉。该系统能实现多个温室的精准灌溉自动控制,具有结构简单、成本低和可靠性高,对于实现节水灌溉和发展高效农业具有指导意义。     

基于频域反射法的便携式土壤水分检测仪研制

根据土壤墒情监测的具体要求,研制了一种新型便携式土壤水分检测仪。基于频域反射(FDR)原理采集土壤容积含水量,采用标准的烘干称重实验对测量结果进行校正,并同时获取检测点经度、维度信息及实时时间,通过GPRS/GSM及时传送给远程数据中心和责任人。实地测试表明:土壤水分测量误差<3%,数据传输无误。该仪器性价比高,操作简便,适合农技人员使用,对土壤墒情实时监测和智能决策具有重要现实意义。     

智能温室大棚节水灌溉系统的设计

本设计结合单片机、土壤湿度传感器、液晶显示器以及控制电路、按键电路、环境温度和光照强度测量电路设计了一套温室大棚节水灌溉系统,实现实时监测与显示土壤湿度、环境温度和光照强度,通过按键完成对设定阈值的修改、自动和手动两种控制方式的自由切换以及水泵电磁阀的控制,从而完成对温室大棚温度光、照和土壤湿度的测量以及自动节水灌溉的控制。     

基于Zig Bee网络的温室节水灌溉系统设计

为了实施有效的温室节水控制,设计了一种基于Zig Bee网络的温室节水灌溉系统。硬件部分以CC2430构建无线土壤水分传感器网络,包括无线传感器节点、控制节点、协调器节点;软件部分包括底层节点数据的采集和传送、协调器节点数据接收和发送、监控终端管理3个部分。采用LabVIEW对上位机监控软件进行了开发,人机交互界面友好。该系统实现了土壤含水量的自动采集,并根据作物的需水状况进行自动灌溉。实验结果表明:该系统具低功耗、低成本、可靠性好、安装维护方便等特点,通过合理设置控制参数,可以实现节水的目的。     

基于单片机和无线通讯的自动农田节水灌溉系统

以STC89C51单片机为核心设计了一种基于无线数据传输的自动农田智能灌溉系统,克服了传统有线农田自动灌溉系统的缺陷.系统采用Visual Basic 6.0开发上位机软件,实时在线自动监测土壤湿度,根据检测数据按照农作物的需水特性实现适时按需灌溉,从而达到高效节水的目的,系统运行良好,可以满足现代农业灌溉的需求.     

橘园无线土壤水分传感器的设计与实现

为了达到以一种低成本方式实时采集土壤水分信息用于指导橘园的节水灌溉,根据土壤电阻率随土壤含水率变化的原理,设计了一种土壤水分传感器.为克服恒定直流电压测量时探针电极的极化效应的影响,提出了一种以H桥正反脉冲间歇电压信号作为激励信号的测量方法.采用无线收发模块CC2420,实现了传感器与上位机之间的无线通信与数据无线传输.利用电源管理技术和睡眠机制,提高了电池的使用寿命.对传感器进行了标定,并在土壤含水率为13.6％～50.2％的范围内进行了验证实验,结果表明:当土壤含水率在21.1％～41.5％范围内,测量的平均误差为2.8％;当土壤含水率小于21.1％或大于41.5％时,测量的平均误差为5.2％.     

电容式土壤水分传感器的电导变异性试验研究

为评估电容式土壤水分传感器受土壤电导率的影响及其对农田土壤电导率变化范围的适用性,配制了一系列土壤等效含水率为40.6%、电导率为0~1.91dS/m的土壤等效介电溶液,分别对激励信号频率为40,50,60,70,80,90,100MHz的7种传感器进行了电导变异性试验,并且配制了相同含水率但电导率分别为0,0.31,0.46和0.61dS/m的4种土样进行了验证试验。试验结果表明:1)土样中的测试结果基本上与介电溶液吻合,可采用等效介电溶液评估传感器的电导变异性;2)传感器的电导变异率随待测介质电导率的升高而近似线性增大,相同电导率下,传感器激励信号频率越高其电导变异率越小;3)在农田土壤电导率基本变化区域0.239~0.650 dS/m内,当传感器激励信号频率从不低于80MHz时,其最大电导变异率为9.2%,能满足工程上的实际应用要求。     

