CAJ | 학술논문

为探究土壤温度和容重对FDR(频率反射)含水率测量结果的综合影响规律,以陕西杨凌地区的塿土为研究对象,以基于 FDR 技术的电流型 DSW-T2型土壤温湿度传感器为测量仪器,研究了土壤的含水率(3.82%~21.43%)、容重(0.91~1.30 g/cm3)和温度(2.5~50℃)对传感器输出信号的影响;建立了传感器的输出电流与土壤含水率、容重和温度的综合测量数学模型,实验分析了模型在预测含水率方面的可行性.结果表明,传感器的输出电流随土壤含水率、温度和容重的增大而增大,可用三元二次方程表示输出电流与土壤含水率、温度和容重之间的关系;在0.05的显著水平上,含水率、温度和容积密度均对模型有显著影响.基于模型的计算输出电流与实际输出电流的绝对误差范围是-1.167~1.216 mA,计算含水率与实际含水率的绝对误差范围是-2.638%~2.812%.本研究对于开发具有温度和容积密度补偿功能的新型FDR土壤含水率传感器的综合测量模型有指导作用.
위탐구토양온도화용중대FDR(빈솔반사)함수솔측량결과적종합영향규률,이협서양릉지구적루토위연구대상,이기우 FDR 기술적전류형 DSW-T2형토양온습도전감기위측량의기,연구료토양적함수솔(3.82%~21.43%)、용중(0.91~1.30 g/cm3)화온도(2.5~50℃)대전감기수출신호적영향;건립료전감기적수출전류여토양함수솔、용중화온도적종합측량수학모형,실험분석료모형재예측함수솔방면적가행성.결과표명,전감기적수출전류수토양함수솔、온도화용중적증대이증대,가용삼원이차방정표시수출전류여토양함수솔、온도화용중지간적관계;재0.05적현저수평상,함수솔、온도화용적밀도균대모형유현저영향.기우모형적계산수출전류여실제수출전류적절대오차범위시-1.167~1.216 mA,계산함수솔여실제함수솔적절대오차범위시-2.638%~2.812%.본연구대우개발구유온도화용적밀도보상공능적신형FDR토양함수솔전감기적종합측량모형유지도작용.
Moisture content of soil is helpful for water-saving irrigation. Soil moisture sensors using frequency domain reflectometry (FDR) are more and more popular in market. Soil temperature is a major factor affecting moisture measurement precision. So it has been widely considered in developing FDR soil moisture sensor. However, volume density, which is also a major factor influencing measurement precision of soil moisture, has been considered hardly. To investigate the comprehensive influence of temperature and volume density on moisture content by FDR moisture sensor, Lou soil in Yangling region, Shaanxi Province, were used as samples , and DSW-T2 soil temperature and moisture sensor (current output type) using FDR technology, was used as instrument to study the influence of moisture content at seven levels (3.82%, 7.58%, 9.29%, 11.65%, 14.87%, 18.61%and 21.43%in wet basis), volume density at five levels (0.91 g/cm3, 1.00 g/cm3, 1.09 g/cm3, 1.21 g/cm3 and 1.30 g/cm3) over temperature range from 2.5℃to 50℃at 2.5℃interval on output current. DM6801 digital temperature sensor was used to measure soil temperature and to detect precision of DSW-T2 on temperature measurement. A comprehensive mathematical model between output current, moisture content, volume density and temperature was established. Newton iteration method was applied to predict moisture content under laboratory conditions. The model’s feasibility in predicting moisture content from 3.82%~21.43% and volume density from 0.91g/cm3-1.30g/cm3 at 2.5-50℃ was verified. The results indicated that the output current of DSW-T2 increased with increasing moisture content, volume density and temperature over the investigated range of each factor. The absolute error between calculated temperature from obtained output current of DSW-T2 and measured one using DM6801 was within-3.8%-10.7%. The absolute error between calculated moisture content by output current of DSW-T2 and measured one by oven-drying method was-2.2℃-2.4℃. A quadratic model with three-degree of freedom could be used to describe the relationship between output current of DSW-T2 and moisture content, volume density and temperature of soil. At 0.05 significant level, soil moisture content, temperature and volume density had significant effect on the model. The absolute error between calculated output current and measured one was between-1.167-1.216mA. The absolute error between calculated moisture content and actual one was within-2.638%-2.812%when the output current, temperature and volume density were given. By comparing the moisture content obtained by DSW-T2 soil temperature and moisture sensor with out volume density information and calculated one by the regressed three-degree model considering the volume density, it showed that considering volume density is helpful to improve moisture measurement precision. The study offers useful information on developing a comprehensive measurement model for FDR soil moisture sensor with temperature and volume density compensation functions.