FDR土壤水分传感器测量重复性研究

Study on repeatability of FDR soil moisture sensor

利用多个不同质地未受扰动的原状土壤样本,对其进行质量体积含水率测量和电容式频域反射FDR(frequency domain refletrometry)土壤水分传感器体积含水率对比测量,得到传感器的标定方程。对每个样本重复多次从含水量饱和至几乎不含自由水状态全过程对比测量,得到不同土壤湿度上的动态测量重复性;同时在土壤湿度不变的每一次对比测量中,等间隔旋转土壤水分传感器,得到在同一湿度值上的不同方位的静态测量重复测性。以实测的数据对两种重复性进行了分析,实验研究表明:在环境温度相差不大的情形下,FDR土壤水分传感器的原状土壤标定有较好的全量程重复性,试验用原状土壤样本体积含水率动态重复性误差最大为3.57%(cm^(3)·cm^(-3)),最小为2.29%(cm^(3)·cm^(-3)),平均为2.81%(cm^(3)·cm^(-3));体积含水率方向性静态误差最大为0.22%(cm^(3)·cm^(-3)),最小为0.01%(cm^(3)·cm^(-3)),平均为0.02%(cm^(3)·cm^(-3))。原状土壤动态重复性较好,能够作为站点后期校准标准物质,体积含水率方向性静态误差小,在测量中可以忽略。

Using undisturbed soil samples with different soil textures,the mass volume moisture content is measured and the volume moisture content of capacitive frequency domain reflectometry(FDR)soil moisture sensor is compared,and the calibration equation of the sensor is obtained.The whole process of comparative measurement from water content saturation to almost no free water was repeated for several times for each sample,and the dynamic measurement repeatability on different soil moisture was obtained.At the same time,in each comparative measurement of soil samples,rotate the soil moisture sensor to obtain the repeatability of static measurement in different directions on the same soil moisture value.Based on the measured data,the repeatability difference between the dynamic error and the static error is analyzed.The experimental research shows that the undisturbed soil calibration of FDR soil moisture sensor has good full-scale repeatability under the condition of little difference in ambient temperature.The maximum undisturbed soil sample dynamic error of volume moisture content is 3.57%(cm^(3)·cm^(-3)),the minimum is 2.29%(cm^(3)·cm^(-3)),and the average is 2.81%(cm^(3)·cm^(-3));The maximum error of directional static volume moisture content is 0.22%(cm^(3)·cm^(-3)),the minimum is 0.01%(cm^(3)·cm^(-3)),and the average is 0.02%(cm^(3)·cm^(-3)).The undisturbed soil has good dynamic repeatability and can be used as the standard material for post station calibration.The error of directional static volume moisture content is small and can be ignored in the measurement.