基于FDR技术的土壤水分传感器设计

本文以土壤的介电理论为基础,通过测量土壤的介电常数随土壤水分变化的规律得知土壤的体积含水量,并利用土壤水分频域反射法实现土壤水分的测量.此方法可以连续检测土壤含水量的变化,较好的反映土壤水分的变化趋势.本文所设计的土壤水分传感器因具有多个测量分探头,因此可测量较深的土壤.因采用RS485总线通信,使传感器具有实时测量、...     

不同频率激励信号下土壤水分传感器性能试验

激励信号频率是影响高频电容式土壤水分传感器性能的重要因素。利用去离子水和2—异丙氧基乙醇(2—isoproxyethanol)或二氧六环(dioxane)2种溶液混合,配制了一系列等效土壤体积含水率为0.9%~51.8%的待测介电溶液来替代土样。从与土壤含水率的函数关系、温度变异性2个方面,分别对激励信号频率为40,50,60,70,80,90,100 MHz的7种土壤水分传感器进行了性能测试与分析。结果表明:7种频率的传感器的输出电压均与土壤体积含水率呈线性负相关,其相关系数R2均大于0.94;激励信号频率不影响传感器输出电压的温度变异性,温差是影响温度变异性的主要因素,其最大变异率均小于4%。试验结果可为设计高频电容式土壤水分传感器时选择激励信号频率提供依据。     

Utilizing space-based GPS technology to determine hydrological properties of soils

Competition for limited water resources is one of the most critical issues being faced by irrigated agriculture in the United States. Site-specific irrigation applies irrigation water to match the needs of individual management zones within a field, significantly reducing water consumption, runoff, and nutrient leaching in ground water. Remote sensing for real-time and continuous soil moisture measurements at specific depths is essential for success of site-specific irrigation system.The overall objective of this study was to investigate the feasibility of utilizing a GPS-based sensor technology to determine site-specific information such as the soil moisture condition by recording the GPS signal reflected from the earth's surface. A modified GPS Delay Mapping Receiver (DMR) tracks and measures the direct, line-of-sight, Right-Hand-Circularly Polarized signal of a GPS satellite. It also simultaneously measures the delayed, earth-reflected, near-specular, Left-Hand-Circularly Polarized GPS signal. These measurements can be used to estimate the surface scattering coefficient and path delays between the direct and reflected GPS signals. Over land, scattering coefficients can be used to estimate changes in soil moisture contents.Our results showed that the space-based technology has a great potential for determining soil volumetric moisture contents in the pursuit of site-specific irrigation management. There were strong correlations between the GPS reflectivity measurements and soil moisture contents. The GPS reflectivity increased as the soil moisture contents increased. Careful analysis of the test data showed very conclusively that the sensitivity of L-Band signal (1.575 GHz) to soil moisture contents changed with soil type and sampling depth. The sensitivity decreased with sampling depth in light soils and increased in heavy soils.     

基于无线传感器网络的小粒种咖啡园滴灌自动控制系统

为实现小粒种咖啡种植园的精量灌溉,达到节水增收的目的,基于无线传感器网络（WSNs）设计了一种滴灌自动控制系统,主要由传感器节点、簇头、控制节点和汇聚节点组成.测试了节点间的有效通信距离为50m,并在此基础上,采用静态簇和节点定位布置的方法进行了灌区划分和节点部署,每个灌区为边长50m的正方形,内设1个簇头、1个控制节点和4个传感器节点.采用定时通信与时间同步技术、休眠技术相结合的方法实现节点数据的无线传输,融合土壤含水率、光强和空气温湿度等信息,采用分区轮灌策略实现滴灌的自动控制.实验结果表明：系统实现了预期设计目标,能应用于小粒咖啡园的精量灌溉管理.     

Modified Alex–Behari model for soil moisture as a function of salinity,texture and frequency

Alex and Behari obtained experimental soil moisture data at microwave frequencies and computed emissivity from these. Following this they suggested an empirical model which provides a good agreement up to a soil moisture value of 25%. Taking into consideration the soil texture, the modified Alex–Behari (MAB) model provides agreement with the available data up to 40%. A non-linear relationship between volumetric soil moisture and emissivity is obtained. The dielectric constant shows an increase with volumetric soil moisture. The dielectric properties of the soil are known to depend on soil moisture content along with other factors like salinity, texture and frequency. In the present investigations the experimental dielectric constant of various types of soils was taken in the frequency range (1.4–18.0 GHz) to fit the modified model in the given range of moisture content. The computed data show that the real part of the dielectric constant decreases and imaginary part increases with soil salinity. It is suggested that the proposed model will be of interest to agricultural scientists, and applicable to remote sensing of salt-affected areas.     

自动观测土壤体积含水量实时资料自动质量控制方法

利用气候界限值（要素允许值）检查、台站气候极值检查、时间一致性检查、内部一致性检查、空间一致性检查,对自动土壤水分站的实时资料进行了自动质量控制。针对各层水分间没有具体的大小关系和等式关系,提出一种通过比较各层水分一小时变化值大小来判别数据质量的内部一致性方法。应用上述质量控制方法,对安徽省2011年4月-2011年7月共4个月近82个自动土壤水分站的8层土壤体积含水量数据进行了质量控制,错误检出率为1．49％。经自动质量控制后,实时水分数据的可靠性有较大程度提高。试验表明,安徽省82站1个时次的体积含水量数据可以在3min内完成质量控制．能保证实时业务运行时效。     

Pixel-scalesoil Moisture Monitoring Network and Its Preliminary Validation of L-band Soil Moisture Products

Soil moisture is a key variable in the process of crop growth,ground-air water heat exchange and global water cycle,which plays an important role in drought monitoring,hydrological land surface processes and climate change.Passive microwave remote sensing has become the main means of monitoring soil moisture with the sensitivity to soil moisture.In this study,the authenticity test of SMAP（Soil Moisture and Active and Passive） and SMOS（Soil Moisture and Ocean Salinity）passive microwave soil moisture products using the soil moisture sensor network monitoring data carried out against the underlying surface of farmlands in Jilin Province was carried out.The following conclusions were obtained：（1）Compared with the in situ measured data,SMOS L3(ascending and descending overpasses) and SMAP L3 passive microwave soil moisture products generally underestimated the ground data,but With the occurrence of rainfall events,there will be the phenomenon which is the value of soil moisture products is higher than the in situ data; although the unbiased root mean square error (unRMSE) of the two soil moisture products was greater than 0.07 m3/m3,the unRMSE of SMAP passive microwave soil moisture product data which was 0.078 m3/m3 was slightly lower;（2）Since the depth of induction of the L-band is lighter than the depth of detection of the sensor(5cm),and the dryness of the soil surface after rainfall causes the vertical inhomogeneity of soil moisture,which is one of the reasons why SMOS and SMAP passive microwave soil moisture products underestimate soil moisture; （3）SMOS has a higher value than the range of SMAP brightness temperature,which may be caused by radio frequency interference (RFI),which makes the error of soil moisture Retrieval and affects the validation accuracy.The comparison of bright temperature distribution of SMOS and SMAP shows that the effect of RFI on SMOS is more serious due to the influence of electromagnetic radio frequency interference (RFI),which may be the reason why the RMSE of soil moisture product of SMOS is higher than that of passive microwave soil moisture product of SMAP.